Download maintaining a balance

MAINTAINING A BALANCE
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. 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. If the temperature drops below 55 degrees 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
ECTOTHERM
ENDOTHERM
Frilled Neck
Lizard
Kangaroos
RESPONSE TO
CHANGE IN
AMBIENT
TEMPERATURE
Flatten or narrow
body shape.
(Sunbaking)
EXPLANATION OF CONTROL
Frilled neck lizards will flatten their body
to absorb as much sun as possible in order
to increase their body 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
surface area.
Access areas of
cooler ambient
temperature
(Shade/burrows.)
Frilled neck lizards move into shades or
burrows to cool 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 water loss which is
beneficial to the lizard.
Dormant states of
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 have a relatively large surface
area. This larger surface area enables the
kangaroo to maintain and lose body heat
during periods of high temperatures.
Surface area to
volume ratio.
Changing patterns
in blood flow.
Kangaroos have a dense network of blood
vessels 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
evaporation of
water.
Kangaroos cool themselves by sweating.
This evaporation of the water cools the
organism down. However in times 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 274 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 274 – 275 of the textbook.
RESULTS:
 Ensure that you have a table of results
 Construct a graph of your results and answer the following questions.
QUESTIONS:
- From your results which temperature clotted the quickest?
- From your results which temperature clotted the slowest?
- From your results what relationships can you describe between temperature
change and enzyme activity. Include possible reasons as to why 10 degrees
and 80 degrees did no clot as well as the phrases, “optimum temperature” and
“denaturation.”
- What was the purpose of test tube “B?”
- Write down ONE safe working practice you used throughout this experiment.
- Write a conclusion. (Did your experiment answer your aim?)
WRITE UP PART B: EFFECT OF pH ON ENZYME ACTIVITY (Pg 275 – 276). 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 page 275 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 275 – 276 of the textbook.
RESULTS:
 Ensure that you have a table of results
 Construct a graph of your results and answer questions 1 – 3 on page 276.
WRITE UP PART C: EFFECT OF SUBSTRATE CONCENTRATION ON
ENZYME ACTIVITY (Pg 276 – 277). 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 page 276 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 276 – 277 of the textbook.
RESULTS:
 Ensure that you have a table of results
 Construct a graph of your results and answer questions 1 – 3 on page 277.
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%2
0-%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
Pygmy
Possum
Red
Kangaroo
Blue Tongue
Lizard
ECTOTHERM ADAPTATION DESCRIPTION AND
or
RESPONSE
ENDOTHERM
Endotherm
Fur
The pygmy possum is covered
in dense fur. 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.
Endotherm
Dense network
The dense network of blood
of blood vessels vessels in the kangaroo’s
in forearms.
forearms are an adaptation to
(Blood flow)
the hot dry conditions they
experience in Australia. The
blood vessels allow the red
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.
Ectotherm
Sun baking
The blue tongue lizard will
generally sun 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
VESSEL
ARTERIES
STRUCTURE/FUNCTION
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.
DIAGRAM
VEINS
CAPILLARIES
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 back
flow of blood, veins have
many valves. Valves open and
close according to the blood
flow. Blood continually flows
in veins due to the contraction
of surrounding muscles. These
contractions also promote the
opening and closing of valves.
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.
CONNECTIVE TISSUE
ELASTICFIBRES/SMOOTH
MUSCLE
ENDOTHELIAL LAYER
NOTE THE VALVE
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 PAGES 277 – 278)
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 PART A 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:
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.
(Part A)
Distilled water and
universal indicator.
(Part B)
Figure 1: Limewater turns milky due a chemical reaction with carbon dioxide.
TASK 2:
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.
PART A PROVES WHETHER OR NOT THE CHEMICAL REACTIONS YOU
ARE PERFORMING CONTAIN CARBON DIOXIDE. THIS THEREFORE
ENSURES THAT YOUR EXPERIMENT IS ACCURATE.
PART B: Ensure you complete BOTH tasks.
TASK 1:
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.
TASK 2:
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:
TASK 1:
pH
0
7
0:30
7
1:00
6
TIME (minutes/seconds)
1:30 2:00 2:30 3:00 3:30
6
5
5
5
5
4:00
5
4:30
5
5:00
5
1:00
6
TIME (minutes/seconds)
1:30 2:00 2:30 3:00 3:30
6
6
5
5
5
4:00
5
4:30
5
5:00
5
TASK 2:
pH
0
7
0:30
7
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: Page 278 of the text book.
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 278 – 279 of the text book.



