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					Unit 1                                              Biology 2201                                                      1



                                        The Development of the Cell Theory
         ºObjective: Students will be expected to describe and explain the contributions of (a) Needham,
                       (b) Redi (c) Spallazani (d) and Pasteur in the debate between abiogenesis and
                       Biogenesis, two theories on how life arises.
         Abiogenesis verses Biogenesis

               -       early scientists thought that some living things could arise from nonliving things eg. frogs
                       could come from mud, flies from rotting meat, plants from the dried out mud of ponds, etc.
                       We call this process “abiogenesis” ( also called spontaneous generation). They did not
                       know about microscopic life such as bacteria. They did not yet know how many organisms
                       reproduced.
               -       Biogenesis - the theory that states that only living things can give rise to other living things.
                       This is the theory we accept today as true.
               -       many scientists, over time, contributed to the debate. Some were:
         1.    Aristotle -     (see p. 7) in 334 BC, he stated that living organisms can arise spontaneously from
                               nonliving matter.
         2.    Francesco Redi (1660) -         (see p. 8, fig. 1.2) challenged the idea of abiogenesis. Many persons
                                               believed that rotting meat produced maggots. Redi observed the
                                               maggots longer than anyone else had and saw them enter a cocoon
                                               stage and later emerge as flies. He recalled flies on the rotting meat
                                               so set out to prove that maggots come from flies and are part of their
                                               life cycle. He used proper scientific methods and performed a
                                               controlled experiment in which one containers of fresh meat were
                                               left opened and other containers of fresh meat were left covered.
                                               Flies could not pitch on the covered meat and no maggots appeared
                                               on that meat. Flies could land on the uncovered meat and in time
                                               maggots appeared.
                                               Many of those that believed in abiogenesis refused to accept his
                                               evidence.

         3.    John Needham (1748) -          (see p. 9, fig. 1.3) believed in abiogenesis. New research had shown
                                              the existence of microorganisms in water and that boiling water
                                              killed them. Needham boiled a meat broth. He placed the boiled
                                              broth in two flasks. One he left opened, the other he sealed.
                                              Microorganisms appeared in both flasks , allowing Needham to
                                              claim that the microorganisms had come from the broth since the
                                              original ones had been killed. ( he did not realize that he needed to
                                              boil the broth longer since bacteria can survive boiling for longer
                                              than 10 minutes)

         4.    Lazzaro Spallazani (1800)-     (see p. 9) retried Needham’s experiment but recognized that
                                              Needham had not boiled his broth long enough to kill all
                                              microorganisms. Needham boiled the same kind of broth for over 1
                                              hour. He then left one container open and sealed others by melting
                                              the glass necks shut to get an airtight seal. No microorganisms
                                              appeared in the sealed flasks but did appear in the open ones. When
                                              he broke the seals on the sealed flasks, microorganisms appeared in
Unit 1                                                Biology 2201                                                        2

                                                 them in hours. Scientists opposing Spallazani argued that he had
                                                 destroyed some “active principle” in the air of the flask by boiling
                                                 the broth for too long.

         5.     Louis Pasteur (1861) -           (see p. 10, fig. 1.4) performed an experiment that convinced people
                                                 once an for all that biogenesis was the correct theory and that
                                                 abiogenesis was false. He placed broth in long - necked flasks. He
                                                 then bent the necks of the flasks into an S - shaped tube. Pasteur
                                                 then heated the flasks long enough to kill any microorganisms
                                                 present. The curve of the flask prevented any microorganisms from
                                                 entering the flasks but allowed air to enter into the flask. No one
                                                 could object that the “active principle” in the air was kept out of the
                                                 flasks. No microorganisms grew in the flasks but when Pasteur
                                                 broke off the S - shaped necks of some of the flasks, microorganisms
                                                 appeared in these flasks.

          How the Invention of the Microscope Permitted Scientists to Discover the Existence of Cells - the
         Contributions of Hooke and Leeuwenhoek

         Hooke -          (1665) published a book full of drawings of tree bark (cork) observed under a microscope.
                          He uses the word “cells” to describe what he sees.

