Maintaining a Balance

Question 1

What are enzymes?

Answer 1

Globular proteins; increase reaction rate (catalyse)

Unchanged at end of reaction

Bind to substrate (active site)

Question 2

Chemical Composition of Enzymes

Answer 2

Protein molecules (amino acid chain) fold in specific shape

Act on reactant molecule (substrate) fit with at specific location on enzyme molecule surface (ac

Question 3

Role of Enzymes in Metabolism

Answer 3

Acceleration of chemical reactions
Lowers activation energy needed for reaction; reaction starts quickly without temp change

Lowering of activation energy
Brings specific molecules together (instead of relying on random collisions)

Action on specific substrates
Only one particular enzyme works on one particular substrate molecules
Active site is reciprocally shaped to bind with that molecule

Question 4

Characteristics of enzymes

Answer 4

Temperature sensitive
Function best at body temp (above 60℃→ stop working)
Heat breaks hydrogen bonds→ alters active site (not reciprocally shaped)
Temp too high or low→ will denature

pH sensitive
Narrow pH range functions efficiently; levels outside optimum; alters shape

Substrate specific
Each enzyme catalyses one particular reaction; act on one substrate

Question 5

Enzyme Models

Answer 5

Induced fit
Enzyme changes shape as substrate approaches (molecules flexible)
Reaction occurs, substrate changes, product released (enzyme returns to original form)

E.g. Gloved hand changes to catch ball; active site is palm, closes around ball when it draws near

Lock and key
Simply fits into active site to form immediate reaction (not considered accurate)
Depends on unlikely random collisions between enzyme and substrate

E.g. Like trying to get key in lock by throwing key at lock with eyes closed

Question 6

Identify data sources, plan, choose equipment or resources and perform a first hand investigation to test the effect of:

Increased temperature
Change in pH

Answer 6

INCREASED TEMP
Milk with rennin; curdled quickly (temp approx 370C)

Temps higher or lower than optimum→ milk with rennin doesn’t curdle (doesn’t react)

CHANGE IN pH
pH affects activity of catalase in potato tissue (has optimum pH)

Height of foam measured when catalase put in hydrogen peroxide

pH of 9 is optimum for catalase (average bubble height was higher)

Question 7

Identify the pH as a way of describing the acidity of a substance

Answer 7

pH scale→ indicates acidity
Lower value; acidic,
Higher value ;alkaline

Question 8

Explain why the maintenance of a constant internal environment is important for optimal metabolic efficiency

Answer 8

Stable for enzyme functioning→ maintain metabolism (enzymes sensitive to change)

Small variations from narrow range→ small decreases in activity

Larger variation from narrow range → reduced metabolic efficiency

Question 9

Gather, process and analyse information from secondary sources and use available evidence to develop a model of a feedback mechanism

Answer 9

Stimuli→ increased or decreased body temp (E.g. hot/cold surroundings, exercise)

Co-ordinating centre→ Hypothalamus detects change; activates cooling or warming mechanism

Effectors:
High temp; Skin vessels dilate (blood carries heat to skin surface) Sweat glands (evaporate)
Low temp; Skin vessel constrict (reduce heat loss from skin surface) Skeletal muscles (shiver)

Negative feedback loop→ body temp increases or decreases, hypothalamus shuts off warming or cooling mechanism

Question 10

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

Answer 10

Maintenance of constant (or almost) internal state, regardless of external environmental change

Body regulates respiratory gas, protects against pathogens, maintain salt/fluid balance, constant temp

Regardless of environmental change→ body temp, blood pH, water/salt balance, blood pressure, oxygen, carbon dioxide concentration; kept constant.

