MAINTAINING A BALANCE by 338L4H

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									                      MAINTAINING A BALANCE
                                    (Last updated 6h May 2011 by SR/IR)


Contextual Outline

Multicellular organisms have specialised organ systems that are adapted for the uptake and
transport of essential nutrients from the environment, the utilisation or production of energy
and the removal of waste products arising from cellular activities.

The basis of healthy body-functioning in all organisms is the health of their cells. The physical
and chemical factors of the environment surrounding these cells must remain within narrow
limits for cells to survive. These narrow limits need to be maintained and any deviation from
these limits must be quickly corrected. A breakdown in the maintenance of this balance causes
problems for the organism.

The nervous and endocrine systems in animals and the hormone system in plants bring about
the coordinated functioning of these organ systems. They are able to monitor and provide the
feedback necessary to maintain a constant internal environment. Enzyme action is a prime
example of the need for this balance. Enzymes control all of the chemical reactions that
constitute the body‟s metabolism. As enzymes normally function only within a narrow
temperature range, even a small rise in body temperature can result in the failure of many of
the reactions of metabolism that are essential to life.

This module increases students‟ understanding of the applications and uses of biology,
implications for society and the environment and current issues, research and developments in
biology.



   1.      Most organisms are active in a limited temperature range


Identify the role of enzymes in metabolism, describe their chemical composition and use a
simple model to describe their specificity on substrates.


Things to consider:
   -    What does identify mean?
   -    What does describe mean?
   -    Understand what you are going to write before you write your answer down.
All chemical reactions taking place within a cell and all chemical processes within the organism
is known as its metabolism. The organism‟s metabolism is maintained by special large proteins
called enzymes. The role of these enzymes is to catalyse steps in metabolic pathways as well
as produce essential molecules for cells. (Maintaining a balance)
Other facts about enzymes:
      They can be used over and over again
      Only small quantities required in cells
      Made by the cell and controlled by nucleus
      Different cells make different enzymes


The major chemical composition of enzymes is proteins. These proteins are made up of amino
acids which are joined by peptide bonds. Certain amino acids code for certain proteins. The
chemical composition can determine the active site, which binds to the substrate.


Enzymes are highly specific which means that enzymes have a specific substrate and that
substrate only can incur a reaction. The models below illustrate enzymes specificity to a
substrate.
LOCK AND KEY MODEL




The above model shows that the enzyme is specific for only one type of substrate. The
enzyme can only react with a substrate which is the reciprocal to its shape. The substrate
binds to the enzyme at the active site whereby a reaction occurs. Once the reaction is
complete the enzyme returns to its regular state and two products are formed.
It is called the lock and key model due to the substrate fitting to the enzyme like a key going
into a lock.

INDUCED FIT MODEL




The above model shows that an enzyme is adaptable to the shape of the substrate. Once the
substrate has attached itself to the enzyme at the active site the reaction occurs and the once
complete the enzyme returns to its regular state and two products are formed.
It is called the induced fit model due to the enzyme changing its shape to accommodate the
substrate. (Inducing itself)


Identify the pH as a way of describing the acidity of a substrate.


Things to consider:
   -   What does identify mean
   -   Be succinct in your answer
The pH scale is a scale which illustrates the hydrogen ion concentration within a substance.
Acidity is when a substance has a large amount of hydrogen ions present in solution. Acidic
substances fall between the pH ranges of 1 – 7. If a substance is neutral it is said to have a pH
of 7. Alkalinity or a base is a substance that contains very little hydrogen ion‟s. Basic
substances fall between the pH range of 7 -14. If we use this scale we can determine how
many hydrogen ions are present in a substrate therefore determining the optimum pH range
for an enzyme.
Explain why the maintenance of a constant internal environment is important for optimal
metabolic efficiency


Things to consider:
   -   What does explain mean?
   -   Underline key words
   -   Define key words. Know what they mean!


There are three main factors that affect the enzymes there activity and hence metabolic
efficiency. These factors are:
      Temperature
      pH
      Substrate concentration
All enzymes have a specific temperature in which they function the best, (optimum
temperature.) If the temperature is low enzymes are “sluggish,” and reactions occur at a slow
rate. When the temperature increases, reaction rates increase until the enzyme is at its
optimum temperature. If the temperature continually increases reactions rates dramatically
decrease. This increase in temperature causes the peptide bonds to break, which in turn makes
the active site inactive, effectively destroying the enzyme. This process is called denaturation.
All enzymes have an optimum pH. This means that if an enzyme carries a pH level of 6 it
needs to be in an environment which has a pH of around 6. Changing the pH slightly will
change the enzyme activity, while changing the pH dramatically will cause irreversible changes
in the enzyme.
Substrate concentration also affects metabolic activity. If we increase the substrate
concentration the enzyme activity increases to a certain point until all active sites are being
occupied by a substrate. So how does the substrate concentration stay at a level which
enables the enzyme to continually function at the optimum level? Enzymes are continually
reacting with substrates to produce a product, these products are then metabolised by
another enzyme. A process called feedback regulates enzyme activity, a key factor in metabolic
efficiency. Feedback also controls temperature and pH.


Describe homeostasis as the process by which organisms maintain a relatively stable internal
environment


Things to consider:
   -   A definition of homeostasis
   -   What does describe mean?
   -   Underline key words
   -   Be succinct in your answer

No matter what is happening on the external environment, the human body is capable of
maintaining a constant internal environment. For example our blood sugar remains fairly
constant, (90mg/100mL) body temperature (37 degrees Celsius) and pH of the blood (7.38 –
7.42). This constant internal environment is known as homeostasis. Homeostasis is the constant
internal composition of a cell or an organism and the mechanisms that maintain it. In simple
terms homeostasis is the steady state of an organism. Homeostasis does not merely occur.
Certain stimuli that cause an imbalance will in effect illicit a response, in turn returning the
organism to its steady state.
OTHER FACTS:
      Idea of homeostasis introduced by Claude Bernard in 1859, did not call the process
       homeostasis.
      Term homeostasis first coined by Walter Cannon (1929.)
Explain that homeostasis consists of two stages:
   -   Detecting changes from the stable state
   -   counteracting changes from the stable state


Things to consider:
   -   What does explain mean?
   -   Determine the best way to answer the question
   -   Diagram?


The human body uses the homeostatic response to maintain a balance in a variety of ways
including body temperature. The homeostatic system has three main parts; the receptor
(detector), the control centre and an effector. The role of the receptor (detector) is to detect
changes within the surrounding internal and external environment. These changes are known
as stimuli. When and if a change takes place the receptor relays a message to the control
centre. The control centre then determines whether or not to illicit a response or maintain the
balance. This response or maintaining a balance is carried out by the effector. This process is
known as feedback:
Receptor/detector  control centre  effector.
Therefore, homeostasis is a two stage process whereby receptors detect changes from the
stable state and counteract these changes to return to the stable state. (e.g.
shivering/sweating)


Outline the role of the nervous system in detecting and responding to environmental changes.


Things to consider:
   -   What does outline mean?
   -   What does the nervous system contain?
   -   Underline key words and be succinct


The nervous system consists of two parts the central nervous system (CNS) and the peripheral
nervous system (PNS). The role of the central nervous system is to coordinate all the
organisms‟ responses. The CNS receives the information, interprets the information and
initiates a response. The PNS is a system of nerves that branches out and around the body.
These nerves are connected to receptors and effectors. When the PNS detects a stimuli it
rapidly relays the message to the CNS and to the control centre to illicit a response.
The endocrine system also plays a pivotal role in maintaining a balance. The endocrine system
secretes certain hormones in response to certain stimuli.
e.g. Thermoreceptors detect a change in the surrounding air temperature, (hot). A message
from the PNS is relayed to the CNS which in turn interprets the message. The CNS then
initiates a response. Effectors start to produce sweat and dilate blood vessels in order to lose
heat, and therefore maintain a balance.


Identify the broad range of temperatures over which life is found compared with the narrow
limits for individual species.


Things to consider:
   -     What does identify mean?
   -     What does compare mean?
   -     Be succinct, make sure in your answer you include a variety of species


On Earth organisms face a vast variety of temperatures ranging from over 100 degrees to -70
degrees Celsius. All organisms have a certain optimum temperature range. When out of their
temperature range the organism risks death or damage to their cells. For example, most
terrestrial organisms are found to function best between 0 – 45 degrees Celsius. Any higher or
lower and the organism risks their cells and proteins denaturing, or their cells becoming
frozen. In comparison thermoacidophiles love a hot climate around 100 degrees Celsius. If the
temperature drops below 55 degrees Celsius the thermoacidophiles will eventually become
inactive and die.


