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					Chapter 6
Suggested Answers: Chapters 2–5
Chapter 2: Molecules of Life: Biomolecules
2-1   Hydrogen (H), oxygen (O), carbon (C) and nitrogen (N) make up 99% of all
      living matter.
       Bond                    Definition                            Strength
       Covalent                involve sharing electrons             very strong
       Ionic                   involve gain or loss of               weak
        Hydrogen               involve a bond between                weak
                               hydrogen and another polar
                               atom such as oxygen
        Van der Waals forces involve non-uniform                     very weak and
                               distribution of electric charge       temporary
2-3   Condensation reactions result in the formation of larger molecules by the
      removal of water from the reactants whereas in hydrolysis reactions water is
      added and larger molecules are split into smaller molecules.
2-4   pH is a measure of the concentration of H+ ions in solution on a scale of 0 to
      14. Acid solutions have a pH lower than 7, neutral solutions have a pH of 7
      and basic solutions have a pH of greater than 7. Cells maintain a relatively
      constant internal pH as their cytosols act as buffers, i.e. by removing added
      hydrogen ions or by releasing them.
       Property of water      Importance for cellular life
       high boiling point     water is a liquid at normal temperatures and can be
                              used as a solvent for chemical reactions
       high specific heat     water can absorb much heat with little change in
                              temperature and this is important for maintaining
                              constant body temperature
       high latent heat of    evaporation of water from the surface of living
       vaporisation           organisms draws heat form the surface cooling it
       density increases      ice forms on the top of water not at the bottom
       between 0oC and        therefore organisms can survive underneath the layer
       4oC                    of ice
       excellent solvent      polar molecules dissociate in solution to form ions
                              which is important for example for the transmission
                              of nervous impulses, transport within organisms and
                              for chemical reactions to occur
       cohesion and           transport within vascular plants
       as a reactant          water is a reactant in photosynthesis and hydrolysis
                              reactions such as digestion
                      Suggested Answers: Chapters 2 –5 121

      Biomolecule       Elements Examples             Use
      Carbohydrates     Cn(H2O)n Glyceraldehyde       Intermediate in resp. and
                                    Glucose           Energy source
                                    Ribose            Component of nucleic acids
                                    Sucrose           Energy store
                                    Glycogen          Energy store animals
                                    Starch            Energy store plants
                                    Cellulose         Structure of cell wall
      Lipids            C, H, O     Triglycerides     Energy store
                        (P, N)                        Insulation
                                    Waxes             Waterproofing of body
                                    Phosopholipids    Structure of cell membranes
                                    Glycolipids       Intecellular signalling,
                                                      receptors and cell
                                    Steroids          Chemical messengers (sex
                                    Cholesterol       Precursors to steroids,
                                                      fluidity of membranes
                                    Carotenoids       Pigment/photoreceptors
      Proteins          C, H, O,    1 Globular
                        N           Enzymes           Catalyse cellular reactions
                                    Insulin           Controls the level of blood
                                    Haemoglobin       Transports oxygen
                                    Antibodies        Immune response
                                    Contractile       Movement
                                    2 Fibrous
                                    Keratin           Structure

      Nucleic Acids     C, H, O,    DNA               Genetic material
                        N, P        RNA               Protein synthesis
                                     ATP/ADP            Energy currency
                                     NAD/NADH           Transport molecule
                                                        Many enzyme cofactors
2-7   Monosaccharides, disaccharides and polysaccharides are all carbohydrates.
      Monosaccharides are the simplest carbohydrates with molecules often
      containing either 5 or 6 carbon atoms. When 2 monosaccharides join together
      in a condensation reaction a disaccharide is formed. The 2 monosaccharides
      are joined by a covalent glycosidic bond. Polysaccharides consist of many
      chains (sometimes 1000s) of monosaccharides.
122 Biology

        Biomolecule           Building block       Bonds within the molecule
        Carbohydrate          glucose              glycosidic linkages
        Lipids                glycerol and fatty   ester linkages
        Proteins              amino acids           peptide link
        Nucleic acids         nucleotides           covalent bonds between phosphate
                                                    and pentose sugar and hydrogen
                                                    bond between the nitrogenous
2-9    Starch and glycogen are used as energy stores. Because they are large and
       insoluble they form solid grains inside cells. These grains do not interfere with
       metabolic reactions taking place in the cell and do not affect the osmotic
2-10   Saturated fatty acids do not contain double bonds in the hydrocarbon chain
       whereas unsaturated fatty acids do.
2-11   Oils have relatively short or unsaturated fatty acid chains, tend to be liquid at
       room temperatures and are more likely to be produced by plants. Fats have
       long or saturated fatty acid chains, tend to be solid and are more likely to be
       produced by animals.
2-12   This means they do not disperse through the cytoplasm where they act as a
       heat insulator and provide buoyancy.
2-13   Cells contain water and are surrounded by water. The cell membrane is made
       up of 2 layers of phospholipids. The hydrophilic heads of one layer line up
       against the internal fluid and the hydrophilic heads of the second layer line up
       against the external fluid. The hydrophobic tails point towards the centre of
       the membrane. The molecules are free to move and this gives the cell
       membrane fluidity but as the tails are hydrophobic and are attracted to each
       other the membrane is also strong.
2-14   Primary structure is the sequence of amino acids joined together by peptide
       bonds in a polypeptide chain. Secondary structure refers to the repeating 3-
       dimensional structure of the twisted and folded polypeptide chain resulting
       from hydrogen bonding. Tertiary structure refers to the final folded 3-
       dimensional shape. This is brought about by hydrogen bonds, ionic bonds,
       disulphide bonds, van der Waals forces and hydrophobic interactions. Where
       there are more than one polypeptide chain, quaternary structure refers to how
       these chains are bonded to make a complete protein.
2-15   Denaturing can be caused by high temperatures. High temperatures break
       hydrogen bonds and van der Waals forces destroying the quaternary and
       tertiary structure. Denaturing can be caused by extremes of pH which break
       ionic bonds again destroying quaternary and tertiary structure. Denaturing can
       also be caused by solvents such as alcohol, by solutes such as urea and by
2-16   Proteoglycans are molecules that contain both carbohydrates and protein.
       They are found in the extracellular fluid, where they are associated with the
       fibrous proteins, elastins and collagen. They have structural and supporting
       functions and have a signalling function when at the surface of cells.
2-17   Glycoproteins are molecules that contain proteins and saccharides. They
       function as recognition signals.
                       Suggested Answers: Chapters 2 –5 123

2-18 The basic building block of DNA (or RNA) is the nucleotide.
2-19 The three major components of DNA nucleotides are:
     –Sugar (deoxyribose)
     –Phosphate (link sugars to form uprights of the DNA ladder)
     –Nitrogen base (pair to form rungs of the DNA ladder).
2-20 The sugar and phosphate parts are constant in DNA.
2-21 The nitrogen base component is variable. Four bases are found in DNA:
     Adenine (A)
     Thymine (T)
     Guanine (G)
     Cytosine (C)
     Difference in base sequences is the basis of the genetic code.
2-22 Bonds will only form between complementary base pairs. The following are
     the complementary base pairs of DNA:
        Adenine and Thymine
        Guanine and Cytosine
2-23 Hydrogen bonds hold the bases together. Two hydrogen bonds hold adenine
     and thymine together while three hydrogen bonds hold guanine and cytosine
2-24 Heating to about 90OC causes hydrogen bonds to break and the bases to
     separate. In heating, the sugar-phosphate bonds are unaffected. Thus if DNA
     is heated, two long chains of nucleotides will result. If allowed to cool
     hydrogen bonds will reform between complementary bases and the chains will
2-25 RNA is a single chain of nucleotides whereas DNA is composed of 2 chains
     running in opposite directions and held together by hydrogen bonds. At the
     nucleotide level they differ in the pentose sugar present. DNA has deoxyribose
     whereas RNA has ribose. They also vary in that a DNA nucleotide may
     contain thymine. This is replaced in RNA with uracil.
2-26 The order of bases in DNA determines the order that amino acids are
     assembled at the ribosomes.
2-27 The cell theory states that all living organisms consist of organised structures
     called cells or the products of cells.
2-28 Technological advances: hand-held lens, light microscope, phase contrast
     microscopes, fluorescence microscopes, transmission and scanning electron
     microscopes, sectioning equipment and improved staining techniques.
2-29 Eukaryotic cells                           Prokaryotic cells
      Relatively large                           Small and lack specialisation
      Unicellular or parts of complex            Unicellular or very simple
      multicellular organisms                    multicellular organisms
      Distinct nucleus                           Nuclear material not membrane-
      Separate membrane-bound                    Little ‘compartmentalisation’
      organelles                                 No membrane-bound organelles
124 Biology

2-30 Organelle/            Structure                        Function
     Cell component
     Cell wall      thick cellulose                     cell support
     Cell membrane lipid bi-layer                       regulates movement in and
                                                        out of a cell
       Nucleus            contains DNA                  control centre (library of
       Nucleolus          within nucleus (contains      ribosome formation
       Cytoplasm          water and soluble             site of cellular activity
                          materials                     formation of fatty acid
       Ribosomes          made of RNA & proteins        site of protein synthesis
       Rough              internal membranes            folds proteins
       Endoplasmic        and ribosomes                 adds carbohydrates to
       Reticulum                                        proteins
                                                        some lipid synthesis
       Smooth             internal membranes            most lipid synthesis
       Endoplasmic                                      (especially phospholipids and
       Reticulum                                        cholesterol)
                                                        detoxification of harmful
       Golgi              internal membranes            processing and packaging of
       Apparatus                                        glycoproteins and
       Vesicles           membrane-bound sac            transport cell products to
                                                        proteins on the vesicle
                                                        membrane determine which
                                                        membranes the vesicle fuses
       Lysosomes          membrane-bound sac            contain self-destruct enzymes
                          containing enzymes            to allow digestion within the
       Vesicles           membrane-bound sacs           transport cell products to
       Mitochondrion      consists of folded            site of aerobic respiration
       Chloroplasts       grana & stroma contain        site of photosynthesis (light
                          chlorophyll                   to chemical energy
2-31 Cell wall: plant cells have a thick cellulose wall and cell membrane. Animal
     cells only have a cell membrane.
     Vacuole: large permanent vacuoles are characteristic of plant cells but not
     animal cells.
     Plastids: pigment-filled organelles such as chloroplasts are found in plant cells
     but not in animal cells.
2-32 Cells are microscopic in size to increase their surface area to volume ratio. It is
     through the surface of a cell that materials enter and leave. An increase in cell
     volume means a decrease in surface area to volume ratio and so the rate of
     exchange of materials (requirements and wastes) between a cell and its
     surroundings is decreased. Surface area can be increased to a certain extent by
                        Suggested Answers: Chapters 2 –5 125

      shape. Remember the ‘biconcave disc’ shape of red blood cells. This increases
      surface area to volume ratio of red blood cells and thus the ability for oxygen
      to diffuse in and out at a rapid rate.
2-33 Ribosomes are the site of protein synthesis (production). Ribosomes are
      attached to the endoplasmic recticulum, which consists of a membrane system
      that provides channels for movement of materials. It is also the site where the
      protein is folded and carbohydrates added. Proteins produced in the cell are
      packaged at the golgi apparatus (packaging) and moved to the cell membrane
      in vesicles (export). Protein markers on the vesicles determine which
      membranes the vesicles can fuse with. If the vesicle fuses with the cell
      membrane, the contents are secreted. The endoplasmic reticulum, the golgi
      apparatus and the vesicles are membranous organelles whose function can be
      summarised as transport, packaging and export.
2-34 The fluid mosaic model proposes that cell membranes consist of a bi-layer of
      phospholipids with embedded proteins. Fat soluble materials can pass through
      the lipid part of the membrane. Other materials pass through protein channels.
2-35                               Definition                   Comparison
 Diffusion       Process where molecules of a       No external energy is required.
                 substance move from a region       Movement is due to the random
                 of high concentration to a         movement of all molecules. Note,
                 region of lower concentration      however, that the rate of diffusion
                 resulting in an even spread of     increases with temperature.
                 molecules. Can occur in gases      Movement of the molecules is
                 or liquids.                        down the concentration gradient.
 Osmosis         A special case of diffusion –      As above but note that movement
                 refers to the movement of water of molecules refers to water only.
                 molecules from solutions of        Water molecules are moving down
                 differing concentrations that are their concentration gradient.
                 separated by a permeable
                 membrane. Net movement of
                 water will be to the side with
                 the higher concentration of
                 dissolved materials (solutes).
 Facilitated Case of diffusion where                Increases rate of movement of
 diffusion       movement of materials is aided materials across membranes when
                 (facilitated) by special protein   the materials concerned do not
                 carrier molecules.                 dissolve readily in the lipid layer of
 Active          Protein carrier molecules          Energy is required. This process
 transport       involved in moving materials       can only occur in living cells that
                 across membranes against a         are respiring and so producing
                 concentration gradient – that ATP. Process is very important in
                 is, material moved to a region     plant root hairs where ions are
                 where it is in higher              actively absorbed from the soil and
                 concentration.                     in the mammalian digestive system.
 Vesicle-        The cell membrane and vesicles Energy is required. Involves the
 mediated        are involved in the movement       movement of very large molecules
 transport       of large molecules into or out of and vesicles fusing with the cell
                 the cell.                          membrane.
126 Biology

2-36 Cellulose cell walls are found in plant cells and have a support function rather
     than forming an envelope for a cell’s living contents. The cell membrane
     provides little support. Its major role is in determining what passes in and out
     of cells. It is described as semipermeable. The cell membrane is made of a
     double layer of phospholipid molecules and embedded with lumps of protein.
     The proteins form channels that allow larger molecules to move in and out of
     the cell.
2-37 [VCAA, SA Q1, 2008]
A process occurring at structure W in this plant cell would be
C protein synthesis. (W is a ribosome. Ribosomes are the site of protein synthesis.
Q is a mitochondrion – site of aerobic respiration. N is a chloroplast – site of
photosynthesis. P is a golgi apparatus – site of packaging of molecules. M is the
nuclear membrane.)
2-38 [VCAA, SA Q2, 2008]
In this plant cell, the light-dependent reactions of photosynthesis occur in structure
A N. (The light-dependent reactions occur in the chloroplast.)
2-39 [VCAA, SA Q3, 2008]
The secondary structure of a protein is represented by

(B is an alpha helix which is a secondary structure, A is an amino acid, D is a chain of
amino acids representing a primary structure and C represents a tertiary structure.)
2-40 [VCAA, SA Q4, 2008]
The four main types of biomacromolecules in a cell are
C nucleic acids, proteins, carbohydrates and lipids. (Monomers and polymers
are terms that apply to very large molecules in general. DNA and RNA are types of
nucleic acids. Monosaccharides, disaccharides and polysaccharides are all
2-41 [VCAA, SA Q7, 2008]
Glycogen is
A a polysaccharide found in animal cells. (Glygcogen is a carbohydrate that is
used to store energy in animal cells.)
2-42 [VCAA, SA Q8, 2008]
Lipids characteristically
A are hydrophobic. (Proteins catalyse reactions, nucleic acids are information –
storage molecules and lipids have high energy content.)
2-43 [VCAA, SA Q12, 2008]
This means that insulin
D has more than one polypeptide chain. (Definition.)
2-44 [VCAA, SA Q1, 2007]
A polysaccharide that can be made in some animal cells is
C glycogen. (Starch, pectin and cellulose are polysaccharides made by plants.)
2-45 [VCAA, SA Q2, 2007]
It is reasonable to expect that
                        Suggested Answers: Chapters 2 –5 127

C the interior of the liposome is aqueous. (If drug 1 is lipophilic it would be
found within the lipid bilayer and if drug 2 is water soluble it would not be found
within the lipid bilayer. Membranes have fluid non-rigid structure. The fluid within
the liposome would be aqueous as the phosphate ends of the phospholipid are
hydrophilic and arrange themselves next to aqueous fluids.)
2-46 [VCAA, SA Q4, 2007]
A protein-based fibre could be constructed from repeated monomers of
A C5H13N4COOH (Proteins contain N nitrogen and A is the only alternative with
N in the chemical formula.)
2-47 [VCAA, SA Q8, 2007]
If this occurs, the compound that is next most accessible for use in glycolysis is
A lipid. ( Fact.)
2-48 [VCAA, SA Q9, 2007]
This nucleotide could be identified as a monomer of DNA but not RNA if
B Z is thymine. (Z is a nitrogenous base and thymine is found in DNA but not
2-49 [VCAA, SA Q11, 2007]
A haemoglobin molecule would be classifed as having a
D quaternary protein structure. (Haemoglobin consists of four polypeptide
chains therefore as more than one chain is involved it is classified as having
quaternary protein structure.)
2-50 [VCAA, SA Q19, 2007]
It would be reasonable to classify myosin as a
A contractile protein. (Myosin is the main component of muscle filaments, the
function of these is contraction.)
2-51 [VCAA, SA Q1, 2006]
Other polysaccharides synthesised by organisms include
D glycogen. (lactose, sucrose and glucose are simple sugars not polysaccharides.)
2-52 [VCAA, SA Q3, 2006]
Cell organelles that are essential for the production of chymotrypsinogen include
A ribosomes. (Chymotrypsinogen is the parent molecule. This means it is the first
molecule produced. Proteins are produced at ribosomes.)
2-53 [VCAA, SA Q4, 2006]
Molecules found in an animal cell membrane include
C cholesterol. (Chitin and cellulose are secreted by cells. Nucleotides are found
within the cell.)
2-54 [VCAA, SA Q5, 2006]
The formula that represents a protein is compound
D C708H1130N180O224S4 (N is found in all proteins and S is found in many.)
2-55 [VCAA, SA Q11, 2006]
The information given suggests that
C adjacent monomers are linked by a peptide bond. (The same DNA
sequences would result in identical chains. This is only a section of the chain so the
total length is not known. Each monomer is specified by 3 nucleotides. Amino acids
are joined by peptide bonds.)
128 Biology

2-56 [VCAA, SA Q13, 2006]
From this data it is reasonable to assume that the seven bases
C must contain the sugar ribose. (The base sequence includes U; therefore the
nucleic acid is RNA.)
2-57 [VCAA, SA Q20, 2006]
The diagram that most closely resembles the arrangement of phospholipids in a
plasma membrane is

