Download Maintaining a Balance

BIO1: Maintaining a Balance
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
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Metabolism: all the chemical processes occurring within an organism
Enzymes increase the rate of reactions that occur in living organisms. Enzymes are necessary to keep metabolic
reactions going at a fast enough rate, so that sufficient energy is available to maintain life.
Enzymes are globular proteins; the basic building blocks of enzymes are amino acids
o Their manufacture is controlled by nucleus
o Are needed only in small amounts
o Enzymes are biological catalysts; they control the rate of a reaction, but are chemically unchanged at the
end of the reaction
o Enzymes are specific, they affect only one type of reaction
Concentration of substrate, temperature, and pH affect enzyme activity
o Saturation point: where substrate concentration is at a level such that all enzyme active sites are occupied,
and the reaction is proceeding at its maximum rate
Enzymes may need cofactors to help functioning (metallic ions such as iron, copper, magnesium)
o Coenzymes are cofactors consist of organic chemicals such as mineral ions or compounds that come from
vitamins
Intracellular enzymes are used within the cells that produce them, e.g. photosynthesis enzymes
Extracellular enzymes are used outside the cells the produce them, e.g. digestive enzymes
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Enzymes provide active site where the reaction can take place
Molecule on which an enzyme specifically acts is called the substrate
Binding of substrate brings about temporary change in enzyme shape known as induced fit
Chemical reaction occurs and substrate is changed
Products are released and enzyme returns to its original form
E.g. maltase catalyses reaction between maltose and water, where maltose is split to produce two glucose molecules
Lock and Key Model:
 The active site has a specific geometric shape such that only one substrate can bond to that site, making the
enzyme specific to that substrate
Induced Fit Model:
 Active site changes shape slightly to accommodate the substrate perfectly
IDENTIFY THE PH AS A WAY OF DESCRIBING THE ACIDITY OF A SUBSTANCE
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0-7 is acid, 7-14 is alkaline
pH is a measure of concentration of hydrogen ions per litre of solution
Human blood: 7.4
Stomach: 2
Small intestine: 8.0
EXPLAIN WHY THE MAINTENANCE OF A CONSTANT INTERNAL ENVIRONMENT IS IMPORTANT FOR OPTIMAL METABOLIC
EFFICIENCY
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Enzymes work optimally in an environment where optimum conditions are met
o Temperature, pH, enzyme concentration, substrate concentration, presence of cofactors/coenzymes
Any variation from optimal conditions reduces their rate of activity
o E.g. enzymes in stomach work best at pH 1.5-2
High temperatures and extreme pH will denature enzymes, and disable enzymes from catalysing their reactions
 Multicellular organisms are at optimal metabolic efficiency if internal environment for their cells
is at a constant level, because enzymes work best under certain conditions, and enzymes control
all metabolic processes
Pg 2
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)
DESCRIBE HOMEOSTASIS AS THE PROCESS BY WHICH ORGANISMS MAINTAIN A RELATIVELY STABLE INTERNAL
ENVIRONMENT
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When deviations occur in the internal environment of a healthy organism, mechanisms act to restore values to the
set value. Homeostasis is critical to the survival of an organism
Homeostasis is the process by which the internal environment is kept within normal limits regardless of the external
environmental conditions
This allows the enzyme's optimal conditions to be met and the body to work efficiently and kept as stable as
possible.
EXPLAIN THAT HOMEOSTASIS CONSISTS OF TWO STAGES: DETECTING CHANGES FROM THE STABLE
STATE/COUNTERACTING CHANGES FROM THE STABLE STATE
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Detecting changes from the stable state
o A receptor detects a change in a specific variable from the desired set value, and transmits this information
to the control centre (nervous system) along neurons
o Stimulus: any information that provokes a response
o Receptor: an organ or other part which receives a stimulus and transmits it to organism’s control centre
 Mechanoreceptors detect sound, touch, pressure, gravity
 Chemoreceptors detect oxygen, carbon dioxide, water, pH, ions, nitrogenous wastes, glucose
 Thermoreceptors detect temperature change
 Photoreceptors convert light stimuli into electrical signals
 Counteracting change
o An effector receives the message from the control centre that an undesirable change must be
counteracted, and causes a response to counteract the change and maintain a stable state (negative
feedback)
 Effectors bring about responses. They may be muscles that cause movement, or glands that secrete
a chemical substance
STIMULUS  RECEPTOR  CONTROL CENTRE  EFFECTOR  RESPONSE
Pg 4
OUTLINE THE ROLE OF THE NERVOUS SYSTEM IN DETECTING AND RESPONDING TO ENVIRONMENTAL CHANGES
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Pg 5
Nervous system coordinates sensory information with the body’s responses (action of various muscles and glands)
o Works to regulate an animal’s internal environment and respond to external environment
Central nervous system: brain and spinal cord (acts as control centre)
Peripheral nervous system: connects central nervous system to receptors/effectors
o Sensory division transmits sensory information about external and internal environment to CNS
o Motor division transmits impulses from CNS to effector organs (muscles and glands)
 Somatic nervous system = voluntary nervous system: controls skeletal muscles
 Autonomic nervous system transmits messages to smooth muscle, heart muscle and glands
Nervous system works closely with endocrine system, which produces hormones
o Hormones travel in the blood, to bring a response in specific areas or organs
o Hormones contribute to homeostasis by negative feedback mechanisms
Hypothalamus regulates release of many hormones as well as controlling many other aspects of homeostasis
GATHER, PROCESS AND ANALYSE INFORMATION FROM SECONDARY SOURCES AND USE AVAILABLE EVIDENCE TO
DEVELOP A MODEL OF A FEEDBACK MECHANISM
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Feedback system: response alters the stimulus
o Positive feedback: response increases effect of the original stimulus
 E.g. in childbirth, contractions cause release of oxytocin, which causes more contractions…
o Negative feedback: response reduces effect of the original stimulus
 Negative feedback mechanisms are major mechanism by which homeostasis is achieved
 E.g. increase in temperature detected, hypothalamus initiates sweating, temperature falls and is
detected, sweating decreased
Controlling Temperature:
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Mammals function optimally at 37⁰ Celsius
Thermoreceptors in the skin receive changes in skin
temperature caused by external conditions
Receptors in hypothalamus, large veins, and parts of
the digestive system detect temperature changes in
the blood
Hypothalamus receives temperature change
information, and initiates responses to change body
temperature. It acts as the ‘temperature control
centre’ of the body
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Heat loss can occur through
o Radiation: Heat radiates from body in all directions
o Conduction: direct contact with objects, and transfer of heat into them
o Convection: if air surrounding a body is moving, air currents carry heat away from body
 This effect is greater in water, since water is continually moving
o Evaporation: evaporation of water requires heat which is provided by the body
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How the body gains heat
o Shivering: involuntary contraction and relaxation of small muscle groups
 Almost all the energy of contraction is converted into heat energy
o Metabolic processes in the body produce heat
 Thyroxine is a hormone, that when released from thyroid gland, increases the metabolic rate of all
cells of the body, resulting in an increase in heat production
- Secretion of adrenaline and noradrenaline also increase metabolic rate
- Brown fat metabolism allows babies to produce about 5 times as much heat from metabolic
pathways as an adult
o Vasoconstriction of superficial arterioles reduces blood flow close to the skin, and hence reduces heat lost
via skin surface
o Piloerection: A layer of air is trapped in erect hair or fur and acts as an insulation layer
How the body cools off
o Sweat glands are activated; evaporation of sweat cools the body
o Metabolic heat production is reduced because less thyroxine is produced
o Vasodilation of superficial arterioles increases surface area across which heat can be lost
Behavioural activities such as increasing level of activity, move indoors, turn on a radiator, put on warm clothing
o Alteration of posture to expose high or low surface area for heat loss
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Pg 3
IDENTIFY THE BROAD RANGE OF TEMPERATURES OVER WHICH LIFE IS FOUND COMPARED WITH THE NARROW LIMITS
FOR INDIVIDUAL SPECIES
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Life, in some form, can be found at extremes ranging from - 70oC to +120oC. There are daily and seasonal variations
in ambient temperature
o Ambient temperature on land varies much more than in aquatic environments
Most individual organisms can tolerate a narrow range of temperatures
o Mammals live in environments of 0-45⁰C
Sugar canes need >15⁰C frost-free environment to grow
 Below 0oC, enzymes many not be active and cells risk ice crystals forming in them
 Above 45oC, enzymes within cells may denature.
Pg 6-8
COMPARE RESPONSES OF NAMED AUSTRALIAN ECTOTHERMIC AND ENDOTHERMIC ORGANISMS TO CHANGES IN THE
AMBIENT TEMPERATURE AND EXPLAIN HOW THESE RESPONSES ASSIST TEMPERATURE REGULATION
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Pg 9
Ecthotherms have a limited ability to control body temperature, depending on external sources of heat to
generate body heat
o Mostly behavioural adaptations to temperature change
o Aquatic ecthotherms usually don’t have any specialised adaptation for temperature regulation
o E.g. Plants, invertebrates, fish, amphibians, reptiles
Poikilothermic: body temperature fluctuates with ambient external temperature