         Leeuwenhoek-            (1673) read Hooke’s book and begins to design his own microscopes. Starting in
                                 1673, he writes long letters to other scientists describing the microscopic life he was
                                 studying. He becomes an expert microscope maker, better than anyone of his time.
                                 His microscopes were the best you could buy. Hooke confirms what Leeuwenhoek
                                 was seeing.



         ºObjective: Students will be expected to describe and explain the contributions of (i) Brown
                     (ii) Schleiden (iii)Schwann (iv)Braun (v) Virchow (vi) Pasteur (see pp. 7 - 10)

         1.     Brown -          (1831) observes darker regions inside of all cells. Today we call this the “nucleus”.

         2.     Schleiden -      (1839) writes “all plants are made up of cells”.

         3.     Schwann -        (1839) writes that “all animals are made up of cells”.

         4.     Braaun -         (1845) writes “ The cell is the basic unit of life”.

         5.     Virchow          (1858) writes “Cells are the last link in a great chain [that forms] tissues , organs,
                                 systems and individuals...Where a cell exists, there must have been a pre-existing
                                 cell...in other words all organisms are made up of cells and only cells can produce
                                 other cells.

         6.     Pastuer          (1860) does an experiment that completely disproves abiogenesis. He concludes
                                 that living organisms do not arise from nonliving matter.
Unit 1                                            Biology 2201                                                   3

              General care, focusing techniques and safety concerns in using microscopes.


         ºObjective: Identify microscope parts and their function.
                            -      see p. 16 of text book. Know theses parts.

         ºObjective: Identify the microscope as an important biological tool.
              -      see handout “Introduction to the Microscope and Microscope Use”

         ºObjective: Identify microscope parts and their function.
              -      see handout “Introduction to the Microscope and Microscope Use”

         ºObjective: Demonstrate general care, focusing techniques and safety concerns in using
                     microscopes.
              -      see handout “Introduction to the Microscope and Microscope Use”

         ºObjective: Prepare, stain, and observe a wet mount of a specimen under the microscope.
              -      see handout “Introduction to the Microscope and Microscope Use”

         ºObjective: Examine and compare images of cell structure generated by both the light and
                     electron microscopes.
              -      see handout “Introduction to the Microscope and Microscope Use”

         ºObjective: Carry out lab activities with respect to microscope use ( there will be various exercises
                     assigned).
              -      see handout “Introduction to the Microscope and Microscope Use”

         ºObjective: Draw a biological drawing which includes the concept of field of view and calculation
                     of specimen size.

                       formulas:             size of specimen = F.O.V. diameter
                                                                # that fit across

                                            Scale of diagram = real size of specimen (um)
                                                                 size of diagram (cm)
                -      also see handout “Introduction to the Microscope and Microscope Use”

         ºObjective: Define “depth of field”.
              -      see handout “Introduction to the Microscope and Microscope Use - also note given on
                     this”

         ºObjective: Compare different microscopes in terms of illumination, magnification, and specimen
                     preparation. Include light microscope, Scanning electron microscope and
                     transmission electron microscope.

                              -      see text pp. 20- 21 for highlighted notes

                U             Students will do core lab in text , investigation 1-A, p. 15 of text and /or similar
                              microscope activities to accomplish these objectives.
Unit 1                                               Biology 2201                                                       4

                                                  The Cell Structure

         ºObjective: Students will be expected to compare and contrast prokaryotic and eukaryotic cells.
                     (Read pp. 23 - 24)

                Cell - the basic structural and functional unit of a living organism; the smallest unit making
                       up living organisms.

                Nucleus -       the part of the cell which controls all of the cell functions, including reproduction
                                and heredity.

                 The nucleus is the control centre of a cell. A “true” or proper nucleus has a protective wrapping
         around it called a nuclear membrane. Organisms which have a true nucleus with a nuclear membrane are
         said to be eukaryotic. Organisms which do not have a nuclear membrane or a “true” nucleus are said to be
         prokaryotic.



                Nuclear membrane -             a protective “wrapping” or barrier around the nucleus.

