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HSC Biology
Module 1 - Maintaining A Balance
Focus 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.
Enzymes:
• Biological catalysts.
- Provide a site for the reaction to take place.
- Reduce the amount of energy required to initiate a reaction.
- Influence the rate at which forward & reverse reactions reach
equilibrium.
- Not consumed in the reaction.
- Required in minute amounts only.
•
Structure & composition.
- 3D protein structure.
- Constructed of AAs.
- 20 different AAs make up proteins & enzymes in organisms.
- Have an active site.
- Specific to substrate.
- Site where reaction takes place.
- May be:
- Elongated (straight chained polypeptide).
- Spherical (coiled polypeptide).
- Many enzymes require the assistance of other chemicals.
- Not made of proteins.
- Coenzymes.
- Organic molecules (vitamins).
- Cofactors.
- Metallic ions (Fe2+, Ca2+, Mg2+, Zn2+, Cu2+, K+).
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•
Location.
- Intracellular (used within the cells that produce them.
- eg. photosynthesis enzymes.
- Extracellular (act outside cells that produce them.
- eg. digestive enzymes.
•
Enzymes & Their Substrates.
- Substrate:
- The compound on which an enzyme acts.
- Ananbolic reaction = bond molecules / substances.
- Catabolic reaction = split molecules / substances.
- Enzymes are highly specific the substrate they catalyse.
- Shape of active site is designed to fit only 1 molecule.
- Models for enzyme-substrate complexes:
- Lock & key model:
- Substrate fits exactly into active site, no modifications.
- Induced fit model:
- Enzyme makes slight adjustments to fit substrate.
- Poisons (cyanide, arsenic) block the active site, preventing the
substrate from joining. Inhibit a reaction.
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Identify the pH as a way of describing the acidity of a
substance.
pH:
•
A measure of the [H+] in 1 litre of a solution.
- A scale used to describe the acidity or basicity of a substance.
- Ranges from 0 (highly acidic) to 14 (highly basic).
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Explain why the maintenance of a constant internal environment
is important for optimal metabolic efficiency.
A Constant Environment:
• Enzymes work most efficiently under optimal conditions.
- For optimal conditions to occur, organisms control:
- Body temperature.
- Concentration of dissolved substances (nutrients & wastes).
- Concentration of foods (BGL).
- Absorption & removal of water.
- Quantities of nitrogenous waste.
- Removal of malfunctioning cells / foreign bodies.
•
Mammals have the highest degree of maintenance.
- Living process controlled by:
- Nervous system.
- Endocrine system.
- Metabolic processes controlled by enzymes:
- Enzymes work optimally in an environment where optimum
conditions are met.
- Temperature.
- pH.
- Enzyme concentration.
- Substrate concentration.
- Presence of cofactors & coenzymes.
•
Enzymes coordinate all processes in organisms.
- Therefore it is important that they function at their optimal level.
- If the conditions are not met they
may be;
- Denatured.
- Active site destroyed.
- Reduced activity.
- Reaction not initiated.
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Describe homeostasis as the process by which organisms maintain
a relatively stable internal environment.
Homeostasis:
• The process by which an organism maintains a constant internal
environment, despite changes to the external environment.
•
Homeostasis allows for the optimum conditions of enzymes to be met.
- Internal conditions are maintained through negative feedback
systems.
- Monitor environment, counteract changes.
- Feedback systems are a self regulating mechanism that maintains
homeostasis (a balance).
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Explain the homeostasis consists of two stages:
o Detecting changes from the stable state.
o Counteracting changes from the stable states.
•
If homeostasis is to be maintained; the body must be able to detect stimuli
that indicate a change in internal / external environment.
Stage 1:
• Receptors in body tissues detect changes in the environment (internal &
external).
- Mechanoreceptors.
- Photoreceptors.
- Chemoreceptors.
- Thermoreceptors.
•
Messages sent along neurones (nerve cells) as an electrochemical impulse.
- Brain receives & interprets message.
•
Receptors detect a change in the variable.
Stage 2:
• Brain responds to message by sending a nervous message to an effector to
counteract the changes in the environment.
- Effectors counteract the change (muscle / gland).
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Outline the role of the nervous system in detecting & responding
to environmental changes.
The Role of The Nervous System:
• Detect changes in the internal / external environment & counteract them.
• Rapid coordination of the internal organ system.
Structure of The Nervous System:
• The nervous control system consists of the brain, spine & all other nerve cells
throughout the body.
•
The central nervous system:
- Brain & spinal chord.
- Thalamus receives impulses from sensory neurones, directs them to
parts of the brain.
- Hypothalamus regulates release of hormones responsible for
controlling many variables (major role in maintaining homeostasis).
•
The Peripheral nervous system:
- All nerve cells that lie outside of the brain & spine.
- Consists of the afferent (sensory) & efferent (motor) divisions.
- The afferent (sensory) division:
- Monitors & informs the CNS of changes to the internal & external
environment.
- 2 types of neurones carry information.
- Somatic sensory neurones (external environment).
- Visceral sensory neurones (internal environment).
- The efferent (motor) division:
- Transmits information away from the CNS to muscles & glands
(effector organs).
- 2 systems of the efferent division.
- Somatic nervous system; signals to the voluntary nervous system
(skeletal muscle).
- Autonomic nervous system: signals to the involuntary nervous
system (smooth muscle, heart muscle & glands).
- Consists of sympathetic & parasympathetic nervous systems.
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• Nerve cells (neurones):
- Basic units of the nervous system.
- Consist of:
- Cell body (contains nucleus).
- Axon (carries info away from the cell body to another neurone).
- Group of bound axons = a nerve.
- Connecting & effector neurones have dendrites (finger-like
projections which receive info).