Compare responses of named Australian ectothermic and endothermic organisms to changes
in the ambient temperature and explain how these responses assist temperature regulation.


Things to consider:
   -     What does compare and explain mean?
   -     Know the key words in this statement such as ectothermic and endothermic.


AUSTRALIAN           RESPONSE TO                      EXPLANATION OF CONTROL
ECTOTHERM -           CHANGE IN
ENDOTHERM               AMBIENT
                     TEMPERATURE
Frilled Neck        Flatten or narrow   Frilled neck lizards will flatten their body to absorb as
Lizard              body shape.         much sun as possible in order to increase their body
            (Sunbaking)         temperature.
                                Frilled neck lizards will narrow their body if the ambient
                                temperature is too high or if their own body temperature
                                is too high. This is performed in order to reduce their
            Access areas of     surface area.
            cooler ambient
            temperature         Frilled neck lizards move into shades or burrows to cool
            (Shade/burrows.)    down from the rising ambient temperature. The
                                temperature in burrows is fairly constant, which enables
                                the lizard to cool down. Burrows in particular also minimise
            Dormant states of   water loss which is beneficial to the lizard.
            reduced metabolic
            activity.           Due to the ambient temperature being too cold frilled
                                neck lizards can go into a state of torpor whereby their
                                body shuts down for the winter and their metabolic rate is
                                slowed.
Kangaroos   Surface area to     Kangaroos have a relatively large surface area. This larger
            volume ratio.       surface area enables the kangaroo to maintain and lose
                                body heat during periods of high temperatures.


            Changing patterns   Kangaroos have a dense network of blood vessels
            in blood flow.      particularly in their forearms. These blood vessels dilate
                                when the ambient temperature is high. This dilation
                                increases blood flow to the forearms and promotes heat
                                loss. To increase cooling kangaroos lick their forearms.


            Cooling by          Kangaroos cool themselves by sweating. This evaporation
            evaporation of      of the water cools the organism down. However in times
            water.              whereby the kangaroo needs to conserve water it will
                                increase its body temperature a couple of degrees in order
                                to maintain water.
            Fur.
                                Kangaroo‟s fur has two main processes when the ambient
                                temperature increases/decreases. When the temperature
                                decreases the fur stands on end in order to reduce heat
                                loss and maintain body heat. When the ambient
                                temperature increases the fur insulates the kangaroo from
                                the hot air surrounding it.
            Regulating
            metabolic rates.    Kangaroos regulate their metabolic rates in order to
regulate their body temperature. This is done by remaining
crouched in the shade during times of extreme heat.
Identify some responses of plants to temperature change.


Things to consider:
   -   What does identify mean?
   -   Be succinct


Desert plants or plants which are exposed to high temperatures elicit a few responses due to
temperature change. For example, due to increasing temperature a desert plant will have
smaller leaves which in turn decreases their surface area which leads to a decrease in water
loss and solar radiation.
An Australian example where a plant reacts to temperature change is the eucalypt. The
eucalypts leaves hang down, vertical in nature. This in turn provides a large surface area for
the rising sun, and at this time of the day it is generally cool in nature. When the sun is higher
in the sky around midday, the ambient temperature generally increases. At this time the
eucalypts leaves are still hanging vertically which in turn reduces the surface area of the leaf as
well as maximising water retention. In some very dry and hot conditions the eucalypt may
even close its stomates in order to stop transpiration from occurring.
Therefore, particularly in Australia, there are numerous responses of plants to temperature
change.


Identify data sources, plan, choose equipment or resources and perform a first-hand
investigation to test the effect of:
   – increased temperature
   – change in pH
   – change in substrate concentrations on the activity of named enzyme(s)


Things to consider:
   -   What does identify mean?
   -   This experiment is referred to frequently in past HSC papers. Understand the task when
       it is performed in class.
   -   Underline key words and know their definitions.


Part A: The effect of temperature on an enzyme


EQUIPMENT:
You need to know what equipment was used in this experiment, as this dot point asks you to
“choose equipment.” Refer to page 8 for the equipment list.
METHOD:
Ensure you have written your own method. This dot point asks you to PLAN your experiment
so in the HSC there is no reason why they can‟t ask you to re-write the method you followed.
Refer to pages 8-9 of the textbook.


RESULTS:
      Ensure that you have a table of results
      Construct a graph of your results and answer the following questions.


QUESTIONS:
   –   Did the enzyme cause a reaction in any of the control tubes? Explain why you used the
       controls.
   –   At what temperature was the enzyme most active? What is your evidence for this?
   –   Explain why the observation or measurement that you recorded in your result was in
       fact a valid indication that enzyme activity had taken place.
   –   (a) Describe the shape of your graph.
   –   (b) What conclusion can you draw about the effect of temperature on enzyme activity?
   –   Explain the effect on the enzyme action of:
           o low temperatures
           o high temperatures. Include possible reasons as to why low temperature and high
              temperature did no bubble as well as the phrases, “optimum temperature” and
              “denaturation.”
   –   Briefly describe your predicted results if you placed the tubes that did not show enzyme
       activity into the bath at the optimum temperature. Suggest an explanation for these
       results.
   –   Discuss whether this investigation is best undertaken individually or by a team.
   –   Evaluate the ways in which reliability and accuracy have been attained.
   –   Write down ONE safe working practice you used throughout this experiment.
   –   Write a conclusion. (Did your experiment answer your aim?)



WRITE UP EXPERIMENT 2: EFFECT OF pH ON ENZYME ACTIVITY (p. 8-9). It must be in your
own words!


EQUIPMENT:
You need to know what equipment was used in this experiment, as this dot point asks you to
“choose equipment.” Refer to The Student Resource CD for the equipment list.


METHOD:
Ensure you have written your own method. This dot point asks you to PLAN your experiment
so in the HSC there is no reason why they can‟t ask you to re-write the method you followed.
Refer to Refer to The Student Resource CD and pages 8-9 of the textbook.


RESULTS:
      Ensure that you have a table of results
      Construct a graph of your results and answer questions.


WRITE UP EXPERIMENT 3: EFFECT OF SUBSTRATE CONCENTRATION ON ENZYME ACTIVITY
(p. 8-9). It must be in your own words! (“PLAN”)


EQUIPMENT:
You need to know what equipment was used in this experiment, as this dot point asks you to
“choose equipment.” Refer to The Student Resource CD for the equipment list.


METHOD:
Ensure you have written your own method. This dot point asks you to PLAN your experiment
so in the HSC there is no reason why they can‟t ask you to re-write the method you followed.
Refer to Refer to The Student Resource CD and pages 8-9 of the textbook.


RESULTS:
      Ensure that you have a table of results
      Construct a graph of your results and answer questions.
Gather, process and analyse information from secondary sources and use available evidence to
develop a model of a feedback mechanism.


Things to consider:
   -    What does gather, process and analyse information mean?
   -    What does use available evidence mean?
   -    Underline key words and be succinct in your answer, if you are unsure of what your
        answer should be ask another student or the teacher.




         Negative Feedback Systems
        Negative feedback
         mechanisms
          –   predominant mechanism for
              homeostatic control
          –   maintain physiological functions
              within narrow ranges
          –   control events which require
              continuous adjustment for
              moment-to-moment well-being


http://www.unisanet.unisa.edu.au/Information/12924info/Lecture%20Presentation%20-
%20Homeostasis.ppt#264,9, Positive Feedback Systems good site
Analyse information from secondary sources to describe adaptations and responses that have
occurred in Australian organisms to assist temperature regulation.


Things to consider:
   -     What does analyse mean?
   -     What does describe mean?
   -     What is an adaptation
   -     Underline key words and be succinct in your answer, if you are unsure of what your
         answer should be ask another student or the teacher.


ORGANISM        ECTOTHERM        ADAPTATION DESCRIPTION AND RESPONSE
                or
                ENDOTHERM
Pygmy           Endotherm        Fur             The pygmy possum is covered in dense fur.
Possum                                           This is due to the fact that the pygmy
                                                 possum inhabits areas where the ambient
                                                 temperature is extremely low. The fur
                                                 enables the pygmy possum to retain body
                                                 heat and therefore maintain a healthy body
                                                 temperature.