Question 11

Explain that homeostasis consists of 2 stages:

• Detecting changes from the stable state
• Counteracting changes from the stable stage

Answer 11

Any internal deviation must be quickly corrected. Counteract; use corrective mechanism

Stage 1: Detect change from stable state: Receptors detect change. E.g. Thermoreceptors in skin

Stage 2: Counteract change: Effector (muscle or gland) receives message to counteract change. Response initiated to reverse change, restore body to stable. E.g. Muscles shiver to generate heat

If variation exceeds normal; NEGATIVE FEEDBACK counteracts, returns body to homeostasis

Question 12

Analyse information from secondary sources to describe adaptations and responses that have occurred in Australian organisms to assist temperature regulation

GENERATE HEAT
RETAIN HEAT

Answer 12

GENERATE HEAT
Shivering: Rapid muscle contractions

Increased metabolism; Activity of thyroid gland stimulated, speeds up metabolism

RETAIN HEAT
Raised hair: traps warm air, reduces heat loss by convection. Muscles contract

Vasoconstriction: Blood vessels construct so heat carried in blood is redirected to core of body, prevents heat loss from body surface

Question 13

Analyse information from secondary sources to describe adaptations and responses that have occurred in Australian organisms to assist temperature regulation

RELEASE HEAT
GENERATE LESS HEAT

Answer 13

RELEASE HEAT
Vasodilation: Arterioles expand, blood directed to body surface, heat lost by radiation, convection

Sweating: liquid secreted onto skin, heat removed to evaporate liquid

GENERATE LESS HEAT
Decreased metabolism: Thyroid gland lowers metabolism, generates less heat

Flattened hairs: Laid flat, increases heat loss

Question 14

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

Answer 14

Function of nervous system→ coordination

Receptors; Thermoreceptors, hypothalamus detects change → converts to message, travels along nerves in CNS (brain, spinal cord)

Control centre: CNS processes info about change in specific parts of brain

Motor nerves; Carry info as nerve impulses from CNS to effectors

Effectors: Muscle or gland receives impulses, instruct effectors to respond

Response; Counteracts original change; ensures homeostasis

Question 15

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

Answer 15

Living creatures can survive temps of -70℃ (poles), high as 56℃ (deserts), 350℃ ( hot vents in sea)

Individual species need much narrower range of temp (have optimum temp they function at)

Tolerance range; temp range species can survive, usually few degrees outside of optimum

Question 16

Endothermic definition

Answer 16

Endothermic; maintain constant internal temp; using internal metabolism to generate heat (mammals)

Question 17

Ectothermic definition

Answer 17

Ectothermic: Body temp governed by external heat sources, environment regulates temp (reptiles)

Question 18

Endothermic example

Red Kangaroo

Answer 18

Hottest part of day→ seek shade; tail, hind legs shade by body (reduces surface are exposed to sun)

Lowers body temp

Question 19

Ectothermic example

Blue tongue Lizard

Answer 19

Cold weather→ remain inactive (buried in shelter) lowers metabolic rate→ conserve energy

Sunny days→ emerge to bask→ raises temp

Question 20

Some responses of plants to temp change

LEAF FALL

SHINY LEAVES

ORIENTATION

ICE FORMATION BETWEEN CELLS

Answer 20

Leaf fall
Hot conditions→ plants drop leaves (reduces surface area to sun, reduces water loss through transpiration)

Shiny leaves
Reflect solar radiation→ reduces heat absorbed

Orientation
Vertical orientation→ reduces surface area to sun, reduces amount of heat exposed to)

Ice formation between cells
Temps below freezing→ ice form in cells, forms in gaps between plant cells; cell walls protects cytoplasm being pierced by ice crystal→ cell survives

Question 21

PLANTS AND ANIMALS TRANSPORT DISSOLVED NUTRIENTS AND GASES IN A FLUID MEDIUM

Answer 21

Transport system; distributes food/oxygen to cells, removes carbon dioxide and waste

Blood; fluid transport medium; contains 3 types of cells

RBC: Carry oxygen, maintain pH of blood

WBC: Part of immune system, protects against invading organism

Platelets: Clotting of blood, stops blood loss

Plasma; Makes up most blood volume; carries nutrients, gases etc

Question 22

Identify the form(s) in which each of the following is carried in mammalian blood:

OXYGEN

Answer 22

Carried from lungs to heart, body tissues

98.5% as hemoglobin in RBC, 1.5% dissolved in plasma

Question 23

Identify the form(s) in which each of the following is carried in mammalian blood:

CARBON DIOXIDE

Answer 23

Cellular respiration product carried to lungs

70% as hydrogen carbonate ions, 7% as plasma, 23% combined with haemoglobin

Travels in RBC, plasma

Question 24

Identify the form(s) in which each of the following is carried in mammalian blood:

WATER

Answer 24

Reabsorbed from nephron to body cells

Travels in plasma as water molecules

Question 25

Identify the form(s) in which each of the following is carried in mammalian blood:

SALTS

Answer 25

Reabsorbed from nephrons to all body cells.