Endotherms maintain an internal body temperature independent of external temperature, depending on internal
metabolic heat production
o Their metabolic activity generates heat
o Generating heat requires more energy, so more food must be consumed by endotherms than by
ecthotherms of the same weight. The advantage is that endotherms can remain active under a wider range
of environmental temperatures
o E.g. mammals, birds
Homeothermic: maintains constant body temperature
ANALYSE INFORMATION FROM SECONDARY SOURCES TO DESCRIBE ADAPTATIONS AND RESPONSES THAT HAVE
OCCURRED IN AUSTRALIAN ORGANISMS TO ASSIST TEMPERATURE REGULATION
Behavioural adaptations
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Migration
o Sharp-tailed sandpiper migrates from Siberia to southern Australia in nonbreeding period
Hibernation/Aestivation
o Hibernation: animals remain in a sheltered spot, metabolism/breathing/heart
rate slows, and in endotherms the body temperature drops
 If external temperature drops suddenly, the organism arouses to ensure
essential functions aren’t impaired, by moving/shivering to produce heat
 Bent-wing bats hibernate in a cave
 Mountain pygmy possum hibernates in winter, maintaining a lowered body temperature, so that
amount of food required by it to survive the winter period is reduced
o Aestivation: ‘hibernation’ in hot conditions
 Bogong moths migrate to Australian Alps to aestivate there in the summer, and return eastwards to
breed in winter
Shelter
o Central netted dragon climbs into bushes to seek cooler conditions off the
ground, and basks in the sun when it needs to get warmer
o Spinifex hopping mouse digs burrows to escape high temperatures
Nocturnal Activity
o Spinifex hopping mouse shelter during the day when it is hot, and are active
at night (nocturnal)
Controlling Exposure
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Central netted dragon alters its posture to expose a larger or smaller surface area to the sun
_________________________
 Spinifex hopping mouse digs burrows to escape high temperatures
 Spinifex hopping mouse shelter during the day when it is hot, and are active at night (nocturnal)
 Mountain pygmy possum hibernates in winter, maintaining a lowered body temperature, so that amount
of food required by it to survive the winter period is reduced
 Red Kangaroo licks forearms in hot weather; moisture evaporates and cools the blood in forearms
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 Bogong moths migrate to Australian Alps in the summer to aestivate
 Central netted dragon climbs into bushes to seek cooler conditions off the ground, and basks in the sun
when it needs to get warmer
 Central netted dragon alters its posture to expose a larger or smaller surface area to the sun
 Magnetic termites pack the walls of their mounds with insulating wood pulp
 Magnetic termites orient the long axis of their mounds north-south to maximise sun exposure in
mornings/evenings, and minimise heat during the day
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Physiological adaptations (mainly endotherms)
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Metabolic Activity
o Shivering in cold conditions to increase metabolic activity
and generate heat
Evaporation
o Sweating: control rate of evaporation of water to keep cool
Control of Blood Flow
o Endotherms control blood flow to skin/extremities, enabling skin temperature to be lowered while
maintaining normal internal body temperature (vasodilation/vasoconstriction)
Counter-current Exchange
o Blood vessels leading to and from extremities of body are placed together, so chilled blood returning in
veins picks up heat from arteries
 Used in feet of the platypus
o Can also be used to cool blood, e.g. in dolphins to maintain testes at a lower temperature, arteries lose heat
to nearby veins before supplying the testes
Anti-freeze substances such as glycol are produced by some animals, so that freezing point of fluids is reduced to a
lower temperature than the ambient temperature.
Piloerection
o Trapped air beneath hair/fur acts as insulation
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 Counter-current exchange used in feet of the platypus to reduce
heat loss
 Mountain pygmy possum hibernates in winter, body temperature
drops and metabolic rate slows
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 Bogong moths avoid ice crystals forming in cells by supercooling body fluids below their usual freezing
point
 Thorny devil can change from pale colour when external temperature is hot to reflect sun’s rays, to a
darker colour when it is cool to absorb heat
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Structural adaptations (mainly endotherms)
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Insulation
o Fur in mammals/feathers in birds maintain insulating layer of air to slow down heat exchange
o Thickness of air layer increased in cold conditions by contracting muscles to lift fur or feathers away from
skin
 Hair/fur
o Trapped air beneath hair/fur acts as insulation
 Body Shape
o Large, round body has smaller SA/V ratio which reduces heat loss
o Bilby: Large thin ears allow for quick heat loss, because blood vessels close
to the surface have high SA
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 Bilby has claws on front feet to dig burrows to escape the heat
 Bilby: Large thin ears allow for quick heat loss, because blood vessels close to the surface have high SA
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Endothermic
Behavioural
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Red Kangaroo licks forearms in hot weather
Mountain pygmy possum hibernates in winter
Spinifex hopping mouse is nocturnal
Spinifex hopping mouse digs burrows to escape
high temperatures
Ectothermic
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Physiological 
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Structural
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Platypus uses a counter-current exchange system
in its feet to reduce heat loss
Mountain pygmy possum hibernates in winter,
body temperature drops and metabolic rate slows
Bilby has claws on front feet to dig burrows to
escape the heat
Bilby: Large thin ears allow for quick heat loss
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Bogong moths migrate to Australian Alps in
summer to aestivate
Central netted dragon alters its posture
Central netted dragon climbs into bushes to
seek cooler conditions off the ground, and
basks in the sun when it needs to get warmer
Magnetic termites pack walls of their mounds
with insulating wood pulp
Magnetic termites orient the long axis of
their mounds north-south
Bogong moths avoid ice crystals forming in
cells by reducing temperature of body fluids
below their usual freezing point
Thorny devil is coloured pale when external
temperature is hot to reflect sun’s rays, and
can change to a darker colour when it is cool
to absorb heat
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IDENTIFY SOME RESPONSES OF PLANTS TO TEMPERATURE CHANGE
Responses to heat:
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High temperature during flower formation produces a poor wheat crop, because meiosis in
anthers is sensitive to temperature
Plants die but leave dormant seeds
Roots, rhizomes, bulbs or tubers survive underground and sprout when favourable
conditions return
o E.g. Mallee eucalypt
Shiny, reflective cuticle to reduce amount of heat absorbed
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Leaves hang vertically to reduce surface area exposed to sunlight, in eucalypts
Transpiration: heat within plant is used to evaporate water from surface of cells, which exits planet through open
stomates
o However, stomates are closed at midday to conserve water
Thin leaf shape with many edges increases surface area over which heat can be lost
Heat-shock proteins, produced at about 40⁰C, protect enzymes and other proteins from denaturation
Responses to cold:
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Vernalisation: plants such as daffodils require exposure to cold conditions before they will develop flowers
Plants may leave dormant seeds
Die back of above-ground parts
Plants usually alter growth rate; in tropical regions growth may cease below 15 degrees
Frost-tolerant leaves
o In plants, when temperatures are very low, ice forms in spaces outside living cells. Inside of cell doesn’t
freeze because concentration of ions in the cytosol is greater. Because water concentration is decreasing
outside the cells (because ice is being produced), water moves out of the cells by osmosis, further
increasing cytosol concentration, and lowering freezing point inside cells even further. Pliable cell
membranes prevent cell rupture.
Pg 10,11
2.
Plants and animals transport dissolved nutrients and gases in a fluid medium
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Interstitial fluid drains into lymphatic vessels, and lymph vessels return the fluid, now known as lymph, to the blood
Composition of human body fluids: 5L blood, 15L extracellular/interstitial fluid, 25L intracellular fluid
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Composition of blood: 55% plasma, 45% cellular matter
o Plasma: 90% water and other substances carried in solution
 Salts carried as ions, and plasma proteins, help maintain pH of 7.4
 Promotes clotting and contributes to immune response
 Waste materials, and products of digestion also carried in plasma
o Red blood cells (erythrocytes): have haemoglobin to transport respiratory gases, especially oxygen
 Disc-shaped, biconcave, thinner at centre than at edges
 Remain in blood circulation for 3 months
o White blood cells (leucocytes): larger than red blood cells, but there are lesser of them
 Phagocytes: Ingest bacteria, foreign bodies and dead cells
 Lymphocytes: act specifically against foreign material; make antibodies
o Platelets: made in bone marrow; important in blood clotting
 Platelets clump together, helping to plug the hole in the vessel, and
release clotting factors
o Lymph: blood without red blood cells, platelets, or large plasma proteins
 Lymphocytes made by lymph glands, and added to lymph
travelling through lymph vessels
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4 functions of mammalian circulatory system
o Transport: of water, gases, nutrients and wastes
o Blood clotting: repairs damage to blood vessels and seals wounds to prevent
blood loss
o Defence against disease: white blood cells and antibodies help fight infection