- 3 kinds of neurones.
- Affector neurones; receptors detect change. Impulse transmitted to
CNS.
- Effector neurones; impulses transmitted away from CNS (to
effectors, causing a response).
- Connecting neurones; located in CNS, connect affector neurones to
effector neurones.
•
Hormones (chemical regulators).
- The endocrine system (hormonal system).
- Works with the nervous system as a major controlling system.
- Hormones; chemicals produced in endocrine glands.
- Transported in bloodstream.
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Identify the broad range of temperatures over which life is
found compared with the narrow limits for individual species.
Temperature Range:
• Organisms on Earth faced with a large range of ambient temperatures.
- From -700C to 1200C.
- Most forms of life can exist between 400C & 1200C.
- Individual organisms can’t withstand temperatures across the whole
range.
- Most live in a narrow range.
•
They must be equipped to withstand daily & seasonal changes.
- Especially land organisms.
- Temperatures on the land vary much more than those in the sea.
•
Some species of Archaea can live outside the range.
- Live in glaciers, volcanoes, hot springs & mid-ocean ridges.
•
Most mammals live in environments between 00C & 450C
- With normal levels of activity between 300C & 450C.
- Human technology allows us to build structures which broaden the
range of temperature we can tolerate.
- eg. Air conditioning, thermal suits, blankets, etc...
Reasons:
• Enzyme activity:
- Above 450C enzymes may become denatured.
- Below 00C enzyme activity reduced.
•
Cell structure:
- Ice crystals may form in cells, causing tissue damage.
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Compare responses of named Australian ectothermic & endothermic
organisms to changes in the ambient temperature & explain how
these responses assist in temperature regulation.
Ectotherms:
• Ectothermic:
- Animals that can’t maintain a constant core body temperature.
- Metabolism & level of activity affected by the temperature of the
environment.
- Low temperature = low metabolic rate = low activity.
- Most animals are ectothermic.
- eg. Reptiles.
•
•
Eg. Magnetic termites.
- Pack walls of their mounds with insulating wood pulp.
- Align mounds north-south to maximise sun exposure in mornings
& evenings, minimise heat during the day.
Eg. Bogong moths.
- Avoid cells freezing by supercooling tissues.
- Reduce temperature of body fluids below usual freezing point to
avoid ice crystals forming & destroying cells.
Endotherms:
• Endothermic:
- Animals that can maintain a constant core body temperature.
- Core temperature controlled by metabolic processes, adaptive
physiology & behavioural mechanisms.
- Control the rate of heat exchange with surroundings.
- More energy required; far more food consumed. (5x more than
reptiles).
- The release of Thyroxine from the thyroid increases metabolic rate.
- Can remain active & keep constant body temperature under a wide
variety of environment temperatures.
- Allows for a broader distribution.
- eg. Mammals & birds.
•
•
Eg. Red kangaroo.
- Licks inside of paws where skin is thinner & blood is closer to the
surface. Heat easily evaporated off.
Eg. Rabbit eared bandicoot.
- Large ears provide a large surface area to pass excess heat
when burrowing.
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Identify some responses of plants to temperature change.
Plant Enzymes:
• Enzymes in plants have same characteristics to those in animals.
- Have optimum temperature at which maximal efficiency occurs.
•
Plants tend to maintain temperature in optimal range for optimal metabolic
activity to occur & to minimise damage.
•
Optimal temperature is also required for germination of seeds & growth.
Responses To Change:
Hot
Radiation:
- Plant radiates heat to surrounding
objects.
Transpiration:
- Heat within the plant is used to
evaporate water off the surface of
cells.
- Water mainly exits through the
stomata.
Convection:
- Air around plant becomes heated.
- Heated air is less dense, rises away
from plant. Takes heat with it.
Leaf shape:
- Thinnest where 2 surfaces come
together, lose most heat from this
section.
Heat shock proteins:
- Produce these @ 400C. Protect
enzymes & other proteins from
denaturing.
Leaf orientation:
- Drooping leaves to minimise surface
exposure to sun (parallel to light rays).
Structure:
- Trunks used to store water.
- Deciduous (drop leaves in summer).
- No stomata, less surface area to
lose water / absorb heat.
Leaf fall:
Cold
- Plants can’t produce an ‘anti freeze’
like animals can.
- Gradually become resistant to low
temperatures.
- Ions within plant cells prevent ice
crystals from forming within them.
- Cytosol (fluid inside cell, consists of
water & ions) has lower freezing
point than water.
- Instead, crystals form outside cells.
- Because ice has formed outside cell,
concentration of water is higher inside
than out.
- Water moves from inside cell to
outside cell.
- Freezing point inside cell further
reduced.
- Ice crystals continue to grow
outside cells. Pliable cell membrane
prevents damage.
- If the temperature drop is extreme,
crystals will form within the cells,
causing them damage.
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- Rate of leaf fall changes throughout
seasons.
Plants may die:
- Leave dormant seeds / roots under
ground.
Alter growth rate:
- Plants change growth rate to
conserve water.
Leaf surface:
- Shiny / waxy cuticles reflect light rays
& prevent water escaping.
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Identify data sources, plan, choose equipment or resources &
perform a first-hand investigation to test the effect of:
o Increased temperature.
o Change in pH.
o Change in substrate concentration.
On the activity of named enzyme(s).
Increased Temperature:
Aim:
To investigate the effect of increased temperature on the activity of an enzyme.
Hypothesis:
The enzyme in the water that is closest to that of the range of the body’s core
temperature will act the fastest. Water that is above the optimal temperature of the
enzyme will destroy its active site, causing it to be denatured. If the temperature is
below the optimal temperature its activity will be reduced as there is not enough energy
to activate the reaction.