Dissolved in plasma as ions

Question 26

Identify the form(s) in which each of the following is carried in mammalian blood:

LIPIDS

Answer 26

Absorbed across villi wall of small intestine to veins in shoulder,

As fatty acids, glycerol dissolved in plasma

Question 27

Identify the form(s) in which each of the following is carried in mammalian blood:

OTHER DIGESTION PRODUCTS (amino acids, glucose)

Answer 27

Proteins broken down into amino acids, transported
across small intestine wall.

Dissolved in plasma to be absorbed into cells for making proteins

Question 28

Identify the form(s) in which each of the following is carried in mammalian blood:

NITROGENOUS WASTES

Answer 28

Urea processed in liver → moves into blood

Transported dissolved in plasma to kidneys (removed across nephrons)

Question 29

Perform a first- hand investigation to demonstrate the effect of dissolved carbon dioxide on the pH of water

Answer 29

Water in beaker (add universal indicator)

Blow bubbles with straw (carbon dioxide) for 2 mins

Colour will change→ estimate pH using colour chart (makes more acidic)

Question 30

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

Answer 30

Known diameter of RBC= 7.5um

Calculate field of view (mini grid) → on slide estimate number of RBC that fit across diameter of fov

Estimate number of WBC, repeat and compare with known

Question 31

What is Haemoglobin?

Answer 31

Oxygen carrying molecule (carries 4 oxygen molecules)

Each RBC carried 200-300 million haemoglobin molecules→ so 800-1200 million oxygen molecules

Protein of 4 polypeptide chains (globins) bonded to iron containing group (haem)

Question 32

Adaptive advantage of Haemoglobin:

Increases oxygen-carrying capacity of blood

Answer 32

1 haemoglobin molecule binds with 4 oxygen molecules

More oxygen can be carried in blood cells

Question 33

Adaptive advantage of Haemoglobin:

Increases binding of oxygen once first oxygen molecule binds

Answer 33

Bonding causes haemoglobin to change slightly, easier for subsequent oxygen molecules to bind

Increases rate and efficiency of oxygen intake

Question 34

Adaptive advantage of Haemoglobin: Release of oxygen increases when carbon dioxide is present

Answer 34

Has to release oxygen from blood to where it’s needed

Metabolising cells release carbon dioxide (lowers pH)

Haemoglobin at lower pH has lowered attraction to oxygen (can release)

Question 35

Adaptive advantage of Haemoglobin: Enclosed in RBC

Answer 35

If it were just dissolved in plasma, oxygen would upset osmotic plasma balance

Question 36

Arteries definition

Answer 36

Carry blood under pressure away from heart to other organs

Question 37

Capillaries definition

Answer 37

Tiny blood vessels carry blood close to cells; link arteries and veins

Question 38

Veins definition

Answer 38

Carry blood towards heart from other organs

Question 39

ARTERIES STRUCTURE TO FUNCTION

Answer 39

Carry blood from heart to other body parts

Thick walls (withstand high pressure of pumped blood)

No valves→ pressure is high (not needed to stop backflow)

Elastic wall fibres→ increases elasticity, expand for increased blood volume pumped in each heartbe

Question 40

CAPILLARIES STRUCTURE TO FUNCTION

Answer 40

Brings blood into contact with tissue (chemical exchange in cells and bloodstream)

Large network to spread blood (no cell far away from blood supply)

Walls only 1 cell layer thick (efficient diffusion)

Small lumen→ Forces RBC to pass in single file (slows flow, increases exposed surface area for gaseous exchange)

Question 41

VEINS STRUCTURE TO FUNCTION

Answer 41

Carry blood from tissues back to heart

Thinner walls→ blood flows in, not pumped

Wider lumen (easy blood flow)

Valves (small pocket folds→ lines lumen) → prevents backflow

Question 42

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 see technologies are used.