o Temperature regulation: blood flow distributes heat, and control of blood flow helps control heat loss
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
Substance
Form
Carried by
From
To
Oxygen
Carbon Dioxide
Red blood cells
Red blood cells and
plasma
Lungs
Body cells
Body cells
Lungs
Water
Oxyhaemoglobin
70% hydrogen carbonate ions, 23%
carbaminohaemoglobin, 7%
dissolved in plasma
Water molecules
Digestive system
Body cells
Salts
Lipids
Dissolved ions in plasma
Chyle, in lacteals
Digestive system
Small intestine
Body cells
Body cells
Nitrogenous Wastes
Mostly as urea, dissolved in blood
plasma
As separate molecules in plasma
e.g. glucose, amino acids
Plasma
(Water is solvent
comprising 90% of
plasma)
Plasma
Lipoproteins (e.g.
chylomicrons)
Plasma
Liver and body cells
Kidneys
Plasma
Digestive system and
liver
Body cells
Other Products of
Digestion
Oxygen
 Oxygen from air diffuses into blood in lungs, and is transported to all body cells
o Oxygen molecule must diffuse across:
 Film of water on alveolus
 Cell membranes of alveolus cell
 Cell membranes of capillary cell wall
 Cell membranes of red blood wall
 Haemoglobin is a respiratory pigment in red blood cells, containing four active sites where an oxygen molecule
can be attached to make oxyhaemoglobin
o Each of the 4 sub-units comprise of a polypeptide chain and a haem group. Each haem group has an iron
atom that can combine with an oxygen molecule
 Iron is needed to produce haemoglobin. Lack of iron makes you anaemic because body cells aren’t
receiving enough oxygen
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4 O2 + Hb  Hb(O2)4
Haemoglobin makes oxygen-carrying capacity of blood 20% v/v
o Oxygenated blood is bright red
o Once transported to tissues where oxygen levels are low, oxygen diffuses into body cells
When one molecule of oxygen combines with haemoglobin, it facilitates the combination of three more molecules
of oxygen, making haemoglobin fully saturated
o Generally, a haemoglobin molecule is either fully saturated or carries no oxygen molecules
o Percentage saturation: proportion of haemoglobin molecules in the blood that are combined with oxygen
Factors affecting association of oxygen with haemoglobin
o Increased PO2 increases percentage saturation of haemoglobin
o As pH is lowered, percentage saturation of haemoglobin decreases
 Because as blood becomes more acidic (higher CO2 concentration), more oxygen dissociates from
haemoglobin
 Lower pH shifts ‘Percentage saturation vs. PO2’ curve to the right
o As temperature increases, percentage saturation decreases as oxygen dissociates from haemoglobin
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In metabolically active tissues, metabolic heat is generated. Increased release of oxygen by
haemoglobin at these higher temperatures ensures adequate oxygen for the metabolic activities
 High temperature shifts ‘Percentage saturation vs. PO2’ curve to the right
o Increasing altitude reduces PO2 in the external environment, and so percentage saturation of haemoglobin
decreases
 Short term effect: breathe more deeply, more often (hyperventilation)
 Long term effects: body produces more red blood cells and haemoglobin, capillaries increase in
extent and diameter, blood volume increases
 Adaptations of mammals living at high altitudes:
 Deeper breathing to obtain more oxygen
 More red blood cells circulating in blood
 A large heart to circulate blood more rapidly
Carbon monoxide binds to active site in haemoglobin, disallowing oxygen from binding and being transported to
tissues
Carbon Dioxide
 70% of carbon dioxide transported as hydrogen carbonate ions which is carried in plasma
o Carbon dioxide reacts with water to form carbonic acid, composed of hydrogen ion and hydrogen carbonate
ion
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In red blood cells:
𝑐𝑎𝑟𝑏𝑜𝑛𝑖𝑐 𝑎𝑛ℎ𝑦𝑑𝑟𝑎𝑠𝑒
𝐶𝑂2 + 𝐻2 𝑂 ↔
𝐻2 𝐶𝑂3
 Then:
𝐻2 𝐶𝑂3 ↔
𝐻𝐶𝑂3 − + 𝐻 +
23% of carbon dioxide combines with haemoglobin to form carbaminohaemoglobin
7% of carbon dioxide dissolved directly in plasma
Lipids:
 Fatty acids and monoglycerides absorbed are reformed into chylomicrons
 These enter lacteals of lymphatic system in intestinal villi, and eventually released into venous circulation
 Cholesterol is transported in the blood by low-density lipoproteins (LDLs) and high-density lipoprotein (HDLs)
Other products of digestion:
 Plasma transports nutrients, which are the products of digestion
o These are either small molecules like glucose, or the products of breakdown of larger molecules
o E.g. polysaccharides broken down into simple sugars, fats into glycerol and fatty acids, proteins into amino
acids
Pg 12,13
EXPLAIN THE ADAPTIVE ADVANTAGE OF HAEMOGLOBIN
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Oxygen is not very soluble in water and so cannot be carried efficiently dissolved in the blood plasma.
Ability to transport large quantities of oxygen to tissues due to haemoglobin, gives these organisms a considerable
survival advantage
o Aerobic respiration can be carried out at a faster rate, and
hence haemoglobin allows mammals to have a high
metabolic rate and activity
Pg 14,15
COMPARE THE STRUCTURE OF ARTERIES, CAPILLARIES AND VEINS IN
RELATION TO THEIR FUNCTION
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Arteries: from heart to body cells
[Arterioles]
o Thick-walled to withstand/maintain high blood pressure
o Very elastic fibres allow vessels to expand and recoil with each heartbeat
 These pulse waves maintain blood pressure, sending it in spurts (pulse) and allowing it to reach the
body extremities
o More muscle fibres, which by relaxing/contracting can control diameter of artery and hence flow rate
 Also have an endothelium (inner layer), and outer non-elastic connective tissue layer that
anchors arteries in place in the body
Veins: from body cells back to the heart
[Venules]
o Thinner walls than arteries
o Less muscle
o Wider diameter tube; blood flows at lower pressure after passing through capillaries
 Blood kept moving by one-way valves, and by muscles pressing on the veins
Capillaries: surround tissue cells
o Extension of inner layer of arterioles and venules
o One cell thick
 Provide a larger surface area over which exchange of materials can occur
 Oxygen diffuses into capillaries, carbon dioxide diffuses out
 Water, ions , some proteins and glucose also move through
 Red blood cells pass through in single file
 5-8 micrometers diameter
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Lymph Vessels
o No muscles in vessel walls, but one-way valves keep lymph moving
o Run between skeletal muscles, whose movements also keep lymph moving
o Lacteals: lymph vessels in villi of small intestine
 Fatty acids, glycerol and small fat droplets absorbed, and reformed as chylomicrons which enter
lymph
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The Heart
o Known as double circulation system, because on every circuit of the body, blood passes through the heart
twice
o Normally beats 60-80 times a minute
o Blood in left and right sides don’t mix
o Valves at two points control one-way flow of blood
 Atrioventricular valves separate atria from ventricles
 Tricuspid valve: between right atrium and
ventricle
 Semilunar valves separate ventricles from arteries
o Blood enters heart from the body via caval vein, into right
atrium, and from there into right ventricle
 Contraction of right ventricle closes tricuspid
valve, forcing blood via pulmonary artery to the
lungs
 Gaseous exchange occurs in lungs
 Oxygenated blood returns via pulmonary vein and
enters left atrium
 Oxygenated blood leaves heart to body cells via the aorta
o ‘Pacemaker’ region of muscle cells in right atrium contract spontaneously sending nerve impulses, causing
atria to contract, which cause the ventricles to contract
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This is controlled by the nervous system
Blood and lymph kept moving through circulation by:
o Heart muscle which pumps blood
o Contraction/relaxation of muscles/elastic fibres in walls of blood vessels
o Contraction of body muscles which press on blood vessels
o One-way valves in veins and lymph 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
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Pulmonary Circuit (lungs)
o Blood flows at lower pressure, but faster, than in systemic circuit
o Blood with low oxygen/high carbon dioxide, gains oxygen, and loses carbon dioxide
 Returns to heart as bright red oxygenated blood
 Systemic Circuit (body cells)
o Blood flows at high pressure, but is slowed down by many blood vessels
 Blood pressure forces out some of the fluid to join body fluid
o Blood gives up its oxygen as it reaches tissues, and takes in carbon dioxide
o Glucose is removed from the blood by body cells, for cellular respiration
o Ions/nutrients needed by cells leave blood, and waste products e.g. urea, enter blood
 Muscles:
o Remove proteins from the blood, and as a result of reactions occurring in muscle tissue, release amino acids
into the blood
o Remove glycogen, and release lactate and pyruvate into blood
 Intestines: products of digestion taken up by blood and carried to liver
 Liver: controls levels of circulating substances, and breaks down unwanted compounds
o Controls glucose level: either releases more, or storing excess as glycogen
o Deamination: converts excess amino acids into urea and an acid which can be used
 Also sends amino acids to all parts of the body where they are used
o Removes lactate and pyruvate from blood
o Produces bile, which is stored in gall bladder: helps to digestion in small intestine via emulsification of lipids
o Regulates cholesterol levels and stores excess lipids
o Breaks down unwanted/poisonous substances e.g. alcohol
o Breaks down old red blood cells
 Kidney: removes urea from blood, and balances water/salt composition
_______________________________________________________
 Simple sugars
o Absorbed into blood in capillaries in the gut villi
o Carried via hepatic portal vein to capillaries in the liver
o Some glucose converted into glycogen in the liver, or sent to skeletal muscle tissue to be stored as glycogen
 Amino acids
o Absorbed in gut
o Carried via hepatic portal vein to liver
o Excess amino acids are deaminated in the liver
 Removal of amino (NH3+), converting amino acids into urea and an acid
 Blood transports urea to kidneys where it is excreted with urine
 Lipids
o Reassembled into chylomicrons, which then enter lacteals of the lymphatic system in villi of intestine
o Released into venous circulation via the thoracic duct