Equipment:
- Distilled water.
- 3x junket tablets.
- 6x test tubes.
- 3x beakers.
- Milk.
- Bunsen burner.
- Beaker.
- Tripod.
- Ice.
- 10mL measuring cylinder.
- Celsius thermometer.
- Timer.
Method:
- Make a rennin solution by dissolving a junket tablet in distilled water.
- Add 5mL of milk to each test tube.
- Place 2 test tubes in a water bath at 35-400C.
- Place 2 test tubes in a water bath below 40C.
- Place 2 test tubes in a water bath at 750C.
- Once milk temperatures have stabilised, add 3 drops of rennin solution to one
of each pair of test tubes.
- Record time taken for enzymes to coagulate milk.
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Results:
Temp0C Range
0-50C
35-400C
75- 800C
N/A
N/A
N/A
Time For Milk To Set
Control
Enzyme
N/A
15 mins
N/A
Conclusion:
Enzymes will only function at their optimum temperature. High temperatures will
denature the proteins in an enzyme, while cold temperatures will only reduce their
activity.
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Change in pH:
Aim:
To investigate the effect of changing pH on the activity of an enzyme.
Hypothesis:
The enzyme in acidic conditions will function most efficiently as it simulates the
environment in the body where the enzyme is active. The solutions that are neutral &
acidic will denature the enzyme as its active site will be destroyed.
Equipment:
- 6x test tubes.
- 3x beakers.
- Distilled water.
- Acetic acid.
- Sodium bicarbonate.
- 3x junket tablets.
- Celsius thermometer.
- Timer.
- Water at 35-400C.
- 10mL measuring cylinder.
- 60mL milk.
Method:
- Make rennin solution by dissolving a junket tablet in distilled water.
- Prepare a water bath at 35-400C.
- Use measuring cylinder to add 10mL milk to each test tube.
- Place test tubes in water baths, allow temperature to stabilise.
- Add acetic acid to 2 test tubes.
- Add sodium bicarbonate to 2 test tubes.
- Add 3 drops of rennin solution to a test tube with acid, base & neutral pH.
- Record time taken for milk to coagulate.
Results:
pH
3
7
9
Time (Control) (sec)
-
Time (Enzyme) (sec)
40
420
-
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Discussion:
The results yielded support the hypothesis. The acidic solution was the quickest to
coagulate. This is because the acidic conditions simulated those found in the stomach
where rennin metabolises milk. The rennin was active in the neutral solution, though its
rate was greatly reduced.
Conclusion:
Rennin functions most efficiently in an acidic environment while its efficiency is greatly
reduced in a neutral environment. Rennin is not active in a basic environment.
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Changing Substrate Concentrations:
Aim:
To investigate the effect of changing substrate concentrations on the action of an
enzyme.
Hypothesis:
The solution with the lowest concentration of milk will coagulate the fastest because
there is a lesser amount of protein per volume to act on. Higher concentrations of
protein will take longer to act on.
Equipment:
- 7x test tubes.
- 1x beaker.
- Distilled water.
- Powdered milk.
- Junket tablets.
- Celsius thermometer.
- Timer.
- Milk.
Method:
- Make different solutions of with different concentrations of substrate by diluting
milk with distilled water or by using powdered milk.
- 5mL milk.
- 3mL milk, 2mL water.
- 2mL milk, 3mL water.
- 1mL milk, 4mL water.
- ¼ tsp powder, 5mL milk.
- ½ tsp powder, 5mL milk.
- ¾ tsp powder, 5mL milk.
- Place each test tube in a water bath at 35-400C, allow temperatures to stabilise.
- Add 3 drops of rennin to each test tube.
- Record amount of time taken for milk to coagulate.
Results:
Concentration
Control
3mL water
2mL water
1mL water
¼ tsp
½ tsp
¾ tsp
Time (minutes)
12
10
15
20
15
25
30
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Discussion:
The milk that was most dilute coagulated the fastest. Higher concentrations of protein
took longer to coagulate.
Conclusion:
Due to lesser concentration of protein per volume, milk & water solutions took the least
time to coagulate. Solutions with a higher concentration of milk took longer to act on as
there was more protein to act on by the same amount of enzyme.
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Gather, Process & Analyse information from secondary sources &
Use Available Evidence to develop a model of a feedback
mechanism.
Feedback Mechanisms:
• The response alters the stimulus.
•
Negative feedback system:
- Feedback reduces the effect of the original stimulus.
- Maintain stable conditions.
- Achieve homeostasis.
Receptor
Set Value
Control Centre
Effectors
Detector
Eg. Pressure, pain,
chemical, heat etc…
Set Value or Range of
Values
Eg. Blood pressure,
glucose, body
temperature,
gas concentration
Negative feedback
Control Centre
Eg. Nervous/endocrine
system
Negative feedback
Regulator
Eg. Organs such as;
liver, kidneys, lungs
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Analyse information from secondary sources to describe
adaptations & responses that have occurred in Australian
organisms to assist temperature regulation.
Behavioural Adaptations:
• Migration:
- Animal moves to avoid temperature extremes.
- eg. Birds.
- Birds spend spring & summer in Australia. Move before cold
weather comes & food becomes scarce.
•
Hibernation:
- Animal remains sheltered.
- Metabolism slows. Body temperature in endotherms drops.
- Aestivation = hibernating in hot conditions.
- eg. Bogong moths.
- Spend the summer in caves in Aust. Alps.
•
Shelter:
- Burrows, caves or rocks to avoid extreme conditions.
- Heat of day or cool of night.
- eg. Central netted dragon.
- Climbs trees when it is hot.
•
Nocturnal activity:
- Active during the night.