To perform this experiment accurately you need to refer to the method on page
278 – 279 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 micrometers (µm) and white blood cells vary from 6 – 12
micrometers (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 WHERE IT IS USED
 Invasive technique. (Goes inside
the body)
 Takes small samples of arterial
blood.
 The analyser measures the oxygen
using two electrodes.
 Oxygen diffuses through a
membrane between the two
electrodes.
 This produces a small electric
current.
 This current is proportional to the
amount of oxygen. E.G. certain
values equal certain amounts of
oxygen.
 Carbon dioxide levels are also
measured by placing the blood
specimen in one chamber and the
other chamber a hydrogen
electrode.
 Dissolved carbon dioxide diffuses
into the hydrogen ion chamber.
The pH is then measured. The
hydrogen ion concentration is
proportional to carbon dioxide
levels. E.G. certain values equal
certain amounts of carbon
dioxide.
 Alternatively instead of taking a
blood sample an arterial probe,
which is inserted into the body,
may take these measurements.
PULSE OXIMETER and
CONDITIONS WHERE IT IS USED
 The pulse oximeter is a non –
invasive technique which
measures the concentration of
oxygen in the body.
 The device is either attached to
the finger or ear lobe of the
patient, which measures oxygen
saturation with haemoglobin and
pulse rate.
 The oximeter works in the
following way: a light source
passes through the blood.
Different amounts of light are
absorbed depending on the degree
of saturation of oxygen to
haemoglobin. A processor then
calculates the light absorption rate
and converts this to saturation of
haemoglobin.
 Oximeters are used in many
hospital situations even though
they do not measure carbon
dioxide levels.
 They are used as monitoring units
during anaesthesia.
 They are very efficient because
they can be used during surgery or
after surgery to monitor oxygen
saturation, pulse rate and blood
flow.
 Oximeters can be used in the
success of ventilation procedures,

Blood gas analysers are
commonly used in intensive care
units especially baby care units
and labour wards. This is due to
the fact that slight changes in
carbon dioxide levels can affect
the development of newly born
babies. Excess carbon dioxide and
poor oxygen saturation levels can
have detrimental affects on the
child. The analyser is used as a
measuring tool to ensure the
patient is looked after and if
oxygen/carbon dioxide levels
change a nurse/doctor can take
necessary action to return
oxygen/carbon dioxide levels to
their optimum values.


to see if the administration of
oxygen is successful for the
patient.
Oximeters can also be used in
intensive care units or after
surgery to monitor unconscious
patients and to notify
nurses/doctors of any changes in
oxygen levels.
Therefore oximeters are an
efficient monitoring system for
oxygen, pulse and blood flow
levels.
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
Whole Blood
Red Blood Cells
White Blood Cells
Plasma
Platelets
Cryoprecipitate
(contains blood
clotting factors)
Prothrombinex –
HTTM (contains
concentrated clotting
factors.)
Biostate (contains
factor VIII clotting
factor)
Monofix® - VF
(contains Christmas
factor)
Thrombotrol® - VF
Albumin
Intagram® P
Hyper – immune
globulins (contain –
antibodies)
USE/TREATMENT
To replace large amounts of blood from sever injury.
Given to patients suffering from anaemia, (iron deficiency in
the blood) and in cases of severe bleeding.
Given to patients with a low white blood cell count or in cases
of severe bacterial infection.
Given to patients after trauma, or following after a surgical
procedure.
Given to patients with severe haemorrhaging (bleeding) or
bleeding due to diseases such as leukemia.
Given to patients suffering from haemophilia A. Alternatively
severe bleeding.
Given to patients with specific bleeding disorders. These
specific disorders pertain to patients who are missing certain
clotting factors.
Given to patients with haemophilia B.
Given to patients with haemophilia B
Given to patients in situations whereby their blood is clotting
too quickly.
Administered to patients who are suffering from burns, shock
due to blood loss and kidney/liver diseases.
Given to patients who suffer from immune disorders such as
AIDS, this in turn reduces susceptibility to infections.
Given to patients to treat and/or prevent specific infections
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 firsthand 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
279 of your textbook; titled: Investigation 4 – Microscope Examination of
Phloem and Xylem.
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
last years 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 and
4. Brain associated problems.
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
FISH