                Eukaryotic - a term used to describe an organism which has a true nucleus which is surrounded
                             by a nuclear membrane.

                Prokaryotic - a term used to describe am organism which does not have a true nucleus.

                Organelle -     specialized structures found inside. Each organelle carries out a special function to
                                keep the cell alive. eg. nucleus, chloroplast, lysosome. etc.

                              Prokaryotes                                            Eukaryotes
          have no nucleus; no nuclear membrane                   have a true nucleus with a nuclear membrane
          all are bacteria                                       includes plants, animals, fungi and protists
          smallest living cells; have very simple internal       larger, more complex than prokaryotes; have many
          structure; lack membrane - bound organelles            specialized cell parts and organelles.
          almost all have a cell wall                            many lack a cell wall


                The organelles of a eukaryotic cell divide its interior into compartments. This allows the many
         chemical reactions taking place inside a cell to proceed at the same time without interfering with each
         other.
Unit 1                                               Biology 2201                                                     5

         ºObjective: Describe the role of the following cellular structures or organelles: cell membrane,
                     cytoplasm, nucleus, nucleolus, endoplasmic reticulum (ER), ribosome, mitochondria,
                     chloroplast, vacuole, vesicle, golgi, microtubules/filaments, cilia, lysosome, cell wall.

                       Also, compare plant and animal cells in terms of types of organelles present in them.
                       (Read pp. 25 - 33)

         U      Have students refer to p. 25 of text for quick reference. Have them highlight relevant terms.


         Major Cell Structures / Organelles and Their Functions:

         Nucleus:

         &      This is the part of the cell that is responsible for controlling all cellular activity and our heredity
                (reproduction).

         &      It is the largest organelle and is visible with the light microscope.

         &      Inside the nucleus is the chromatin (long strands of material containing DNA). When cell
                division occurs the chromatin become chromosomes, a divide so that each daughter cell
                produced will have the same genetic material as the mother cell.

         &      The nucleus also contains the nucleolus (site for manufacturing ribosomes).

         &      Nuclear envelope surrounds the nucleus and is a porous membrane.

         Nucleolus:

         &      a distinct dark area seen inside the nucleus; aids in the making of ribosomes.


         Cytoplasm:

         !      This is not an organelle but rather the medium in which all organelles are suspended. The
                liquid is called cytosol and is rich in proteins. The entire suspension including cytosol,
                organelles, and raw material is the cytoplasm.

         Ribosomes:

         !      Small organelles that are either free floating in the cytosol or attached to the endoplasmic
                reticulum.

         !      They are the sites of protein synthesis. ( where proteins are made)




         Endoplasmic Reticulum or ER:
Unit 1                                                 Biology 2201                                                  6


         !      Two kinds of ER:

         !      Rough - where ribosomes are attached to it.

         !      Smooth - where ribosomes are not attached.

         !      It is a folded tube that acts as a transport system for proteins that will be further processed by
                the Golgi apparatus.

         Golgi Apparatus:

         !      where Protein packets from the ER are further refined

         Mitochondria:

         !      Composed of two membranes, the outer is smooth and covers the organelle, the inner is folded and
                increases the surface area.

         !      It is the site that releases energy into the cell. Special enzymes break down food molecules
                releasing their energy.

         !      This energy can be used for synthesis of proteins or other molecules or simply production of heat.


         Chloroplast:

         !      Found in plant cells; they are the sites where carbohydrates are produced.

         !      Inside chloroplasts, energy from the sun is combined with carbon dioxide and water to produce
                simple sugars in a reaction called photosynthesis.

         Vacuoles:

         !      They are the storerooms of the cell.

         !      Contain mostly water and are found in plant cells more than animal cells.

         !      Plant cell vacuoles may contain food particles, salts, or pigments.

         Vesicles:

         !      small , membrane - bound transport sacs that travel through the cytoplasm
         !      often contain macromolecules which need further processing or are harmful to the cell. Often
                pinch off from the ER to transport macromolecules to the golgi apparatus. Can also pinch off from
                the golgi apparatus to transport macromolecules to the cell membrane.


         Lysosomes:
Unit 1                                                 Biology 2201                                                        7


         !        They are the recycling center in the cell.