Bilirubin
o When red blood cells die, bilirubin is produced as a waste product of haemoglobin breakdown
o Removed from blood by the liver
o Excreted into the gut with bile
o Moved out of the gut with faeces
Electrolytes
o Concentration of these changes near skin surface, through sweat glands
OUTLINE THE NEED FOR OXYGEN IN LIVING CELLS AND EXPLAIN WHY REMOVAL OF CARBON DIOXIDE FROM CELLS IS
ESSENTIAL



Living cells need oxygen for aerobic respiration, to produce ATP (form in which energy is used in the body)
When carbon dioxide dissolves in blood, it forms carbonic acid, which lowers pH
o Exists in blood as hydrogen carbonate ions
o Carbon dioxide must be removed quickly to maintain pH within viable limits for living tissue
 Cellular enzymes work best at 7.4 pH
 If carbon dioxide accumulated within cells, pH would fall, metabolic activities would be
impaired/cease, and cells would die. Also, low pH reduces haemoglobin oxygen saturation,
depriving cells of oxygen.
Change in pH monitored by receptors in medulla, walls of aorta and carotid arteries
o Breathing altered in response to nerve messages to the breathing control centre in medulla
 Too much carbon dioxidelow pHrate/depth of breathing increases
 Low carbon dioxide levelshigh pHrate/depth of breathing decreases
PERFORM A FIRST-HAND INVESTIGATION TO DEMONSTRATE THE EFFECT OF DISSOLVED CARBON DIOXIDE ON THE PH OF
WATER
DESCRIBE CURRENT THEORIES ABOUT PROCESSES RESPONSIBLE FOR THE MOVEMENT OF MATERIALS THROUGH PLANTS
IN XYLEM AND PHLOEM TISSUE

In the stem, cambium divides, and cells produced
differentiate to form xylem to the inside and phloem to the
outside
o Tylosis: Each year, parenchyma cells deposit oils,
resins into xylem tubes through the pits
 Deposits harden, stopping tubes from
transporting water, forming heartwood
o
o
Vascular bundles unite to form a continuous annual growth rings
New xylem/phloem produced after ring has formed are known as secondary xylem/phloem
 Actively conducting secondary xylem known as sapwood
 Secondary growth arises from secondary meristematic tissues, the vascular cambium and cork cambium
_____________________________________
Xylem: transports water and dissolved minerals upwards from roots throughout the plant, especially to leaves
 Xylem vessels:
o Lignin deposited in cell walls in ring patterns to strengthen them and make them impermeable to water
o Pits in walls allow water/solutes to pass through
 Pits are areas where cell wall is very thin
o End walls of cells break down to form a continuous tube, cytoplasm disappears, and cell dies
o Tubes surrounded by xylem fibres for support/strength
o Water flows more rapidly through vessels than tracheids because vessels are continuous/larger and offer
less resistance to movement

Tracheids
o Tubes of thin, overlapping cells
o Water passes from one tracheid to another through pits
Phloem: transports simple sugars, especially sucrose, produced in photosynthetic leaves, to regions of the plant where they
are used such as growing points and storage organs
 Sieve elements are elongated cells joined end-to-end, connected by perforated sieve plates
o Thin layer of cytoplasm pressed against cell wall, with few organelles
o Companion cell linked by plasmodesmata takes on metabolic functions of the sieve element
Movement in xylem:

Water can travel across cortex of root to xylem in 3 ways
1) By osmosis, crossing cell walls and cell membranes
2) Moving in symplast/cytoplasm through plasmodesmata in cell
walls
3) Moving along apoplast/cell walls
Movement in xylem occurs via the transpiration-cohesion-tension mechanism
 Transpiration
o Water moves out through stomates, and evaporates from walls of mesophyll cells to replace that lost from
air spaces through the stomata. This initiates pull of the transpiration stream
 Tension
o Water leaving mesophyll cells creates a tension in the xylem due to the concentration gradient
o Xylem shrinks slightly as there is a negative pressure created within the xylem
 Cohesion
o Water is drawn up xylem tubes to replace the loss of water due to transpiration, by capillarity
(adhesive/cohesive forces)
o As water molecules are removed from the leaf by transpiration, the next molecule moves upwards to take its
place, pulling the stream of molecules continuously along. This is passive transport.
 Root pressure plays a minor role in causing water to rise up the stem
o At night mineral ions actively taken up by roots, causing osmotic water intake, building pressure
o Pressure pushes water up the stem
 Seen as drops on end of leaves in the morning (guttation) when pressure puts water out of leaves
 As water is pulled upwards, some leaks out through pits
o More water lost by leakage in smaller, finer branching vessels
Movement in phloem:
o
Translocation is the movement of organic materials to wherever they’re needed, especially to growing points and
reproductive structures
Occurs by a mechanism known as ‘source-path-sink system’ or ‘pressure-flow mechanism’, and is driven by a pressure
gradient generated osmotically
 Phloem loading at the source: as sugars actively transported into phloem, water follows and osmotic pressure at
the ‘source’ increases
o 2 theories for how nutrients in a leaf are ‘loaded’ into the phloem
 Symplastic loading: sugars/nutrients move in cytoplasm from mesophyll cells to sieve elements
through plasmodesmata
 Requires that there be many plasmodesmata
 Apoplastic loading: sugars/nutrients move along cell walls until they reach the sieve element, then
cross cell membrane by active transport to enter phloem tube
 Phloem unloading at the sink: as sugars are actively removed from the phloem, water follows, and pressure is low
o Sink is a region of the plant where sugars/nutrients are being actively removed e.g. roots, stem, flowers,
storage areas
 The building up of pressure at the source, and the reduction of pressure at the sink, causes water to flow from source
to sink. As sugar is dissolved in the water, it flows at the same rate as the water.
o *Near the source, water moves from xylem vessels to phloem; near the sink, water moves from phloem to
xylem vessels
CHOOSE EQUIPMENT OR RESOURCES TO PERFORM A FIRST-HAND INVESTIGATION TO GATHER FIRST-HAND DATA TO
DRAW TRANSVERSE AND LONGITUDINAL SECTIONS OF PHLOEM AND XYLEM TISSUE
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
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:


Measures oxygen saturation, and pulse rate
Peg-like device sits on finger, and measures transmission of red and infrared light
through tissues
o Absorption of the LED lights it emits differs between oxyhaemoglobin, and
deoxygenated haemoglobin, and so amount of O2 in blood can be calculated
o Signal fluctuates with each heart beat because arterial vessels expand and contract
o Pulse reading is thus necessary, so the variation in maximum and minimum signals can be calculated, and
change caused by arterial blood flow discerned
o Alarm rings is oxygen saturation falls below 90%
Conditions under which a pulse oximeter is used
 On patients who are undergoing procedures that require anaesthesia or sedation, to alert staff to unexpected
hypoxia
 With patients who are on a ventilator (artificial breathing machine), to monitor success of ventilation procedures
 Helps assess whether a patient’s oxygen therapy is adequate
 Used in sleep laboratories, for patients who are having difficulty breathing when they sleep
Blood Gas Analyser:

Monitors rate of diffusion of oxygen and carbon dioxide between two electrodes through an artificial membrane to
measure concentration of these gases in a sample of blood
o Oxygen causes an electrochemical reaction with the sensor, producing an electrical current which can be
detected; current is proportional to oxygen saturation
o Carbon dioxide changes pH of the solution, because it forms carbonic acid in solution. Hydrogen ion
concentration is measured by a pH meter attached to the analyser, to calculate p(CO2)
Conditions under which a blood gas analyser is used
 Monitoring a patient during therapy
 Diagnosis of a respiratory disease
 To investigate function of kidneys
 Intensive care units: baby care units and labour wards
ANALYSE INFORMATION FROM SECONDARY SOURCES TO IDENTIFY THE PRODUCTS EXTRACTED FROM DONATED BLOOD
AND DISCUSS THE USES OF THESE PRODUCTS



Donors screened for health, past medical history, and risk of viral infections e.g. HIV
450mL blood collected in a bag with anti-clotting agent
Compatibility testing to make sure there are no antibodies in recipient’s blood that react with donor’s red cell
antigens


Whole blood: emergency transfusions
Red blood cells: for treatment of anaemia and bleeding after trauma/surgery
o Filtered red cells: for patients who have antibodies against white cells
Platelets: for control of haemorrhage; patients with low platelet count; often in patients with leukaemia
White blood cells: for patients who are not producing their own white cells or who have a serious bacterial
infection
Immunoglobulins: for treatment/prevention of inflammatory diseases or acute infection; immune deficiency
Fresh frozen plasma: to treat patients who have bleeding problems after trauma, provides components that
coagulate the blood
o Can be stored up to 12 months
Clotting factor VIII: for management of haemophilia; treats bleeding
Albumex-20: for patients with kidney or liver disease
Cryoprecipitate: contains blood clotting factors; used in treatment of massive bleeding or haemophilia







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
Pg 69 in textbook
Why artificial blood is needed




Antigen-antibody reactions to antigens on donated red blood cells are dangerous complications, so donor blood
must be cross-matched and typed
o Can be avoided using artificial blood, when no red blood cells are given
Artificial blood can be stored for more than one year, compared with about one month for donor blood using
standard methods
Donor blood can transmit viruses such as HIV. Some pathogens may escape screening.
o Many countries are prohibiting blood donations who have a risk of carrying the causative agent for bovine
spongiform encephalopathy (BSE)
o With artificial blood, pasteurisation may be used to remove all pathogens
Shortage of donor blood to help victims of emergencies, civil conflicts, and natural disasters. Artificial blood could
be manufactured on a large scale, dropping prices and making it more readily available in poorer counries.
Current uses:

Administration of normal saline (solution of 0.9% sodium chloride) as substitutes for plasma
Modified haemoglobin



Advantages
o Haemoglobin has a high oxygen-carrying capacity
o Haemoglobin can be extracted from donor blood and used by itself: doesn’t need to be cross-matched
o Can be sterilised to remove pathogens without affecting its function
o Can be stored as a stable dried powder
Problems
o However, currently it cannot be used as a blood substitute in isolation from red blood cells, as toxic changes
occur to haemoglobin in isolation
 Red blood cell membrane contains a cofactor which is needed by haemoglobin to release oxygen as
required
o In circulation, haemoglobin is rapidly broken down and excreted by the kidneys
 This is toxic to the kidneys
o Researchers are attempting to stabilise isolated haemoglobin and make it safe to use as a blood substitute.
Advances
o Encapsulated haemoglobin
 Artificial red blood cells have been produced which have the necessary cofactor, and hence an
oxygen dissociation curve similar to real RBCs
 Haemoglobin is not broken down inside these
 These artificial RBCs have no blood group antigens
 However, these artificial cells are rapidly removed from circulation, and current research focuses on
improving circulation time
o Crosslinked haemoglobin
 A diacid is used to crosslink haemoglobin to make polyhaemoglobin, which does not break down in
isolation
 Research is being done into both intramolecular and intermolecular crosslinking
o Recombinant haemoglobin is also being investigated, using genetic engineering to produce haemoglobin
that does not break down in circulation
Perfluorocarbons