- eg. Brown snake.
- When it is hot become active in the night.
- Shelters underground / under rocks during the day.
•
Controlling exposure:
- Control surface area exposed to sunlight.
- eg. Endotherms.
- Mammals curl up & tuck legs & tails around body in cold
conditions.
•
Clothing:
- Clothing traps a warm layer of air against the skin.
- eg. Humans.
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Structural Adaptations:
• Insulation:
- Fur in mammals & feathers in birds trap a layer of air that slows down
heat exchange with the external environment.
- Thickness of fur / feathers can be changed with changing seasons.
- Subcutaneous fat traps heat beneath skin.
- eg. Cockatoo.
- Can contract muscles to lift feathers up in cold conditions.
- eg. Whales.
- Have layer of blubber to prevent transfer of heat to water.
•
Piloerection:
- ‘Hair standing on end’
- Important for most mammals.
- Trapped air beneath hair/fur acts as insulation.
- Sympathetic neurones carry impulses from hypothalamus to base of
each hair, muscle contracts, hair stands on end.
•
Surface area : volume:
- Large volume with small surface area loses heat less efficiently than
large surface area & small volume.
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Physiological Adaptations:
• Metabolic activity:
- Endotherms generate heat through metabolic activity.
- Metabolic activity dependent on physical activity & other processes.
•
Control of blood flow:
- Blood flow to extremities controlled.
- Heat exchange with environment increased / decreased.
•
Counter-current exchange:
- Blood vessels leading to & from extremities placed close together.
- Chilled blood returning in veins picks up heat from arteries.
- Prevents shock & preserves heat.
- eg. Platypus.
- Feet have vessels close to each other.
•
Evaporation:
- Heat from body used to evaporate water off surface of skin.
- eg. Kangaroos.
- Lick forearms, moisture evaporates off.
HSC Biology
Module 1 - Maintaining A Balance
Focus 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:
o
o
o
o
o
o
o
Carbon dioxide.
Oxygen.
Water.
Salts.
Lipids.
Nitrogenous waste.
Other products of digestion.
Substance
From
To
Form
Carried By
O2
Lungs
Cells
Oxyhaemoglobin RBCs
CO2
Cells
Lungs
HCO3- ions
RBCs,
plasma
Nitrogenous
waste
Liver, body
cells
Kidneys
Mostly urea
Plasma
H2O
Digestive
system, body
cells
Body cells
H2O molecules
Plasma
Salts
Digestive
system, body
cells
Body cells
Ions in plasma
Plasma
Other
digestion
products
Digestive
system &
liver
Body cells
Separate
molecules (AAs,
glucose...)
Plasma
Oxygen Transport:
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•
Mammals require a continuous supply of O2 for respiration.
- O2 diffuses from the external environment into the blood; through alveoli.
- Diffuses from air into blood due to concentration gradient.
- Less in blood than in the air ... moves into the blood.
- Circulates throughout body to cells via circulatory system.
•
O2 highly insoluble in H2O.
- 100mL of blood can carry just 0.2mL of O2 if only dissolved in plasma.
- Blood of mammals contains haemoglobin (Hb), increasing the blood’s
capacity to carry O2 by 100 times.
- Each Hb molecule contains 4 sites in which O2 can bind to.
•
In the lungs:
- When O2 concentration is high;
Hb
+
4O2 Æ
Hb(O2)4
Haemoglobin + Oxygen Æ Oxyhaemoglobin
In body tissues:
- O2 concentration is low;
Hb(O2)4 Æ Hb + 4O2
•
•
The concentration of O2 in the atmosphere decreases with altitude.
- Mammals can adapt to the changes physiologically & behaviourally.
- Breathe deeper.
- Produce more RBCs.
- Larger heart.
Carbon Dioxide Transport:
• In high concentrations in body tissues.
- Diffuses into the circulatory system.
- 70% of CO2 dissolves in water to form HCO3- in RBCs.
CO2 + H2O Æ
H2CO3 Æ
H+
+
HCO3Carbonic acid Æ Hydrogen ions + Hydrogen carbonate ions
- 23% combines with Hb to form carbaminohaemoglobin (does not
prevent the reaction between Hb & O2).
- Remaining 7% dissolved in plasma.
•
Respiratory surfaces:
- CO2 levels low.
- CO2 diffuses out of the blood, across respiratory surface, into external
environment.
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Explain the adaptive advantage of haemoglobin.
Red Blood Cells (erythrocytes):
• Disc shaped, biconcave cells.
• Contain the respiratory pigment haemoglobin (Hb).
• Each RBC contains 200-300 million Hb molecules.
Haemoglobin:
• Gives blood red colour.
• Each Hb molecule consists of 4 sub units.
- Subunits comprised of the polypeptide chain; globin & haem.
• There are 2 types of globins;
- Alpha chains.
- Beta chains.
• Haem contains an iron atom that is able to combine with an oxygen molecule.
- Each Hb molecule has the ability to carry 4 oxygen molecules.
- Oxyhaemoglobin.
Adaptive Advantage:
• The ability of Hb to carry oxygen.
- Oxygen is not readily soluble in water.
- Not carried efficiently by plasma.
• Structure of Hb allows it to dissociate O2 readily to tissues.
- Loosely combines with O2 (oxyhaemoglobin).
Hb + 4O2 ÅÆ Hb(O2)4
• Takes O2 from lungs & CO2 to lungs.
• Increases the blood’s capacity to carry O2.
• Hb is enclosed in RBCs.
- Many mammals have Hb molecules in plasma, upsetting osmotic
balance of their blood.
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Perform a first-hand investigation to demonstrate the effect of
dissolved carbon dioxide on the pH of water.