         !        They contain digestive enzymes that break down damaged or worn out cell organelles so the
                  molecules can be reused by the cell.

         !        The digestive enzymes do not affect the lysosome membrane.

         !        There are specific types of lysosomes, each containing a unique collection of enzymes. They can
                  breakdown only certain kinds of molecules or structures.

         !        Most abundant in animal cells.


         Microtubules\Filaments ( also called the Cytoskeleton):

         !        This is a miniature internal support system.

         !        Composed of microtubules it gives the cell its structure.

         !        Scientists have proven that it plays a role in the positioning of organelles.

         Cell Membrane (also called the Plasma Membrane): see diagram p. 52 of text

         !        Scientists are still not sure of the exact structure of the plasma membrane but the accepted theory is
                  that it is composed of a double layer of phospho-lipids. Each phospho-lipid is composed of a lipid
                  attached to a phosphate group. Throughout this membrane we find that proteins are scattered.

         !        Proteins that are in contact with both the interior and the exterior of the cell are responsible for the
                  movement of certain molecules through the plasma membrane.

         Cell Wall:

         !        Plant cells have an additional protective layer known as the cell wall.

         !        It is the outer most layer of the cell and is composed of cellulose. Cellulose is macromolecule
                  made up of smaller sugar molecules.

         !        The cell wall adds rigidity to the cell and does not control the passage of material through the cell.
                  That is accomplished by the plasma membrane.

         !        There are two kinds of cell walls, the primary, that occurs in soft flexible plants and a thicker and
                  stronger secondary cell wall, such as in woody plants.

         !        Separating the primary cell walls of adjoining cells is middle lamella. It is composed of another
                  sugar compound called pectin.


         Cilia:
Unit 1                                              Biology 2201                                                  8

         !      hair - like structures extending from the cell membrane that beat in a coordinated rhythm to
                produce movement. Many microscopic , one - celled organisms have cilia, allowing them to move
                through water.

         Flagella:

         !      long, hair - like projections extending from the cell membrane that use a whip - like motion to
                move the cell. eg. sperm cells have flagella which allow them to swim in the seminal fluid.



                How ER , ribosomes , Golgi apparatus and vesicles interact to make proteins
                for secretion:

         !      Ribosomes on the rough ER manufacture proteins that then enter the ER. These proteins move
                from the rough ER to the smooth ER where part of the ER’s membrane engulfs the protein and
                forms a vesicle. The vesicle “protein packet” can then be transported to the golgi apparatus. The
                vesicle attaches to the Golgi apparatus and dumps its proteins inside where they undergo chemical
                change (carbohydrates can be added or water removed).

         !      As these packets move to the end of the Golgi apparatus part of the membrane surrounds the
                protein and pinches off forming another vesicle. The packet can then be transported to another
                organelle or moved to the cell membrane. Once there, it fuses with the plasma membrane and
                dumps its contents outside of the cell.




         ºObjective:            Compare plant and animal cells in terms of organelles present:

                               Animal Cell                                          Plant Cell
           no cell wall- only cell membrane; has irregular     cell wall present surrounding cell membrane; has
          shape -                                              “boxy shape
          lacks chloroplasts                                   has chloroplasts
          has more lysosomes                                   has fewer lysosomes
          has many smaller vacuoles                            can have one very large, central vacuole
Unit 1                                              Biology 2201                                                        9

                              The Cell and Its Environment: ( text ref. - read pp. 52 - 61)

         ºObjective:            Explain how materials are able to move into and out of cells through a
                                selectively permeable membrane. Include (a) passive transport - (i)osmosis, (ii)
                                diffusion and (iii) facilitated diffusion and (B) active transport - (i) exocytosis
                                (ii) endocytosis (pinocytosis, phagocytosis) (pp. 50 - 60)



                 The concentration of chemicals inside the cell is different from that outside the cell. The cell
         membrane is responsible for controlling the flow of material from the outside to the inside and vise versa.
         All cells require oxygen, and nutrients so that it can exist and grow. The process of absorption brings these
         substances into the cell through the cell membrane, also waste products such as carbon dioxide and water
         have to be excreted from the cell.
                 There are a number of processes that control the passage of chemicals across the cell membrane.