Answer 42

Levels of chemical in blood→ indicate state of health

Changes in level→ ineffective metabolic functioning (results in poor health)

Carbon dioxide/oxygen concentrations in blood→ how well lungs function, blood circulates

PULSE OXIMETER
Clip with sensor placed on finger→ shows pulse rate and oxygen saturation level

Check blood oxygen levels; people with heart attacks, cancer etc (non-invasive)

ARTERIAL BLOOD GAS ANALYSIS (ABG)
Invasive→ blood removed from artery, blood analysed in sample

Used to discover is patient has lung/kidney disorder, lung disease

Details about level of chemicals in blood (pH, bicarbonate ions, oxygen levels)

Question 43

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.

Answer 43

Circulatory system; transport of substances to and away from parts (gases, nutrients, wastes, hormones)

Metabolism→ relies in correct chemical balance brought to cells, removal of wastes

Function of organ→ determines difference in chemical concentration of blood entering or leaving

All organs→ Internal gae exchange (cellular respiration) lungs→ external

Deoxygenated blood→ arrives at lungs, releases CO2 and picks up oxygen→ Haemoglobin carries
CO2→ cells release,diffuses into capillaries→ carried in haemoglobin→ travels back via veins

Question 44

Blood passing through and change

LUNGS

Answer 44

Increase Oxygen, & Decrease CO2

Question 45

Blood passing through and change

ANY ORGAN NOT LUNGS

Answer 45

Decrease Oxygen & Increase CO2

Question 46

Blood passing through and change

ANY ORGAN INVOLVING ABSORBING DIGESTED FOOD

Answer 46

Increase in digestive end products (glucose)

Question 47

Blood passing through and change

LIVER

Answer 47

Decrease in digestive end products (E.g. Glucose, fatty acids, amino acids)

Increase nitrogenous wastes (Urea)

Question 48

Blood passing through and change

KIDNEY

Answer 48

Decrease nitrogenous wastes (filter and excrete)

Question 49

Blood passing through and change

GLANDS

Answer 49

Increase in hormones (secreted and travel to where needed)

Question 50

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

Answer 50

Oxygen→ necessary for cellular respiration (combines with glucose during CR to release energy ATP)

CO2→ Must be removed to prevent pH changes in cells and bloodstream

CO2 reacts with water (in cytoplasm or plasma) → forms carbonic acid (build up is toxic) lowers pH

Lowered pH→ prevents enzyme functioning (reduces metabolic efficiency)

Question 51

Analyse information from secondary sources to identify the products extracted from donated blood and discuss the uses of these products

Answer 51

First transfusions (most killed) 120 years ago → discover specific blood types (incompatible groups= fatal)

Before blood donations→ cross matching of blood groups needed

RBC→ helps patients carry more oxygen (helps replace lost cells after bleeding)

Platelet→ treats bleeding from diseases where platelets don’t function properly
Frozen plasma→ patients who need immediate clotting (E.g. After large transfusions

LIABLE PRODUCTS
Perishable→ short shelf life
Need to be transported in refrigerated conditions
E.g. RBC, platelets, plasma

STABLE PRODUCTS
Longer shelf life
Produced by- separating different protein components from plasma
E.g. Blood clotting factors, immunoglobulins

Question 52

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

XYLEM

Answer 52

Carries water ions from roots to leaves
Made of vessels, tracheids, fibres, parenchyma cells

Transpiration stream theory
Water sucked up stem; evaporative pull of transpiration

Water drawn up tubes; replace water loss from evaporation in leaves

Evidence:
Vessels are hollow→ offer little resistance to water

Concentration gradient; leaf surface (high), centre of leaf (low) creates tension as moves across gradient→ doesn’t break due to cohesion/adhesion of molecules

Question 53

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

PHLOEM

Answer 53

Carries nutrients (sugars, amino acids) to all parts of plant, moves both ways

Made of fibres, parenchyma, sieve cells and companion cells

Pressure flow theory
Active process (needs energy) driven by osmotic pressure gradients (generated by differences in sugar water concentration)