Advantages
o Oxygen and carbon dioxide are highly soluble in Perfluorocarbons (PFCs).
o Since a PFC microdroplet is seventy times smaller than a red blood cells, these PFCs can carry oxygen to
places in the body that red blood cells cannot
o Inert and can be sterilised
o Can be stored at room temperature, so can be carried in emergency vehicles
o Shelf life of 12 months or more
o No matching of blood types required
o Can be used temporarily during surgery to partially replace patient’s blood, so that blood loss during
surgery is minimised
 *Must be combined with lipids to form an emulsion that can mix with blood
o
Problems
o Maximum amount used is only 20% because of viscosity of PFC emulsion at high concentrations. Because of
this smaller amount used, and also because oxygen is dissolved in PFCs rather than bound to it, sufficient
oxygen carriage can only take place when patients are breathing >70% oxygen
o PFCs are rapidly removed from circulation
o

The retention of PFCs in the reticuloendothelial system (RES) suppresses the system, resulting in lowered
resistance to infection
Advances
o One current PFC product, ‘Oxygent’, can be used in higher concentrations than normal
 Oxygent is being used in clinical trials in surgical patients, to offset blood loss during surgery
o In the future, the small PFC particles may also help affected tissues in thromboses or embolisms
________________________
These substitutes can only carry oxygen and/or carbon dioxide, whereas blood has many other functions such as transport of
nutrients, clotting, and initiation of immune reactions. Further research is needed before artificial blood substitutes can be
considered true blood substitutes rather than oxygen carriers
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




If water loss from an organism is not balanced by water intake, then dehydration occurs.
Why do cells need water?
o Water is a reactant in many metabolic reactions
o Many molecules/ions important for metabolism are carried in aqueous solution and diffuse through the
water in the cell. Loss of water from cells reduces their ability to retain compounds in solution, which
inhibits metabolic processes.
o Without water, vital functions (e.g. removal of wastes by excretory systems) decline, and wastes
accumulate in tissues
o Water is essential for functioning of cells and organs, and is used for body temperature maintenance, as a
lubricant, and for excretion of waste products
o Water is necessary to maintain blood pressure and circulation
Living cells work best in isotonic environment: solute concentration is same inside and outside the cell
o Cells lose/gain large amounts of water if concentration in internal environment changes too much,
causing cell death
o Living organisms try to ensure
water balance is maintained so
cells can function properly
 Interstitial fluid that
bathes cells is kept
isotonic to internal solute
concentration of cells
The Spinifex hopping mouse lives in
extremely hot conditions with very little
free water
Behavioural:
o Nocturnal habits result in animal collecting seeds at a time when their water content is likely to be at its
highest (since higher air humidity)
o Seeds are stored in deep burrows to prevent water loss
o
o
Physiological:
o
o
Loss of water from having to feed young with milk is balanced by mother drinking the urine her young
produce
Evaporation from skin minimised by animals huddling together in a burrow, causing humidity in burrow to
rise
Metabolic water is used by the hopping mouse
Produces the most concentrated urine of any mammal in the world
EXPLAIN WHY THE REMOVAL OF WASTES IS ESSENTIAL FOR CONTINUED METABOLIC ACTIVITY



Waste products could poison cells if they accumulate
o Ammonia, the nitrogenous waste product from protein metabolism, is highly toxic
 A solution of ammonia is highly alkaline, causing enzymes to stop functioning
 Nitrogenous wastes can also interfere with membrane transport
 Needs to be removed quickly, or converted into less harmful form
o Aquatic animals, fish and invertebrates excrete toxic ammonia, because it can be released continuously and
is quickly diluted in large volumes of water
o Mammals excrete urea in urine
 Some desert-dwelling animals excrete small amounts of highly concentrated urine
o Reptiles, birds and insects excrete insoluble uric acid with faeces, and lose very little water
Carbon dioxide, a waste product of cellular respiration, causes the cellular environment to become more acidic,
which may result in the cessation of metabolic processes since enzymes are denatured in acidic environments
 Excreted via the lungs
Metabolic wastes are the product of metabolic reactions. If they are not removed their concentration in the cell
increases. This inhibits the reactions that produce them, interfering with normal metabolic activity.
IDENTIFY THE ROLE OF THE KIDNEY IN THE EXCRETORY SYSTEM OF FISH AND MAMMALS

Primary roles of kidneys are regulation of salt/water concentrations in the body (osmoregulation), and removal of
nitrogenous wastes
o Kidneys also filter the blood, excrete hormones and vitamins, maintain a correct balance of salts by
excreting those in excess, help to maintain pH of the blood, and reabsorb nutrients that are needed
o In fish, kidneys maintain constant concentration of internal fluid for the cells
o In mammals, excretion of urea, and regulation of internal salt/water concentrations, occurs in the kidney
ANALYSE INFORMATION FROM SECONDARY SOURCES TO COMPARE AND EXPLAIN THE DIFFERENCES IN URINE
CONCENTRATION OF TERRESTRIAL MAMMALS, MARINE FISH AND FRESHWATER FISH

Significant amounts of water are reabsorbed through the loop of Henle, resulting in hypertonic urine production
o Animals without loops of Henle in their kidney tubules produce a hypotonic urine
______________________
Freshwater Fish
Excrete large amounts of dilute (hypotonic) urine, to lose water
 Problem: Water tends to diffuse into body and ions tend to
diffuse out, so fish needs to remove water, and keep salts
o Kidneys produce copious amounts of dilute urine to
remove water
o Kidneys actively reabsorb salts (NaCl) to prevent salt
loss
o Freshwater fish rarely drink water


Maintain higher concentration of solutes in their body (hypertonic to their surroundings)
Ammonia is excreted in large volumes of dilute urine, and across the gills
Saltwater Fish
Excrete small amounts of isotonic urine, to remove salt while limiting water loss
 Problem: Water tends to diffuse out of their body and ions tend to diffuse into body, so fish needs to retain water
o Excrete small amount of isotonic urine to retain water and excrete salt
o Kidneys and gills actively excrete salts (MgSO4)
o Constantly drink saltwater to replace water losses
 Internal body fluids are less concentrated than surroundings
(hypotonic to their surroundings)
 Ammonia is excreted via the gills
*Marine cartilaginous fish (sharks and rays) have tissues isotonic to
seawater, so avoid osmoregulation problems
Terrestrial Mammals
Excrete small amounts of concentrated (hypertonic) urine. Those in dry or
desert environments excrete very small amounts of highly concentrated
urine to retain as much water as possible
 Problem: conserving water while excreting nitrogenous wastes
 Deamination: Excess amino acids are broken down to urea in the liver
o Removing amino group (-NH2) to form urea, and converting the rest to a carbohydrate
o Kidneys remove urea from the blood, and excrete urea with the urine
 Urine leaves kidneys via ureters, and is stored in the bladder until urination
Reptiles (the goanna)
Excrete semi-solid uric acid
 When goanna is dehydrated, number of active tubules in kidney is reduced, reducing amount of filtrate produced
and conserving water
 As water taken in increases, the number of tubules activated also increases
Pg 16
EXPLAIN WHY THE PROCESSES OF DIFFUSION AND OSMOSIS ARE INADEQUATE IN REMOVING DISSOLVED NITROGENOUS
WASTES IN SOME ORGANISMS