         Diffusion: (p. 53)

         !      Molecules are in constant motion due to the kinetic energy each molecule has.

         !      As molecules move they bump into each other causing the energy from one to be transferred to
                the other. This is similar to billiard balls hitting one another. Each molecule will maintain its
                direction until another collision occurs. In this way molecules scatter in all directions.

         !      Molecules that are closer together have more collisions, as a result they tend to spread out and fill
                the space available. Over time the molecules will be equally distributed throughout the
                available space.

         !      This movement of molecules from areas of high concentration to areas of low concentration is
                known as diffusion.

         !      Diffusion occurs in both air and liquids.

         Concentration Gradient (p.53)

         !      It is natural for diffusion to occur from areas of higher concentration to areas of lower
                concentration. This is called the conc. gradient.

         Permeability: (.ie. ability to pass through)

         !      The cell membrane is permeable to certain chemicals because there are spaces large enough for
                them to pass through. Molecules such as oxygen, carbon dioxide, and water can diffuse through
                the cell membrane.
Unit 1                                             Biology 2201                                                     10

         Selective Permeability

         !      The plasma membrane is selectively permeable because it controls what passed through it.

         !      permeability depends upon the size, charge, and solubility of the molecule.

         Osmosis: (p.54)

         !      Osmosis is the diffusion of water molecules through a selectively permeable membrane. ;
                water is moving from a region of high concentration to an area of low concentration.

         !      Osmotic Pressure - is the pressure caused inside a selectively permeable membrane due to the
                movement of water. The pressure can be increased if water moves inside the membrane and
                decreased if water moves out of the membrane.

         !      dynamic equilibrium - the point at which the rate where the molecules entering the membrane
                is equal to those leaving the membrane.

         Types of Solutions Affecting Cells:

         ºObjective:           Define the terms hypotonic, hypertonic and isotonic.

         These terms can only be used when you are comparing one solution to another solution. The two
         solutions we will be comparing are the cell’s environment (its medium = the liquid solution
         surrounding it) and the cell’s cytoplasm.

         !      Hypotonic Solution - lower concentration of dissolved substances or solutes than to the solution it
                is being compared. It has a higher concentration of water. As a result the water molecules move
                from the region of high concentration to the region of low concentration.

         !      Hypertonic Solution - contains a higher concentration of solutes than the solution to which it is
                being compared. Water molecules tend to move into the hypertonic solution.

         !      Isotonic Solution - contains equal concentrations of dissolved substances in both samples. In this
                case water enters and leaves the solutions at the same rate.
Unit 1                                              Biology 2201                                                11




                   Fig 1: Cell in a hypertonic (has more solute) interstitial
                   solution.. The cell cytoplasm is hypotonic ( has less solute)




                There are two solutions present above because they both have differing solute concentrations:
                       1. cytoplasm -         5% solute solution - This solution is hypotonic to the interstitial
                                              fluid because it has a lower conc. of solute. ( hypotonic; remember
                                              “po” rhymes with “LOW” - meaning low solute)

                       2. interstitial fluid - 10% solute - this solution is hypertonic to the cell cytoplasm
                                               solution because it has MORE solute. ( remember “hyper” means
                                               “lots” of solute)

                They also have differing water molecule concentrations:
                       1. cytoplasm - 95% water
                       2. interstitial fluid - 90% water

                 These differences set up a concentration gradient. Substances will diffuse from areas of
         higher conc. to areas of lower conc. If the substances are permeable to the cell membrane ,
         diffusion/osmosis will occur:
Unit 1                                                Biology 2201                                                     12




                  Here, salt diffuses into the cell. Water leaves the cell by osmosis. This situation will continue and
         try to reach a state of balance, called dynamic equilibrium. It will try to reach a point where both
         solutions have equal concentrations of solute and solvent. Once dynamic equilibrium is reached, the two
         solutions will be isotonic to each other.