Sugar loaded into phloem at source then uploads into surrounding tissue (sink)

Loading attracts water flow (osmotic pressure)
Offloading at sink→ water moves out

Question 54

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

Answer 54

Past→ attempts to treat bleeding in WW1 & WW2→ failed. Encouraged modern artificial blood

Blood transfusions work (Problems; need cross matching and short storage life)

1980’s→ urgent research; response to sudden appearence of HIV in blood transfusion patients

AIDS crisis in South Africa- driving force in becoming one of the first countries to clear artificial blood for limited use in patients

Question 55

Ideal characteristics of artificial blood

Answer 55

Can be stored for long periods of time and easily transported

Doesn’t need to be cross matched for different blood types

Continues to circulate (doesn’t settle) and has no toxic effects on body

When patient’s own blood is restored→ can be safely excreted

Question 56

Oxygen carriers being developed: Perfluorocarbons, haemoglobin based oxygen carriers and microcapsules

Answer 56

Perfluorocarbons
Carry oxygen in dissolved forms
Carry up to 50x more dissolved oxygen than plasma

Haemoglobin- based oxygen carriers
Extract haemoglobin from outdated human blood; modify for use in artificial blood

Microcapsules
Artificial red cell currently being developed as microcapsules
Phospholipid- haemoglobin can be placed inside

Question 57

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

Answer 57

Changes in water concentration lead to corresponding changes in solute concentration in cells

Water in cells→ determines osmotic pressure of cells

Water moves by osmosis→ water movement into/ out of cells depends on solute concentration inside/ out of cells

Water provides necessary medium in which all chemical reactions of metabolism occur:

Chemical reactions occur→ only if reactants are dissolved in water; levels must be constant

Water concentration; Too much→ cells may burst. Too little→ cell contents shrink

Too little water→ increase in solute concentration→ lowers pH (must be maintained→ enzymes)

Water accumulates→ may dilute reactants and slow down metabolism

Question 58

Explain why the removal of wastes is essential for continued metabolic activity

Answer 58

Accumulation of wastes is toxic→ must be removed to maintain homeostasis

If build up→ alters conditions→ stops enzyme functioning. Can change pH→ stops enzymes

Accumulation that doesn’t alter pH→ alters reaction rates, osmotic imbalance→ affects membrane functioning

E.g. Accumulation of Carbon Dioxide→ internal environment becomes too acidic

Question 59

Gather, process and analyse information from secondary sources to compare the process of renal dialysis with the function of the kidney

KIDNEY

Answer 59

Filters blood, remove waste/excess fluids→ turn into urine (excreted)

Passive: Glomerular capillaries diffuse wastes through membrane

Active: Reabsorption in nephrons, wastes reused into bloodstream

180 L blood filters everyday (entire blood volume filtered 20-25 x per day)

Maintains chemical balance in blood

Question 60

Gather, process and analyse information from secondary sources to compare the process of renal dialysis with the function of the kidney

RENAL DIALYSIS

Answer 60

Carries out function of failed kidneys (cleans blood)

Haemodialysis→ transfers blood to machine to be filtered before returned to body

Glucose levels same in fluid (so doesn’t diffuse)

Passive transport; diffusion of substances in dialysis membrane between blood and fluid

Blood filtered for 3-4 hours (2-3 times a week)

Removes wastes to stop accumulating; maintains chemical balance in blood

Question 61

Identify the role of the kidney in the excretory systems of fish and mammals

OVERVIEW

Answer 61

Water accumulates in body→ by eating/drinking, metabolism. Nitrogenous wastes→ metabolism

Water potential: Tendency of a solution to lose water by osmosis (typical; high water concentration)

Water concentration in environment; Determines organism’s need to conserve or lose water

Question 62

Identify the role of the kidney in the excretory systems of fish and mammals

FRESHWATER FISH

Answer 62

Live in rivers/lakes (high water potential) water freely available (few salts)

Urinate frequently; water accumulates (osmosis→ high concentration surroundings to low in fish)