Red             Endotherm        Dense           The dense network of blood vessels in the
Kangaroo                         network of      kangaroo‟s forearms are an adaptation to
                                 blood vessels   the hot dry conditions they experience in
                                 in forearms.    Australia. The blood vessels allow the red
                                 (Blood flow)    kangaroo looses body heat from the
                                                 forearms in hot conditions. For additional
                                                 heat loss the red kangaroo will lick its
                                                 forearms in an attempt to cool itself down.
                                                 This adaptation assists the red kangaroo in
                                                 regulating its own body temperature.


Blue Tongue Ectotherm            Sun baking      The blue tongue lizard will generally sun
Lizard                                           bake in the sun when its core body
                                                 temperature needs to be increased. This is
                                                 due to the fact that the lizard is cold
blooded. Due to the body shape of the
lizard it will flatten itself out in order to
increase its surface area and therefore
increase its body temperature. In order to
maintain its body temperature the lizard
will move out of the sun into the shade.
The lizard will repeat this process in order
to regulate its own body temperature.
   2.       Plants and animals transport dissolved nutrients and gases in a fluid
            medium.
Identify the form(s) in which each of the following is carried in mammalian blood:
   – carbon dioxide
   – oxygen
   – water
   – salts
   – lipids
   – nitrogenous waste
   – other products of digestion


Things to consider:
   -     What does identify mean?
   -     Make sure you know all means of transport as the statement is form(s)
SUBSTANCE                               FORM(S) IN WHICH IT IS CARRIED IN
                                        MAMMALIAN BLOOD
CARBON DIOXIDE (CO2)                       -   Dissolved in blood plasma
                                           -   Bind to haemoglobin. Forming
                                               carbaminohaemoglobin.
                                           -   Hydrogen carbonate ions. (HCO3)
OXYGEN (O2)                                -   Oxygen is carried by haemoglobin in
                                               red blood cells.
WATER (H2O)                                -   Dissolved in blood plasma.
SALTS                                      -   Dissolved in blood plasma.
LIPIDS                                     -   Carried in a package called a
                                               chylomicron.
NITROGENOUS WASTE                          -   Nitrogenous waste such as urea, uric
                                               acid and creatinine is dissolved in
                                               blood plasma.
OTHER PRODUCTS OF DIGESTION                -   Dissolved in blood plasma.


Explain the adaptive advantage of haemoglobin


Things to consider:
   -     What does explain mean?
   -     Be succinct in your answer
Haemoglobin is an adaptive advantage for organisms that contain haemoglobin in their blood
for the following reasons:
      Haemoglobin, the red pigment in all red blood cells, transports oxygen from the lungs
       to body cells around the body. This in turn allows the organism to carry out certain
       metabolic functions such as cellular respiration.
      Haemoglobin transports some carbon dioxide from body cells to the lungs. This in turn
       allows the organism to maintain blood pH as excess carbon dioxide in the bloodstream
       can alter blood pH and have adverse effects on the organism.
      Each red blood cell contains approximately 280 million haemoglobin molecules. This
       adaptive advantage indicates that a large proportion of oxygen can be transported
       within the organism therefore the organism can function at an optimum level.
      The major role of haemoglobin is to transport oxygen. As oxygen is not very soluble in
       water, (meaning it does not dissolve in water) it therefore does not dissolve in blood
       plasma. The adaptive advantage of haemoglobin allows four oxygen molecules to bind
       with the iron ions within the haemoglobin structure. This forms a molecule known as
       oxyhaemoglobin.




   (NOTE THE FOUR OXYGEN MOLECULES ATTACHED TO EACH HAEM UNIT.)


Compare the structure of arteries, capillaries and veins in relation to their function


Things to consider:
   -   What does compare mean?
   -   What is the best way to represent this answer?
   -   Make sure you know the differences between the relative structures


BLOOD             STRUCTURE/FUNCTION                   DIAGRAM
VESSEL
ARTERIES   Arteries are composed of three
           layers; an outer layer of
           connective tissue, a layer of
           elastic fibres and smooth
           muscles and an inner endothelial
           layer. The elastic fibre/smooth
           muscle layer is much thicker in
           arteries compared to other blood
           vessels as it needs to transport
           blood around the body under
           high pressure. This layer enables
           the artery to stretch at times as
           well as return to its normal
           diameter according to blood
           pressure level.
VEINS      Veins are composed of three
           layers; an outer layer of
           connective tissue, a layer of
           elastic fibres and smooth
           muscles and an inner endothelial
           layer. Blood is transported in
           veins at low pressure. Due to this
           low pressure, and to prevent
                                                CONNECTIVE TISSUE
           back flow of blood, veins have
                                                ELASTICFIBRES/SMOOTH MUSCLE
           many valves. Valves open and
                                                ENDOTHELIAL LAYER
           close according to the blood
                                                NOTE THE VALVE
           flow. Blood continually flows in
           veins due to the contraction of
           surrounding muscles. These
           contractions also promote the
           opening and closing of valves.
CAPILLARIES      Capillaries have a very thin
                 structure to allow the transport
                 of substances between blood
                 and cells. The lumen (hole) is
                 very small, only allowing one red
                 blood cell at a time to move
                 through.
                                                      NOTE THAT THE WALL OF THE CAPILLARY
                                                      IS VERY THIN COMPARED TO THAT OF
                                                      THE OTHER BLOOD VESSELS.



Describe the main changes in the chemical composition of the blood as it moves around the
body and identify tissues in which these changes occur.


Things to consider:
   -   What does describe mean?
   -   What does identify mean?
   -   Understand what it means by chemical composition.


The main changes in the chemical composition of the blood as it moves around the body are
due to two systems, the pulmonary system and the systemic system.


In the pulmonary system the blood flows from the heart to the lungs then back to the heart.
The flow of blood is at a fast rate and is usually under low pressure. The blood has just
returned from the body and contains large amounts of carbon dioxide. This carbon dioxide is
then released from the blood into the alveoli of the lungs. Subsequently the carbon dioxide is
breathed out. Oxygen, however, is diffused from the alveoli into the red blood cells. This
oxygenated blood is then carried back to the heart. Therefore, as part of the pulmonary circuit,
carbon dioxide levels are decreased and oxygen levels increased.


The systemic system pumps oxygenated blood to the rest of the body except the lungs.
During this process oxygen is delivered to cells so they can function efficiently, while carbon
dioxide is picked up. Urea is also picked up by the blood from the liver and is transported to
the kidneys. Products of digestion are also picked up and returned to the liver for
metabolising. The deoxygenated blood is then returned to the heart. Therefore, as part of the
systemic system oxygen levels decrease as it is delivered to certain tissues and cells, carbon
dioxide levels increase as they it needs to be removed from the blood, urea levels increase
until they are delivered and filtered by the kidneys and products of digestion increase until
they are delivered and metabolised by the liver.


Outline the need for oxygen in living cells and explain why removal of carbon dioxide from
cells is essential


Things to consider:
   -   What does outline mean?
   -   What does explain mean?
   -   Underline key words


Oxygen is a necessity in living cells as it is a requirement for cellular respiration. Respiration is
the process by which glucose is broken down using oxygen to produce energy, (ATP). Cellular
respiration is outlined below.
Glucose + oxygen    → carbon dioxide + water + energy (ATP)

As indicated by the equation above all living organisms require oxygen in order to break down
glucose. Oxygen is supplied to cells via the haemoglobin.


It is essential for cells to breakdown glucose in order to obtain energy. However as the
equation indicates a by – product of this process is carbon dioxide. Carbon dioxide is no
longer required by the cell and must be removed from the cell and tissue in order to maintain
a balance. Carbon dioxide is removed by the blood in the body in three main ways, dissolved
in plasma, attached to haemoglobin or as hydrogen carbonate ions in plasma. The blood
carries these forms to the lungs where carbon dioxide is breathed out. On the other hand if
carbon dioxide is not removed there can be severe effects on body chemistry. For example, if
carbon dioxide is not removed it will affect the pH of blood; this in turn effects the ability of
haemoglobin to bind to oxygen, a necessity for cellular respiration. Therefore, it is essential
that the body maintains a balance by removing all carbon dioxide from cells and tissue.