                Note that in equilibrium, the concentrations are now equal. For every one water molecule
         that moves into the cell, one will move out of the cell. For every salt ion that moves into the cell, one
         will move out of the cell. The solutions are now isotonic to each other.


         How Plant and Animal Cells Behave Differently in Hypertonic and Hypotonic Solutions :

                  The above example is good to help explain hypertonic/hypotonic/isotonic situations, but in real
         life, it might not all work out that easily.

                  Plant cells are different than animal cells in that they have a rigid cell wall. When the plant cell is
         placed in a hypotonic solution the cell swells but does not break due to the cell wall. This is what gives
         soft tissue plants their rigid shape in the stems and leaves. If the plant cell were to be placed in a
         hypertonic solution it would loose water and become limp (less rigid).
                  Animal cells require that the concentrations of water inside the cell and outside the cell be equal. If
         an animal cells is placed in a hypotonic solution it will swell up and burst. If placed in a hypertonic
         solution, it will lose water and shrivel up (shrink)

         So, animal cells:
                can explode in hypotonic solutions
                will shrivel up in hypertonic solutions

         So plant cells:
                will swell and become rigid in hypotonic solutions
                will have their cytoplasm shrivel up in a hypertonic solution but the cell will still maintain its
                shape due to the cell wall
Unit 1                                              Biology 2201                                                   13


         The Cell (Plasma) Membrane:

                 The cell must adjust constantly to changes within its environment. The process of maintaining a
         relatively constant environment regardless of the changes within its environment is known as
         homeostasis. Some of the ways that it maintains these changes have already been discussed. They include
         diffusion and osmosis.

         Passive Transport:

         Both of these processes are known as passive transport because the cell does not use any of its own energy
         to move materials across the cell membrane.
                In many cases the cell must move substances against the concentration gradient. When this
         happens, the cell must expend energy and the process is known as active transport. Many types of ions
         and amino acids are moved across the cell membrane in this fashion.

         Facilitated Diffusion: (p. 56 - 58)

         !      When changes occur gradually within a cell, diffusion and osmosis are generally sufficient.

         !      When rapid changes occur, the cell, must be able to respond quickly or it will die. These changes
                require that the cell use a special type of passive transport known as facilitated diffusion. Here,
                there is an increase in the rate of diffusion caused by carrier proteins within the cell membrane.

         !      The carrier proteins are shaped to recognize certain types of molecules and when required they
                bind with the molecule and change shape creating an opening so the molecule can move quickly
                through the membrane.

         !      Once inside the molecule breaks with the carrier protein and the protein returns to its original
                shape.

         !      Note: this diffusion, though faster, still follows the concentration gradient, from HI to LOW

         Active Transport: (p. 58 - 61, pp. 62 - 64)

         !      This occurs when substances must move into the cell against the concentration gradient, from LO
                to HIGH - this requires the use of energy by cells to do this. They must do work to go against
                the concentration gradient. There are two types of active transport.

         !      Like facilitated diffusion, carrier proteins are used to quickly move material across the cell
                membrane. The main difference here is that the movement is against the concentration gradient.

         !      Endocytosis is the process of transporting substances into the cell via vesicles. When the particles
                are very small the process is known as pinocytosis. Tiny particles (molecules or liquid droplets)
                enter indented areas of the cell membrane. The membrane pinches off forming a vesicle and the
                particle are then inside. When the particles are larger the process is known as phagocytosis. Large
                food particles are taken into single celled organisms in this way. Also your immune system has
                specialized cells known as macrophages that work in a similar manner. The organism locates a
Unit 1                                                Biology 2201                                                      14

                 piece of food and moves towards it. The cell membrane flows around the particle and engulfs the
                 particle. It then pinches off forming a food vesicle.

         /       Assign questions:       p. 61 - # 7,8,9,12,13,14,15
                                         pp. 65- 66       # 11, 12, 13, 14,15,16, 26


         /       Assign “Thinking Lab” - p. 59


         /       Do core lab on osmosis in text - p. 56


         ºObjective : Students will perform an experiment that illustrates why cells are limited in their size
                      ( the relationship between surface area and volume)



         The Relationship Between Cell Membrane Surface Area and Cell Volume:


                Students will have to arrive at a conclusion as to how the size of a cell is restricted based upon how
         the speed of diffusion slows down inside the cell. Diffusion from the extracellular fluid and through the
         cell membrane is much faster than that which occurs through the cell cytoplasm. This slow diffusion
         speed inside of the cell means that cells are restricted in their size. To be efficient, a cell must have a larger
         cell membrane surface area than its volume.