Too much water in bodies→ Kidneys excrete excess and wastes. Conserve salt

Question 63

Identify the role of the kidney in the excretory systems of fish and mammals

MARINE FISH

Answer 63

Live in sea- urinate less (lose body water across gills to surroundings)

Salt diffuses into bodies→ main kidney function (remove excess)

Kidneys conserve water rather than extract

Question 64

Identify the role of the kidney in the excretory systems of fish and mammals

TERRESTRIAL MAMMALS

Answer 64

Water and salt loss from body;respiration ,excretion (sweat, urine)

Control mechanism; ensure balance maintained of amount excreted

Urine; dilute or concentrated (adjusted depending on body needs)

Large amount of salt lost by sweat→ needs replacing for stable osmotic pressure in body

Question 65

Explain why the process of diffusion and osmosis are inadequate in removing dissolved nitrogenous wastes in some organisms.

OVERVIEW

Answer 65

Both are slow (rely on concentration gradient difference; slows as difference is smaller, stops; equal)

Solution; combine active transport and osmosis (quick; removes waste even against gradient)

Used to pump salts from urine back into kidney (draws water with them by osmosis)

Question 66

Explain why the process of diffusion and osmosis are inadequate in removing dissolved nitrogenous wastes in some organisms.

PROBLEMS WITH OSMOSIS

Answer 66

Too much water may be lost in urine

Contains too much nitrogenous wastes, water will be drawn into urine to dilute waste (equalise concentration) → dilute urine (loses too much)

Movement of water may make wastes too dilute for excretion by diffusion

Slows down excretion by diffusion (lowers concentration gradient)

Question 67

Explain why the process of diffusion and osmosis are inadequate in removing dissolved nitrogenous wastes in some organisms.

PROBLEMS WITH DIFFUSION

Answer 67

Rate of movement is slow

Wastes must be dissolved with water when removed→ Concentrations equalise movement slows and stops

Not all wastes can be removed by diffusion

If concentrations equalise and no further wastes removed→ pH would be altered

Question 68

Present information to outline the general use of hormone replacement therapy in people who cannot secrete aldosterone

Answer 68

Adrenocortical insufficiency (Addison’s disease) some immune systems cause inflammation in own glands, other causes are tuberculosis and cancer

Decreased secretion of aldosterone→ increased sodium loss

Clinically; Person is weak, thin, have salt-cravings, faintness, feel light-headed, low blood-sugar

Most patients → require treatment with fludrocortisone plus cortisone as a replacement glucocorticoid

Question 69

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

OVERVIEW

Answer 69

Passive→ diffusion, osmosis (molecules move along concentration gradient) no energy input

Active→ needs cellular energy to move molecules against concentration gradient

Diffusion; Particles from region of high concentration to low until equilibrium is reached

Osmosis; water molecules from high water concentration to low,through semi permeable membrane

Question 70

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

PASSIVE TRANSPORT IN THE KIDNEY

Answer 70

Limitations; relies on difference in concentration gradient (slow)

Tubules→ wastes from bloodstream to be excreted as urine

Substances needed→ removed from urine and returned to bloodstream

Passive moves water (osmosis), some wastes (ammonia, urea) into kidney

Question 71

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

ACTIVE TRANSPORT IN THE KIDNEY

Answer 71

Sometimes have to move against gradient

Carrier proteins spans membrane and carrier molecule actively move chemicals from low to high concentration using cellular energy

Mainly sodium ions, glucose, amino acids across wall of nephron (reabsorbed)

Sodium pump in tubules→ transports salts from urine back into kidney (conserve salt and water→ salt draws water)

Question 72

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

Answer 72

Urine concentration; depends on need to conserve water.