Pg 17
To remove these wastes, the water in which they are dissolved must also be excreted. The water required to
remove these wastes is an important consideration for osmoregulation
If kidney tubules relied only on diffusion and osmosis in the removal of nitrogenous wastes, accompanying loss of
excess water and other substances might be detrimental
o Kidney’s ability to use active transport and avoid such losses is the key to its successful function
Diffusion does not select for useful solutes, and will not work against a concentration gradient
Diffusion is too slow to maintain normal functioning of the body.
Osmosis only deals with the movement of water and thus would only allow water to move out of the body, not the
nitrogenous wastes.
In terrestrial organisms, the external environment is not water, so diffusion and osmosis cannot directly be used to
excrete dissolved nitrogenous wastes. On the other hand, since the water around fish is continually moving, a
concentration gradient can be maintained and wastes are excreted mostly passively.
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
Animals excrete nitrogenous wastes in different forms because they have different amounts of water available to them.
 Ammonia
o Highly soluble in water and highly toxic
o It must be diluted in large quantities of water and quickly excreted along with the water
o Least amount of energy required as it does not have to be converted to a less toxic form first.
 Hence, it is the waste product of most aquatic animals
 Urea
o Moderately soluble and moderately toxic
o Can be safely stored in the body for longer in a more concentration solution. Therefore urea requires less
water to remove than ammonia
 Hence, it is the waste product of mammals, some other terrestrial animals, adult amphibians,
sharks, and some bony fish
o Nevertheless, excreting urea is the major source of water loss in mammals
 Uric acid
o Least soluble (highly insoluble) and low toxicity
o Can be safely stored in the body for extended periods of time, so little water is expended to remove it
 Hence, it is the waste product of birds, many reptiles, and insects, which need to conserve water
Organism
Waste product(s) Explanation
Spinifex hopping Urea, in a
Lives in a very arid environment. Drinks very little water and
mouse
concentrated form excretes urea in a concentrated form, so that water can be
conserved.
Red kangaroo
Urea, in
concentrated
urine
Insects
uric acid
(e.g. ‘Lord Howe
Island Stick
Insect’)


Has a very efficient excretory system that recycles nitrogen and urea
to make a very concentrated urine. This allows them to survive in
very arid environments
Covered with a cuticle impervious to water.
Conserve water by producing a dry paste of uric acid.
Australian terrestrial mammals that live in predominantly arid areas, such as the Bilby, must produce very
concentrated urine and tolerate high levels of urea in their systems.
Some insects excrete ammonia as a vapour across the body surface rather than as a solution of urine, an adaptation
for conserving water.
EXPLAIN HOW THE PROCESSES OF FILTRATION AND REABSORPTION IN THE MAMMALIAN NEPHRON REGULATE BODY
FLUID COMPOSITION
http://www.uic.edu/classes/bios/bios100/lecturesf04am/lect21.htm

Each kidney is made up of about one million small filtering units called nephrons, which produce urine
o *Nephrons surrounded by dense network of capillaries
o Starting point is Bowman’s capsule, situated in the cortex
o Leads to a narrow, convoluted tube, which makes a loop in the medulla back to the cortex, then joins a
collecting duct
o
o
Collecting duct transports urine to pelvis of kidney, which leads to the ureters
3 processes in formation of urine: filtration, reabsorption, secretion
Filtration




Blood brought to kidneys by renal artery, which divides into smaller vessels
Vessels form a network of capillaries called a glomerulus, when they reach Bowman’s capsule
Very high blood pressure in glomerulus, as well as very permeable capillary walls, non-selectively force some
parts of blood through Bowman’s capsule into the kidney tubule to become ‘glomerular filtrate’
o Glomerular filtrate consists of blood plasma, and small soluble molecules which pass through by passive
filtration; no blood cells, platelets or large plasma proteins
 Water, nitrogenous wastes (urea), food materials (glucose, amino acids, vitamins), other ions (e.g.
bicarbonate), other ingested substances (penicillin), and hormones
Filtrate forced into proximal part of tubules nephron’s tubules
o Along length of tubule, composition of filtrate adjusted until it contains only unwanted substances (urine)
Reabsorption


As filtrate travels down the tubule, materials the body can re-use are selectively reabsorbed into the large
capillary network surrounding the tubules
o Glucose, amino acids, vitamins, bicarbonate, and water reabsorbed through microvilli on tubule walls
o Reabsorption of ions occurs at different rates depending on feedback from body
Occurs in proximal/distal parts of tubule, and in loop of Henle
o Glucose, amino acids reabsorbed in proximal tubule
o Sodium/potassium ions reabsorbed in proximal/distal tubules; chlorine ions and water follow passively into
the blood
o Bicarbonate ions reabsorbed in proximal/distal tubules to maintain blood pH
Secretion

Selective process by which body actively transports substances from blood into nephrons
o Hydrogen ions secreted in proximal/distal tubules to regulate blood pH
o Drugs (e.g. penicillin) and poisons identified by liver are actively secreted into proximal tubule
Regulation of Body Fluid Composition: Recap



Proximal tubule
o Nutrients such as glucose and amino acids reabsorbed
o Salts reabsorbed, and water follows by osmosis
o Hydrogen ions and drugs/poisons secreted
Loop of Henle
o Descending part: walls permeable to water but not to salt
 Water passes by out by osmosis, until filtrate is
isotonic with external medulla
o Ascending part: walls permeable to salt but not to water
 Salt (NaCl) passes out passively across thin-walled
section as external solute concentration
decreases, and then actively across thick-walled
section
 *Salt passing out makes interstitial fluid of
medulla quite concentrated
Distal tubule
o Salts reabsorbed, and water follows by osmosis
o Bicarbonate reabsorbed, hydrogen ions secreted

Collecting Duct
o Walls permeable to water but not salt, so water passes out by osmosis
Pg 18-20
DISTINGUISH BETWEEN ACTIVE AND PASSIVE TRANSPORT AND RELATE THESE TO PROCESSES OCCURRING IN THE
MAMMALIAN KIDNEY

Passive transport does not require expenditure of energy (e.g. diffusion, osmosis), as materials move down a
concentration gradient
o Facilitated diffusion: specific carrier protein molecule assists diffusion
o Occurs in filtration, and in osmosis of water back into the blood
 Proximal tubule: K+ and HCO3- ions out, ammonia (NH3) in
 Thin section of ascending limb of loop of Henle: NaCl out
 Osmosis of water out in tubules, descending limb of loop of Henle, and collecting duct