Aim: To investigate the effect of dissolved carbon dioxide on the pH of water.
Hypothesis: As more breaths are added to the water the pH will decrease. This will
cause the pH to decrease, increasing its acidity.
Equipment:
- Test tubes.
- Drinking straw.
- Universal indicator.
- Distilled water.
Procedure:
- Set up a control experiment consisting of 15mL of distilled water & 5 drops
of universal indicator in a test tube (A).
- Add 15mL of distilled water & 5 drops of universal indicator to 4 test tubes
(B, C, D & E).
- In test tube B, breathe once through the drinking straw.
- In test tube C, breathe twice.
- In test tube D, breathe 3 times.
- Breathe 4 times into test tube E.
- Record the pH of each solution.
Results:
1st Trial
Number of Breaths
0
1
2
3
4
pH
7
6
5
4.5
4
2nd Trial
Number of Breaths
0
1
2
3
4
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pH
7
6
5
4.5
4
Discussion:
The results of the experiment show that the water becomes more acidic as the
number of breaths is increased, supporting the hypothesis. This is due to carbonic
acid forming when CO2 is dissolved in water. As the number of breaths is increased,
the concentration of CO2 increases & the pH decreases. The results cannot be
considered reliable due to a number of variables being beyond control. The duration
of the breath decreases each time & the concentration of CO2 varies as the number
of breaths are increased. The intensity of each breath also varies.
In the body CO2 is created by respiration, creating an acidic environment in body
tissues. This leads to the denaturation of enzymes & cells being poisoned. Removal
of CO2 through the blood is essential to maintain homeostasis.
Conclusion:
The pH of H2O decreases as the number of breaths increases.
5 of 17
Compare the structure of arteries, capillaries & veins in
relation to their function.
Arteries:
• Carry blood away from the heart.
• Under high pressure.
- Thick elastic walls enable vessels to
withstand pressure.
• Structure:
- 3 layers.
- Endothelium (lining).
- Smooth muscle (contract vessel).
- Gives strength to arteries.
- Controlled by sympathetic nervous
fibres.
- Allows stretch & recoil as heart beats.
- Contain 40-10% elastic tissue.
- Connective tissue.
- Non elastic
- Anchors arteries in place.
- Muscular arteries branch into smaller & smaller arteries, creating
arterioles.
- Lead into capillaries.
- Control rate of flow into capillaries through muscle contractions.
Veins:
• Carry blood to the heart.
- Same quantity as arteries.
• Low pressure.
- Thin walls with valves to prevent
backflow.
• Structure:
- 3 layers.
- Endothelium (lining).
- Smooth muscle.
- Thinner than arteries.
- Connective tissue.
- Thinner than arteries.
- Thinner layers make veins more flexible.
- Blood enters veins from capillaries through venules.
- Contraction of muscles surrounding veins helps to push blood through.
Capillaries:
• Thin walled vessels between 5-8um in diameter.
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•
•
•
Materials pass through cells or between cells.
Structure:
- 1 cell thick (endothelium).
Function:
- Thin walls allow substances to diffuse across.
- eg. O2 & CO2, H2O, water soluble molecules (glucose, ions).
- Phagocytic cells also move out through endothelial cells.
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Describe the main changes in the chemical composition of the
blood as it moves around the body to identify tissues
in which these changes occur.
Chemical Composition of Blood
Tissue Where Change
Occurs
Blood receives O2, CO2 released.
Lungs
Blood receives CO2, O2 released.
Body tissues
H2O diffuses into blood. Other substances pass into blood.
Stomach tissue
Digested foods (AAs, glucose) diffuse into blood, carried to liver.
Small intestinal tissue
Vitamins, Fe, fats removed from stored. C6H12O6 added/removed.
Poisonous substances removed. Excess AAs absorbed, converted to urea.
Liver tissue
H2O, salts & vitamins absorbed into blood.
Large intestinal tissue
Excess H2O & salts removed from blood.
Kidney tissue
Hormones secreted directly into blood stream.
Endocrine tissue
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Circulation:
• Blood circulates through 2 systems.
- Pulmonary system.
- Systemic system.
• Pulmonary system:
- Blood flows to the heart Æ lungs Æ heart.
- Right ventricle (pulmonary artery) to lungs.
- CO2 released into alveoli.
- O2 released from alveoli, diffuses into RBCs.
- Pulmonary vein carries oxygenated blood back to the heart.
- Blood under higher pressure than systemic system.
- Flows faster.
• Systemic system:
- Blood flows from the heart to the rest of the system.
- Out of the left ventricle, through the aorta.
- Flows through capillaries where O2 diffuses out & CO2 diffuses in.
- Other waste products picked up from the liver & taken to kidneys.
- Glucose transported (picked up at liver, dropper off at cells).
- Deoxygenated blood returns to right ventricle via super vena cava.
Transport of Nutrients:
• Nutrients are transported in the plasma.
• Simple sugars (monosaccharides):
- Cross the membranes of cells lining the gut & enter blood through
capillaries.
- Carried in hepatic portal vein to capillaries in the liver.
- Some removed for storage (converted to glycogen, about 100g),
excess moved to skeletal muscles for storage.
• Amino Acids:
- Produced by the digestion of protein.
- Absorbed into the hepatic portal vein in the gut.
- Transported to the liver & to all parts of the body to be used.
• Lipids:
- Digestion of fat produces fatty acids & glycerol.
- Some fatty acids & glycerol diffuse through cells lining the small intestine
into the hepatic portal vein & carried to the liver.
9 of 17
Outline the need for oxygen in living cells & Explain why
removal of carbon dioxide from cells is essential.
Oxygen:
• Needed for the process of aerobic respiration.