High solute; concentrated. Low solute; dilute

FRESHWATER FISH
Only dilute
Sources; drinks, osmosis into fish

MARINE FISH
Only concentrated
Sources; Drinks,osmosis out of fish

TERRESTRIAL MAMMALS
Conserve water (concentrated)
Consumes water (dilute
Source; Drinking, eating

Question 73

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

FILTRATION

Answer 73

Occurs between glomerulus, lining of Bowman’s capsule

High pressure; blood flowing through glomerulus (small substances squeeze through capillary wall under pressure→ pass through cell layer in Bowman’s capsule→ move into lumen)

Pass through; blood cells, proteins, water→ carry dissolved amino acids, glucose, salts, wastes (fluid; glomerular filtrate)

Substances body needs; reabsorbed into bloodstream (so not lost with urine)

Question 74

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

RE ABSORPTION

Answer 74

Filtrate with molecules needed; amino acids, glucose→ actively reabsorbed into proximal tubule

Passed to interstitial fluid, capillaries surrounding nephron→ to renal vein; carried back to general circulation

99% water reabsorbed by osmosis, only 1% excreted as urine

Ascending loop→ salts actively pumped into interstitial fluid in medulla (draw water out by osmosis)

Question 75

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

SECRETION

Answer 75

Toxic substances removed from capillaries, tissues

Drugs secreted in proximal tubule, urea in descending loop of Henle

Question 76

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

Answer 76

Limited water availability→ must conserve water and excrete waste

High water availability→ water conservation not necessary (waste may be dilute)

Moth, blowfly→ uric acid as paste (low toxic) high energy needed, but conserve water

Spinifex hopping mouse→ concentrated urea; conserve water (moderate toxic)

Humans, moth, blowfly→ water not freely available (must be sourced)

Question 77

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

ADH

Answer 77

Dehydration, blood volume drops→ detected by hypothalamus in brain; stimulates pituitary gland to release ADH→ acts on nephrons to increase reabsorption of water

Increases permeability of membranes lining distal, collecting tubule; water reabsorbed (conserved

Question 78

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

ALDOSTERONE

Answer 78

Decrease in sodium ion concentration in blood→ secreted from adrenal gland cortex (above kidney)

Aldosterone via bloodstream reaches kidney; increase permeability of nephron to sodium→ reabsorption into surrounding kidney tissue (less lost by urine)

Question 79

Process and analyse information from secondary sources and use available evidence to discuss processes used by different plants for salt regulation in saline environments.

Answer 79

MANGROVE
Concentrate salt accumulation to certain parts (leaf) → fall off, salt leaves mangrove.

Leaves; salt glands secrete salt entering; can be blown or washed away

Roots; first line of defense→ filter out incoming salt

BLADDER SALTBUSH
Salt enters roots, travels to leaves. Stored in vacuole and moves to bladder cell

Bladder cell ruptures→ salt released

Question 80

Enantiostasis:

Answer 80

Survival mechanism; organisms cope with extreme fluctuations in environmental conditions

Question 81

Estuary

Answer 81

Water/salt concentrations fluctuate daily→ high tide; salt in river. Low tide; freshwater in

Organisms need to maintain normal metabolic functioning (despite fluctuations)

Question 82

OSMOCONFORMERS

Answer 82

Tolerate change; alter internal solute concentration to match external environment

E.g. Fiddler crab accumulates additional solutes in high salt, then pumps out excess when low salt

Question 83

OSMOREGULATORS

Answer 83

Avoid change in internal environment; keep solutes at optimal level regardless of environment

E.g. Mussels in rock pools close valves when tide it out (keeps salt concentrate same as seawater)

Question 84

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

Answer 84

Sheoaks
Needle like leaves→ reduces surface area, reduces water loss

Eucalyptus
Waxy cuticle→ reflects sun, reduces water loss by evaporation
Leaves hang vertically→ reduces exposure to sun

Grevillea
Small curled leaves→ Retain more water
Hairy leaves→ hair returns water, increases humidity

Wattle
Grey colour→ Light colour to reflect sunlight, reduces evaporation
Hair on undersurface→ retains water

Question 85

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

Answer 85

Needle-like leaves→ reduces surface area, water loss. E.g.She-oakes

Woody fruits→ Less water loss that in fleshy fruits. E.g She-oakes

Leaf curling→ Reduce surface area. Traps humid layer of air→ reduced water loss.

Hanging leaves→ reduce exposure to sun

Hairy/shiny leaves→ hairy undersurface→ reduces air movement, increase humidity→ less water loss. Upper surface, reflects radiation from sun (reduced heat gain)

Water directing leaves/stems→ shaped so water runs down to roots. E.g. Acacia