B            (This is the only diagram which shows the phosphate heads pointing
out and the fatty acid tails pointing inwards.)
2-58 [VCAA, SA Q1, 2005]
A plant cell can be distinguished from an animal cell because of the presence of
B a cell wall. (All plant cells have a cell wall whereas only photosynthetic plant
cells have chloroplasts.)
2-59 [VCAA, SA Q2, 2005]
When using a light microscope, magnification of the structure being observed can be
increased by a variation in the
C objective lens power. (It is the lens that is involved in magnification.)
2-60 [VCAA, SA Q3, 2005]
The plasma membrane of a cell
D is relatively impermeable to large water-soluble molecules due to the
presence of the bilipid layer. (The plasma membrane is flexible because of the
presence of cholesterol, substances can move through the membrane by many
processes e.g. diffusion but the bilipid layer is composed of phospholipids, the tails
of which are hydrophobic.)
2-61 [VCAA, SA Q5, 2005]
A prokaryotic cell contains
C ribosomes. (All other organelles mentioned are membrane-bound.)
2-62 [VCAA, SA Q7, 2005]
The length of the organisms (shown as X on the diagram) is approximately
C 150 µm. (The diameter of the field of view is 450 µm. The organism is
approximately 1/3 of the diameter.)
2-63 [VCAA, SA Q8, 2005]
The purpose of the iodine stain is to
D provide contrast between structures of the cell. (Iodine stains starch blue-
black. Cell membranes do not contain starch so iodine will not help show the
structure of cell membranes.)
2-64 [VCAA, SA Q12, 2005]
From the information in the diagrams you can conclude that while the cell was in the
sucrose solution
D water molecules passed through the cell membrane. (The contents of the
cytoplasm and vacuole have decreased so substances must have passed across the
vacuole and the cell wall.)
                        Suggested Answers: Chapters 2 –5 129

2-65 [VCAA, SA Q3, 2004]
The ongoing death of these skin cells is an example of
C apoptosis. (This is a definition question.)
2-66 [VCAA, SA Q4, 2004]
The cell membrane of a nerve cell
D is composed of phospholipids and protein. (Glucose and water enter the cell
across the cell membrane and the membrane pores are composed of protein.)
2-67 [VCAA, SA Q1, 2004]
Area X would comprise
D tissue fluid. (Area X is the space between cells and would therefore contain
tissue fluid.)
2-68 [VCAA, SA Q2, 2004]
The section under the microscope would be best represented by

(Line FG crosses through 2 cells therefore D is incorrect. The first cell has a smaller
drop of fat as shown in B.)
2-69 [VCAA, SA Q5, 2004]
A prion is a form of
C protein. (This is a definition question.)
2-70 [VCAA, SA Q9, 2004]
You would expect
A the level of water to rise on the left of the membrane. (The membrane is not
permeable to sucrose so the sucrose concentration on the right side will not change.
There will be a net flow of water into the left side by osmosis.)
2-71 [VCAA, U4 SA Q9, 2004]
The complementary base found at the fourth nucleotide (marked *) in a sequence
transcribed from this sequence would be
D U (During transcription complementary mRNA nucleotides pair with the
exposed DNA bases. Note that mRNA’s U is complementary to DNA’s A.)
2-72 [VCAA, U4 SA Q10, 2004]
In a double-stranded molecule formed from this DNA template strand the number
of deoxyribose sugar units you would expect to find is
C 16 (Each strand is composed of 8 nucleotides therefore there are 16 nucleotides
and each nucleotide contains 1 deoxyribose sugar unit.)
2-73 [VCAA, SA Q2, 2003]
This process is known as
D phagocytosis. (Osmosis involves the movement of water, apoptosis is
programmed cell death and pinocytosis involves the uptake of liquids.)
2-74 [VCAA, SA Q3, 2003]
Biological polymers include
A cellulose composed of glucose. (Glycogen and starch are composed of glucose
and proteins are composed of amino acids.)
2-75 [VCAA, SA Q4, 2003]
This single layer is best represented by the black strip in diagram
C (C is the only diagram showing only a single layer.)
130 Biology

2-76 [VCAA, SA Q5, 2003]
Analysis of the data reveals that
D experiment 6 represents a plant cell in solution X. (The cells in experiments
1–3 are animal cells, the rest are plant cells. The cells in experiments 1 and 5 show no
net gain or loss of water thus must be in solution Y. The cells in experiments 3 and 4
have lost water thus must be in solution Z. The cells in experiments 2 and 6 have
gained water thus must be in solution X.)
2-77 [VCAA, SA Q6, 2003]
The changes observed during these experiments were due to
B osmosis. (Mitosis is a nuclear division, pinocytosis is a vesicle-mediated uptake
of a liquid and active transport involves movement against a concentration gradient.)
2-78 [VCAA, S1 Q1, 2002]
A typical prokaryotic cell has
A nucleic acid. (All other structures are found in eukaryotic cells.)
2-79 [VCAA, S1 Q19, 2002]
Each scale division was calculated to be 20 micron. The length of the organism is
C 100 micron. (The organism covers about 5 scale lines i.e. 5 x 20 microns in
2-80 [VCAA, S1 Q20, 2002]
For each cell, it would be reasonable to expect the student to be able to see
D a nucleus. (Chromosomes would only be seen in a dividing cell, chloroplasts in a
photosynthesising cell, and vacuoles in animal cells are small.)
2-81 [VCAA, SB Q1, 2008]
a   i Structure A
      Chemical composition: phospholipid (bilayer)
      The role of the phospholipid bilayer is to provide a boundary between the
      contents of the cell and the surrounding fluid. The phosphate end of each
      molecule is hydrophilic while the fatty acid chains are hydrophobic as a result
      the molecules line up with the phosphate ends of one layer next to the
      surrounding fluid and the phosphate ends of the other layer next to the
      cytosol. In this way a barrier is formed.
      The role of the phospholipid bilayer is to transport molecules into or out of
      the cell. The bilayer is flexible. This allows the formation of vesicles that carry
      large molecules into or out of the cell.
      The role of the phospholipid bilayer is to allow lipid soluble molecules to
      enter or leave the cell. Lipid soluble molecules can move easily through the
      phosopholipid bilayer.
    ii Structure B
      Chemical composition: protein
      Structure B is a carrier molecule where active transport occurs. The tertiary
      structure of the molecule determines it’s specific shape.
                       Suggested Answers: Chapters 2 –5 131

      This allows ATP to bind with the molecule resulting in the molecule changing
      shape and allowing it to bind with the substance that is transported against the
      concentration gradient across the cell membrane.
      The specific shape allows it to bind with the specific shape of the molecules
      that are transported into the cell against the concentration gradient.
2-82 [VCAA, SB Q2, 2008]
a    Any 2 of the following differences
                      DNA                               RNA
      Difference 1 contains deoxyribose sugar           contains ribose sugar
      Difference 2 thymine is complementary to uracil is complementary to
                      adenine                           adenine
      Difference 3 is usually composed of two is usually composed of one
                      chains of nucleotides (double- chain of nucleotides (single-
                      stranded)                         stranded)
b    Any one of the following kinds of RNA and corresponding function.
      Kind of RNA                    Function
      mRNA                           determines the order amino acids are
                                     assembled at the ribosome
                                     carries the information that determines the
                                     order amino acids are assembled, from the
                                     nucleus of eukaryotic cells to the ribosome
      tRNA                           brings specific amino acids to the ribosome
      (note transport RNA is         or
      incorrect)                     pairs with the specific codon on mRNA
      rRNA                           forms ribosomes where amino acids are
                                     assembled during protein synthesis
c    amino acid
d    Any one of the following fibrous proteins with its function.
      Fibrous protein             Function
      Spindle fibres during as the fibres contract the chromosomes move
      meiosis and mitosis         apart
      Myosin or actin             aid in muscle relaxation and contraction
      Silk                        spider webs – involved in trapping prey and spider
      Collagen                    connective tissue
                                  provides strength
e    Any one of the following
     -strength. This is determined by the parallel arrangement of the polypeptides
     into long fibres and sheets.
     -elastic. This is determined by the arrangement of the polypeptides which
     allows them to be stretched and then to return to their original shape.
     (Note: This question asks you to refer directly to the arrangement of the
132 Biology

2-83   [VCAA, SB Q6, 2007]
         Large molecules                          Monomers (subunits)
         Protein                                  Amino acids
         Lipid                                    Fatty acids and glycerol
         Polysaccharide (not carbohydrate) Monosaccharide
         DNA                                      Nucleotide
Note: most lipids are not polymers but many do have repeating subunits of fatty
acids and glycerol.
b      Monosaccharides enter an epithelial cell by diffusion or facilitated diffusion
       through protein channels in the cell’s membrane
       by active transport through protein carrier molecules in the cell’s membrane.
c      Any one of the following:
       - to make or repair membranes
       - to make steroid hormones/wax/oil/cuticle
       - as an energy store
       - as an energy source.
d           ATG           AAC           AGC            GGC
            TAC           TTG           TCG            CCG
e      G stands for guanine .
2-84 [VCAA, SB Q7, 2007]
a      Detection of early changes in telomere DNA would mean that very early
       detection and treatment of cancer would be possible. This would reduce the
       spread of the cancer and increase the chance of survival of the affected
b      The doctor will not be concerned. The changes in nucleotides do not result in
       the production of a different protein therefore cancer is not likely to develop.
c      Any one of the following and corresponding significance:
         Application               Significance
         Genetic screening         Early diagnosis means that treatment can begin
                                   before development is impaired or damage occurs
         Gene therapy              The genetic defect is corrected allowing the body
                                   to function correctly
         Rationale drug design     As the drug is designed to attack only affected
                                   cells, normally functioning cells will not be
                                   damaged leading to less side effects
         Vaccine development       Using genetically harmless organisms like yeast that
                                   can produce antigens of a more dangerous
                                   pathogen provides immunity without the danger of
                                   contracting the disease or suffering from side
         Manufacturing         of Using genetically modified organisms to produce
         biological     molecules human insulin increases supply and reduces the
         such as insulin           dangers of using insulin designed to work best in
                                   other organisms and problems with contamination
         Nanoparticles             Using nanoparticles to deliver drugs directly to
                                   affected cells will reduce damage to normally
                                   functioning cells and lead to less side effects
Note: Genetic engineering or proteomics without relating to the synthesis of
       vaccines or hormones would not be accepted.
                         Suggested Answers: Chapters 2 –5 133

2-85   [VCAA, SB Q1, 2006]
a      Proteins do not act in isolation. Many proteins (enzymes) may be involved in a
       chemical pathway by studying only one protein, information about the whole
       pathway will not be obtained.
b      The secondary structure of a protein determines the strength of the final
       protein and whether it can be stretched or not. This is important in structural
       proteins such as wool and silk. Wool can be stretched and then return to its
       original length whereas silk cannot.
c      Function of protein       Example
       structural                Any one of: silk, collagen, keratin, microfilaments
       transport                 Any one of: protein carrier of lipid hormones,
       regulatory                Any one of: enzyme, some hormones (not steroids)
2-86  [VCAA, SB Q1, 2005]
     Cellular structure in the     Matching function choose
     plant cell                    one from (A-H)
     Golgi apparatus                              D
     mitochondria                                 A
     chloroplast                                  F
     lysosome                                     B
     vacuole                                      H
     cell membrane                                E
2-87 [VCAA, SB Q1, 2004]
           Cell type           Particular cell structure           Function of
       neuron                Thin processes extending from cell To transmit nerve
                             body                               impulses
       microglia             Flexible cell membrane which phagocytosis
                             allows material to be engulfed
                             by the cell
       ependymal cells       cilia on one surface               To move material
                                                                over the cell
b     Celery in beaker A.
      Osmosis is the net movement of water across a semi-permeable membrane
      from an area of low solute concentration to an area of high solute
      concentration. The greater the difference in solute concentration the greater
      and faster the movement of water. Beakers A and B contain the highest
      concentration of glucose (10%). The concentration of glucose is greater
      outside the celery than within therefore there will be a net flow of water by
      osmosis out of the celery leading to a greater loss in mass. Beaker A not only
      has a 10% solution of glucose but it is also at a higher temperature. The higher
      the temperature the faster the molecules move therefore the faster the loss in
      mass over 30 minutes.
2-88 [VCAA, SB Q3, 2004]
a     After the flagella are removed, new flagella are produced. These flagella do not
      reach the same length as the flagella which have not been removed (10 цm
      compared with 12 μm of the original).
134 Biology

b        Lens C
         The average flagella length was 11 μm. If lens A was used about 100 flagella
         would fit across the diameter, whereas if lens C was used about 7 flagella
         would fit across the diameter. Therefore it would be easier to count accurately
         if lens C was used.
c        This cell is not typical of a true plant cell in that its cell wall is made of a
         glycoprotein rather than cellulose as in true plant cells.
d i X is the Golgi apparatus.
      ii The golgi apparatus packages molecules for secretion from the cell.
e        Oxygen is the waste product of the light-dependent phase of photosynthesis.
f        ATP or adenosine triphosphate is produced during cellular respiration.
g i The presence or absence of oxygen determines how much ATP is produced.
      ii 36–38 molecules of ATP are produced per molecule of glucose if oxygen is
         present whereas only two are produced if oxygen is absent.
2-89 [VCAA, SB Q1, 2003]
a        Absence of cell wall or outer covering is a cell membrane. Plant cells have a
         cell wall, animal cells do not.
         (Note: lack of a large vacuole or presence of chloroplasts are not correct as
         not all plant cells show these features.)
b        Structure Y is a mitochondrion.
c i The function of X is exchange of material into/out of the cell.
      ii Any one of the following:
         ● high surface area for exchange of material
         ● many mitochondria therefore ATP is available to provide energy for active
         ● presence of golgi apparatus which is involved in the packaging of material
              for secretion.
2-90 [VCAA, S2 Q1, 2002]
                                      Name and function
    i    Mitochondrion.
         Function: site of production of ATP through aerobic respiration
   ii Structure X Ribosome.
         Function: site of protein (polypeptide) synthesis.
  iii Structure Y Endoplasmic reticulum.
         Function: transport throughout the cell of the products of protein
  iv Golgi body.
         Function: packaging of products to be secreted from the cell.
   v     Chloroplast.
         Function: site of photosynthesis
b        Structure A: protein channel
         Structure B: phospholipid bi-layer
c        Sodium ions, Na+, diffuse into the cell and are then actively transported out of
         the cell against the concentration gradient. More sodium ions are transported
         out than in therefore the net effect is more sodium ions in the plasma. When
         an animal cell is placed into distilled water, water enters the cell.
d        Osmosis is used to describe this movement of water into a cell. Animal cells
         placed in distilled water swell and burst. Plant cells placed in distilled water do
         not burst.
                       Suggested Answers: Chapters 2 –5 135

e     Plant cells have a cell wall. As the cell fills with water the cell wall exerts
      pressure on the cell membrane stopping further expansion and forcing water
      to leave the cell. The plant cell does not burst. Animal cells do not have a cell
      wall therefore water continues to enter the cell faster than it leaves so the cell
Chapter 3: Molecules of Life: Biochemical Processes
3-1  An enzyme is an organic catalyst. They are proteins that alter the rate of
     reactions – usually to speed them up to a biologically useful rate. Many
     reactions occur naturally but at extremely slow rates. Enzymes only alter the
     rate (amount produced in a given time) of reaction. They do not alter the final
     amount of product produced.
3-2 Specific enzymes catalyse (alter the rate) of specific reactions. Enzymes bind
     with the substrates (reactants or ingredients) to form a temporary enzyme
     substrate complex. The enzymes have areas called active sites. The shape of a
     specific substrate molecule will match the active sites on a specific enzyme.
     Only the correct enzyme with the correct molecular shape will bind to the
     substrate molecule, in the same way that a particular key will open a particular
3-3 Substrates are the materials that are to be processed. The processing could be
     a breakdown reaction (e.g. digestion) or a synthesis reaction (e.g. making
     proteins). The materials present at the end of the reaction are the products.
     Enzymes allow the formation of product from substrate in a time that allows
     the efficient operation of an organism. Many of the reactions catalysed by the
     enzyme would otherwise occur too slowly.
3-4 Enzymes do not increase the amount of product produced. They alter the time
     it takes to produce the product.
3-5 The rate of reaction refers to the amount of product produced in a given time.
     For example, the rate of reaction could be measured in micrograms of product
     produced per minute.
3-6 Some factors that affect the activity of enzymes are: temperature, pH, the
     amount of enzyme present, and initial substrate concentration.
3-7 Different enzymes work best in particular environments. Digestive enzymes
     produced in the stomach work most efficiently in a low pH environment
     (acidic). Enzymes present in the ice fish of Antarctic waters work best at about
     4o C.
3-8 Enzymes are proteins. The folding of the protein into its tertiary structure
     provides a site that matches with specific substrates. This site is called the
     active site.
3-9 Enzymes are proteins so they can be denatured by
     - high temperatures (break H bonds and van der Waals forces destroying the
     quaternary and tertiary structure)
     -extremes of pH (break ionic bonds destroying the quarternary and tertiary
     Denaturation by extremes of pH is usually reversible but denaturation by high
     temperatures i.e. about 60o C is not. This means the active sites are
     permanently altered and the enzyme can no longer function. In terms of the
     lock and key hypothesis the shape of the key is altered.
3-10 Energy is never used. In doing work, energy is converted from one form to
     another and at the end of the process may be unusable. Most organisms store
136 Biology