C6H12O6 + O2 Æ 6CO2 + 6H2O + Energy (ATP) + Heat
Carbon Dioxide:
• CO2 is produced during respiration.
- Causes pH to drop from normal 7.4 which provides optimal function of
nerve cells & enzymes.
• CO2 needs to be removed to keep a constant pH (maintain homeostasis).
- Removed via blood in plasma & combined with Hb.
Concentration Changed of CO2:
• CO2 diffuses down a concentration gradient; like O2.
• Diffuses out of cell, into interstitial fluid. Then diffuses into capillary.
• Moves into the right chamber of the heart through veins.
- Enters lung capillaries & diffuses out through alveoli.
- Pco2 leaving lungs is 40mmHg.
Transport of CO2:
• Little CO2 can be carried in the blood compared to the amount of O2.
- CO2 has low solubility in H2O.
- Reactions take place in blood to convert it to a more soluble form.
- Dissolves in plasma to form H2CO3 Æ HCO3- (very soluble).
- Equilibrium between CO2 & HCO3- important for buffering &
maintaining pH7.4.
- Some binds to Hb to form carbaminohaemoglobin.
Mammals:
• pH of blood monitored by the receptors in the medulla, walls of the aorta & the
carotid arteries.
• Nerves send messages to the breathing control centre in the medulla to alter the
rate & depth of breathing.
10 of 17
Response
Rate of breathing increased
Effector
Rib muscles, diaphragm
Control System
Breathing control system in medulla
Receptor
Receptors in aorta, carotid arteries
Stimulus
Increase in CO2 levels in blood
11 of 17
-ve feedback
CO2 levels decrease
Describe current theories about processes responsible for the
movement of materials through plants in xylem & phloem tissue.
Xylem:
• Transport of H2O & mineral ions.
• Move from roots to leaves (up only).
Transport in the Xylem:
• The transpiration, tension, cohesion theory.
• Transpiration:
- Water evaporates off mesophyll cells. Vapour exits through stomata.
- Water then moves out of mesophyll cells, onto mesophyll cell walls
(keeping them moist).
- Roots of the plant draw water in through osmosis (passively).
- Concentration gradient created as water moves up the xylem to
replace water lost off mesophyll cells.
• Tension:
- Water moving out of stomata creates tension in the xylem.
- Xylem shrinks slightly.
- Negative pressure created within xylem.
• Cohesion:
- Tensile strength (created by cohesive forces of water) allows a
continuous column of water to move up the xylem.
- Diameter of xylem increases / decreases tensile strength of water.
• This process was discovered by conducting various experiments & observing the
movement of water.
- Accurate measurements of xylem.
- Cutting off roots & observing water movement.
• If water relied on air pressure to move it would not exceed 10m. Many trees are
up to 100m tall.
Phloem:
• Transport of organic material.
- Hormones, sugar, AAs.
• Up & down.
Transport in the Phloem:
• Pressure flow theory.
- Movement on phloem very rapid (1m/h).
12 of 17
•
•
•
Translocation:
- The movement of sugars, AAs & hormones.
- Enables the plant to distribute resources to wherever they are needed.
- The process ceases when the phloem cell dies.
- Translocation is an active process (energy required).
The process:
- Sugar is loaded into the phloem tube at the source (eg. a leaf).
- Water follows through osmosis (follows concentration gradient).
- This creates an increase in pressure at the source & a decrease in
pressure at the sink.
- Solute flows from source to sink.
At the sink:
- Sugar leaves phloem tube where it is used or stored.
- Water also leaves phloem, water pressure in tube decreases.
13 of 17
Analyse information from secondary sources to identify the
products extracted from donated blood & discuss the uses of
these products.
Donated Blood:
• Used to treat severe haemorrhage (accidents & child birth).
• Apheresis:
- Blood extracted from donor.
- Platelets, leukocytes & plasma retained.
- Blood retransfused into donor.
- Donor can donate more frequently.
•
Plasma:
- Red & white cells suspended in plasma.
- 70% H2O, minerals, CHOs, from digestion, hormones, waste products
& antibodies.
- Most versatile blood component.
- Stored up to 12 months.
14 of 17
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.
Artificial Blood:
• The military has actively pursued Hb based blood substitutes.
- Use as an oxygen carrying plasma expander for use in the battle field.
• The 1st generation of artificial blood could hit the market within 2 years, greatly
reducing the pressure on donated blood supplies.
•
Advantages:
- May prevent shock.
- Stored at room temperature.
- Stored for more than a year.
- No need to match patent’s blood type.
- Doesn’t contain blood type antigens.
- Unlikely to be infected.
- Pasteurisation used to remove any pathogens.
•
Disadvantages:
- Not capable of replacing the real thing.
- Only substitutes RBCs (carries O2).
- Potential safety problems.
- Some cause hypertension Æ stroke Æ cardiac arrest.
- Decomposes rapidly.
15 of 17
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.
Pulse Oximeter:
• Function:
- Senses a change in the colour of blood as it circulates through the skin.
- Red & infrared light emitted from the tip of the peg.
- Amount of light passing through the skin determined by an electric
sensor.
- Amount of O2 in blood in arterial capillaries calculated.
- Normally 95-100%.
•
Uses:
- Monitor level of O2 in blood during heavy sedation or anaesthesia.
- Used during stress testing (heart function).
- Monitor response to medication.
Arterial Blood Gas Analysis:
• Function:
- Measurement of O2 & CO2 in a sample of blood.
- Uses the diffusion of gases through an artificial permeable membrane.
- Movement of O2 molecules produces an electrical current.
- Current converted to a digital reading.
- Diffusion of CO2 through a separate membrane changes the pH of a
solution.
•
Uses:
- Monitoring of a patient during therapy.