Describe current theories about processes responsible for the movement of materials through
plants in xylem and phloem tissue.


Things to consider:
   -   What does describe mean?
   -   Identify the correct theories and identify the characteristics as well as their differences.


The two processes responsible for the movement of materials through plants in xylem and
phloem are the transpiration stream in the xylem and translocation in phloem.


BACKGROUND:
Transpiration is the loss of water through the leaves of plants. Water moves up the plant
against gravity from the roots to the leaves. This process is known as the transpiration stream.
Water enters the plant roots by osmosis and continues to move through the roots cells until it
has reached the xylem. There is continual movement of water in xylem due to two reasons:
   -   There is a continual water potential meaning that water is constantly moving through
       the root cells due to the concentration gradient. (Moving from high to low.)
   -   Root pressure pushes the water towards the centre of the plant towards the xylem.
EVIDENCE: Eduard Strasburger‟s research supported the transpiration stream hypothesis. He
tested 20 meter tall plants and noted that the leaves “pull” water/dissolved nutrients up the
plant, not the xylem itself.


The process of transpiration can be outlined below:
      Sunlight gives water molecules near the leaves surface enough energy to evaporate
       through the stomata. This process is known as transpiration.
      Transpiration causes tension within the xylem column. This tension causes water
       molecules further up the xylem to attract water molecules below them. This is known as
       cohesion.
      Xylem tubes are relatively thin. This means that water adheres to the walls of the xylem
       due to the attraction of water to other molecules. In smaller tubes this is known as
       capillarity and this also helps drag water up the xylem to the leaves.
      The transpiration stream is also known as the evaporation – tension – cohesion
       mechanism. Basically leaves lose water due to evaporation. This in turn causes tension
       further down the xylem. Cohesion then draws up water further down the xylem,
       eventually to the leaves.
      Therefore water and dissolved mineral ions moves from the roots to the leaves in one
       direction only due to the transpiration stream.


The process of translocation can be outlined below:
      Translocation is the movement of sugars in the phloem of all plants in any direction.
       Sugars are always translocated from an abundance of sugar (sugar source) to an area
       where sugar is required (sugar sink).
      Sugar is made as a product of photosynthesis, in the form of glucose. Sugar can also be
       stored as starch in cells.
      Complex sugars such as glucose are broken down into simpler molecules such as
       sucrose. These simpler molecules are much easier to transport, as they are smaller they
       find it easier to transport across biological membranes.
      Scientists documented the movement of sugars in plants using radioactive dye and
       carbon – 14. From this research the pressure – flow mechanism was developed.
      Consider the sugar source first. Sugar is loaded into phloem vessels from nearby cells
       by active transport, (ATP). This increases solute concentration in the phloem which in
       turn causes water to move into the phloem by osmosis.
      Now consider the sugar sink. Sugar is loaded from the phloem vessels into nearby cells
       by active transport, (ATP). Water also follows the sugar into the cell by osmosis.
   Now consider the phloem vessel as a whole. At the sugar source there is a large
    amount of solute and a large amount of water. The large amount of water exerts
    pressure within the vessel known as hydrostatic pressure. At the sugar sink there is a
    small amount of solute and a small amount of water. The small amount of water exerts
    low pressure or low hydrostatic pressure.
   Due to the pressure differences the water flows from high pressure to low pressure
    carrying the solute and nutrients with it.
   Therefore, pressure flow drives the sugars from areas of high concentration (source) to
    areas of low concentration. (sink)
Perform a first-hand investigation to demonstrate the effect of dissolved carbon dioxide on the
pH of water


Things to consider:
   -   Underline key words
   -   Write out an experiment that is controlled as well as an experiment that illustrates
       validity, reliability and accuracy.
   -   Identify variables
   -   Identify safe work practices


                                    PRACTICAL INVESTIGATION


Perform a first-hand investigation to demonstrate the effect of dissolved carbon dioxide on
the pH of water. Refer to Refer to The Student Resource CD and pages 45-47 of the textbook.
AIM:
To investigate the effect of dissolved carbon dioxide on the pH of water.


HYPOTHESIS:
I think that the dissolved carbon dioxide will cause the water to turn acidic.


EQUIPMENT/MATERIALS:
      Solid calcium carbonate (CaCO3)
      Dilute hydrochloric acid (HCl)
      Distilled water
      A 100 mL measuring cylinder
      2 test tubes
      Cork and bent glass tubing
      Test tube rack
      Universal indicator and a card to check the pH
      Lime water solution (calcium hydroxide = Ca(OH)2
      Straw


METHOD:
COMPLETE TASK 1 FIRST: Detecting carbon dioxide
To ensure that the reaction we are performing contains carbon dioxide we must complete
BOTH of the following depending on the reaction we choose:
TASK 1 (Part A):
   1. Using a measuring cylinder measure out 10 ml of limewater (calcium hydroxide) and
      pour it into a test tube.
   2. To a second test tube add some calcium carbonate and hydrochloric acid. Attach a cork
      and bent glass tube to the calcium carbonate/hydrochloric acid test tube and run this
      to the test tube which contains limewater. (See figure 1 below.)
   3. Observe any colour change in the limewater. If the limewater turns a milky colour there
      has been a chemical reaction with the limewater and carbon dioxide.




                                                              Limewater solution.
                                                              (TASK 1 Part A)
                                                              Distilled water and
                                                              universal indicator.
                                                              (TASK 2 Part A)


Figure 1: Limewater turns milky due a chemical reaction with carbon dioxide.


TASK 1 (Part B):
   1. Using a measuring cylinder measure out 10ml of limewater and pour it into a test tube.
   2. Using a straw exhale into the limewater solution.
   3. Observe what happens to the limewater. If the limewater turns a milky colour it means
      that the limewater has reacted with carbon dioxide, proving that our breath contains
      carbon dioxide.


TASK 1 PROVES WHETHER OR NOT THE CHEMICAL REACTIONS YOU ARE PERFORMING
CONTAIN CARBON DIOXIDE. THIS THEREFORE ENSURES THAT YOUR EXPERIMENT IS
ACCURATE.


TASK 2: Ensure you complete BOTH parts.
PART A:
     1. Using a measuring cylinder measure out 10 ml of distilled water and add it to a test
        tube. Add 2 – 3 drops of universal indicator to the test tube. Using a pH card determine
        the pH of the distilled water and record your results in the results table below. Place
        this test tube back in the test tube rack.
     2. To a second test tube add a small amount of calcium carbonate.
     3. Using the measuring cylinder measure out 10 ml of dilute hydrochloric acid.
     4. Add the dilute hydrochloric acid to the calcium carbonate solution and quickly insert
        the cork stopper and bent glass tubing as indicated by figure 1 above.
     5. At every 30 second, for a total of 5 minutes, observe and record the pH change using
        the pH card in the results table below.
     6. Repeat steps 1 – 5 three times to gather reliable results.


PART B:


     1. Using a measuring cylinder measure out 10 ml of distilled water and add it to a test
        tube. Add 2 – 3 drops of universal indicator to the test tube. Using a pH card determine
        the pH of the distilled water and record your result in the results table below.
     2. Using a straw continually exhale into the distilled water solution for a total of 5 minutes.
        At 30 second intervals note the colour change. Using your pH card determine the pH of
        the solution and record your results in the results table below.
     3. Repeat steps 1 – 2 three times to gather reliable results.


RESULTS:


PART 1:


                               TIME (minutes/seconds)
          0    0:30   1:00   1:30   2:00   2:30   3:00   3:30   4:00   4:30   5:00
pH        7     7      6      6      5      5        5    5      5      5      5


PART 2:


                               TIME (minutes/seconds)
          0    0:30   1:00   1:30   2:00   2:30   3:00   3:30   4:00   4:30   5:00
pH        7     7      6      6      6      5        5    5      5      5      5
Depending on the exam question you may have to draw a graph.


DISCUSSION/QUESTIONS:


Consider the following as part of your discussion:
      Was your experiment accurate?
      What improvements could you make to the experiment? For example weighing out the
       calcium carbonate solution with a set of scales, having a smaller measuring cylinder in
       order to obtain a more accurate measurement.
      Are there any safety requirements for this experiment? Goggles?