       energy in chemicals such as fat or starch. The energy is made available to do
       cellular work during cellular respiration.
3-11   Cells need energy to do cellular work. Processes that require energy are: cell
       division, synthesis of new parts and materials, muscular contraction, active
       transport and nervous conduction.
3-12   Anabolic reactions are those involving the building or synthesis of molecules
       whereas catabolic reactions are breakdown reactions.
3-13   Exergonic reactions (breaking things) release energy: e.g. cellular respiration.
       Endergonic reactions (making or doing things) require an input of energy
       for them to proceed: e.g. any synthesis reaction such as protein synthesis.
3-14   ATP is a molecule containing adenosine attached to ribose which is bound to
       a chain of 3 phosphate groups. Energy is released for cellular reactions when
       the terminal phosphate group is removed to form ADP. ATP is the
       immediate source of energy for cells. When energy is released by cellular
       reactions, it is stored in ATP.
3-15   Autotrophic organisms make their own organic materials through processes
       such as photosynthesis or chemosynthesis. Heterotrophs rely on an external
       source of ready-made organic material. For example, you are a heterotroph
       and use organic materials found in animal or plant material that you eat.
3-16   Compound                                 Form absorbed
       Protein                                    amino acids
       Carbohydrates                             glucose
       Fats                                      fatty acid and glycerol
       Nucleic acids                             nucleotides
3-17 Photosynthesis:
     carbon dioxide + water + light energy                glucose + oxygen + water
                (This process occurs in plant cells that contain chlorophyll)
       6CO2 + 12 H2O                           C6H12O6 + 6O2 + 6H2O
       (Note that you can cancel 6 molecules of water from both sides of the
       equation and be mathematically correct. From a biochemical point of view,
       water is both a product and a reactant in the photosynthesis equation.)
3-18   Photosynthesis occurs in chloroplast-containing cells if they are exposed to
       light and are supplied with carbon dioxide and water.
3-19   Your diagram should show the following:
       cuticle, epidermis, palisade mesophyll cells, spongy cells, air spaces, stomata
       and vascular tissue. Draw arrows to indicate which way various gases move
       into and out of the leaf.
3-20   Some environmental factors that can effect photosynthesis:
       light intensity, water availability, air humidity, wind, and carbon dioxide
3-21   Pigments trap the light energy required for the photosynthetic process.
       Different pigments trap different wavelengths (colours) of light. Green
       pigments are effective at absorbing red and blue light. A range of pigments
       means that a plant can trap a wider range of light. Seaweeds that live in deeper
       water tend to have more red pigments. These are best for absorbing blue light,
       which penetrates water to a greater depth. The pigments a photosynthetic
                        Suggested Answers: Chapters 2 –5 137

       organism has will enable it to photosynthesise efficiently in its particular
3-22   In the light-dependent stage, light is absorbed by chlorophyll causing electrons
       to be emitted. Some of the energy is used to make ATP. Water is split and
       oxygen given off. In the light-independent (dark) stage through the Calvin
       cycle hydrogen from the light stage is added to carbon dioxide to form
       carbohydrate. ATP produced in the light stage provides the energy for this.
3-23   NADP is used to carry H ions from the grana to the stroma where the Calvin
       cycle takes place.
3-24   glucose + oxygen                        carbon dioxide + water + energy released
3-25   C6H12O6 + 6O2 + 36 Pi + 36 ADP                      6CO2 + 6H2O + 36 ATP
       Note that technically it is not necessary to put in the 36 molecules of ATP. For
       completeness, however, it demonstrates that you know what has happened to
       the energy that is released during the breakdown of glucose. The chemical
       energy in glucose is converted to chemical energy stored in ATP molecules.
3-26   a Anaerobic respiration in animals
       glucose                                    lactic acid + 2 ATP
       b Anaerobic respiration in plants
       glucose                                    carbon dioxide + alcohol + 2 ATP
3-27   Stage 1 Glycolysis. This occurs in the cytoplasm. Glucose is converted to
       pyruvate and 2 ATP are produced. Stage 2 Krebs cycle. This occurs on the
       matrix of the mitochondria. Hydrogen ions are removed, carbon dioxide is
       formed and 2 ATP are produced. The hydrogen ions and electrons are picked
       up by the coenzymes NAD and FAD. Stage 3 Electron transport chain. This
       occurs in the inner membranes of the mitochondria and requires oxygen.
       Reduced NAD and FAD provide electrons which are passed down the
       electron transport chain producing 32ATP. The oxygen is used to make
3-28   Aerobic respiration is more efficient as the glucose molecule is broken down
       to simple inorganic materials, carbon dioxide and water, and the maximum
       amount of energy is extracted – enough to make 36 molecules of ATP.
       Anaerobic respiration represents the partial breakdown of a glucose molecule
       to alcohol and lactic acid (still large molecules) and releases only enough
       energy to make 2 molecules of ATP.
3-29   Respiration can be thought of as photosynthesis in reverse. The reactants of
       one reaction are the products of the other! They are different in terms of
       energy. Respiration is an exergonic reaction. Photosynthesis is an endergonic
3-30   ATP is the source of energy for immediate use within cells. Animals convert
       glucose to glycogen for short-term storage. In the longer term the favoured
       storage material is fat. This is because a gram of fat stores about double the
       energy that carbohydrates or proteins can store.
3-31 [VCAA, SA Q5, 2008]
The graph showing the change in glucose concentration in the tube is
138 Biology

(No maltose remained at the end. This means that all the maltose was converted to
glucose. At this point the graph will level off and the glucose concentration will
remain constant.)
3-32 [VCAA, SA Q6, 2008]
At a light intensity of 10 units
C oxygen produced by photosynthesis is equal to the oxygen used by
aerobic respiration. (Plants both respire and photosynthesize in the light. Oxygen is
produced in photosynthesis and is used in aerobic respiration. At 10 units there is no
net uptake or output of oxygen therefore oxygen produced by photosynthesis is
equal to that used by aerobic respiration.)
3-33 [VCAA, SA Q15, 2008]
Facilitated diffusion is a form of cell transport that
C requires specific protein channels. (Facilitated diffusion is the rapid
movement of molecules down a concentration gradient across a membrane through
protein channels. It is a passive process.)
3-34 [VCAA, SA Q18, 2008]
With reference to this process it can be stated that
B the production of sucrose is an endergonic reaction. (Glucose and fructose
are monosaccharides that combine to produce sucrose. This requires energy.)
3-35 [VCAA, SA Q19, 2008]
Activation energy in a biological reaction
C is the energy required to start the reaction. (Definition.)
3-36 [VCAA, SA Q20, 2008]
From the graph you can conclude that
B a cell gets rid of urea more slowly than excess water. (The solubility of
alcohol in oil is about 0.01 arbitrary units compared with water which is about 0.0008
arbitrary units therefore alcohol is more lipid-soluble. The permeability coefficient
for urea is about 0.04 compared with water which is about 7 therefore a cell is more
permeable to water. Alcohol and codeine have a higher permeability coefficient than
ethylene glycol therefore they enter cells faster. Diethylurea has a slightly higher
permeability coefficient than ethylene glycol therefore it will enter a cell more easily.)
3-37 [VCAA, SA Q7, 2007]
The only correct comparison listed by the student is
    Photosynthesis                              Aerobic respiration
D Uses water as a reactant in the first         Forms water as a product in the
  stage                                         final stage
(Photosynthesis is endergonic and aerobic respiration is exergonic. The first stage of
aerobic respiration, glycolysis, occurs in the cytoplasm and electron transport is
involved in both processes. Note electron transport occurs in the light dependent
stage of photosynthesis.)
3-38 [VCAA, SA Q14, 2007]
It is reasonable to argue that
                        Suggested Answers: Chapters 2 –5 139

D ATP is produced as a result of this reaction. (The bacteria obtains energy
from the reaction therefore the reaction is exergonic and heat is produced. The
energy released would be harnessed to make ATP. Oxygen is a reactant so the
reaction is aerobic not anaerobic.)
3-39 [VCAA, SA Q20, 2007]
Cell organelles and membranes that are involved in the transport of biomolecules
from inside a cell to outside a cell include
D secretory vesicles that bud off from the Golgi complex. (Ribosomes are the
site of protein synthesis, microtubules are part of the cell’s cytoskeleton and
movement from inside the cell to outside is exocytosis.)
3-40 [VCAA, SA Q21, 2007]
It is reasonable to conclude that
D material is able to pass from cell to cell without having to travel through
a plasma membrane. (Structure X is endoplasmic reticulum. This is made of
membrane and not cellulose. The cytosols of each cell are connected to each other
via the gaps in the wall; this allows material to pass directly and freely from one cell
to another.)
3-41 [VCAA, SA Q2, 2006]
Anabolic reactions, also called endergonic reactions, include
C photosynthesis. (glycolysis, Kreb’s cycle and protein digestion are breakdown or
exergonic reactions.)
3-42 [VCAA, SA Q6, 2006]
In chloroplasts
D the light reactions occur in the grana. (The light dependent reactions require
water. The light independent reactions occur in the stroma and the final product is
3-43 [VCAA, SA Q15, 2006]
The product, X, in this biochemical process is
D a monosaccharide. (The biochemical process is photosynthesis.)
3-44 [VCAA, SA Q17, 2006]
The packaging and transport of biomolecules within a cell involves their
C movement from the ribosomes into the endoplasmic reticulum.
(Microfilaments are involved in the cell’s cytoskeleton, transport goes from the ER
to the Golgi apparatus and secretory vesicles move from the cytosol to the plasma
3-45 [VCAA, SA Q18, 2006]
Considering events that occur in a chloroplast during photosynthesis it is reasonable
to claim that
B carbon dioxide is an input to reactions at Q. (Photosynthesis occurs in the
chloroplast. Oxygen is an output not input in photosynthesis. P is the grana and Q is
the stroma.)
3-46 [VCAA, SA Q19, 2006]
The most likely reason that the bacteria are able to carry out their metabolic
functions in this environment is that the bacteria
B have enzymes with a high optimal temperature. (Enzymes are proteins. It
would be very difficult to lower the temperature of the cellular environment.)
140 Biology

3-47 [VCAA, SA Q24, 2006]
The three types of movement are correctly described as
      X                      Y                       Z
B active transport           facilitated diffusion diffusion
(X movement is against the concentration gradient, so it must be active. Y is down
the concentration gradient through a protein channel, so it is facilitated diffusion. Z
is through the phospholipids bilayer and down the concentration gradient, therefore
is diffusion.)
3-48 [VCAA, SA Q25, 2006]
It is reasonable to conclude that in
D BP 2, providing all enzymes are present, the production of arginine would
be continuous if there was a continuous supply of substrate. (If enzyme 3 in
both biochemical pathways stops very little isoluecine or arginine would be
produced. BP1 is self regulating so production would not be continuous whereas
BP2 is not self regulating, so production would be continuous.)
3-49 [VCAA, SA Q4, 2005]
Based on the internal structure, the cell is likely to
C require high levels of oxygen. (This cell has many mitochondria. These are the
sites of aerobic respiration; therefore the cell would require high levels of oxygen.)
3-50 [VCAA, SA Q9, 2005]
The production of organic molecules in a crop is reduced when leaves begin to wilt
B stomata close preventing the entry of CO2. (When plants wilt the stomata
close. This prevents entry of carbon dioxide.)
3-51 [VCAA, SA Q19, 2005]
The most likely reason for the enucleated half-cell to die after seven days is that
B protein synthesis was reduced. (The nucleus directs the synthesis of proteins.)
3-52 [VCAA, SA Q20, 2005]
      Modification of culture medium                            Effect on time for
                                                                amoebae to reproduce
A bubble carbon dioxide into the pond water                     more than 50 hours
(Increasing density will increase competition for resources and increase time for
reproduction. Decreasing temperature will slow reaction rates and increase time for
reproduction. These organisms do not photosynthesise, so changing light intensity
will not affect time for reproduction, but bubbling carbon dioxide through will
decrease reproduction time.)
3-53 [VCAA, SA Q21, 2005]
Warming the yeast suspension increases the rate at which sucrose is broken down to
glucose and fructose because warming
B increases the frequency of collisions between molecules. (Fact.)
3-54 [VCAA, SA Q22, 2005]
The graph that shows the effect of adding more sucrose to the yeast suspension is
A (This curve shows an increase in rate at first and then a levelling of rate as
another limiting factor, i.e. enzyme concentration, takes effect.)
3-55 [VCAA, SA Q6, 2004]
A defining characteristic of a prokaryote is the
                        Suggested Answers: Chapters 2 –5 141

D absence of membrane bound organelles. (Some eukaryotes and prokaryotes
have cell walls and ribosomes are found in both types of cells. Some mature
eukaryote cells, i.e. red blood cells do not contain a nucleus but do contain other
membrane bound organelles.)
3-56 [VCAA, SA Q7, 2004]
The temperature at point X is most likely to be
D 100oC. (These microorganisms live in springs of boiling water therefore their
optimal temperature for enzyme activity is likely to be close to this temperature.)
3-57 [VCAA, SA Q8, 2004]
A graph with the same shape would be obtained if the variable plotted on the
horizontal axis was
A pH. (Enzyme activity would have an optimal pH.)
3-58 [VCAA, SA Q1, 2003]
D contain layers of internal membranes. (Glycogen is a carbohydrate storage
compound found in animal cells. Not all plant cells contain chloroplasts; root cells
and bacteria are prokaryotes therefore do not contain membrane-bound organelles.)
3-59 [VCAA, SA Q10, 2003]
The rate of production of carbon dioxide was greatest
C at point N. (The graph peaks at N.)
3-60 [VCAA, SA Q11, 2003]
The low rate of production of carbon dioxide at point P is most likely because
B most of the glucose has been used. (Up to P the yeast is respiring without
oxygen. Glucose is required to produce carbon dioxide and therefore is the limiting
factor. All the yeast cells have not been killed as the line does not touch the X axis.)
3-61 [VCAA, SA Q12, 2003]
If oxygen had not been bubbled through the culture after point P, it is reasonable to
assume that
A the rate of production of carbon dioxide would have continued to fall. (If
glucose is not added it is the limiting factor and therefore rate of carbon dioxide
production would continue to fall.)
3-62 [VCAA, SA Q13, 2003]
The concentration of alcohol in the culture would have been
B greatest at point P. (Alcohol is only produced without oxygen. Point P will
therefore have the greatest accumulation of alcohol as oxygen is required to break it
3-63 [VCAA, SA Q17, 2003]
The limiting factor at point X is the
C amount of enzyme. (pH and temperature would give a bell-shaped graph and
substrate concentration is represented by the X axis therefore is not limited.)
3-64 [VCAA, S1 Q13, 2002]
The effect on animals that eat these plants is
A a decrease in ATP production. (Less ATP will result and as energy is released,
not stored, in respiration there will not be an increase in storage. Oxygen is a reactant
not a product of respiration.)
3-65 [VCAA, S1 Q24, 2002]
It is reasonable to conclude that
142 Biology

B the rate of breakdown of glucose in tube 8 is 60 µmol/min. (C is incorrect as
all tubes had the same amount of enzyme. If all the substrate had been used the rate
would be zero.)
3-66 [VCAA, SB Q3, 2008]
a      Light is required for the light dependent stage of photosynthesis. The light is
       absorbed by plant pigments therefore the more light that is absorbed by the
       pigments the greater the rate of photosynthesis as shown by the graphs.
b i Any one of the following:
       water, ADP and Pi, NADP
    ii Any one of the following:
       ATP, oxygen, NADPH
c      34-38 ATP
d i The electron transport stage occurs on the inner membranes (cristae) of the
       mitochondria. Note: mitochondria is not specific enough.
    ii During the electron transport stage electrons are passed down an electron
       transport chain (or along electron acceptors/cytochromes) releasing energy in
       the form of 32 ATP and finally combining with oxygen to form water.
3-67 [VCAA, SB Q3, 2008]
a      Enzymes lower the activation energy for metabolic reactions allowing them to
       occur fast enough at body temperature to maintain life.
b      The tertiary structure of an enzyme determines its three dimensional shape.
       The specific part of an enzyme that fits the shape of its substrate is called its
       active site. The active site allows the enzyme to bind with the specific substrate
       increasing the rate of the reaction.
c      Rational drug design refers to the production of drugs that are specifically
       designed in terms of shape to interact with target molecules that are associated
       with the cause of a disease or disorder. For example a drug is designed to bind
       with a receptor that allows a virus to be released from a cell.
d i Designed drug two
    ii Designed drug one has one site that is complementary to the active site of
       ACE and designed drug three has three sites that are complementary to the
       active site of ACE whereas designed drug two has four sites that are
       complementary to the active site of ACE. This means that designed drug two
       would bind more effectively to the active site of ACE thus less ACE would be
       available to convert Angiotensin I to Angiotensin II.
e      The drug would bind with ACE active site thus there would be less ACE
       available to bind with Angiotensin I and less Angiotensin II would be
       produced. This would in turn result in lower blood pressure levels.
3-68 [VCAA, SB Q3, 2007]
a      Hydrogen peroxide (H2O2) is the substrate.
b      Agree. The optimal temperature for enzyme activity is usually close to the
       temperature of the tissue in which it is found. The tissue temperature of
       carrots (16oC) would usually be lower than humans therefore you would
       expect carrot catalase to have a lower optimal temperature for enzyme activity
       than human catalase.
c      Place the same amount of carrot in 20 test tubes. Note the carrot is taken from
       samples of similar place, age and size.
       Add the same amount of 3% H2O2 solution to 10 test tubes.
       Add water to the other 10 test tubes.
                       Suggested Answers: Chapters 2 –5 143