                 Use the activity involving the construction of model cells using agar/phenolphthalein cubes which
         are soaked in sodium hydroxide solutions of varying concemtrations. Results will illustrate visually the
         difficulties cells will encounter as their size increases.

         or:
                 Use activity involving the use of potato cubes which are immerses into potassium permanganate
         solution.


                 Any data collected should be collected and organized so that it can be visually compared:

          Radius of Sphere            Surface Area 4Br2                                        surface/volume ratio
                                                                   Volume
Unit 1                                               Biology 2201                                                   15


         ºObjective: Compare and contrast matter and energy transformations associated with the processes of
                     photosynthesis and aerobic cellular respiration.

                        “It is not intended for students to investigate biochemical processes ( such as the
                        Kreb’s cycle, glycolysis, fermentation, and so on) or light and dark reaction associated
                        with plant growth”

         Photosynthesis and Cellular Respiration

                One of the basic characteristics of life is the need for energy. Organisms require it to do work and
         no matter what kind of organism you have they all do work.

         There are two main classifications of organisms based upon the method of obtaining energy.

                1.      Autotrophs- able to make their own food.

                        Plants –       use the process of photosynthesis to make their own food (sugars, starches)
                                       and carry out cellular respiration to “burn” the food they make for energy.

                2.      Heterotrophs – not able to make their own food.

                        Animals – must get their food from their environment and carry out respiration.

                 All energy ultimately comes from the sun. The energy of the sun can only be utilized by the
         chemical reaction called photosynthesis. Photosynthesis allows inorganic compounds, such as carbon
         dioxide and water, to be converted into organic, energy rich substances such as sugars which cells can then
         use as an energy source. Photosynthesis is the base of all foodchains - it is the source of all life on earth.

                Photosynthesis is the process of converting carbon dioxide, CO2 (g) and water, H20 (l) into simple
         sugar by using the sun’s energy. Oxygen, O2 (g) is given off as a waste product.

                Photosynthesis:

                CO2 (g) + H2O (l) º C6H12O6 (s) + O2 (g)

                Plants use carbon , in the form of CO2 (g) during photosynthesis to make carbohydrates. This takes
         carbon from its inorganic state and transforms it into organic compounds. This carbon then gets passed up
         the food chain through consumers.

                 Carbon is returned to its inorganic state when organisms break down carbohydrates to get energy.
         They use carbohydrates in a cell reaction process called cellular respiration. Cellular respiration requires
         oxygen. This reaction releases energy to the body and gives off inorganic carbon dioxide and water vapor
         to the air. Decomposer organisms also release carbon dioxide to the air.
Unit 1                                              Biology 2201                                                   16

                Respiration:

                C6H12O6 (s) + O2 (g) º CO2 (g) + H2O (g)

                In fact, photosynthesis and cellular respiration are complementary reactions; they are the opposite
         of each other in terms of reactants and products:

                      Reaction                            Reactants                            Products
                                              Carbon dioxide + water              glucose sugar + oxygen
                   Photosynthesis
                                              CO2 + H2O                           C6H12O6 + O2
                                              glucose sugar + oxygen              Carbon dioxide + water
                     Respiration
                                              C6H12O6 + O2                        CO2 + H2O



         The importance of the processes of photosynthesis and aerobic respiration on a global basis:

                 Photosynthesis is the base of all food chains. It also produces the oxygen necessary for the process
         of cellular respiration. Photosynthesis is the route by which inorganic molecules , carbon dioxide and
         water, are converted into organic molecules such as glucose which are useable in organisms for their
         metabolism. Cellular respiration recycles carbon back into inorganic form by releasing carbon dioxide.
         This allows the oxygen and carbon cycles to continue.