Questions WITH answers:


1a.) What was the effect of carbon dioxide on the pH of water?
The carbon dioxide caused the water to change from its neutral state (pH 7) to a more acidic
state (pH 5).
b.) How does pH relate to hydrogen ion concentration?
The pH range directly relates to hydrogen ion concentration. Firstly hydrogen ions cause any
solution to be acidic. The purpose of a pH test is to see how many hydrogen ions are present
in that certain substance. We can relate this to the pH scale. A substance that has a pH of 1
has a high hydrogen ion concentration. A substance that has a pH of 14 is said to have a very
low hydrogen ion concentration. Therefore pH relates to hydrogen ion concentration.
c.) From your knowledge of biology, explain how carbon dioxide changes the pH.
From my knowledge of biology carbon dioxide can lower the pH of the blood. When carbon
dioxide diffuses into the bloodstream it reacts with an enzyme known as carbonic anhydrase,
which in turn catalyses its reaction with water. (Indicated below)




            Carbonic Anhydrase

CO2 + H2O                              H2CO3


Therefore an increase in carbon dioxide leads to an increase in carbonic acid which leads to an
increase in hydrogen ions which leads to a decrease in pH which in turn lowers the binding
rate of oxygen with haemoglobin.


2a.) What sources of carbon dioxide did you use?
The sources of carbon dioxide we used in this experiment was a chemical reaction between
calcium carbonate and hydrochloric acid to produce carbon dioxide and using our own
breath/exhaling.
b.) Which of these sources is relevant to body physiology? Explain how it is made in the
body.
Our own breathing/exhaling is relevant to body physiology. Carbon dioxide is made in the
body as a by product of cellular respiration. Cellular respiration is a process by which glucose
and oxygen react to produce carbon dioxide, water and energy usually in the form of ATP.
This is indicated below.


Glucose + Oxygen                           Carbon dioxide + water + energy (ATP)


It is important that the body “gets rid” of this waste. This is done exhalation. This in turn
maintains a steady chemical state within the human body.
c.) Would the change in pH be dangerous for the body? Explain.
A change in the pH of blood composition would be detrimental to the human body. Excess
carbon dioxide causes the bloodstream to turn more acidic, it also affects the binding of
oxygen to haemoglobin to drop. Cells require oxygen to respire. If this can no longer occur
cells will no longer function. On a larger scale excess carbon dioxide in the body will cause the
person to die.
d.) If so, how does the body solve the problem?
The body solves this problem in a simple matter. As carbon dioxide is a waste product of the
cell it is quickly diffused into the bloodstream. Carbon dioxide can be carried three ways in the
blood; it can be carried dissolved in plasma, as carbonic acid or as carbaminohaemoglobin
(attached to haemoglobin). As carbon dioxide diffuses in the bloodstream it is carried via the
pulmonary circuit to the lungs. Here the carbon dioxide diffuses into the alveoli of the lungs
and is subsequently breathed out.
3. What essential measurement did you have to make before testing the effect of carbon
dioxide on the water? Why?
The essential measurement that we took before testing the effect of carbon dioxide was the
pH of the distilled water. This was performed to ensure and to illustrate a pH change. If the
original pH was not recorded we would not know if the carbon dioxide affected the pH of the
dissolved water.
4. Having designed and performed this experiment, what do you think are the key points
about it – assume you are explaining it to another student who has not done it before.
The key points from this experiment would be:
       Carbon dioxide does effect the pH of water
      We ensured that our chemical reactions were producing carbon dioxide. This was
       illustrated by testing our experiments with limewater which turns milky in the presence
       of carbon dioxide.
      This experiment can be linked to the human body.
      We repeated the experiment and got similar results. (Reliability)


CONCLUSION
The experiment performed illustrates that carbon dioxide has a direct effect on the pH of
distilled water. This fact can be linked with the human body. We know that the pH of the
human blood is in a narrow range being 7.35 - 7.45. This pH range is similar to that of the
distilled water. The experiment therefore shows what could happen if carbon dioxide levels
were too high in the bloodstream.
Perform a first-hand investigation using the light microscope and prepared slides to gather
information to estimate the size of red and white blood cells and draw scaled diagrams of
each


Things to consider:
   -   Before undertaking this experiment ensure you can estimate the size of red and white
       blood cells. There is no point performing this experiment if you can not calculate the
       size of the cells.
   -   Refer to pages 37 to 39 of the text book.


      To perform this experiment accurately you need to refer to the method on page 37 to
       39 of the text book.
      The method tells you exactly what to do as well as how to measure the size of red and
       white blood cells. Ensure you know how to calculate the and draw a scaled diagram of
       red and white blood cells because there is no reason why in the HSC they can‟t ask you
       to draw a scaled diagram or calculate the size of the cell based a diagram they give
       you.
      According to https://histo.life.uiuc.edu/histo/lab/lab1/text.htm red blood cells are 6 – 8
       micrometres (µm) and white blood cells vary from 6 – 12 micrometres (µm).
Analyse information from secondary sources to identify current technologies that allow
measurement of oxygen saturation and carbon dioxide concentrations in blood and describe
and explain the conditions under which these technologies are used


Things to consider:
   -   What does analyse mean?
   -   What does identify mean?
   -   What does describe mean?
   -   What does explain mean?
   -   Ensure you account for all the verbs in your answer.


The two main current technologies that allow measurement of oxygen and carbon dioxide
concentrations in blood are the blood gas analyser and the pulse oximeter. Their function(s)
are outlined below.


 BLOOD GAS ANALYSER and CONDITIONS                  PULSE OXIMETER and CONDITIONS
              WHERE IT IS USED                                 WHERE IT IS USED
      Invasive technique. (Goes inside the body)      The pulse oximeter is a non – invasive
      Takes small samples of arterial blood.           technique which measures the
      The analyser measures the oxygen using           concentration of oxygen in the body.
       two electrodes.                                 The device is either attached to the finger
      Oxygen diffuses through a membrane               or ear lobe of the patient, which
       between the two electrodes.                      measures oxygen saturation with
      This produces a small electric current.          haemoglobin and pulse rate.
      This current is proportional to the             The oximeter works in the following way:
       amount of oxygen. e.g. certain values            a light source passes through the blood.
       equal certain amounts of oxygen.                 Different amounts of light are absorbed
      Carbon dioxide levels are also measured          depending on the degree of saturation of
       by placing the blood specimen in one             oxygen to haemoglobin. A processor then
       chamber and the other chamber a                  calculates the light absorption rate and
       hydrogen electrode.                              converts this to saturation of
      Dissolved carbon dioxide diffuses into the       haemoglobin.
       hydrogen ion chamber. The pH is then            Oximeters are used in many hospital
       measured. The hydrogen ion                       situations even though they do not
       concentration is proportional to carbon          measure carbon dioxide levels.
       dioxide levels. E.G. certain values equal       They are used as monitoring units during
       certain amounts of carbon dioxide.               anaesthesia.
      Alternatively instead of taking a blood         They are very efficient because they can
       sample an arterial probe, which is                  be used during surgery or after surgery
       inserted into the body, may take these              to monitor oxygen saturation, pulse rate
       measurements.                                       and blood flow.
      Blood gas analysers are commonly used              Oximeters can be used in the success of
       in intensive care units especially baby             ventilation procedures, to see if the
       care units and labour wards. This is due            administration of oxygen is successful for
       to the fact that slight changes in carbon           the patient.
       dioxide levels can affect the development          Oximeters can also be used in intensive
       of newly born babies. Excess carbon                 care units or after surgery to monitor
       dioxide and poor oxygen saturation levels           unconscious patients and to notify
       can have detrimental affects on the child.          nurses/doctors of any changes in oxygen
       The analyser is used as a measuring tool            levels.
       to ensure the patient is looked after and          Therefore, oximeters are an efficient
       if oxygen/carbon dioxide levels change a            monitoring system for oxygen, pulse and
       nurse/doctor can take necessary action to           blood flow levels.
       return oxygen/carbon dioxide levels to
       their optimum values.


Analyse information from secondary sources to identify the products extracted from donated
blood and discuss the uses of these products.
Things to consider:
   -   What does analyse mean?
   -   What does discuss mean?
   -   What does identify mean?
   -   Determine whether the products from donated blood are a benefit or not.