      Incubate one test tube with carrot and H2O2 solution and one test tube with
      carrot and water at 0oC for 10 minutes, repeat at 5oC and so on (range 0oC to
      All other factors the same.
      Measure the amount of oxygen produced.
      Repeat the experiment many times.
      Results: If maximum oxygen production occurs in a test tube with carrot and
      H2O2 solution at a temperature below 30oC the student’s prediction would be
3-69 [VCAA, S2 Q4, 2007]
a     Y the granum or thylakoid absorbs light.
b     Plant B is the plant from the shaded area.
      The grana in chloroplasts absorb light for photosynthesis. The greater the
      number of grana, the greater the amount of light that can be absorbed. In
      shady environments the amount of light is low, thus if a plant has many grana,
      it will be able to absorb more of the available light. Plant B has more grana
c     Diffusion or osmosis
d     Photosyntheis is controlled by enzymes. Enzymes are made of proteins which
      in turn are made at the ribosome.
      The ribosomes are used to make chlorophyll which form part of the grana
e     Either one of the following:
      Chloroplasts and mitochondria contain DNA that is circular like prokaryotes
      and unlike the linear DNA of eukaryotes. This enables chloroplasts and
      mitochondria to replicate and pass on their own genetic material like
      independent organisms.
      Chloroplasts and mitochondria contain small ribosomes that are similar to the
      ribosomes found in prokaryotes and not the same structure as those found in
      eukaryotes. This enables mitochondria and chloroplasts to make their own
      proteins like independent organisms.
f     Carbon dioxide
g     Any one of the following sources of NADPH and ATP
      - the light dependent reactions (the splitting of water/electron transport chain
      of photosynthesis)
      - the grana
h     PGAL (glyceraldehyde 3-phosphate) or triose phosphate
      Note: even though the diagram shows a 3-carbon molecule, the examiners
      accepted glucose and/or water.
3-70 [VCAA, S2 Q4, 2006]
a     Anaerobic respiration.
b     Electron transport and ATP production occur on the inner membranes of the
c     Field crickets are pests and eat crops. An agricultural company could sell the
      toxin to farmers so that crop yields would be higher.
d     In trial 1, 2,4-dinitrophenol had been added. This means heat has been
      produced instead of ATP. The energy produced in electron transport has not
      been converted into chemical energy in ATP as phosphorylation of ADP has
      not occurred, whereas the control was able to produce ATP. ( Note: this is a
      comparison question so both trial 1 and the control must be referred to.)
144 Biology

e     Temperature went down after the fifth observation as the temperature of the
      cell had risen high enough to denature enzymes and the cell has begun to die.
f Observations                             Temperature oC
    made at
    equal time       control                 trial 1                trial 2
    intervals        (no                     (2,4-dinitrophenol
                     2,4-dinitrophenol)      added)
       1 (start)              28                      28                  28
           2                  27                      28                  29
           3                  28                      29                  31
           4                  29                      31                  36
           5                  28                      36                  23
           6                  28                      23                  21
           7                  27                      21                  19
g     Adding pyruvate would not cancel the effect of the toxin. Pyruvate is the
      product of glycolysis which occurs before electron transport and ATP
3-71 [VCAA, S2 Q3, 2005]
a i Oxygen.
   ii Oxygen and hydrogen ions are produced by the splitting of water.
b     Glucose. (Note: not sucrose or starch.)
c     Plants photosynthesise. They absorb energy from sunlight to produce glucose
      and oxygen. Glucose and oxygen are used in aerobic respiration. The products
      of photosynthesis are the reactants for aerobic respiration.
d     Aerobic respiration produces more ATP (36) per molecule of carbohydrate
      compared to anaerobic respiration (2). (Must mention numbers of molecules
      of ATP per molecule of carbohydrate.)
e     Conclusion 1: The apical meristem inhibits the growth of lateral buds.
      Evidence: Apical meristem present (Group 1), no growth of lateral buds but
      when the apical meristem was removed (Group 2) the lateral buds grew. (The
      only difference between Group 1 and Group 2 was the presence of apical
      meristem; therefore the presence of apical meristem inhibits lateral bud
      Conclusion 2: Auxin inhibits the growth of lateral buds.
      Evidence: When the apical meristem was removed (Group 2) the lateral buds
      grew but when auxin was applied to a shoot without an apical meristem
      (Group 3) no growth occurred. (The only difference between Group 2 and
      Group 3 was the presence of auxin; therefore auxin inhibits lateral bud
      Conclusion 3: The apical meristem produces a compound that inhibits growth
      of lateral buds.
      Evidence: Apical meristem intact (Group 1), no growth of lateral buds but
      when a barrier to the movement of compounds was placed under the tip
      (Group 4), growth occurred. (The only difference between Group 1 and
      Group 4 was the ability for substances to move down from the apical
      meristem; therefore the apical meristem produces a lateral bud growth
                       Suggested Answers: Chapters 2 –5 145

3-72 [VCAA, S2 Q5, 2002]
a i Balanced chemical equation for photosynthesis:
      6CO2 + 12 H2O                      C6H12O6 + 6O2 + 6H2O
  ii As oxygen is a product of photosynthesis, the rate it is produced indicates the
      rate of photosynthesis.
b     The oxygen concentration in the air surrounding the plants decreased during
      the first 10 minutes of the experiment as the plants were in the dark. No
      photosynthesis was occurring but aerobic respiration was. Oxygen is a reactant
      of aerobic respiration therefore its levels fell.
Chapter 4: Detecting and Responding:
Coordination and Regulation
4-1   The internal environment in multi-cellular organisms refers to the fluid in
      which cells are bathed. Included are the tissue fluid, lymph, and blood plasma.
      The external environment refers to that outside an organism and is separated
      from the internal environment by a layer of cells. You need to be careful as
      some areas that seem to be inside the body are technically part of the external
      environment. For example, the contents of the gut and the air in your lungs
      are parts of the external environment.
4-2   Conditions such as temperature and humidity may vary considerably in the
      external environment. Cells, to function efficiently, require constant internal
      conditions. In particular, enzyme function is affected by changes in
      temperature and pH. The maintenance of internal environment within a
      narrow range is called homeostasis and allows efficient functioning of cells.
      Homeostasis literally means one state.
4-3   Homeostasis allows enzymes to function efficiently. This is important as
      enzymes regulate all chemical processes that occur inside cells.
4-4   Major problems for desert organisms are:
      1 large fluctuations in environmental temperature leading to heat balance
      2 little water available that leads to water balance problems and lack of
      constant food supply.
4-5   Overcoming heat problems
      Structural Adaptations: thick layer of fur to insulate, big ears or large
      external surfaces with extensive blood supply to radiate excess heat, light
      colouring to reflect heat and minimise absorption.
      Functional Adaptations: sweating, panting, the ability to reduce metabolic
      heat production when hot and allowing body temperature to rise during the
      day and fall when cooler (this helps conserve water that might be lost as
      sweat), dilation of arterioles and constriction of shunt vessels.
      Behavioural Adaptations: being nocturnal to avoid hottest times, living
      underground, spreading out to lose heat and huddling at night to conserve
      Overcoming water problems
      Structural Adaptations: reduced number of sweat glands to decrease water
      loss (causes problems for heat loss), especially long kidney tubules to allow
      greater reabsorption of water, elongated large intestine to maximise water
      absorbed from undigested food.
146 Biology

     Functional Adaptations: ability to tolerate high levels of urea (nitrogenous
     wastes) in the blood and produce concentrated urine – saving water. As
     mentioned in heat balance, allowing body temperature to rise helps heat
     balance and conserves water that might otherwise be lost as sweat. Ability to
     use metabolic water produced during cellular respiration. Panting and licking
     are also better in terms of water conservation when compared to sweating.
     Behavioural Adaptations: burrowing, being nocturnal, drinking young’s
     urine, drinking dew and frost, and eating plants with high water content.
4-6 It is through the body surface that organisms can lose or gain heat. The greater
     the surface area to volume ratio, the greater the rate of heat flow from or to
     the external environment. Direction of flow is determined by the difference in
     temperature between an organism and its environment. Large animals tend to
     lose and gain heat from the external environment slowly. Smaller animals will
     tend to lose or gain heat at a faster rate. Species of animals that live in cool
     climates often will be larger compared to members of similar species that live
     in warm climates. The difference can be related to surface area to volume ratio
     and heat gain/loss problems.
4-7 Vasoconstriction refers to the narrowing of arterioles so the flow of blood to a
     particular region is reduced, e.g. the extremities (hands & feet) in cold weather.
     This is caused by constriction of muscles in artery and arteriole walls
     narrowing the lumen of the blood vessel. Vasodilation occurs when the
     muscles in artery walls are relaxed. Therefore more blood can flow through
     them to the surface capillaries, e.g. skin red after exercise due to increased
     blood flow toward the body surface.
4-8 Living in very cold climates provides two major problems:
     1 heat loss
     2 damage to tissues due to water freezing (frostbite).
4-9 Heat loss can be overcome through such features as thick insulation (fat layers
     – blubber, thick layer hair or feathers), large enough fat deposits to allow
     increase in metabolic heat production, shivering, reduced heat flow to
     extremities through use of counter-current systems and shunt vessels, and
     behaviour such as huddling and avoidance of the worst conditions (e.g.
     To prevent freezing of tissues animals can maintain the minimum blood flow
     to take warmth to the extremities. Some organisms can produce natural
     antifreeze to prevent frostbite. Remember that when water freezes it expands
     and so will cause damage to cells.
4-10 Terrestrial environments lack water compared to aquatic environments. This
     leads to a greater danger of dehydration. There is also a greater fluctuation
     in temperature. Water temperature tends to vary less. In the large oceans it is
     nearly constant. More oxygen is available to terrestrial organisms. The
     solubility of water varies with temperature. It is more soluble at lower
     temperatures. Even so, at best, the amount of oxygen in water is about a fifth
     of that available in the same quantity of air. Water offers support for
     organisms. Terrestrial organisms need stiff skeletons to support their bodies.
4-11 Any of the following features will increase aquatic mammals’ diving capacity:
     1 a greater concentration of red blood cells. This increases the ability of the
     blood to carry oxygen
     2 greater concentration of myoglobins (oxygen storing proteins similar to
     haemoglobin) in muscles so greater stored oxygen for use during diving
                         Suggested Answers: Chapters 2 –5 147

       3 greater ability to restrict blood flow to essential organs
       4 greater tolerance to high levels of lactic acid.
4-12   Intracellular fluid refers to the fluid within cells. Cytosol is an intracellular
       fluid. Extracellular fluid refers to any fluid outside cells. Examples of
       extracellular fluids are lymph, blood plasma and tissue fluid.
4-13   Interstitial fluid (sometimes called intercellular fluid) is extracellular fluid. Inter
       means between in this context. If fluid is between cells it must be outside cells.
4-14   Requirements such as glucose, amino acids, fatty acids and vitamins can pass
       between the fluids and cells. Processes involved are diffusion and active
       transport – these depend on concentration and substance. Gases such as
       carbon dioxide and oxygen pass from the various body fluids to and from
       cells. Waste products such as urea and carbon dioxide pass from cells back
       into tissue fluids to move out of the body. Urea leaves the internal
       environment at the kidneys. Carbon dioxide passes from the capillaries in the
       lungs to the alveoli.
4-15   Systems that contribute to homeostasis:
       Skin barrier forms the boundary between the external and internal
       environment. It helps to control water loss and prevents entry of micro-
       organisms. The skin is also involved in temperature regulation.
       Respiratory system allows exchange of oxygen and carbon dioxide in the
       lungs. Sufficient oxygen is necessary to maintain aerobic respiration. Raised
       levels of carbon dioxide affect the pH of the blood.
       Digestive system is the site of entry for organic nutrients, vitamins, minerals
       and water.
       Circulatory system is the transport system that carries material from one area
       to another. In a sense it provides a physical link between the different systems.
       Excretory system provides a means of removing urea, carbon dioxide, excess
       water and ions. Thus it is important in regulating the osmotic potential and pH
       of body fluids.
       Nervous and endocrine systems regulate all the other systems of the body
       by transmitting information from one area to another either by nerves or
       hormones in the bloodstream.
4-16   The stimulus-response model
             stimulus               receptor
                                                            (Control centre)/
             response               effector

4-17 Negative feedback occurs when the response to a stimulus results in a
     reduction of, or counteracts, that stimulus whereas in positive feedback the
     response to a stimulus results in reinforcement of the original stimulus.
       Receptor              Stimuli
       Chemoreceptor         Smell, taste
       Mechanoreceptor       Pressure, touch, sound
       Photoreceptor         Light
148 Biology

        Thermoreceptor         Temperature
       Pain receptor         Pain
4-19 Major components of a nerve cell are axon, axon terminals, dendrite and cell
4-20 Sensory neurones have long dendrons (long dendrites or peripheral axons)
     that carry nervous information from a sense organ towards its cell body and
     the central nervous system.
     Connecting neurones (sometimes called intermediate or associate neurones)
     have short dendrites and axons. They are found entirely within the central
     nervous system (CNS).
     Motor neurones have long axons and carry information from the CNS to
     effector organs such as muscles.
                                                     cell body
                               sensory neurone


                                                          connecting neurone

                               motor neurone

4-22 A nerve impulse is an electrical message that passes along the conducting
     fibres (dendrites and axons) of a neurone. The impulse is conducted along a
     fibre as a change in charge on the fibre membranes. At rest the cell membrane
     of a neurone is polarised. Sodium-potassium pumps actively pump sodium
     ions out and potassium ions into the cell. The net result is more sodium ions
     outside the cell than potassium ions inside the cell, therefore the inside is more
     negative. As the impulse passes along the cell the membrane becomes more
     permeable to sodium ions which move into the cell. At this point the inside of
     the membrane will have a positive charge compared to the outside. Once the
     impulse has passed the ions involved are returned to their original position so
     the nerve is ready for another impulse. These changes are extremely rapid.
4-23 Nerve impulses are generated at sense organs and the dendrite end of
     neurones therefore they always pass from the dendrites to the axon terminals
     within a nerve cell. Note that an artificially induced impulse can travel in either
     direction along a neurone.
4-24 A tiny gap exists between nerve cells (neurones). This is called the synaptic
     gap. An impulse does not pass directly from one cell to the next. At the ends
     of axon terminals are synaptic knobs with many mitochondria and vesicles
     containing neurotransmitter. When an impulse reaches a synaptic knob,
     calcium ions diffuse into the cell from the ECF. This stimulates the vesicles to
     move towards and fuse with the cell membrane releasing the neurotransmitter
     into the synaptic gap. It diffuses across the gap to protein receptors on the
                        Suggested Answers: Chapters 2 –5 149

       dendrites of an adjacent nerve cell. This results in the opening of protein
       channels allowing sodium ions to move in and stimulates the production of a
       nerve impulse in this neurone. In this way the message can be passed from
       one nerve cell to the next.
4-25   The Peripheral Nervous System (PNS) consists of sensory neurones collecting
       information from receptors around the body (at the periphery) and motor
       neurones taking information to effector organs such as muscles and glands.
       The Central Nervous System (CNS) consists of connecting neurones
       (intermediate neurones) located in the spinal cord and the brain. These are
       enclosed by the bones of the skull and vertebral column. The sensory
       neurones end at the CNS and the motor neurones begin at the CNS.
4-26   Information involved in reflex arcs can involve a minimum of three neurones
       and no connection to the brain. If a conscious decision is involved the impulse
       must travel to the brain before travelling to motor neurones.
4-27   The autonomic system is involved in the control of organs such as the heart,
       lungs and digestive system where there is normally no conscious control. The
       somatic system involves nerve pathways where an individual has conscious
4-28   Hormones are chemical messengers produced in small amounts by endocrine
       glands. They are transported through the bloodstream to all parts of the body
       but will only have an effect on specific target organs. Hormones modify the
       activity of cells as a result of interaction with specific receptors.
4-29   Hormones only affect target cells as target cells alone have the protein
       receptors that match the specific hormone.
4-30   Hormones are secreted into the bloodstream. The term excretion refers to the
       movement of metabolic waste materials out of the body across an external
       boundary. For example the movement of carbon dioxide from the lung
       capillaries to the alveoli of the lungs.
4-31   Exocrine glands (e.g. tear glands) are involved in the excretion of materials
       through ducts from the internal environment to the external environment.
       Endocrine glands (ductless glands) are involved in internal secretion into the
       bloodstream. Hormones are produced by endocrine glands.
150 Biology

4-32 Gland                     Hormones                                Regulation
 Pituitary                Growth hormones and others         Master gland
 Hypothalamus             Many                               Many activities including
                                                             temperature regulation
 Thyroid                  Thyroxine                          Metabolism & growth
 Adrenals                 Adrenalin                          Response to stress
                          Cortisol                           Metabolism
 Pancreas                 Insulin                            Blood glucose
                          Glucagon                           concentration
 Testes                   Testosterone                       Fertility & secondary sex
 Ovaries                  Oestrogen                          characteristics
   Type of  Solubility         Site of         Action within   Speed    Example
  hormone                     receptor            the cell
 Proteins   Water -         External         Interact with G- fast   thyroxine
 and amino soluble          cell surface     linked proteins         adenaline
 acid-based                 membrane         to produce a            insulin
                                             second                  glucagon
                                             which affects the
                                             activity of
 Steroids     Lipid-        Cytoplasm        Alters gene       slow oestrogen
              soluble       /Nucleus         transcription           testosterone


Stimulus            Receptor               Message             Effector            Response
Presence of         Receptor               Active              DNA                 Specific
steroid             protein within         receptor-                               enzyme
                    the cell               hormone                                 production

Signalling           Receptor                Transduction of the signal             Response
molecule             protein of              through the cell                       Specific
steroid              target cell             Active receptor-hormone                enzyme
                     Receptor                complex interacts with DNA             production
                     protein within
                     the cell

4-36 Steroid hormones are lipid soluble so are therefore able to pass easily through
     cell membranes.
4-37 High Glucose Concentration
     Beta cells in the pancreas are stimulated to secrete insulin that makes cells
     more permeable to glucose and stimulates the liver to convert glucose to
     glycogen (animal starch). These two actions will decrease concentration of
     glucose in the blood and result in negative feedback. The initial stimulus, high
     glucose concentration, is reduced.
     Low Glucose Concentration
     Alpha cells in the pancreas are stimulated to secrete glucagon that makes cells
                        Suggested Answers: Chapters 2 –5 151

       less permeable to glucose and stimulates the liver to convert glycogen to
       glucose. This results in an increase in blood glucose concentration and
       negative feedback. The initial stimulus of low glucose concentration is
4-38   1 Speed of transmission: nerve impulses travel at rates thousands of times
       faster than hormones.
       2 The hormone system is a purely chemical system. The nervous system
       involves chemical and electrical components.
       3 The effects of a nervous impulse are short-lived and act on a directly
       connected organ. The effects of hormones can be long lasting and widespread.
       For example growth hormones can have effects all around the body.
4-39   Pheromones are released into the atmosphere whereas hormones are released
       into the blood. Pheromones are usually more volatile than hormones. They
       provide communication between individuals whereas hormones provide
       communication between cells within one individual.
4-40   Pheromones are chemicals that are released by animals(usually insects) to
       attract members of the opposite sex of the same species.
4-41   Major environmental factors that plants respond to are:
       light (phototropism), gravity (geotropism), water (hydrotropism), and touch
4-42   Positive tropisms result when a plant grows towards an environmental
       stimulus e.g. plant growing toward the light.
       Negative tropisms involve growth away from the stimulus e.g. plant stems
       grow upwards away from gravity even if light is not present.
4-43   Plant growth regulators control growth responses in plants so that growth
       occurs in the correct way and so that timing of plant activity is optimal. For
       example, many plants grow rapidly in the spring and then flower. At this time
       growth conditions are best. There is plenty of water and warmth. In a good
       season the plant will grow rapidly, flower and produce seeds within a few
       months. All of these events are regulated by plant growth regulators.
4-44   A receptor is a group of cells that detect changes in the environment. These
       cells produce plant growth regulators that move through the plant tissue,
       usually by diffusion, to effectors. The effectors will bring about the response
       to the stimulus detected by the receptors.