- Diagnosis of respiratory disease.
- Function of kidneys.
16 of 17
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.
Aim:
Using to light microscope & prepared slides, estimate the size of red & white
blood cells.
Materials:
- Monocular light microscope.
- Microslide grid.
- Red blood smear.
Method:
* Only rack up to prevent breaking slides.
* Wear covered footwear to prevent injury from laboratory equipment.
- Prepare microscope by adjusting light source & focus.
- Place microslide grid on stage, focus at 100x magnification.
- Calculate size of field of view.
- Refocus at 400x.
- Calculate size of field of view.
- Estimate field of view using microslide grid.
- Place red blood smear on microscope & focus at 100x.
- Refocus at 400x.
- Draw image in field of view.
- Count number of RBCs across field of view.
- Calculate size.
- Count number of WBCs across field of view.
- Calculate size.
Calculations:
RBC:
350um ÷ 50
= 7um
WBC:
350 ÷ 17
= 20um
17 of 17
HSC Biology
Module 1 - Maintaining A Balance
Focus 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.
Water:
• Makes up 50-60% of the human body.
•
Solvent in which all metabolic reactions take place.
- Catabolic & anabolic reactions.
- Polar nature allows it to dissolve many substances (hydrophilic
substances).
•
Transport medium (95% of plasma).
- Sugars, salts, hormones, wastes.
Concentration Kept in Narrow Range:
• Amount of water affects the concentration of solutes.
- Affects ability to diffuse in & out of cells.
- An isotonic environment allows most efficient functioning of organism.
•
Lack of water causes dehydration.
- Blood pressure falls, circulation fails.
- Inability to thermoregulate.
Explain why the removal of wastes is essential for continued
metabolic activity.
Metabolic Wastes:
• Metabolic processes constantly produce wastes.
- Disrupt the homeostatic balance in cells.
- Metabolism slows.
- Cells become poisoned, enzymes may be denatured.
Ammonia:
• Nitrogenous waste.
•
Produced by the breakdown (metabolism) of proteins.
- When dissolved in water, produces a highly alkaline environment.
- Enzyme activity affected.
- Ammonia removed through the kidneys.
Carbon Dioxide:
• Product of cellular respiration.
•
Creates an acidic environment; causing reduced enzyme activity.
Identify the role of the kidney in the excretory system of fish
and mammals.
The Kidney:
• Control water balance.
•
Eliminate nitrogenous wastes.
•
Osmoregulation; regulate salt & water concentration.
•
Stabilise the internal environment.
- Filter the blood, reabsorb required nutrients.
•
Excrete hormones.
- eg. Aldosterone.
Fish Kidney:
• Excrete ammonia across the gills.
•
Freshwater fish:
- Excrete hypertonic urine.
•
Marine fish:
- Excrete isotonic urine.
Explain why the processes of diffusion and osmosis are
inadequate in removing dissolved nitrogenous wastes.
Diffusion:
• Too slow for normal functioning.
•
Non selective (random movement of molecules).
•
Passive (will not work against a concentration gradient).
Osmosis:
• Movement of water only.
- Water moves out of body, wastes remain.
•
Passive (will not work against a concentration gradient).
•
Random movement of molecules.
Distinguish between active and passive transport and relate
these to processes occurring in the mammalian kidney.
Active Transport:
• Involves the expenditure of energy provided through the process of ATP splitting.
- Moves against concentration gradient or chemical or physical properties
may prevent active transport
- eg. Hydrophobic lipids or large proteins.
•
Endocytosis is 1 form of active transport.
- Specific proteins in membrane binds with substance to carry it through.
Passive Transport:
• No energy required.
•
Substance move with the concentration gradient (many towards none).
Explain how the processes of filtration and reabsorption in the
mammalian nephron regulate body fluid composition.
Filtration:
• The nephron is the functional unit of the kidney.
- Approximately 1million in each kidney.
- Found in the outer cortex & central medulla.
•
Blood flows into the nephron under high pressure.
- Network of capillaries known as the glomerulus carries blood.
- Thin walls of capillaries & high pressure cause all substances to leave
the blood.
•
Filtration is non selective; all components are removed except erythrocytes &
large proteins.
Reabsorption:
• Feedback mechanisms determine the quantities of substances reabsorbed.
•
Substances re-enter through distal & proximal tubules, the loop of Henle & the
collecting duct.
•
All excess nutrients & wastes removed for excretion.
Outline the role of the hormones, aldosterone and ADH (antidiuretic hormone), in the regulation of water and salt levels in
blood.
Aldosterone:
• A steroid hormone produced in the adrenal cortex of the adrenal gland located on
the kidney.
•
Aldosterone is synthesised from cholesterol by the enzyme aldosterone
synthase.
•
Regulates the flow of Na+ & K+ ions back into the blood.
- Aldosterone is released when a drop in blood pressure is detected,
causing more ions to enter the blood.
- This causes water to follow, restoring blood pressure.
Vasopresin:
• Produced in the hypothalamus.
•
Released when a high concentration of solutes in the blood is detected.
•
ADH acts to increase the permeability of the distal tube walls, allowing more
water to re-enter the blood.
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.
Enantiostasis:
• The maintenance of metabolic & physiological functions in response to variations
in the environment.
- Occurs in the absence of homeostasis.
Importance:
• Enantiostasis is important in animals that live in estuarine environments where
salt concentrations constantly change.
Osmoconformers:
• Organisms that allow their body’s osmotic pressure to vary with the environment.
• Don’t maintain homeostasis.
• Concentrations of internal fluids remain isotonic to external fluids.
• Vary the concentration of solutes within cells to maintain functioning.
Eg. Sharks are osmoconformers. They are euryhaline; meaning they can
tolerate changes in salt concentration.