The main products extracted from donated blood are:
      Red blood cells
      Platelets
      Plasma
These products are spun in a centrifuge to separate them into different products. Further
products can be extracted from the plasma. The uses and further products that can be
extracted are outlined by the table below:


BLOOD PRODUCT                         USE/TREATMENT
Whole Blood                           To replace large amounts of blood from sever injury.
Red Blood Cells                       Given to patients suffering from anaemia, (iron deficiency in
                                      the blood) and in cases of severe bleeding.
White Blood Cells                   Given to patients with a low white blood cell count or in cases
                                    of severe bacterial infection.
Plasma                              Given to patients after trauma, or following after a surgical
                                    procedure.
Platelets                           Given to patients with severe haemorrhaging (bleeding) or
                                    bleeding due to diseases such as leukemia.
Cryoprecipitate (contains blood     Given to patients suffering from haemophilia A. Alternatively
clotting factors)                   severe bleeding.
Prothrombinex – HTTM (contains      Given to patients with specific bleeding disorders. These
concentrated clotting factors.)     specific disorders pertain to patients who are missing certain
                                    clotting factors.
Biostate (contains factor VIII      Given to patients with haemophilia B.
clotting factor)
Monofix® - VF (contains Christmas   Given to patients with haemophilia B
factor)
Thrombotrol® - VF                   Given to patients in situations whereby their blood is clotting
                                    too quickly.
Albumin                             Administered to patients who are suffering from burns, shock
                                    due to blood loss and kidney/liver diseases.
Intagram® P                         Given to patients who suffer from immune disorders such as
                                    AIDS, this in turn reduces susceptibility to infections.
Hyper – immune globulins (contain   Given to patients to treat and/or prevent specific infections
– antibodies)                       such as tetanus or chicken pox.
Rh(D) immunoglobulin (Anti – D)     This product prevents haemolytic disease in newborn babies
                                    of Rh negative babies. Haemolytic disease basically pertains to
                                    the mother producing certain antibodies that destroy the
                                    baby‟s red blood cells.
Analyse and present information from secondary sources to report on progress in the
production of artificial blood and use available evidence to propose reasons why such research
is needed


Things to consider:
   -   What does present mean? Choose whatever means you think is appropriate for this set
       of information.
   -   Break to question into two parts.
   -   In the second half of your answer refer reliable resources as to why artificial blood
       requires further research


As stricter controls arise from blood donations, scientists have concentrated on developing a
synthetic blood known as artificial blood. Research so far has highlighted the importance of
carrying oxygen in the blood. Scientists have therefore concentrated on developing artificial
blood that mimics the characteristics of real blood. The main areas of research into artificial
blood so far are haemoglobin and perfluorocarbons.
Haemoglobin has been extracted from organisms such as cows and humans and has been
used in the free state. This means that only the haemoglobin molecule has been used, no the
whole blood product. Problems have arisen from using the haemoglobin molecule from other
organisms. These include; the instability of the molecule itself, the molecule having a high
affinity to oxygen (meaning it binds lots and lots of oxygen) but the inability to let the oxygen
molecules go, (into tissues and cells) and the damage it causes to the kidney in its filtration
products. These problems are continually researched to the extent that scientists have
chemically changed the haemoglobin molecule to yield better results.
Perfluorocarbons (PFCs) are an advantageous alternative because oxygen is approximately 100
times more soluble in perfluorocarbons compared to that in blood plasma, which is about 1
percent. However the problem with PFCs is that they are not soluble in aqueous solutions
meaning they can not dissolve in blood plasma. To overcome this problem scientists have
added an emulsifying agent to the PFCs. This agent enables the PFC to form an emulsion
when it is joined with the plasma. The first trial of emulsified PFC was called fluosol. This trial
was unsuccessful as oxygen yields were poor. Subsequently further research has led to better
emulsion technology. Scientists have developed a greater emulsified PFC which has a greater
oxygen dissolving capacity.


It is only early days when it comes to artificial blood. Currently scientists have only developed
“parts” of the blood (haemoglobin and perfluorocarbons) and used them as substitutes. These
substitutes only account for the oxygen carrying characteristics of blood. Scientists are yet to
create a whole artificial blood component which accounts for all characteristics of blood.
Further research is needed in the development of artificial blood for the following reasons:
      It enables hospitals to have an ample supply of blood, not merely the blood supplied
       by donors.
      It can be used as a treatment tool. e.g. to increase oxygen carrying levels in the blood.
      Universally if it is successful donations would not be required.
      It could be mass produced
      Used in emergencies
      Maintaining organs before transplant
These reasons outline the prospects of further research and development of artificial blood
and its benefits.
Choose equipment or resources to perform a first-hand investigation to gather first-hand data
to draw transverse and longitudinal sections of phloem and xylem tissue


Things to consider:
   -   Choose your own resources for this experiment.
   -   Decide what data you need to collect in order to draw a transverse and longitudinal
       section of phloem and xylem tissue.


      To perform this experiment accurately you need to follow the method on page 68 to 69
       of your textbook; titled: Investigating xylem and phloem in plants (using a light
       microscope).
      You must draw a longitudinal section and transverse section of phloem and xylem
       tissue. A longitudinal section is the equivalent of a SIDE VIEW. A transverse section is
       the equivalent of a TOP VIEW.
      You need to know the difference between side views and top views because in the 2009
       HSC they had a diagram of a longitudinal section of a plant and students had to
       identify the structure(s) of the plant.




Transverse section (top view) of a plant cell. Note the xylem which looks like a big x. The
phloem bundles are indicated by the„s.‟
Longitudinal section (side view) of a plant cell. The xylem and phloem are indicated by
different stains. Pink = xylem Black/purple = phloem.
   3.      Plants and animals regulate the concentration of gases, water and
           waste products of metabolism in cells and in interstitial fluid


Explain why the concentration of water in cells should be maintained within a narrow range for
optimal function.


Things to consider:
   -    What does explain mean?
   -    Break down the question so you understand what it is asking.
   -    Underline/understand key words, such as optimal.


Water makes up a large proportion of all living things. The concentration of water in cells
should be kept within a narrow range for the following reasons:
   -    It is an excellent solvent which means it can break down or suspend complex organic
        and inorganic molecules such as sugars in solution. Too much or not enough water can
        lead to slower reactions.
   -    For larger molecules such as proteins water acts as a hydration layer preventing the
        protein from breaking down. This is called a colloid.
   -    Water needs to be within a narrow range of concentration (Osmotic Balance) in order
        for cells to function efficiently. Too much water within the cell (hypotonic) causes the
        cell to swell and burst. Not enough water within the cell (hypertonic) causes the cell to
        shrivel. The correct concentration is called isotonic where the normal concentration of
        water is the same out of the cell as it is in the cell.
   -    Water is a lubricating substance. Right concentrations leads to the production of
        substances such as mucus.
   -    Water is important in metabolism. e.g. Hydrolysis.
   -    Water is the major transport medium for products around the body.
   -    Water plays an important role in maintaining body temperature.
   -    Water has a cushioning effect for the body.
From the points above it is necessary for water to be at its optimum level in order for
chemical reactions and certain functions to take place. If this level is uneven reactions are too
slow, cells becomes damaged (shrivelled/lysed) or reactions do not take place at all.
Explain why the removal of wastes is essential for continued metabolic activity.


Things to consider:
   -   What does explain mean?
   -   Underline key words
   -   Metabolic????


The removal of wastes is essential for continued metabolic activity for the following reasons:
                CAUSE                                          EFFECT
   1. Wastes affect enzyme activity.         1. Optimum enzyme activity not reached.
                                                Enzymes not catalysing reactions. Disrupts
                                                metabolism.
   2. Damage to cellular components.         2. Organelles damaged to the extent that
                                                they no longer function. Damage to
                                                organelles cause organelles to illicit
                                                no/incorrect response. Excessive damage
                                                may cause cell death.
   3. Excess Hydrogen ions.                  3. Makes surrounding ion increase in acidity.
                                                This in turn affects the reaction rate of
                                                enzymes and the saturation rate of
                                                haemoglobin.
   4. Excess ammonia, urea, toxins           4. Brain associated problems.
       and drugs.




Identify the role of the kidney in the excretory system of fish and mammals.


Things to consider:
   -   What does identify mean?
   -   Underline key words → role?
   -   Be succinct; maybe use a table to represent your information.