Signalling            Receptor             Transduction of the signal           Response
molecule              protein of           through the cell                     Specific
ethylene              target cell          Chemical reactions within the        enzyme
                      Receptor             cell that result in activating       production
                      protein on the       genes                                leading to
                      external                                                  fruit
                      surface the                                               ripening

4-46 Auxins are made in the young leaves and buds of plants. They control the
     enlargement and elongation of cells in the growth regions.
4-47 Auxins make the cell walls more plastic. Thus cells affected by auxins will
     grow faster as the wall stretches when water and other materials enter.
152 Biology

4-48 At low concentrations auxins stimulate the elongation of stem cells. At high
     concentrations auxins inhibit root growth.
4-49 Indolacetic acid (IAA) is an auxin.
4-50 Cytokinins promote cell reproduction (division). In tissues where cell division
     is rapid cytokinin concentration is high. In particular, they are found in high
     concentration in growing fruits.
4-51 Gibberellins are found in high concentrations in growing stems and leaves.
     Gibberellins promote cell elongation and reproduction (division).
4-52 Abscisic acid is found in high concentrations in dormant buds and ripe fruit. It
     inhibits growth. Abscisic acid also affects stomatal aperture.
4-53 If abscisic acid promotes stomatal closure, spraying a crop during hot weather
     should reduce water loss. Plants wilt when dehydrated and if water is not
     available the plants could suffer permanent damage. This strategy might
     reduce water bills from irrigation authorities!
4-54 A coleoptile is a young seedling. Biologists often use oat coleoptiles for growth
4-55 Charles Darwin observed bending of oat coleoptiles towards the light. He then
     did experiments covering the coleoptile tips and removing the tips. When he
     did so he observed the plants did not bend, regardless of light direction. Later
     scientists extracted substances from the tips of coleoptiles that caused
     bending. The active substances have been identified as belonging to the auxin
4-56 Short-day plants flower when day length decreases to a certain critical point.
     Long-day plants flower when day length has increased to a certain point.
     Long-day plants will tend to flower in the spring or summer as the days
     lengthen. Note that it is the uninterrupted length of dark that determines when
     a plant flowers.
4-57 Flowering at a particular time may be important for a number of reasons. A
     plant species may be pollinated by an insect active for a short time. Weather
     might be important. Production of seeds should be produced at a time when
     the chance of successful germination is high.
      Signalling      Receptor                        Cellular            Example
      molecule                                        response
      Neuro           Proteins on the external cell Excitation or         Dopamine
      -transmitters membranes of neurones,            inhibition          Acetylcholine
                      muscle or gland cells
      Hormones        Proteins on the external cell Affect the            Insulin
                      membranes or in the             activity of         Steroids
                      cytoplasm/                      enzymes or gene
                      nucleus of target cells         transcription
      Pheromones Protein receptors on the             Affect the          Scent trails
                      smell and taste receptors of activity of
                      another individual              enzymes or gene
      Plant growth Proteins on the external cell Affect the               Auxin
      regulators      membranes or within the         activity of         Ethylene
                      cell                            enzymes or gene
                        Suggested Answers: Chapters 2 –5 153

4-59 Signal transduction is the series of pathways occurring within a cell after a
     hormone is detected by the cell and results in the cellular response.
4-60 The receptors that detect particular signalling molecules are designed to
     identify and respond to that molecule only. The mechanism is similar to that
     involved in the enzyme – substrate lock and key model.
4-61 The molecules that act as relay molecules in signal transduction generally are
4-62 [VCAA, SA Q10, 2008]
In a multicellular organism, the term ‘internal environment’ refers to the
D extracellular fluid. (Definition.)
4-63 [VCAA, SA Q11, 2008]
The arrows X, Y and Z point respectively to a
B pre-synaptic terminal, a vesicle and a neurotransmitter. (The diagram does
not include a golgi body or a mitochondrion. Y is a vesicle not a vacuole.)
4-64 [VCAA, SA Q22, 2008]
The Venn diagram that best represents the relationship between hormones,
neurotransmitters, gibberellins and signalling molecules is

(Hormones, neurotransmitters and gibberellins are all types of signalling molecules.
Gibberellins and hormones both may be involved in growth responses.)
4-65 [VCAA, SA Q23, 2008]
From this information it would be expected that
B reduced production of PTH results in increased calcium in the faeces.
(Increased PTH results in increased vitamin D activation and lower calcium in bones.
Reduced PTH results in less calcium uptake from the alimentary canal therefore
more calcium in faeces. Low levels of blood calcium would stimulate release of PTH
as this will result in an increase in blood calcium levels.)
4-66 [VCAA, SA Q24, 2008]
Signal transduction is represented by stage
A 1 (Definition.)
4-67 [VCAA, SA Q3, 2007]
From this information it is reasonable to conclude that in the affected people
B ion channels are blocked in one group of specialised neurons. (As members
of the family respond normally to touch, temperature and pressure; neurons are able
to respond to external stimuli, are able to produce neurotransmitters and the brain
does respond to electrical signals. This also means that only one group of specialised
neurons are affected. If ion channels are blocked then these neurons will not be able
to produce an action potential or nerve impulse.)
154 Biology

4-68 [VCAA, SA Q5, 2007]
If neurons J, K, L and M were activated at the same time, you would expect neuron
N to activate the muscle fibre in network.

 (In C all stimulated neurons produce activation signals whereas in A and B the
activation signals are cancelled by inhibition signals. In D no activation signal reaches
4-69 [VCAA, SA Q15, 2007]
It is reasonable to conclude that
A signalling molecules carry messages from the duodenum to both the gall
bladder and the pancreas. (The presence of fats and proteins in the duodenum is
the stimulus which results in signalling molecules stimulating the pancreas and the
gall bladder to secrete bile and digestive enzymes. The signalling molecules would
travel in the blood.)
4-70 [VCAA, SA Q16, 2007]
In such systems, the component being kept relatively constant is
A the variable. (Fact.)
4-71 [VCAA, SA Q22, 2007]
Signal molecules that pass from one cell to another in plants include
B ethylene that gives the instruction for fruits to ripen. (Each other alternative
includes signalling molecules but their function is incorrect. Giberellins promote seed
germination, abscisic acid promotes senescence and abscission of leaves and auxin
promotes growth.)
4-72 [VCAA, SA Q24, 2007]
Signals between neurons in the olfactory lobe would occur by means of
D neurotransmitters. (Fact.)
4-73 [VCAA, SA Q25, 2007]
From the data provided on the graph, one can conclude that
B a grey-headed flying fox can hear the sound at 10kHz better than can the
little red flying fox. (The higher the value of the threshold the harder it is to hear.)
4-74 [VCAA, SA Q9, 2006]
From this data, you could reasonably conclude that
C apical buds produce a substance that inhibits lateral shoot growth. (The
apical bud is removed; all other factors are the same so the production of lateral
shoots must be due to the absence of apical bud.)
4-75 [VCAA, SA Q10, 2006]
Signal transduction commences
                         Suggested Answers: Chapters 2 –5 155

D at the synapse between cells X and Y. (Cell X is transmitting a signal to cell Y;
therefore signal transduction must begin at the synapse.)
4-76 [VCAA, SA Q16, 2006]
In organ Y
B there must be sensors for compound X levels. (The cells act as an endocrine
gland and compound Z must decrease levels of X.)
4-77 [VCAA, SA Q21, 2006]
Pheromones are
D chemicals that often act as sex attractants. (Fact. Pheromones are produced
by animals to attract the opposite sex. They can be effective over large distances.)
4-78 [VCAA, SA Q10, 2005]
From this data it is possible to conclude that germination of lettuce
C is influenced by whether the last flash is red or far red light. (Germination
does not require red or far red as germination still occurs with none. Maximum
germination occurs with 2 exposures of red and 1 exposure of far red. This is not an
equal amount. Germination is highest when red is flashed last.)
4-79 [VCAA, SA Q13, 2005]
If body temperature rises above normal limits then
D the sweat glands act as an effector. (Responses 2 will decrease body
temperature but constriction of blood vessels and shivering will increase body
temperature. The hypothalamus is the sensor. Production of sweat would decrease
body temperature.)
4-80 [VCAA, SA Q14, 2005]
If a person becomes dehydrated, the concentration of the solutes in their body fluids
increases and
A this change is detected by sensor cells within the hypothalamus. (Fact.
Responses 1 and decrease in reabsorption would increase, not decrease, the
concentration of solutes.)
4-81 [VCAA, SA Q15, 2005]
Considering the information in Figure 4.1, the component that is being kept
relatively constant is
B the variable. (The variable only varies a small amount until a response occurs
that counteracts the variation.)
4-82 [VCAA, SA Q23, 2005]
From the information given it would be reasonable to conclude that
B at 12.00 noon, mammal H would be a gaining heat by radiation. (Between
midnight and 6.00 am the mammals would lose heat as the surroundings are at a
lower temperature than their body temperature. G would not be sweating. At 12:00
noon both mammals would gain heat by radiation.)
4-83 [VCAA, SA Q24, 2005]
One behavioural adaptation could be
C curling up into the shape of a ball. (Decreasing food intake would not affect
rate of heat loss; fur is a structural adaptation and isolation would increase heat loss.)
4-84 [VCAA, SA Q10, 2004]
A hormone that increases the rate at which mature fruit ripens is
B ethylene. (Fact.)
156 Biology

4-85 [VCAA, SA Q11, 2004]
In mammals, organs are grouped into systems, for example the endocrine system, on
the basis that they are
C related through function. (This is a definition question.)
4-86 [VCAA, SA Q12, 2004]
It is reasonable to conclude that
C the rate of water loss through stomata was greatest in group X. (If the
stomata were closed in group Z or no water was lost, the transpiration rate would be
zero. At 12.00 noon water loss in group X is about 2 times greater than in group Y.)
4-87 [VCAA, SA Q17, 2004]
A variable being investigated is the
D saltiness of the drinking water. (The factor that is being deliberately altered is
the amount of salt in the drinking water.)
4-88 [VCAA, SA Q18, 2004]
Design 1 was chosen for the investigations because it better accounted for
A variation between individual ducks. (In design 2, different groups of duck are
exposed to different salinity therefore any difference in results may be due to the
duck not the salinity.)
4-89 [VCAA, SA Q19, 2004]
In making their assumption about water balance, students had overlooked the point
B water would be lost in faeces and saliva. (If water is also lost in faeces and
saliva then the amount of water consumed will not be equal to the amount of urine
produced. Instead the amount of water consumed will be equal to the amount of
urine produced plus the amount of water lost in faeces and saliva.)
4-90 [VCAA, SA Q21, 2004]
The effector in the regulation of carbon dioxide concentration is the
A respiratory muscles. (These bring about an increase in breathing and a return to
normal carbon dioxide levels. Nerve impulses are messengers and the respiratory
centre is the control centre.)
4-91 [VCAA, SA Q22, 2004]
When the concentration of carbon dioxide returns to normal it would be reasonable
to conclude that the
B rate and depth of breathing decrease. (If the respiratory muscles stopped
contracting or the respiratory centre failed to send efferent nerve impulses, breathing
would stop. The number of afferent nerve impulses would decrease.
4-92 [VCAA, SA Q7, 2003]
They can survive for many years in this state which is called
A dormancy. (Geotropism involves growth in response to gravity, hibernation
refers to animals and germination is the development of the seed into the new plant.)
4-93 [VCAA, SA Q14, 2003]
It is reasonable to conclude that when a person lacks sufficient iodine in the diet
A TSH production would increase. (As little thyroxine would be produced, the
anterior pituitary would be stimulated by TRH and the lack of thyroxine to produce
4-94 [VCAA, SA Q15, 2003]
Homeothermy is the
B maintenance of a relatively constant body temperature. (Definition.)
                        Suggested Answers: Chapters 2 –5 157

4-95 [VCAA, SA Q16, 2003]
Both systems
D release chemical signals that act on tissues they control. (Nervous responses
tend to have a faster response time and to be of shorter duration than endocrine
responses. Only the endocrine system uses the blood. Neurotransmitters produced
by neurons act on muscles, glands and other neurons.)
4-96 [VCAA, SA Q18, 2003]
Compared with the large ears of modern elephants, small ears would have assisted
the survival of the mammoths by
D decreasing the surface area through which heat is lost. (Mammoths lived in
a cold climate. Heat loss would be a problem. All other alternatives would result in
increased heat loss.)
4-97 [VCAA, S1 Q4, 2002]
From the information given you can conclude that
A plant 2 will be more likely to survive in a dry environment than plant 1.
(Over the course of the day plant 2 loses less water than plant 1. At noon both plants
lose about the same amount of water, at 10.00 a.m. plant 2 lost more water therefore
its stomatal aperture will be greater and at 5.00 p.m. plant 2 lost less water therefore
lower stomatal aperture, decreased gas exchange and decreased photosynthesis.)
4-98 [VCAA, S1 Q6, 2002]
Transmission of messages within the nervous system
B involves both electrical impulses and chemical messengers. (Transmission
occurs in one direction, is faster via a myelinated axon and relies on diffusion of the
neurotransmitter across the gap. Note the neurotransmitter is actively secreted from
the cell but diffuses across the gap.)
4-99 [VCAA, S1 Q7, 2002]
Homeostasis is the condition of a relatively stable internal environment. The internal
environment of a multicellular organism includes
A tissue fluid. (Digestive fluid and urine are part of the external environment and
cytosol is within the cells.)
4-100 [VCAA, S1 Q8, 2002]
The plant hormone involved in the development of flower buds is
C gibberellin. (Fact – learn them!)
4-101 [VCAA, S1 Q9, 2002]
An elephant maintains its body temperature within a narrow range. In conditions of
extreme heat, factors that contribute to increased heat loss from an elephant include
D flapping the ears. (All other alternatives would decrease heat loss.)
4-102 [VCAA, S1 Q14, 2002]
The sensory neuron is represented by
D X. (Sensory neurons carry the impulse from the receptor to the CNS.)
4-103 [VCAA, S1 Q15, 2002]
The effector neuron is represented by
B Z. (Effector neurons carry the impulse from the CNS to the effector.)
158 Biology

4-104 [VCAA, SB Q7, 2008]
a      Positive phototropism
b i Any one of the following:
       - amount of water available to the seeds
       - size of the seeds
       - temperature the seeds are grown in
       - growth medium the seeds are grown in
       - age of seeds
       - time period of the experiment
    ii The presence of light – some seeds should be placed in the dark and others
       should be placed in light.
c      T
d      Reflex arc
e      If the myelin sheath is damaged nerve impulse transmission along the axon
       would be slower resulting in slower movement, numbness or tingling
4-105 [VCAA, SB Q8, 2008]
a      Any of the following or any other example of homeostasis. The answer must
       include stimulus, receptor, effector, response and arrows indicating negative
       Homeostatic control of blood glucose levels

                       Suggested Answers: Chapters 2 –5 159

b     Change in copper concentration
c     Too little copper may affect cellular metabolism or too much copper may be
      toxic to the cell.
4-106 [VCAA, SB Q1, 2007]
a     Pheromone
b      The cells that had receptors to the hormone responded to its presence whereas
        the cells that did not have receptors to the hormone did not.
c      This question asks you to choose a hormone you have studied. Any hormone
       with correct gland and outcome is acceptable. Some possible answers for c i, ii
       and iv include the following:
       i                  ii                                   iv
  Hormone               Gland                      Target cell and outcome
                                          Note: target cell must be mentioned and
                                               outcome is in terms of the cell
                                      Target cell     Outcome
Insulin           Beta cells of the Liver or body Increased uptake of glucose from
                  pancreas            cells           the blood into the cell
Glucagon          Alpha cells of Liver cells          Glycogen is converted into
                  the pancreas                        glucose which is then released
                                                      into the blood
Antidiuretic Hypothalmus              Cells of the Increases permeability of the cells
hormone                               kidney’s        lining the duct leading to
                                      collecting      increased water reabsorption
Thyroxine         Thyroid             Body cells      Increases respiration rate
Adrenalin         Adrenal gland       Liver cells     Glycogen is converted into
                                                      glucose which is then released
                                                      into the blood
                                      Muscle cells    Increased heart rate
Oestrogen         Ovary               Uterus cells    Increases thickness of lining of
                                                      the uterus
                                      Breast cells    Increases growth of breasts
160 Biology