Osmoregulators:
• Maintain homeostasis regardless of the concentration of the external
environment.
Eg. Freshwater & marine fish regulate their internal environment to
maintain homeostasis.
Describe adaptations of a range of terrestrial Australian plants
that assist in minimising water loss.
Plant Adaptations:
• Aim to:
- Increase water taken in by the roots.
- Decrease water lost through evaporation.
Extensive underground root systems
Close stomata when temperature reaches a certain threshold
Hard leaves with a thick waxy cuticle
Surface with crystalline appearance
Thick bark
Hairs or other similar structure
- Reduces airflow over the surface, decreasing evaporation
Reduced leaves & branchlets, false leaves performing photosynthesis
Extra thickening of cell walls throughout branches
- Prevents wilting even when large quantities of water are lost
Gather, process and analyse information from secondary sources
to compare the process of renal dialysis with the function of
the kidney.
Dialysis:
• Means to separate.
•
Simulates the role of the nephron in the kidney.
- Separates molecules from the blood.
•
Prevents waste products of metabolism building up.
- High concentrations can lead to tiredness, weakness, loss of appetite.
•
Sustains the life of people with impaired kidney function.
Renal Dialysis:
• Removes wastes in blood by diffusion across a semipermeable membrane.
•
Blood drawn out of a vein, into dialysing solution.
- Moves through plastic tubing into the machine.
- A bundle of semipermeable fibres that allow
wastes to pass out into dialysing solution.
•
Clean blood taken back into the blood stream.
Peritoneal Dialysis:
• Undertaken in the peritoneal cavity of the body.
•
Dialysing solution put into peritoneal cavity through a catheter.
- Natural membrane lining of the cavity is semipermeable.
The Kidney:
• Filters the entire blood volume once every ½ an hour.
•
Faster & more efficient than dialysis.
Present information from secondary sources to outline the
general use of hormone replacement therapy in people who cannot
secrete aldosterone.
Addison’s Disease:
• Inability to secrete aldosterone from the adrenal cortex.
- Caused by shrinking or destruction of the adrenal gland.
•
Water balance unable to be maintained.
- Blood volume & pressure drops.
- Dehydration occurs.
- Body functions disrupted.
•
Treatment:
- Patient takes fludrocortisone.
Analyse information from secondary sources to compare and
explain the differences in urine concentration of terrestrial
mammals, marine fish and freshwater fish.
Animal
Urine Concentration
Reason
Terrestrial Mammal
Concentrated, volume
varies depending on
availability.
(Desert mammals highly
concentrated).
Problem of conserving
water while removing
nitrogenous waste.
Marine Fish
Highly concentrated.
Problem of osmosis.
Concentration of ions
lower in the body than in
the water. Water diffuses
out, salts diffuse in.
Excess salts excreted
through gills, little urine
excreted. Large amounts
of water drank to replace
it.
Freshwater Fish
Dilute
Concentration of
dissolved ions higher in
the body, water diffuses
in. Must remove excess
water through large
quantities of dilute urine.
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.
Ammonia:
• Highly toxic.
- Removed immediately.
• Product of most aquatic animals.
• Immediate product produced from the breakdown of amino acids.
• Highly soluble in water.
- Requires large quantities of water to be safely removed.
Urea:
•
•
•
•
•
•
10,000 times less toxic than ammonia.
Can be stored in body fluid for a limited time.
Produced by mammals, sharks, amphibians.
Highly soluble in water.
- Small amounts of water required to remove it.
Produced from the breakdown of amino acids.
Major source of water loss in mammals.
Uric Acid:
• < toxic than urea & ammonia.
• Stored in the body for extended time.
• Product of terrestrial animals.
- Birds, reptiles, insects.
• Highly insoluble in water.
- Minimal water required to remove it.
Spinifex hopping mouse
Terrestrial
Urine in concentrated form.
Arid environment.
Drinks little H2O.
Wallaroo
Terrestrial
Concentrated urine.
Efficient excretory system.
Recycles N & urea to make concentrated urea.
Survives in an arid environment.
Insects
Terrestrial
Uric acid.
Insects covered in a cuticle impervious to H2O.
Conserve H2O by producing a dry paste of uric acid.
Process and analyse information from secondary sources and use
available evidence to discuss processes used by different plants
for salt regulation in saline environments.
Halophytes:
• Plants adapted to live in a salty environment.
- Able to tolerate higher levels of salt than other organisms.
- Have mechanisms to control the levels of salt.
Mechanisms:
• Salt barriers.
- Tissues in roots & lower stems stop salt from entering the plant, but
allow water to enter.
•
Secretion.
- Able to concentrate salt & secrete it through glands on the leaves;
where it is washed off.
•
Salt deposits.
- Salt deposited in old tissue which is disregarded.
Eg.
- Grey mangrove secretes salt.
- Salt marsh plants use salt deposits.
Perform a first-hand investigation to gather information about
structures in plants that assist in the conservation of water.
- Location & number of stomata.
- Arrangement, shape & size of leaves.
- Phyllodes / cladodes rather than leaves.
- Thick, waxy cuticles.
- Hairy leaves.
- Leaves reduced to spines.
- Leaves rolled inwards.
- Reflective leaf surface.
Eg. Boab tree.
- Large H2O storage in trunk.
- Drop leaves when H2O is scarce.
- Large root system.
Eg. Xanthorrhoea (grass tree).
- Long, thin stem.
- Diverts H2O to roots.
- Small surface area on leaf reduces H2O loss.
Eg. Eucalypts.
- Thick, waxy cuticle.
- Vertical leaves.
- Reflective leaves.
- Thick trunk to hold H2O.
- Large root system.