                ORGANISM                                  ROLE OF THE KIDNEY
FISH                                                 The main role of the kidneys is
                                                      osmoregulation. Osmoregulation is
                                                      the regulation of salt and water
              concentrations in the body.
             Fish excrete nitrogenous wastes
              across the gills. The kidneys adjust
              the level of water and mineral ions
              within the body in order to maintain
              a balance of internal fluid within the
              cells.
MAMMALS      Regulate the internal salt and water
              concentrations of the body.
             To excrete urea and nitrogenous
              waste.
Explain why the processes of diffusion and osmosis are inadequate in removing dissolved
nitrogenous wastes in some organisms.


Things to consider:
      What does explain me?
      What is diffusion and osmosis?
      Underline key words, understand the question


The processes of diffusion and osmosis are inadequate in removing nitrogenous waste in
many organisms. Firstly diffusion and osmosis are slow processes. In order for organisms to
function efficiently the quick removal of nitrogenous waste is a necessity. Diffusion and
osmosis do not offer an efficient and fast removal system of nitrogenous wastes. Secondly
nitrogenous wastes are predominately made up of large complex protein molecules. These
molecules need to be broken down by the liver into simpler products such as urea. (This
process is known as deamination.) Once broken down into simple substances diffusion may
take place usually within the kidney, due to the nature of smaller molecules. Thirdly osmosis is
the transport of water across a semi-permeable membrane. As nitrogenous wastes are a waste
product they are not made up of water. Only products of metabolic reactions within the body
that produce water would require osmosis. Therefore, diffusion and osmosis are inadequate in
removing dissolved nitrogenous waste.




Distinguish between active and passive transport and relate these to processes occurring in
the mammalian kidney.


Things to consider:
      What does distinguish mean?
      Ensure you relate these terms to only the mammalian kidney.
      Be succinct


       PASSIVE TRANSPORT                                ACTIVE TRANSPORT
The net movement of substances          The net movement of substance requires cellular
that does not require any cellular      energy to be expended. Movement of substances is
energy. Movement of substances is       against the gradient meaning movement is from a low
from high concentration to low          concentration to a high concentration.
concentration.
Passive and active transport play an important role in the mammalian kidney. Filtration and
reabsorption occur in thousands of tiny units known as nephrons. It is in these nephrons that
active and passive transport take place. Active transport occurs in the proximal tubule, the
ascending loop of henle and the distal tubule. It is at these areas that important nutrients are
filtered and reabsorbed. Passive transport occurs in the proximal tubule, the descending loop
of henle, the ascending loop of henle, the distal tubule and the collecting duct. Passive
transport plays an important role in the mammalian kidney in removing waste and reabsorbing
essential nutrients. (See kidney diagram.)


Explain how the processes of filtration and reabsorption in the mammalian nephron regulate
body fluid composition.


Things to consider:
   -   What does explain mean?
   -   What is filtration and reabsorption?
   -   What is the nephron?
   -   Refer answer back to question.
Filtration in the mammalian nephron regulates body fluid composition in the following ways:
   -    Blood crosses from the glomerulus to the Bowman‟s capsule by the process known as
        filtration.
   -    Blood pressure forces small molecules such as urea, amino acids, salts and water across
        and into the capsule.
   -    Blood cells and proteins are too large and are filtered out.
   -    When small molecules are filtered across they form glomerular fluid.
Filtration is essential in the mammalian kidney as it controls what molecules enter the nephron
as well as regulating glomerular fluid composition.


Reabsorption in the mammalian nephron regulates body fluid composition in the following
ways:
   -    Essential molecules in the filtrate are reabsorbed in the blood in the proximal and distal
        tubules. (Glucose, amino acids, salts and water.)
   -    Toxins are absorbed from the blood and secreted.
   -    Maintains a constant concentration of essential metabolites.
Reabsorption is essential in the mammalian kidney as essential metabolites are reabsorbed
back into the blood stream. If this did not occur large portions of these metabolites would be
secreted leaving the body unbalanced. Reabosrption maintains homeostasis within the kidney
reabsorbing nutrients from the filtrate and secreting toxins.


Outline the role of the hormones, aldosterone and ADH (anti-diuretic hormone) in the
regulation of water and salt levels in blood.


Things to consider:
   -    What does outline mean?
   -    Know and understand the difference between aldosterone and ADH.
   -    Relate these hormones to salt and water.


             ALDOSTERONE                            ADH (Anti – Diuretic Hormone)
       Aldosterone is one mechanism           ADH prevents water from being lost in the urine.
        that controls glomerular blood          (Diuresis)
        pressure.                              Its function is to make the collecting ducts more
       Aldosterone is found in the             permeable so that water can be reabsorbed back
        adrenal cortex, above the               into the blood and body tissues.
        kidney.                                ADH is released by the hypothalamus (brain.)
       The primary function of                Receptors in hypothalamus detect lowered water
       aldosterone is to regulate the          levels in the blood.
       salt levels in the blood. This is      ADH is then released.
       done by increasing the                 ADH then targets the collecting ducts.
       reabsorption of sodium ions in         Collecting ducts become more permeable.
       the loop of henle and the distal       Water retention is increased.
       tubule.                                When there is too much water, or low solute
      This therefore regulates the            concentrations water needs to be excreted.
       concentration of sodium in the          Therefore less ADH is released.
       blood and body fluids.
      Sodium ions enter the blood at
       the distal tubule. Water then
       follows by the process of
       osmosis. Water and sodium
       increase blood volume and
       therefore blood pressure.
      Aldosterone conserves sodium
       ions.
      Maintains blood pressure.
      This process enables for
       glomerular filtration to function
       efficiently.




Define enantiostasis as the maintenance of metabolic and physiological functions in response
to variations in the environment and discuss its importance to estuarine organisms in
maintaining appropriate salt concentrations.


Things to consider:
   -   What does define mean?
   -   What does discuss mean?
   -   Underline key words
   -   Split the question into two separate parts. One for definition the other for discussion.


Enantiostasis is the maintenance of metabolic and physiological functions in response to
variations in the environment. (Aubusson et al 2004) Enantiostasis is important for estuarine
organisms in order to maintain appropriate salt level concentrations as their surrounding
environment constantly varies in its salt and water concentration.
Marine fish and fresh - water fish are constantly maintaining their internal environment
according to their external environment. Marine fish drink large amounts of water and excrete
small amounts of concentrated urine. Fresh – water fish gain large amounts of water so they
excrete copious amounts of dilute urine and absorb salts across the gills. As both marine and
fresh – water fish regulate salt and water between their internal and external environments
they are known as osmoregulators, meaning their internal environment differs to that of their
external environment.


Another group of fish called the osmoconformers maintain their internal fluids at
approximately the same concentration as their external environment.


In an estuarine environment the concentration of salt and water is constantly changing due to
the changing of the tides. However many organisms whom live in this estuarine environment
survive. These organisms are able to tolerate a range of salt concentrations. Crabs and sharks
are osmoconformers who can tolerate large changes in salt concentrations. This is due to the
fact that they use a small organic molecule to vary the concentrations in their cells to match
the environment. Therefore it is important for osmoregulators and osmoconformers to
maintain appropriate salt concentrations within their body as it maintains metabolic function.


Describe adaptations of a range of terrestrial Australian plants that assist in minimising water
loss.


Things to consider:
   -     What does describe mean?
   -     Underline key words
   -     Understand what the question is asking before you write an answer.


AUSTRALIAN PLANT                                      ADAPTATION
Banksia                  A range of banksias contain woody fruits. These woody fruits are fire
                         resistant enabling the banksia to survive tough dry seasons. The fruit is
                         not fleshy which also enables the banksia to reduce water loss.
Hakeas                   The hakea has an unusual adaptation in that it has sunken stomates.
                         The stomates allow humid air to be concentrated above the stomate in
                         turn reducing water loss.
Baobab                   The baobab tree has a unique storage system. A baobab will store a
                         large proportion of its water in the trunk, and sometimes the leaves.
                         This allows conservation of water.
Eucalypt   Eucalypts have a variety of adaptations one of them being vertically
           hanging leaves. This allows the leaf to reduce its exposure to the sun
           and hence reducing water loss.
Mulga                   The mulgas structure is unique as the stems and leaves are shaped in
                        such a way that water runs down their surface towards the root of the
                        plant, therefore optimising water consumption.