Testosterone    Testes               Sperm             Increases sperm production
Parathyroid     Parathyroid          Bone cells        Release calcium into the blood
hormone         gland
Calcitonin      Ultimobranchial      Bone cells        Increases uptake of calcium by
                glands                                 bone cells
    iii Signal transduction refers to the series of events that occur within a cell after it
        has received a specific signal. The original signal is converted into other signals
        by a series of relay molecules and other proteins. Signal transduction results in
        a particular cellular response.
4-107 [VCAA, SB Q9, 2007]
a i 4:30pm
   ii No, the highest air temperature occurred at about 1:30pm. The lizards were
        lying in the sun at 4:30pm. This means they were absorbing more heat so their
        body temperature increased.
b       Nervous system. Change in environmental and skin temperature happens
        frequently and is of short duration. The animal must respond quickly to these
        short term changes. Nervous responses tend to be fast and of short duration
        whereas hormonal responses tend to be slower and of long term duration.
4-108 [VCAA, SB Q2, 2006]
a       Hormone.
b       The shape of the receptor can only fit the shape of specific signalling
c       Different proteins usually act as intermediate or relay molecules.
d       Any one of the following:
        -increased/decreased production of a hormone
        -increased/inhibition of transcription of a gene
        -increased/decreased cellular respiration.
4-109 [VCAA, SB Q5, 2006]
a       As carbon dioxide has high solubility in water and fish live in water, carbon
        dioxide is easily removed from the fish. Terrestrial mammals are not
        surrounded by water and carbon dioxide is harder to exchange with air by
        breathing therefore it tends to build up within the mammal.
b       Effector: intercostal muscles.
        Response: decreased breathing rate therefore less carbon dioxide lost.
        Effector: heart.
        Response: decreased heart beat rate therefore less carbon dioxide lost.
        (Note: this question refers to an increase in blood pH. This means the blood
        has low carbon dioxide.)
c       Underwater pearl divers would hyperventilate to decrease the level of carbon
        dioxide in the blood. It would therefore take longer for the level of carbon
        dioxide to build up enough to stimulate the urge to breathe. The diver could
        then stay underwater longer.
d       Hyperventilating causes a person to become unconscious because the urge to
        breathe is delayed. If it is delayed long enough, oxygen levels in the blood
        going to brain cells will drop and the person will become unconscious.
4-110 [VCAA, SB Q6, 2006]
a                      Signalling molecule          neurotransmitter
          point R
                         Suggested Answers: Chapters 2 –5 161

                      Type of cell producing sensory neuron
                      the molecule
                      Signalling molecule    neurohormone
         point S
                       Type of cell producing neuron or neurosecretory cell
                       the molecule
b       A control system must be able to control an increase and a decrease in a
        stimulus. For this to occur it must be able to promote and inhibit an action. If
        the system only promotes then positive feedback occurs and the stimulus will
        increase. It will not be brought back to the norm. To be able to inhibit as well
        gives a far greater level of fine control.
4-111   [VCAA, SB Q6, 2005]
a       M diffuses from the axon terminal where it is in high concentration to the
        receptors on the next neurones dendrites where it is in low concentration.
b       Chemical N is secreted into the blood and is carried to the capillaries close to
        cell Y where it diffuses from where it is in high concentration in the capillary
        across the capillary wall to the target cell membrane where it is in low
c i     Nervous system.
  ii    Any one of the following
        -messages travel along nerves as electrical impulses. This movement is more
        rapid than the movement of the blood.
        -hormones travel the greater distances than do nerve impulses. Because the
        distance is greater it takes a longer time.
        -the pathway of nerve impulses is direct, i.e. from one neurone to the next,
        whereas hormones circulate in the blood until they randomly find a target cell.
        This undirected response takes longer.
d       Each type of endocrine cell produces a particular hormone that is only able to
        bind with specific receptors on specific target cell. Cells without receptors
        cannot bind with the hormone and their functioning is not affected.
e       The decrease in responsiveness is brought about by slight changes to the
        receptors on the target cells. These receptors then do not recognise the
        hormone thus cell function is not altered.
4-112   [VCAA, SB Q7, 2005]
a       Any one of the following
        -skin forms a waterproof covering which stops the loss of water from the
        body (water balance).
        -sweat glands in the skin allow for evaporative cooling of the body, thus
        helping to maintain body temperature (heat balance).
        -the skin provides a large area to which blood can be diverted when the body
        temperature rises. This leads to increased heat loss and a return to normal
        body temperature (heat balance).
        -the skin forms a barrier against infection.
b       The body provides the optimal conditions for it’s own cells in terms of cell
        growth and division. In vitro conditions try to match the conditions in the
        body but all factors cannot be replicated so cell division and growth is slower.
c       Glucose is water soluble therefore does not readily pass through lipid cell
        membranes. In facilitated diffusion glucose moves into the cell via proteins
        which span the cell membrane instead of through the lipid bilayer.
d i     The liver.
162 Biology

   ii When glucagon reaches the liver cells it binds with receptor molecules and
      causes the cells to break down glycogen to glucose. The glucose is released
      into the blood increasing blood glucose level.
e     An advantage of form C is that it only needs to be taken once a day.
f     It would be an advantage to use form A if the person had forgotten to take
      any form of the hormone and had a very high blood glucose level. Form A
      would act quickly to bring the level back under control.
4-113 [VCAA, SB Q8, 2005]
a     In a hot dry environment water loss is a problem as the water lost is not easily
      replaced. The camel loses less (1-2%) percentage body water each day so is
      likely to survive for a longer time than the cattle (7-8%) and the sheep (4-6%).
b i The heat energy required for evaporative cooling comes from the body, thus
      reducing body temperature.
   ii Any one of the following
      -water may be lost with exhaled air. This air is warm and moist.
      -water may be lost in urine. Urine is mainly composed of water and urea.
      -water may be lost in faeces. As food moves through the digestive tract
      secretions containing water are added. Some of this water may be lost from
      the body with the undigested matter.
c     A continuous current of air is passed over the tongue in panting, thus more
      evaporative cooling is likely to occur.
d     Any one of the following
      -ability to extract much water from faeces.
      -ability to produce more concentrated urine.
      -ability to use water produced as a product of cellular respiration means that
      less water needs to be found in hot, dry environments.
      -lower metabolic rates which means less heat is produced through cellular
      respiration, less heat will need to be lost through sweating and less water will
      need to be found in the hot, dry environment.
      -ability to allow body temperature to rise during the day and fall when cooler.
      This helps conserve water that might be lost as sweat.
4-114 [VCAA, SB Q2, 2004]
a     Auxin which promotes cell elongation is produced in the coleoptile tip.
      Groups 1 and 2 (even though the tip had been cut) had the tip therefore
      produced auxin and cell elongation and growth occurred. Group 3 did not
      have the tip so no auxin was produced and cell elongation and growth did not
b     Group 5 had agar with coleoptile juices placed on the top. Auxin was present
      in the coleoptile juice. This auxin diffused out of the agar and into the
      coleoptile where cell elongation and growth occurred. Group 6 had no auxin
      present in the agar therefore no cell elongation and no growth occurred.
                                                      Experimental group
        Predicted growth result              7           8          9          10
        no growth                                                           √
        vertical growth                  √
        bending to left                                         √
        bending to right                              √
                                      Suggested Answers: Chapters 2 –5 163

4-115 [VCAA, SB Q4, 2004]
a      decrease in concentration               blood concentration
                                                2.2 to 2.5 mmol/L
                                                                       increase in concentration
             of blood calcium                                               of blood calcium

           cells in parathyroid
                                                                              cells in thyroid

                  release                                                        release

          parathyroid hormone

                  acts on                                                         acts on

      bone cells called osteoclasts
                                                                                 bone cells

                                                                                 results in

         break down of bone to
        release calcium into the                                       increased calcium deposited
                  blood                                                           in bone

        increase in concentration                blood concentration    decrease in concentration
             of blood calcium                     2.2 to 2.5 mmol/L
                                                                             of blood calcium

b      Chemoreceptor is the general name for a structure that detects the changes in
       blood-calcium concentrations.
c      Negative feedback is used to maintain conditions within a narrow range. When
       a change (stimulus) is detected the response results in conditions returning to
       within the original narrow range. For example if the stimulus is a rise in blood-
       calcium concentration, the response will result in a decrease in blood-calcium
4-116 [VCAA, SB Q5, 2004]
a      Metabolic reactions within cells are fuelled by ATP produced in cellular
       respiration. Oxygen is required for cellular respiration.
b      15oC to 25oC is the thermoneutral zone for the springhares.
c i Curling up reduces the exposed surface area across which the springhares lose
   ii Shivering results in higher respiration rate and thus heat production.
  iii Dilating blood vessels in the ears and legs diverts blood to the body surface
       thereby increasing the surface area for heat loss. Spreading saliva over faces
       and throats increases cooling by evaporation.
d      Water produced in cellular respiration would be the water source for these
e      Burrow temperature is lower than outside temperature therefore the
       springhares would lose less water cooling their bodies.
       Or The burrow is an enclosed space that would quickly become humid thus
       lowering the diffusion gradient for water loss from the springhare.
4-117 [VCAA, SB Q3, 2003]
a     Neuron M is an interneuron.
164 Biology

b      The importance of the reflex arc is to allow the fast removal of the limb away
       from a source of danger. The response is automatic and does not involve the
       brain. This ensures that the endangered area is protected.
c      The myelin sheath acts as an insulator, improving the speed of conduction of
       the nerve impulse along the neuron.
d i X
   ii The function of structure P is to store and release the neurotransmitter that
       diffuses across the neuromuscular gap.
       The function of structure Q is to provide ATP from aerobic respiration as a
       source of energy for the secretion of the neurotransmitter.
4-118 [VCAA, SB Q4, 2003]
a      Any two of the following:
       ● 90% of water gain for mammal species A is from metabolism.
       ● 0% of water is gained through drinking and only 6% through eating
          therefore the mammal is able to survive where water is not readily available
          for drinking or from food.
       ● Only 23% of water loss is lost as urine. Therefore water is conserved
          suggesting dry environment.
       ● 73% of water loss is through evaporation suggesting that the climate is hot
          and evaporation is used to cool the animal.
b i Any one of the following:
       ● not very active during the day or nocturnal behaviour
       ● living in a burrow. This traps a humid layer of air around the animal,
          lowering the diffusion gradient and therefore reducing water lost due to
       ● having a low SA:V ratio therefore reducing the SA for water loss due to
   ii Water may be lost with faeces.
  iii Mammal A would have a longer loop of Henle. The longer the loop of Henle
       the more water that is reabsorbed in the kidney.
4-119 [VCAA, SB Q5, 2003]
a      The purpose of the control is to show that any change in results is due to
       diabetes and not some other factor. The control provides a standard of
       comparison with the experimental group.
b      Group X included the people with diabetes.
       Reason 1: The level of insulin in the plasma has not increased whereas it has
       in group Y. If the group are diabetic then insulin may not be produced when
       blood glucose level increases.
       Reason 2: Plasma glucose level remains high 60 minutes after ingestion in
       Group X, suggesting that glucose uptake has not increased as a result of high
       glucose levels. In Group Y the level is lower, suggesting that glucose has been
       taken up by cells.
c      In Group Y insulin in the plasma has circulated to the cells in the body tissues.
       Insulin binds with receptors on these cells and this increases uptake of glucose
       from the tissue fluid and blood by the cells.
d i Glucagon is secreted from the pancreas.
   ii High levels of glucagon affect the cells in the liver. In these cells glycogen is
       converted to glucose and released into the tissue fluid and plasma, resulting in
       an increase in plasma glucose level.
4-120 [VCAA, S2 Q3, 2002]
a     Phototropism is used to describe a plant’s growth response to light.
                            Suggested Answers: Chapters 2 –5 165

b i      Treatments A, E, F and G would show a growth response to light.
  ii     In these treatments the tips of the seedlings have not been covered. It is the
         tip that detects the light.
                              Auxin produced in                 Directional light
                              tip moves away from

       concentration of
       auxin results in
       the elongation of
       cells on side away
       from light

4-121 [VCAA, S2 Q4, 2002]
a      Negative feedback is when the response to a stimulus results in a reduction of
       that stimulus.
b i Relaxation of the smooth muscles in the peripheral blood vessels results in the
       dilation of these blood vessels. More blood then flows to the surface so more
       heat can be lost resulting in a decrease in body temperature.
  ii Any one of the following:
       ● thyroid gland
       ● sweat glands.
c      285 mOs/kg (Note: always include the unit.)
d     Antidiuretic hormone is released by the posterior pituitary gland.
e      When the osmotic concentration of the blood increases, the hypothalamus
       produces antidiuretic hormone. ADH passes to the pituitary where it is
       released into the blood. The blood transports ADH to the kidney tubules
       where it increases their permeability to water. As a result more water is
       reabsorbed into the blood (less urine produced) and the blood’s osmotic
       concentration decreases.
f      After the injections NPH insulin was effective for 13 hours and LANTUS
       insulin was effective for 22 hours. (Note: Insulin is regarded as being effective
       when the glucose uptake in cells is above 0.4 mg/kg/min. It took 1 hour
       before either insulin was effective.)
g      LANTUS insulin brings about a faster and longer response than NPH insulin.
       This would result in better control of insulin with fewer injections.
4-122 [VCAA, S2 Q6, 2002]
a      Rapid movement of the eyes is controlled by the nervous system because this
       movement is under conscious control like many nervous responses and unlike
       most hormonal responses.
       The movement of the eyes is rapid. Most nervous responses are rapid
       (impulses can travel rapidly along neurons from the brain to the eye muscles)
       whereas the responses of the endocrine system tend to be slower as the
       hormone must be released into the blood and travel to the target organs.
166 Biology

b      Receptors on the cell membrane of cells allow them to respond to hormones.
       All cells in the body have insulin receptors on their membrane but only cells in
       the thyroid gland have receptors for thyroxine.
Chapter 5: Detecting and Responding:
Pathogens and the Immune Response
5-1    A disease is any condition that alters the normal functioning of an organism.
       Infectious diseases are caused by some organism or agent (e.g. virus) that has
       ‘infected’ the diseased individual. Not all diseases are infectious. Scurvy and
       rickets are examples of nutritional diseases. Cancers may be caused by
       carcinogens in the environment.
5-2    A pathogen is the organism or agent that causes an infectious disease. The
       adjective pathogenic describes organisms/agents that cause infectious disease.
5-3    The host is the individual that has been invaded by the pathogen. Most
       pathogens are internal parasites. That is, they obtain food and shelter from
       their host.
5-4    Non-cellular pathogens include viruses, viroids and prions. Cellular pathogens
       include bacteria, fungi and eukaryotic parasites.
5-5    Viruses are not active unless they are inside a living cell. They are best
       described as infectious particles that have the ability to get themselves
       reproduced by true living cells.
5-6    Examples of viral diseases are:
       influenza, herpes, measles, poliomyelitis, chicken pox, AIDS and the mumps.
5-7    Bacteriophages are viruses that infect bacteria. Scientists have studied them
       intensively, as it is easier to study viruses in bacteria than in larger organisms
       (such as humans).
5-8    The virus attaches to the surface of the host cell. Viral nucleic acids are
       injected into the cell and take over the host cell resulting in the production of
       viral nucleic acids and protein coats. These are assembled resulting in many
       copies of the original virus. The cell lyses releasing the new viruses.
5-9    Prions are small infectious proteins.
5-10   Mad cow disease is caused by a prion.
5-11   Most bacteria are not pathogenic. The majority of bacteria are active outside
       living organisms and are responsible for the breakdown of organic materials in
       dead organisms.
5-12   Features used by microbiologists to distinguish bacteria include:
       ● presence/absence of flagella
       ● the position and number of flagella
       ● shape of bacteria (e.g. cocci, bacilli and vibrios)
       ● the types of groupings formed (e.g. chains, pairs, tetrads, and clusters)
       ● the ability to take up stains (e.g. gram positive or negative)
       ● modes of nutrition (e.g. photosynthetic, chemosynthetic or heterotrophic)
       ● particular nutritional requirements (e.g. a certain protein or vitamin must
            be available).
5-13   The function of spores is to allow bacteria to survive unfavourable conditions.
       In ideal conditions they reproduce rapidly. When conditions deteriorate they
       form highly resistant spores to survive until conditions become more suitable.
5-14   Anaerobes survive in an oxygen-free environment. Some bacteria cannot
       survive in the presence of oxygen.
                        Suggested Answers: Chapters 2 –5 167

5-15 The statement is false. Bacteria often produce poisonous waste products called
     toxins. Cooking may kill the bacteria but the toxins produced by the bacteria
     will remain and may not have been made harmless by cooking. In food
     poisoning it is usually toxins rather than the bacteria that cause the problem.
5-16 Bacteria can be heterotrophic or autotrophic. Some of the autotrophs are
     chemosynthetic, obtaining energy from chemical reactions in the environment
     to synthesise organic material. Some species survive in hot mineral springs rich
     in sulfur compounds that can be used as an energy source.
     Scientists often grow bacteria on agar plates. In doing so they can often
     separate bacteria by their nutritional requirements. Particular nutrients can be
     mixed into the agar before it is poured. Depending on their requirements
     particular bacteria will only survive if particular nutrients are present.
5-17 Major means of transmission:
     ● airborne infection (often in water droplets)
     ● animal transfer – vector is present e.g. malaria spread by mosquitoes
          food borne transfer
     ● sexual intercourse & un-sterile needles
     ● breaks in the skin.
5-18 Examples of bacterial diseases:
     typhoid, pneumonia, gonorrhoea, syphilis, and tetanus.
5-19 The most effective means of treating bacteria has been antibiotics. Some
     antibiotics cause damage to the cell walls of bacteria, which make them
     unstable. Streptomycin causes leakage from membranes and so death. Other
     antibiotics slow cell division and growth. This can be achieved by inhibiting
     protein synthesis.
5-20 Viruses are much smaller and simpler than bacteria. Bacteria are small
     compared to eukaryotic cells. Viruses are about one-fiftieth the size of
     bacteria. Viruses are little more than some DNA or RNA wrapped in a protein
     coat. Bacteria are more complex. Some have flagella with which they move.
     Although bacteria do not have the true membrane-bound organelles found in
     eukaryotes, they are capable of metabolic processes including respiration and
     protein synthesis. Some bacteria are photosynthetic.
5-21 Viruses, as they are active inside living cells, are difficult to treat. Antibiotics
     are ineffective against viruses. Interferon (not an antibiotic) is a substance
     produced by infected cells. Scientists have isolated it and have had some
     success with its use. The best strategy, however, with viruses is prevention
     through vaccination.
5-22 Thrush, ringworm and tinea are fungal diseases. In all three cases the fungi
     obtain their nutrition from the human host.
5-23 Eukaryotic parasites are much bigger and more complex than bacteria and
     viruses. Perhaps because of their size they have been easier to study and
     develop strategies for treatment. Examples of parasitic organisms are some
     protozoans, fungi, insects and worms.
5-24 Malaria is caused by a protozoan parasite. It is transferred from an infected
     human to an uninfected human by the female Anopheles mosquito. The life
     cycle of the parasite is complex. In the mosquito the parasite reproduces in the
     salivary gland. In the human host the protozoan enters red blood cells. The
     symptoms of malaria, recurrent bouts of fever, are caused by toxins released
     by the parasite when it is in its reproductive stage.
168 Biology