MAMMALS


ROLE OF THE KIDNEY
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.
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
The net movement of substances that
does not require any cellular energy.
Movement of substances is from high
concentration to low concentration.
ACTIVE TRANSPORT
The net movement of substance requires
cellular energy to be expended.
Movement of substances is against the
gradient meaning movement is from a
low concentration to a high
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
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
Aldosterone is one mechanism
that controls glomerular blood
pressure.
Aldosterone is found in the
adrenal cortex, above the kidney.
The primary function of
aldosterone is to regulate the salt
levels in the blood. This is done
by increasing the reabsorption of
ADH (Anti – Diuretic Hormone)
 ADH prevents water from being
lost in the urine. (Diuresis)
 Its function is to make the
collecting ducts more permeable
so that water can be reabsorbed
back into the blood and body
tissues.
 ADH is released by the
hypothalamus (brain.)





sodium ions in the loop of henle
and the distal tubule.
This therefore regulates the
concentration of sodium in the
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.






Receptors in hypothalamus detect
lowered water levels in the blood.
ADH is then released.
ADH then targets the collecting
ducts.
Collecting ducts become more
permeable.
Water retention is increased.
When there is too much water, or
low solute concentrations water
needs to be excreted. Therefore
less ADH is released.
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
Banksia
Hakeas
Baobab
Eucalypt
Mulga
ADAPTATION
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.
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.
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.
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.
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 279 – 280
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.
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RENAL DIALYSIS
Patients blood is past through a
tube.
This tube is separated from the
dialysis tubing by a semipermeable membrane.
The dialysis tubing contains
molecules and ions that are
essential for the human body at
the right concentration. Therefore
only wastes such as urea pass
through the membrane into the
dialysis tubing. No reabsorption.
ONLY filtration occurs in
dialysis.
Process takes 4 – 6 hours.
Wastes are removed, dialysis fluid
is discarded and blood which has
been filtered returns to the body
through a vein.
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MAMMALIAN KIDNEY
Blood is filtered through millions
of nephrons.
Nephrons contain membrane
which is permeable to essential
and non-essential wastes.
Concentrations of essential
molecules vary from person to
person. Essential molecules are
either passively or actively
transported in or out of the
nephron at the proximal tubule,
the distal tubule and the loop of
henle. Wastes pass through the
nephron into the collecting duct
and eventually into the bladder.
Filtration and reabsorption occur
in the kidney
Process varies in time depending
on 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
Terrestrial Mammal
Marine Fish
Freshwater Fish
URINE CONCENTRATION
EXPLANATION
(CONCENTRATED/DILUTE)
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.
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.
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
Grasshopper
Kangaroo
TYPE OF
NITROGENOUS
WASTE
Uric Acid which is a
paste like substance.
Organisms which
excrete uric acid are
called uricotelic
organisms. E.G.
Insects and birds.
Main type of
nitrogenous waste is
urea in the form of
urine. Organisms that
mainly excrete urine
are known as
ureotelic. E.G. Most
mammals.
HOW THIS CONSERVES WATER
Grasshoppers contain tube like extensions in
their digestive system called Malphigian
tubes. Wastes and salts diffuse into these
tubes and are followed by water through
osmosis. The tubes increase the surface area
for the transport of wastes into the digestive
system. By the time the nitrogenous waste
gets to the rectum most of the 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.
Ammonia and other complex molecules are
initially broken down in the liver into simpler
substances, in this case urea. Urea is then
transported to the kidney to be filtered. The
kangaroo’s kidneys are unique as they enable
the excretion of concentrated urine and the
reabsorption of water. This in turn conserves
water for the kangaroo. This adaptation has
led to the survival of the species within
Australia’s 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.
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State an aim for this experiment.
Copy out the materials and method on page 280 of the text book.
Answer questions 1 – 3 on page 280 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 table 5.15.1 on page 270 of the
text book.