Active transport requires expenditure on the part of the organism, and often goes against concentration gradient
 Specific carrier proteins in membrane may bind with substance and carry it across the membrane
 Endocytosis: a pouch forms that carries matter through the membrane
o Enables cells to maintain stable internal conditions in spite of extreme variation in the external environment
o Occurs in secretion of substances into the nephrons, reabsorption of nutrients back into the blood, and
selective reabsorption of salts required by the body
 Proximal tubule: glucose/amino acids out, H+ in
 Distal tubule: HCO3- out, K+ and H+ in
 Na+ out in tubules, thick segment of ascending limb of loop of Henle, and collecting duct
 Poisons and drugs secreted in proximal and distal tubules
Pg 18-20
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
GATHER, PROCESS AND ANALYSE INFORMATION FROM SECONDARY SOURCES TO COMPARE THE PROCESS OF RENAL
DIALYSIS WITH THE FUNCTION OF THE KIDNEY
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Renal dialysis: artificial process in which wastes in blood are removed by diffusion across a partially permeable
membrane
o Used for people who have impaired kidney function, where products of metabolism (including urea) build
up in the body
 High concentrations of these cause tiredness etc.
Haemodialysis
o Blood is drawn from an artery, and passes through dialysis tubing made of semipermeable material
 Tubing passes through a container of dialysing fluid (balanced salt solution)
o Membrane allows wastes to diffuse across into dialysis solution, but not blood cells, platelets or proteins
 Excess water is also removed by osmosis
 This step is similar to filtration stage of normal kidney function
o
o
o
o
Any salt or drug that is in a higher concentration in the dialysing fluid than in the blood, will diffuse into the
blood
 This step is similar
to the passive
transport
components of
reabsorption
Dialysing fluid is constantly
replaced to maintain
concentration gradients and
ensure maximum waste
removal
Anti-clotting agent heparin
is added to the cleaned
blood, and the blood is
returned to the body
Haemodialysis can be used only 4-5 hours at a time, 3 times a week
 Because heparin is dangerous, risk of infection, and blood cells may be damaged as they pass
through plastic tubes
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Peritoneal dialysis
o Unlike haemodialysis, peritoneal dialysis undertaken inside the body
o Dialysis solution introduced into peritoneal (abdominal) cavity through a catheter
o Natural membrane lining peritoneal cavity is a partially permeable membrane, so waste products and
excess water from body can pass through membrane into dialysis
solution
o Continuous ambulatory peritoneal dialysis (CAPD)
 Sterile dialysis fluid is introduced into abdomen through a
catheter, and fluid ‘dwells’ in the cavity until the next change
 At the end of the dialysing period, used fluid is allowed to
run out into an empty drainage bag
o Automated peritoneal dialysis (APD)
 Person connects via a catheter to a cycler machine to
perform overnight dialysis
______________
 Renal dialysis successfully replicates the passive transport components of the
kidney’s functions, but cannot replicate kidney’s use of active transport.
 Urea and excess water/salts diffuse from blood to dialysis fluid, instead of
leaving by pressure filtration as in the nephron
 Dialysis is a slower and less efficient process than natural processes found in a healthy kidney
OUTLINE THE ROLE OF THE HORMONES, ALDOSTERONE AND ADH (ANTI-DIURETIC HORMONE) IN THE REGULATION OF
WATER AND SALT LEVELS IN BLOOD
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When glomerular filtrate passes through nephron tubules, amount of water/salts reabsorbed matches body’s
needs
o E.g. excess water excreted as dilute urine, or kidneys reabsorb maximum possible amount of water on a hot
day, forming a small amount of concentrated urine
o *Diuresis is loss of urine
Antidiuretic hormone (a.k.a vasopressin): increases water retention
o
o
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Made in hypothalamus but stored/released from pituitary
If receptors in hypothalamus detect high blood concentration (due to sweating/water loss), ADH is released
into the blood and goes to kidneys
 ADH increases permeability of walls of collecting ducts to water, allowing water to pass freely by
osmosis back into the body
o As blood returns to normal concentration by negative feedback, less ADH is secreted
o If blood concentration is low (after drinking a lot of water) very little ADH is released, and water passed out
with urine
o Water retention reduces concentration but not total amount of salt
Aldosterone: increases salt retention
o Produced by adrenal glands
 Aldosterone increases permeability of walls of distal tubules to Na+ ions; Cl- ions follow by
diffusion. Water then flows from nephron into blood by osmosis, increasing blood pressure
o Pressure-sensitive receptors in the kidney detect fall in blood pressure
 If blood pressure falls, body needs more salt, so adrenals release more aldosterone, and more salt is
reabsorbed in tubule
o If there is increased blood volume/pressure (resulting from high salt concentrations), aldosterone output
reduced
 Less salt/water reabsorbed by nephrons tubules, and more salt/water lost in urine
PRESENT INFORMATION TO OUTLINE THE GENERAL USE OF HORMONE REPLACEMENT THERAPY IN PEOPLE WHO
CANNOT SECRETE ALDOSTERONE
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Causes of low aldosterone levels
o Diseases of adrenal glands or pituitary glands, surgery on adrenals, medications that prevent thrombosis
Hypoaldosteronism is a condition where people fail to secrete aldosterone.
Addison's disease is a disease with these symptoms
o Inability to secrete aldosterone from adrenal cortex, caused by shrinking/destruction of adrenal gland
Effect of low aldosterone levels due to Addison’s disease
o Excessive amounts of sodium are excreted with high urine output
o Results in dehydration, low sodium levels, high potassium levels, high acid levels, and lowered blood
pressure/volume, which can lead to heart failure
o Symptoms: fatigue, muscle weakness, weight loss, skin changes
Treated with hormone replacement therapy using a synthetic hormone called fludrocortisone (Florinef)
o Careful monitoring needed to avoid fluid retention and high blood pressure
Patients advised to increase salt intake
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
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Enantiostasis: maintenance of metabolic and physiological functions in response to variations in the environment
Estuary is formed when freshwater from a river, meets saline water from the sea
Estuaries are nutrient traps; water from river/sea are slowed, and sediment settles, forming a rich soup that
supports a vast community
o Warmer conditions, more sunlight for photosynthesis; lots of mangroves and seagrasses
Salinity gradient in an estuary, with high salinity in ocean end, and low salinity at other end
o Daily cycle of tides, and major periodic changes (king tides, drought, flood) alter salinity
o Organisms experience great changes in salinity
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Enantiostasis is fully tested in estuaries, as some organisms have a narrow salinity tolerance and major changes will
kill them
o Fast-swimming organisms, e.g. fish, can move away
o Molluscs can close their shells
o Bottom-dwellers can burrow into mud/sand
o Plants cannot move, and so must find ways to cope with salt entering their tissues
Stenohaline organisms that remain in the open sea can tolerate little or no change in the salinity of their
environment
Euryhaline organisms can tolerate a wide range of salinities
o Such organisms must either be able to function with fluctuating internal salt concentrations
(osmoconformer), or must have physiological mechanisms to control salt concentrations of their bodies
(osmoregulators)
o Most marine invertebrates are osmoconformers (so are sharks). In contrast, marine mammals and most fish
are osmoregulators, maintaining homeostasis regardless of the osmotic pressure of the environment.
For normal functioning to be maintained, another body function must be changed in a way that compensates for
the decline in enzyme activity due to change in environmental conditions.
o One example of enantiostasis is when a change of salt concentration in body fluids reduces the efficiency of
an enzyme, and this is compensated for by a change in pH, which increases the efficiency of the same
enzyme.
PROCESS AND ANALYSE INFORMATION FROM SECONDARY SOURCES AND USE AVAILABLE EVIDENCE TO DISCUSS
PROCESSES USED BY DIFFERENT PLANTS FOR SALT REGULATION IN SALINE
ENVIRONMENTS
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Halophytes are plants adapted to living in salty environments
Genus Atriplex, of the chenopod family, known as ‘saltbushes’, have special
salt excretion glands on their leaves
o Dominant species in salt-marsh communities throughout Australia
Grey mangrove
o Leaves accumulate excess salt, and this is lost from the mangrove
when leaves fall
o Endodermis in roots forms a barrier against passage of most salt into
xylem
o Secretes salt solution through glands on their leaf surfaces
DESCRIBE ADAPTATIONS OF A RANGE OF TERRESTRIAL AUSTRALIAN PLANTS THAT
ASSIST IN MINIMISING WATER LOSS
o Plants that live in dry areas are known as xerophytes
Leaves which are well adapted to the arid climate have:
 Ability to close stomates when temperatures rise at midday
 Hairs that reduce airflow over surface, thus reducing evaporation
 Woody petiole to reduce water loss
 Leaves close together to reduce air flow around leaves
 Hard leaves with waxy cuticle
 Extra thickening of cell walls throughout their branches, so they don’t
wilt even though they may lose large amounts of water
 Thicker bark
Australian examples of plants which are well adapted to the arid climate
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Creosote bush:
o Roots produce a poison that prevents other plants from growing too close, so that roots have no
competition for water in their area
Sydney blue gum
o Thick, waxy cuticle
o Light, reflective leaf surfaces to reflect solar radiation and reduce evaporation
o Leaves in upright position to minimise exposure to sun, and hence evaporation
o Stomates sunk in pits, inside the rolled surface
Acacia pycnantha:
o Has phyllodes instead of true leaves, which carry out photosynthesis but have
no stomates through which water can be lost
Porcupine grass:
o Shallow and widely spread roots
o Long narrow leaves which are rolled, with stomates on
inside surface
 High humidity is maintained around stomate
openings, reducing effect of wind on water loss
Boab tree: thick, bottle-shaped trunk that can store water; sheds
all leaves in summer so that the tree has no stomata during
summer, and far smaller SA through which water can be lost and
heat absorbed
PERFORM A FIRST-HAND INVESTIGATION TO GATHER INFORMATION ABOUT STRUCTURES IN PLANTS THAT ASSIST IN THE
CONSERVATION OF WATER