Perform a first-hand investigation of the structure of a mammalian kidney by dissection, use of
a model or visual resource and identify the regions involved in the excretion of waste
products.
Things to consider:
   -    What does identify mean?
   -    Underline key words that inform what your answer should require.
   -    Reference p. 77-78




Renal Medulla – Contains thousands of filtration units called nephrons.
Renal Cortex – Outer protective layer of the kidney.
Calyces – Individual tubing that connects to every medulla. The word calyces refers to the
opening (hole) of the tube.
Ureter – The tube that collects all the urine and passes the urine to the urinary bladder.
Gather, process and analyse information from secondary sources to compare the process of
renal dialysis with the function of the kidney.


Things to consider:
   -   What does gather, process, analyse and compare mean?
   -   Be succinct
   -   Ensure you know what dialysis is.


                 RENAL DIALYSIS                        MAMMALIAN KIDNEY
      Patients blood is past through a           Blood is filtered through millions of
       tube.                                       nephrons.
      This tube is separated from the            Nephrons contain membrane which
       dialysis tubing by a semi-permeable         is permeable to essential and non-
       membrane.                                   essential wastes.
      The dialysis tubing contains               Concentrations of essential
       molecules and ions that are essential       molecules vary from person to
       for the human body at the right             person. Essential molecules are either
       concentration. Therefore only wastes        passively or actively transported in or
       such as urea pass through the               out of the nephron at the proximal
       membrane into the dialysis tubing.          tubule, the distal tubule and the
       No reabsorption.                            loop of henle. Wastes pass through
      ONLY filtration occurs in dialysis.         the nephron into the collecting duct
      Process takes 4 – 6 hours.                  and eventually into the bladder.
      Wastes are removed, dialysis fluid is      Filtration and reabsorption occur in
       discarded and blood which has been          the kidney
       filtered returns to the body through       Process varies in time depending on
       a vein.                                     the need for nutrients or for the
                                                   removal of waste.
                                                  Waste is removed in the form of
                                                   urine. Filtered blood is returned to
                                                   the body via the renal vein.
Present information to outline the general use of hormone replacement therapy in people
who cannot secrete aldosterone.


Things to consider:
   -   What does present mean?
   -   What does outline mean?
   -   Underline key words?
   -   What is the question asking?


People who do not secrete or secrete insufficient amounts of the hormone aldosterone usually
suffer from the disease known as Addison‟s disease. Addison‟s disease is an inability of the
adrenal cortex to secrete sufficient amounts of hormone, in this case aldosterone.


People who can not secrete aldosterone in sufficient amounts undergo hormone replacement
therapy. The purpose of this therapy is to replace the hormone aldosterone. This is performed
by the patient who takes a mineralocorticoid known as fludrocortisones (Florinef) orally once a
day. People who suffer from Addison‟s disease are also encouraged by their doctor to increase
their salt intake.


If a patient has an Addisonian crisis, which can be life threatening, the patient is administered
with hydrocortisone injections, saline solution and dextrose. Usually the patient recovers and is
returned to their usual therapy which is fludrocortisones tablets.
Therefore it is important for patients who suffer from aldosterone secretion inefficiency to
partake in hormone replacement therapy.


Analyse information from secondary sources to compare and explain the differences in urine
concentration of terrestrial mammals, marine fish and freshwater fish.


Things to consider:
   -   What does analyse mean?
   -   What does compare and explain mean?
   -   What would be a good way to present this information?


       ORGANISM            URINE CONCENTRATION                        EXPLANATION
                          (CONCENTRATED/DILUTE)
Terrestrial Mammal        Concentrated                   A terrestrial mammal‟s urine is usually
                                 concentrated. This is due to the lack of
                                 water in its surrounding environment. This
                                 in turn causes the mammal to secrete
                                 concentrated amounts of urine and
                                 maintain a water and salt balance.
Marine Fish       Concentrated   A saltwater fish continually drinks water to
                                 avoid water loss from its body. The water
                                 is absorbed into their body while the salt
                                 is actively secreted by the gills and the
                                 kidneys. This results in the fish secreting
                                 concentrated amounts of urine. Therefore
                                 maintaining its water.
Freshwater Fish   Dilute         A fresh – water fish always excretes
                                 copious amounts of dilute urine. This is
                                 due to their surrounding environment.
                                 (Large amounts of fresh water) This
                                 causes their urine to be extremely dilute.
Use available evidence to explain the relationship between the conservation of water and the
production and excretion of concentrated nitrogenous wastes in a range of Australian insects
and terrestrial mammals.


Things to consider:
   -   What does explain mean?
   -   Underline key words?
   -   Be succinct. Understand what the question is asking so that you can answer the
       question correctly


ORGANISM              TYPE OF                     HOW THIS CONSERVES WATER
                NITROGENOUS
                      WASTE
Grasshopper   Uric Acid which is a    Grasshoppers contain tube like extensions in their digestive
              paste like substance.   system called Malphigian tubes. Wastes and salts diffuse
              Organisms which         into these tubes and are followed by water through
              excrete uric acid are   osmosis. The tubes increase the surface area for the
              called uricotelic       transport of wastes into the digestive system. By the time
              organisms. e.g.         the nitrogenous waste gets to the rectum most of the
              Insects and birds.      water and other important solutes have been returned to
                                      the blood. Products that are no longer needed by the
                                      insect are excreted in a dry paste form known as uric acid.
                                      This adaptation has led to the survival of the species within
                                      Australia‟s harsh arid conditions.
Kangaroo      Main type of            Ammonia and other complex molecules are initially broken
              nitrogenous waste is    down in the liver into simpler substances, in this case urea.
              urea in the form of     Urea is then transported to the kidney to be filtered. The
              urine. Organisms        kangaroo‟s kidneys are unique as they enable the excretion
              that mainly excrete     of concentrated urine and the reabsorption of water. This
              urine are known as      in turn conserves water for the kangaroo. This adaptation
              ureotelic. e.g. Most    has led to the survival of the species within Australia‟s
              mammals.                harsh arid conditions.
Other information:
      Fish excrete ammonia.
      Due to their surrounding environment the ammonia is easily broken down.
      These organisms are known as ammonotelic.
Process and analyse information from secondary sources and use available evidence to discuss
processes used by different plants for salt regulation in saline environments.
Things to consider:
   -   What does process mean?
   -   What does analyse mean?
   -   What does discuss mean?
   -   Read and re-read the question until you understand what the question is asking.


Mangroves play an important role in the life of an estuary. The majority of Australian waters
contain mangroves. These mangroves are well adapted to survive within their ecosystem. This
is due to many ingenious adaptations which enable the different species of mangroves to
cope with varying salt and oxygen levels. All mangroves have adapted for the lack of oxygen
within the soil. You may have seen the small protruding stumps that surround mangroves.
These are called pneumatophores and their role is to absorb oxygen from the air. Mangroves
in general have also adapted to the range in salt levels within their environment. The following
are some different species of mangroves and their processes used for salt regulation:
The Grey Mangrove: The Grey mangrove (Avicennia marina) has special tissues in their roots
and lower stems which prevent the uptake of salt but increase the uptake of water. This
process is known as exclusion as the grey mangrove excludes the uptake of salt.
The River Mangrove: The River mangrove (Aegiceras corniculatum) is able to concentrate and
excrete salt through special glands on the leaves. The salt then begins to build up on the
outside of the leaf where it washed off the leaf during periods of rain. This process is known
as secretion as the river mangrove secretes the salt out of their leaves.
The Milky Mangrove: The Milky mangrove (Excoecaria) accumulates salt in older tissues such
as leaves, which is then discarded. This process of salt regulation is known as accumulation
and it enables the Milky mangrove to accumulate large amounts of salts and then discard the
large amounts of salts therefore maintaining a healthy level of salt.




Perform a first-hand investigation to gather information about structures in plants that assist
in the conservation of water.


Things to consider:
   -   What does perform mean?
   -   What does gather mean?
   -   Ensure you draw/outline the structures in plants that assist in the conservation of water.


      State an aim for this experiment.
      Copy out the materials and method on page 101 of the text book.
      Answer questions 1 – 3 on page 101 of the text book.
      Ensure you can identify and describe different adaptations in Australian plants that
       enable the conservation of water, for example the shape of eucalypt leaves and the way
       they hang.
      If you are unsure of certain adaptations refer to p. 97 - 100 of the text book.

								
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