5-25 In the digestive tract and the blood there is a constant source of the basic
     building blocks of organic matter (glucose, amino acids, fatty acids, and
     glycerol). The parasitic worm can absorb these items directly without need for
     a complex digestive system.
5-26 Parasitic worms have hooks and suckers that allow them to stay in one
     position in the host. If they did not they would be washed along in the
     ‘current’, possibly out of the body.
5-27 Pathogens have well-developed reproductive structures to produce numerous
     offspring. The chances of, say, one egg or spore ending up in a suitable host
     are extremely low.
5-28 Sexual intercourse allows direct contact between potential hosts. The skin in
     the genital area has a good chance of being damaged and so provides easier
     access to the body. The area is rich in blood vessels, warm and moist. All of
     these features assist a pathogen’s entry into the body.
5-29 AIDS is caused by the Human Immunodeficiency Virus.
5-30 Physical barriers of plants against disease include: thick cuticles, hairs, thorns
     or spikes, thick cell walls and thick bark. Chemical barriers include: secretion
     of resin and antibiotic-like substances called phytoalexins.
5-31 The external barriers of the body are the first line of defence. The skin is
     relatively tough and impermeable unless broken. The skin produces its own
     antiseptic – sebum. An antiseptic in tears protects the eyes. Hairs and mucus
     protect the entrance to the respiratory system. Stomach acid has a role in
     killing pathogens that enter in food. The vagina’s secretions are acidic which
     helps reduce chances of bacterial or fungal infection. Urine, itself acidic, helps
     to flush out any pathogens that enter the urethra.
5-32 Cells in an organism have their own particular molecules on their surfaces.
     These molecules are usually made of proteins, carbohydrates, glycoproteins or
     glycolipids. Cells with different molecules on their surfaces are recognised as
     foreign or non-self and are attacked by the immune system.
5-33 The second line of defence is inside the body. It will attempt to neutralise any
     pathogens that have got past the first line of defence. Involved are scavenger
     cells called phagocytes which respond to chemicals produced by damaged
     cells. The lymphatic system’s lymph nodes filter the lymph. Remember that
     lymph is the excess fluid drained from around cells. Other scavenger cells in
     the lymph nodes remove any cell fragments and foreign material.
5-34 The second line of defence is non-specific in that any pathogen or foreign
     material can be removed. The scavenger cells involved will attempt to attack
     any potential threat.
5-35 The role of the specific defence system is to combat any threats that have
     overcome the first two lines of defence.
5-36 T cells (T lymphocytes) and B cells (B lymphocytes) are both formed from
     stem cells in the bone marrow of long bones. The B cells mature in the bone
     marrow to be released into the blood where they become antibody producers.
     B cells are involved in humoral immunity. The T cells travel to the thymus
     gland to complete their development. (T stands for ‘thymus dependent cell’.)
     The T cells are involved in cell-mediated immunity. Some become killer cells.
5-37 In terms of the immune system, an antigen is a molecule that provokes the
     production of antibodies. Antibodies are the bullets produced by B cells
     designed to damage pathogens. The molecules on the surface of pathogens, or
                        Suggested Answers: Chapters 2 –5 169

       for that matter on the body’s own cells, can act as antigens. A specific antigen
       will provoke the production of one type of antibody.
5-38   Antibodies are protein molecules made to precise shapes. A form of the B cell
       called a plasma cell makes them. The plasma cells are antibody factories. One
       type of plasma cell can only produce one specific type of antibody.
5-39   Antibody shape is important because it determines the antigen to which it can
       stick. In a similar way to enzymes and substrate molecules, there is a lock and
       key relationship. One antibody type combines with one antigen type. Thus the
       defence is specific.
5-40   Humoral immunity:
       ● Macrophages engulf pathogens and then display some of the pathogen’s
            antigens on their surface (antigen-MHC complex)
       ● T-helper cells are attracted to the macrophages and are activated by the
            antigen-MHC complex
       ● T-helper cells stimulate B cell activity
       ● If the appropriate B cell is present with the antibody specific to the
            microbe antigen it will bind to the antigen-MHC complex on the
       ● The B cell divides to form a clone of plasma cells that produce a specific
       ● Also produced are ‘memory cells’ that are identical to the original B cell.
5-41   Cell-mediated immune response
       ● Infected cells display antigen-MHC complex
       ● T-helper cells are actived by the antigen-MHC complex
       ● T-helper cells stimulate cytoxic T cells to destroy infected cells.
5-42   After combating a disease successfully there will be a large number of memory
       cells. After having mumps once, the memory cells that ‘remember’ how to
       make mumps antibody are common. If the mumps virus invades again, the
       defence system springs into action more quickly because of the large
       population of the specific memory cell. The body can overcome the second
       attack without symptoms.
5-43   The last example is active immunity in action. With active immunity the body
       is producing its own antibodies. Immunisation with a vaccine that contains a
       harmless form of a microbe can produce immunity without suffering the
5-44   With passive immunity the body does not produce the needed antibody and
       there is no immune memory. In the case of a snakebite where the toxin is fast
       acting, a dose of the appropriate antivenene (which contains antibodies
       specific to the snake toxin) is necessary for the patient’s survival. The body has
       not got the time to produce the specific antibody required. In cases of active
       immunity, the body’s own immune system produces the antibody and memory
       cells, which in the long run is more effective than passive immunity. In crisis
       situations, such as snakebite, passive immunity is more effective!
5-45   Like B cells there are many kinds of T cells. Helper T cells recognise foreign
       antigens and assist B cells. Some T cells become the killer cells involved in
       graft rejection after transplant operations. Each person’s antigens are different
       and transplant tissue is seen as foreign. The immune system tries to destroy it!
       Cytotoxic T cells are involved in destroying cells infected with virus and
       cancer cells.
170 Biology

5-46 A particular antigen, the Rhesus antigen (Rh), is present on the red blood cells
     of most people who are described as being Rh +ve. Some people (Rh -ve) do
     not have the antigen and produce the antibody if cells with the antigen enter
     the body. If an Rh -ve mother produces an Rh +ve child she may start
     producing Rh antibodies. At birth a few of the baby’s Rh +ve cells may get
     into the mother’s circulatory system. This is a problem for a second Rh +ve
     child whose body will be attacked by these antibodies that can cross the
     placenta. If the mother is given a dose of Rh antibody immediately after the
     birth of her first child, any of the baby’s cells can be removed before they
     provoke the mother’s immune system to produce Rh antibody.
5-47 In autoimmune diseases the body’s immune system is attacking itself. A
     transplanted organ may be useful but as far as the immune system is
     concerned, the tissue is foreign.
5-48 Rejection can be reduced by using immunosuppressant drugs which suppress
     the immune system. The disadvantage is that the patient will be more
     susceptible to infectious disease.
5-49 Histamines are chemicals that are produced by damaged cells. They trigger the
     non-specific inflammatory response. In people with a condition like hay fever
     the cells detect foreign material (e.g. pollen) and respond over-vigorously.
     Antihistamines are designed to reduce the response.
5-50 The initial exposure to the allergen results in B cells producing IgE antibodies.
     These antibodies attach to mast cells. When the allergen is encountered again
     it reacts with the antibodies on the mast cells causing them to release large
     amounts of histamines.
5-51 The AIDs virus (HIV) disarms the T4 helper cells. Thus the immune response
     to all sorts of disease is reduced. In the end it may be a relatively harmless
     disease, such as the flu, that kills an AIDs victim.
5-52 A pathogen is a disease causing organism or infectious particle whereas an
     antigen is a specific molecule recognised by the immune system. Molecules on
     the pathogens surface may be antigens. An allergen is a molecule that
     provokes an over-reaction of the immune system. An antibody is a molecule
     produced as a result of the presence of an antigen.
5-53 [VCAA, SA Q9, 2008]
The lymphatic system
D contains phagocytic cells. (Arteries have thick muscular walls and the blood
circulatiory system contains red blood cells and controls blood clotting.)
5-54 [VCAA, SA Q13, 2008] Question 13
First-line defences that mammals have against invasion by disease-causing bacteria
A lysozymes. (Lysozymes are enzymes found in tears. They catalyse the
breakdown of bacterial cell walls before the bacteria enter the body.)
5-55 [VCAA, SA Q14, 2008]
A six-month old baby boy, whose mother and father both had diphtheria as children,
will develop active immunity against diphtheria if he
C receives an injection of dead diphtheria bacteria. (This is the only alternative
where the baby’s immune system will produce plasma cells, antibodies and memory
cells against diphtheria. The other alternatives involve the baby receiving antibodies
without producing them.)
                       Suggested Answers: Chapters 2 –5 171

5-56 [VCAA, SA Q16, 2008]
The part of the virus labelled R is its
C protein coat. (The viral genome is found in the centre of the virus and the
antigenic markers are on the external surface. The lipid envelope is on the outside of
the protein coat.)
5-57 [VCAA, SA Q17, 2008]
A typical characteristic of such a virus is that it
D manipulates the host cell’s DNA to produce copies of itself. (This is a
definition. Bacteria release toxins into the body and are destroyed by antibiotics.)
5-58 [VCAA, SA Q21, 2008]
With regard to this pathogen, we can conclude that
D memory cells for antibodies against the pathogen exist at the time of the
second exposure. (Memory cells existed at the time of the second exposure and this
is why the response is faster and greater.)
5-59 [VCAA, SA Q25, 2008]
The advice is likely to include directions to
B stock any garden pool with fish that eat mosquito larvae. (Swimming pools
free of chlorine would provide an ideal place for mosquitoes to breed which would
increase the numbers of mosquitoes and spread of the disease. Opening windows
and doors would provide access to people for the mosquito and therefore increase
the spread of disease.)
5-60 [VCAA, SA Q6, 2007]
Autoimmune diseases such as RA occur when
A B and T cell lymphocytes mistakenly attack ‘self’ tissue (Definition.)
5-61 [VCAA, SA Q10, 2007]
It could be expected that the
C build up of tissue fluid in the arm would contain leucocytes. (There are
lymph nodes in other areas of the body that would contain lymphocytes and
leucocytes travel in the blood to all sides of the body.)
5-62 [VCAA, SA Q12, 2007]
The non specific responses made by his immune system as a result of this injury
could include
C removal of foreign material by neutrophils. (Blood vessel permeability would
increase and body temperature would stay the same or increase. Antibodies are
involved in the specific response. Neutrophils indiscriminately remove foreign
material so the response is non specific.)
5-63 [VCAA, SA Q13, 2007]
Given the information above, it would be reasonable to claim that the
C 2-week-old baby had naturally acquired chicken pox antibodies. (The baby
would have acquired antibodies across the placenta or through the mother’s milk as
the mother had already had chicken pox. Note the injection would be of chicken pox
antigens not antibodies.)
5-64 [VCAA, SA Q17, 2007]
This information suggests that canavanine
D in insect proteins reduces the ability of an insect to feed. (Plant hormones
act on plants. Pheromones act only on the animal species that produce them.)
172 Biology

5-65 [VCAA, SA Q18, 2007]
A specific immune response involves
B T lymphocytes recognising antigens presented by macrophages.
(All other alternatives are not specific responses to a particular antigen.)
5-66 [VCAA, SA Q23, 2007]
It is reasonable to suggest that
D the recipient plants produce a substance that kills pathogens. (Pheromones
are produced by plants not animals. The plant produces methyl salicylate in response
to infection and the neighbouring plants recognise and respond to the message.)
5-67 [VCAA, SA Q7, 2006]
The kind of antibodies most effective against this type of bacterium would be

B                  (The antigen binding sites must be the same on each antibody and
B is the only alternative that has antigen binding sites that are complementary to the
proteins on the surface of the bacterium.)
5-68 [VCAA, SA Q8, 2006]
Long-term immunity results from
A administration of chicken pox vaccine. ( A is the only alternative in which the
body produces memory cells.)
5-69 [VCAA, SA Q12, 2006]
This form of disease could be due to
D the immune system failing to recognise cells of the adrenal organs as self.
(The immune system attacks adrenal cells as they are not recognised as self.)
5-70 [VCAA, SA Q14, 2006]
This happened because, shortly after the first infection, the child
B grew B memory cells specific to polio. (Immunity relies on B memory cells
and they are specific.)
5-71 [VCAA, SA Q22, 2006]
This diversity of B cells is due to the
A rearrangement of gene segments. (Fact.)
5-72 [VCAA, SA Q23, 2006]
The lymphatic system
C contains white blood cells. (The lymphatic system has valves, does not contain
red blood cells and the fluid travels in only one direction.)
5-73 [VCAA, SA Q11, 2005]
The beef tapeworm, Taenia saginata, is called a parasite because it
B benefits at the expense of the host. (This is a definition. Note: not all parasites
live within the body of its host. Some live on the host.)
5-74 [VCAA, SA Q16, 2005]
Macrophages are large white blood cells that
B engulf bacteria and destroy them. (Monocytes give rise to macrophages.)
                        Suggested Answers: Chapters 2 –5 173

5-75 [VCAA, SA Q17, 2005]
An example of specific immunity is the
D action of memory cells when an individual is subjected to a second
infection of measles. (All other responses are general responses to any pathogen.
This response is specific to the pathogen causing measles.)
5-76 [VCAA, SA Q18, 2005]
During an allergic reaction, the material that causes most tissue damage is
B histamine. (Fact.)
5-77 [VCAA, SA Q25, 2005]
The pathway involved when a person has pernicious anaemia is
B (this is the only alternative that shows the factor binding with the antibody.)
5-78 [VCAA, SA Q5, 2004]
A prion is a form of
C protein. (This is a definition question.)
5-79 [VCAA, SA Q13, 2004]
It would be reasonable to claim that strain X was a new strain if
D strain X failed to react with both strain Y and strain Z antibodies. (If strain
X is new then it will fail to react to antibodies from other strains.)
5-80 [VCAA, SA Q14, 2004]
The advantage of a naturally acquired active immunity is that it
A is long lasting, sometimes for life. (Naturally acquired active immunity does
not produce antibodies immediately on first exposure, develops on exposure to the
antigen and produces antibodies that are specific to that particular antigen.)
5-81 [VCAA, SA Q15, 2004]
It is reasonable to assume that
C the virus is eliminated by the action of plasma antibodies and cytotoxic T
lymphocytes. (Vaccines are available for viral and bacterial diseases; antibiotics are
only effective against bacteria as viruses only replicate within living cells.)
5-82 [VCAA, SA Q16, 2004]
Defence mechanisms that plants have against insects include the
B production of toxic chemicals in some tissues. (Cell walls and presence of an
internal vascular system are involved in supporting the plant and/or transport within
the plant. The ability of stomata to open and close is related to control of water loss
from the plant.)
5-83 [VCAA, SA Q25, 2004]
Based on the result received it is reasonable to conclude that the individual tested is
allergic to
B garlic and pollen only. (Antigen-antibody complex forms when the person is
allergic to that substance. Two complexes form, one in the garlic position and one in
the pollen position. Therefore the person is allergic to both garlic and pollen.)
5-84 [VCAA, SA Q8, 2003]
Evidence that a vascular plant has an infectious disease includes the
C presence of spores on fungal hyphae growing out of stomata. (This is the
only alternative that is caused by an infectious particle or disease.)
5-85 [VCAA, SA Q20, 2003]
It is reasonable to conclude that
B the flagellum is important for locomotion. (The organism lives in the blood
where food is already digested and there is not evidence of structures i.e. suckers that
174 Biology

could be used to attach to the blood vessels. If the organism caused immediate death,
then it would not have time to find another host and so it too would die.)
5-86 [VCAA, SA Q21, 2003]
A vector would have been involved in the case of a person developing
D malaria after a bite by a mosquito. (This is the only response that involves
another organism transporting the disease from one person to another.)
5-87 [VCAA, SA Q22, 2003]
If this occurs, they encounter features of specific immunity, including
A B cells. (Each of the other alternatives are examples of the non-specific defence
against disease.)
5-88[VCAA, SA Q23, 2003]
It is reasonable to assume that antibiotics are most likely to be used to treat
B boils. (Antibiotics are most effective against diseases caused by bacteria.)
5-89 [VCAA, SA Q24, 2003]
Examination of the data reveals that
C protein T is present in all four of the heart-muscle extracts. (For A to be
correct there should be a reaction between 4 and anti-R. For B to be correct 2 and 3
should have the same responses on each plate. U is only present in two extracts.)
5-90 [VCAA, SA Q25, 2003]
The pig breed most likely to be chosen for ongoing experimentation and trials is pig
breed number
C 3. (3 reacts the least with the antibodies and therefore is the best candidate as a
potential donor.)
5-91 [VCAA, S1 Q5, 2002]
Viruses that infect bacteria are called bacteriophages. Each bacteriophage
D has a protein coat. (The coat of the bacteriophage remains on the outside of the
bacteria, viruses multiply within cells and contain either DNA or RNA, not both.)
5-92 [VCAA, S1 Q10, 2002]
It is reasonable to suggest that features important to the parasitic lifestyle of the adult
beef tapeworm include
B production of both male and female gametes by each individual. (The
tapeworm lives in the gut where food has already been digested. It would have a high
surface area to volume ratio and as it does not need to find its food it would not have
well-developed sensory organs.)
5-93 [VCAA, S1 Q12, 2002]
Scrapie, a disease which causes severe brain damage in sheep, is caused by prions.
Prions are composed of
C protein. (Fact.)
5-94 [VCAA, S1 Q16, 2002]
Illness in animals is often accompanied by fever, which is a rise in body temperature.
Fever is caused by the resetting of the temperature control centre. This control
centre is located in the
B hypothalamus. (Fact.)
5-95 [VCAA, S1 Q17, 2002]
The structures X indicated by the arrows are called
C flagella. (Villi are found in the digestive tract, axons are part of neurons and hair
cells are not parts of a cell.)
                        Suggested Answers: Chapters 2 –5 175

5-96 [VCAA, S1 Q18, 2002]
The function of the structures indicated in the above diagram is
B locomotion. (Fact.)
5-97 [VCAA, S1 Q22, 2002]
In humans, non-specific immunity includes
C destruction of bacteria by enzymes in saliva. (A, B and D are all part of
specific immunity.)
5-98 [VCAA, SB Q5, 2008]
a i Any one of the following:
       Antigen presenting cells, macrophages, dendritic cells, T helper cells
   ii These cells are have receptors that are able to distinguish between the MHC1
       markers found on the surface of non self and self cells.
b      Cytoxic T cells are stimulated by Helper T cells to produce perforin which
       destroys the membrane of non-self cells.
c      DFTD tumour cells must lack MHC1 markers on their surface thus they are
       not identified as non-self cells.
       DFTD tumour cells have similar MHC1 markers on their surface thus they are
       not identified as non-self cells.
       There is little genetic variation in Tasmanian Devils therefore their MHC1
       markers on the surface of their cells are similar and DFTD tumour cells are
       not identified as non-self cells.
d      Yes pathogens are cells or infectious particles that cause disease in a host. The
       tumour cells do cause disease in a host.
       No, pathogens are cells or infectious particles that cause disease in other
       organisms as the tumour cells are from individuals of the same species they are
       not pathogens.
       No, the tumour cells are part of an organism they are not the entire organism.
       No as antigens on the tumour cells do not bring about an immune response.
5-99 [VCAA, SB Q6, 2008]
a     i & ii

b     In autoimmune diseases the body recognises self cells as non self and destroys
c     A hormone is a chemical that is produced by cells, that either remains within
      the cell or is released by cell and is able to bind with receptors on or in cells
176 Biology

        resulting in a cellular response. (Note: transport by blood should not be
d       Hypothesis: If mice are injected with vitamin D then less mice will develop
        rheumatoid arthritis than mice injected with a placebo.
        Experimental procedure:
        - take 100 of the strain of laboratory mice that normally develop rheumatoid
        - these mice should be of similar age and size
        - divide the 100 mice into two groups (A and B) of 50 mice
        - Group A mice inject with vitamin D
        - Group B mice inject with a placebo
        - both groups of mice should be kept in the same conditions with only the
            contents of the injection varying
        - record the incidence of rheumatoid arthritis
        - repeat the experiment a number of times.
        If less group A mice develop rheumatoid arthritis than group B then the
        hypothesis will be supported.
5-100 [VCAA, SB Q2, 2007]
a i Phagocytes have receptors on their surface that recognize and bind to certain
        molecules in foreign or damaged tissue. These are then engulfed and destroyed
        by the phagocyte. Some phagocytes present foreign antigens to other cells of
        the immune system leading to the production of antibodies.
     ii Complement proteins stick to invading pathogens. This attracts phagocytes to
        the site of infection, helps the phagocyte to identify the pathogen and
        stimulates the phagocyte to destroy the pathogen.
b i R
   ii Cell R has more non-self antigens (8) than cells Q (0) or P (4).
5-101 [VCAA, SB Q5, 2007]
a     Any one of:
      - dust mite faeces (not just dust)
      - pollen (not just grass)
      - peanuts
      - penicillin
      - animal dander (not just fur)
b i Rough endoplasmic reticulum (not endoplasmic reticulum or rough ER)
   ii The ribosomes on the rough endoplasmic reticulum produce antibodies.
c i Mast cell or basophil
   ii Any one of the following:
      - respiratory tract
      - digestive tract
      - skin
      - eyes
  iii Any one of the following:
      - increased permeability of blood vessels
      - contraction of smooth muscle in airways
      - dilation of blood vessels
      - swelling
      - itching
      - production of tears
      - increased mucus production
      - inflammation
                       Suggested Answers: Chapters 2 –5 177

  iv Exocytosis
5-102 [VCAA, SB Q8, 2007]
a     Any one of the following:
      - intact skin (not just skin)
      - sweat
      - tears
      - mucus
      - cilia
      - stomach acid
      - saliva
      - lysozymes
b     Interferons act on nearby unaffected cells increasing their resistance to viruses
      and interfering with virus replication in cells.
c     The vaccine does not contain the genetic material of the virus therefore cells
      will not be able to produce new viruses.
d     The purpose of injecting some women with a saline solution was to show that
      any increase in antibody level was due to the vaccine and not some other
e     The antibody response increases with each vaccination as each vaccination
      results in an increase in number of memory cells. The first vaccination results
      in the recognition of the antigen and cloning of B cells. Some of the B cells
      produce antibodies and their level begins to rise. Some of the B cells produce
      memory cells. These memory cells divide quickly when exposed to future
      vaccinations to produce more antibody producing plasma B cells. The more
      memory cells the faster and greater the number of antibodies produced.
5-103 [VCAA, SB Q3, 2006]
a     Designed drug is a chemical that is specifically designed to interact with the
      infective agent and hence make it inactive.

      Any one of:
      Design a drug that attaches to the attachment proteins on the virus coat. This
      drug would have the complementary shape to the attachment protein. It
      would attach permanently to the attachment proteins before the virus came in
      contact with the cells. As the drug would be permanently attached there would
      be no free attachment proteins to attach to the host cell. As the virus could
      not bind with the host cell, it would not be able to inject its DNA into the
      host cell and therefore could not reproduce.
178 Biology

       Design a drug that has the same shape as the attachment protein on the virus
       coat. This drug would compete for host attachment sites; therefore the virus
       would not be able to attach to the host cell, viral DNA would not enter the
       host cell and the virus would not be able to reproduce.
       Design a drug that attaches to the proteins that assist in release from host cell.
       This drug would have the complementary shape to the proteins that assist in
       release. It would attach permanently to the release protein; therefore the virus
       would not be able to be released from the host cell. It would not be able to
       spread to other cells where it could reproduce.
       Design a drug that has the same shape as the proteins that assist in virus
       release from the host cell. This drug would compete for the proteins on the
       host’s cell membrane that allow release of the virus; therefore the virus would
       not be able to bind with these proteins and would not be released from the
       host cell. It would not be able to spread to other cells where it could
       Important aspects to consider:
       -the drug would not interact with the host in any adverse way
       -the drug would permanently bind with the attachment protein
       -the shape of the drug is complementary to the attachment site
       -how the drug would be taken into the body
c      Take two groups of 100 genetically similar mice.
       Infect both groups of mice with the virus.
       Treat one group with the drug.
       Keep mice in a similar environment.
       If the group treated with the drug do not develop the disease or recover more
       quickly, then the drug would be effective.
       Repeat the experiment many times.
5-104 [VCAA, SB Q7, 2006]
a i Any one of the following
       -presence of thick layer of bark or wax
       -secretion of chemicals which kill the infective organism on the plant’s surface.
    ii Any one of the following
       -presence of mucus in the nose, respiratory system and intestine
       -presence of cilia in respiratory system
       -secretion of chemicals which make the surface acidic and unsuitable for the
       infective organism
       -presence of intact skin
       -secretion of acid in the stomach.
b      Plants confine the infective agents to galls. This stops the spread of the
       infective organisms and therefore reduces damage to other tissue.
       Plants may drop infected leaves before the infection spreads to other areas of
       the plant
       Plants produce gum which seals the infected area off and therefore prevents
       spread of the infection.
c      Any 2 of the following
       -increased permeability of blood vessels to allow macrophages to move to the
       site of infection and engulf the infective organisms
                         Suggested Answers: Chapters 2 –5 179

      -increased blood flow to the area will bring more macrophages to the site of
      infection. The macrophages then engulf the infective organisms
      -chemicals released from damaged cells and macrophages attract more
      macrophages to the site of infection. The macrophages then engulf the
      infective organisms.
d     Non-self molecules or markers on the surface of cells are able to bind with
      receptor molecules on T helper cells. Self molecules cannot.
e     The body produces antibodies specific to the particular antigen.
f     When an allergen enters the body, it is engulfed by a macrophage which then
      displays parts of the allergen on its surface. T helper cells with receptors to
      these displayed allergens, stimulate B cells to produce IgE antibodies. These
      antibodies travel in the blood to mast cells where they bind with receptors on
      the surface. Next time the person comes in contact with the allergen the
      allergen binds with these antibodies and causes the release of histamine from
      the mast cell. Histamine then brings about the allergic response.
5-105 [VCAA, SB Q8, 2006]

b       In the first year after infection, the body is responding to the presence of the
        virus by producing more T cells. HIV concentration increases in the first 6
        months and then drops dramatically.
c       Lymph (tissue fluid) is filtered by the lymph nodes where there is a high
        concentration of T and B cells. There will be a high concentration of virus
        particles in the lymph nodes and the inflammation response will cause the
d       Nine years after the infection, the level of T cells are very low. This means that
        the level of T helper cells are low and as the T helper cells stimulate B cells
        and other T cells the immune system of the patient will be very suppressed.
e       Using a range of drugs, increases the chance that at least one drug will be
        effective against the genetically changed virus particles.
5-106   [VCAA, SB Q2, 2005]
a i     Ribosomes.
   ii   Site of protein synthesis.
b i     Virus.
   ii   Pathogenic agents are not living, whereas pathogenic organisms are.
        Pathogenic agents cannot respire; they rely on the host to produce new
        pathogenic agents. They are not cellular.
c       The mosquito is a vector. It transports and disperses the parasite from one
        human to another.
d       Any one of the following
        -cuticle to protect against stomach enzymes of the mosquito
        -cuticle to protect against extremes of pH found within the mosquito’s gut
        -teeth to help burrow through the stomach wall
180 Biology

e     Any one of the following
      -suckers or hooks to stop flushing from lymph glands
      -high SA:V ratio to maximise the absorption of nutrients
      -streamlined shape to stop flushing from lymph glands
      -cell surface molecules that mimic the host’s surface molecules, thereby
      escaping detection from the host’s immune system.
f     Any one of the following
      -destroy the habitat of the mosquito
      -kill the mosquito by spraying
      -provide sleeping nets for people in areas where mosquitoes are active at night.
      -vaccinate humans against the proteins of larvae and adult.
5-107 [VCAA, SB Q4, 2005]
a     An organism’s weight is determined by the amount of organic matter present
      and the amount of water present. Dry weight is a measure of the organic
      matter present in the organism. Growth refers to an increase in organic matter
      or dry weight. In this experiment dry weight was used to see if the parasite was
      obtaining organic matter from the plants.
b     The root parasites were obtaining organic matter (sucrose/starch) from the
c     Growth in alfalfa is reduced by root parasites.
5-108 [VCAA, SB Q5, 2005]
a     Conclusion 1: the immune system of four-week-old strain A mice will reject
      skin grafts from strain B mice.
      Evidence: the graft was rejected from the mouse with no treatment.
      Conclusion 2: Recognition of self/non-self by the immune system of mice can
      be altered by early exposure of newborn mice to cells from other strains of
      Evidence: the strain A mouse that was treated did not reject or identify the
      skin graft for a strain B mouse as non-self.
b     The skin graft from strain C will be rejected. The newborn mice have been
      exposed to strain B leucocytes. They therefore do not detect strain B cells as
      non-self. They have not been exposed to strain C cells, therefore they will still
      identify these as non-self and reject the graft.
c     Apoptosis is programmed cell death. Tumours are formed when cells do not
      undergo apoptosis and proliferate in an unregulated manner.
d     Select 2 groups of 50 mice of similar age, weight and sex.
      Group 1: inject dead tumour cells.
      Group 2: raise in exactly the same conditions as Group 1 but do not inject
      tumour cells.
      2 weeks later, inject the mice in both groups with living cells from the tumour.
      Repeat the experiment.
      If Group 1 mice remain healthy and Group 2 mice develop tumours then
      vaccination is possible.
e     Q or N or P.
      Q will result in the production of 4 different antibodies that will be effective
      against all strains shown. N will result in the production of 2 antibodies that
      are again effective against all strains shown and P will result in the production
      of 3 antibodies that are again effective against all strains shown.
f     M, N , P, Q and R.
g     Student X’s antibody would be most effective as the antigen-binding sites
      drawn correspond with an antigen that is found twice on strain P. This would
      be more effective than student Z’s antibody as the antigen-binding sites drawn
                         Suggested Answers: Chapters 2 –5 181

      correspond with an antigen that is only found once on strain P. The more
      antigens on the surface the greater the number of sites for the antibody to act
      on. Student Y is incorrect as each antibody has 2 identical antigen-binding
      regions not 2 different regions as drawn.
5-109 [VCAA, SB Q7, 2004]
a     Dead or attenuated cells contain antigens on their surface. When these
      antigens are injected the body is stimulated to produce antibodies.
b     Antigen containing vaccine would circulate in the body. They would be
      engulfed by macrophages that would then display them on their cell
      membranes. These displayed markers would be identified by T helper cells,
      which would then activate specific B cells to divide and produce many copies.
      Some of these (plasma cells) would produce antibodies against the antigens
      and others would become B memory cells. The B memory cells would react
      immediately to future infections.
c     The mother would be the likely source of antibodies between the ages of 0
      and 2 months. Antibodies are able to pass across the placenta and are present
      in breast milk.

  Level of

              2      4           6                      12               18

      In drawing the graph you should have noted the following points:
      After each injection there should be a peak, each being higher than the
      previous peak. The response time is quicker for the late injections as the
      immune system already has memory cells that recognise the diphtheria antigen.
      After the last injection there would be a slow reduction in the antibody levels
      over the length of the experiment.
5-110 [VCAA, SB Q8, 2004]
a     Mitosis
b     Any 2 features and benefit:
      Feature: sucker/hooks
      Benefit: allow the blood fluke to remain in the intestinal veins without being
      swept away.
      Feature: flagella or cilia
      Benefit: allows the blood fluke to move through the body.
      Feature: streamlined body
      Benefit: allows the blood fluke to remain in the intestinal veins or move
      through tissue.
      Feature: thin, flat shape
182 Biology

       Benefit: provides a large SA:V for absorption of food and oxygen.
       Feature: thick outer covering of eggs
       Benefit: prevents digestion in the digestive tract.
c i and ii
       External parasites live in an environment where the temperature varies
       whereas blood flukes live in an environment where temperature is relatively
       constant as it is under homeostatic control.
       The tick overcomes this problem by attaching to the skin of the animal which
       is below its fur. The fur would provide an insulated environment thereby
       reducing exposure to temperature variation.
       External parasites live in an environment where water availability varies
       whereas blood flukes live in a moist environment.
       The tick has a hard exoskeleton to prevent water loss.
       External parasites must seek their host in order to obtain food whereas
       internal parasites are bathed in food.
       A tick is able to burrow under the fur and attach to the skin. It is then able to
       take in a huge amount of food before it drops off.
       External parasites can be knocked off their hosts whereas internal parasites
       Ticks produce chemicals which inhibit inflammation and thus reduce
d      Viruses replicate within living cells. The cells then burst resulting in a jump in
       the number of viruses. The plateaus correspond to when the viruses are being
       produced within the cells. Bacteria do not need to be within cells to reproduce
       therefore they reproduce exponentially with no plateaus.
5-111 [VCAA, SB Q2, 2003]
a i Bacteria belong to the prokaryotes.
   ii Prokaryotes lack membrane bound organelles.
b      The very acidic environment of the stomach makes it unsuitable for the
       survival of some bacteria.
c      The bacterium may have a protective outer layer (capsule) that protects it from
       the acidic environment.
d i Vaccine is a substance that when introduced to an animal brings about an
       immune response.
   ii Vaccines stimulate the immune system to produce B memory cells. Future
       contact with the bacterium results in rapid division of these cells to produce
       more memory cells and plasma cells. The plasma cells produce specific
       antibodies which then destroy the bacterium.
  iii The plasma cells produced as a result of the vaccine produce antibodies that
       are specific to the Helicobacter pylori and therefore will not protect against other
                        Suggested Answers: Chapters 2 –5 183

5-112 [VCAA, SB Q7, 2003]
    Prior to operation One day after            One month after        One year after
                         transfusion              transfusion           transfusion
       Structure 1       Structure 1              Structure 1           Structure 1
                         Structure 2             (Structure 2)          Structure 3
                                                  Structure 3
b      If only structure 1 and 3.
       Structure 1 is present because the man will be continually replacing his dead
       red blood cells with new similar red blood cells.
       Structure 3 is present because when structure 2 was introduced to the body the
       man’s immune response would have been activated to produce specific B
       plasma cells which in turn produce rhesus antibodies.
       If structure 2 is included then these cells would have not died from the
       original transfusion.
c      Agree. Memory cells would have been produced after the first transfusion.
       These cells would quickly divide to produce more memory cells and plasma
       cells after another transfusion. In this way many rhesus antibodies would be
       produced and these would result in blood clotting and possible death of the
5-113 [VCAA, S2 Q2, 2002]
a      Any one of the following:
       ● enables Giardia to survive unfavourable conditions between human
       ● enables Giardia to survive dehydration between human infections
       ● enables Giardia to survive unfavourable temperature conditions between
            human infections.
b       Feature                              Survival assistance
        Presence of sucker                   Stops it being passed out of the intestine
        Flattened ventral side               Increases SA:V ratio for absorption of
        Presence of flagella                 Allows it to move to the intestine or back
                                             into position if it has been dislodged
       Giardia infections are more common in children than in adults.
c      Any one of the following:
       ● children do not wash their hands as well as adults and are therefore more
           likely to infect others and themselves
       ● the natural defence mechanisms are less well developed in children than
       ● children are more likely to eat infected food
       ● adults have developed immunity after earlier infections.
d      Bacterial cells reproduce by binary fission. (Note this is very different to
e      Any two of the following:
       ● constant optimum temperature for Salmonella activity
       ● rich supply of digested food
       ● plentiful supply of water required by Salmonella
       ● appropriate pH for Salmonella activity
       ● as the intestinal lumen is an extension of the external environment,
           Salmonella is not exposed to the full immune response.
184 Biology

f      The separation of areas is important as raw food may contain Salmonella, which
       may then infect food that has been cooked if it is not separated.
5-114 [VCAA, S2 Q7, 2002]
a      Mast cells are found around blood vessels. (Note: they are not found in
b      Structure X: antibody
       Structure P: antigen or allergen
c      Compound Z: histamine
d      Inflammation is the result of increased blood flow to site of the infection. This
       increased blood flow brings more phagocytes to the site of infection.
e      The injected antigens result in the production of allergen antibodies. In the
       future, when the person comes in contact with the allergen the antibodies
       present will react with the allergen before it can react with the mast cells.

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