exam 3

Question 1

Explain the relationship between body mass and oxygen consumption in these mammals

Answer 1

1. smaller mammals consume more oxygen per kg

2. Smaller mammals have a larger surface area to volume ratio so they lose more heat by respiration

Question 2

Explain the effects of calcium ion concentration on the rate of uptake of calcium ions through the pancreatic cell membrane

Answer 2

1. rate of diffusion increases as there is a higher concentration gradient
2. The rate of uptake then levels off as calcium ion channels
   limit the rate (1)

3, Because (calcium) ions enter by facilitated diffusion

Question 3

Explain how the student could convert these readings into a transpiration rate
using the units mm3
cm–2 min–1.

Answer 3

1. multiply cross-sectional area by distance moved by bubble / ∏r
   2 × d
2. divide by total area of leaves (1)
3. divide by 5

Question 4

Explain the results of this investigation

Answer 4

1. moving air moves {water molecules

away (from leaf) and therefore increases the concentration gradient

Question 5

Explain the role of air sacs in the gas exchange system of locusts

Answer 5

1. They supply and store oxygen so respiration can occur in the moving locusts

Question 6

Explain why the properties of lipoproteins enable the transport of cholesterol and fattyy acids

Answer 6

1. fatty acids and cholesterol are insoluble in water fatty acids have a hydrophopic tails so are isoulbe in water.
2. A lipoprotein helps lipids be transported as they form complexes which allow the lipid to be carried so the receptors on lipoproteins help them carry lipids.
3. Lipoproteins are soluble so they can be transported in the blood and have a triglyceride core surrounded by a layer of phospholipids where the hydrophilic head of the phospholipids are on the outside allowing the protein to be soluble

Question 7

Explain how the mass flow hypothesis accounts for thr movement of sugars from leaves to roots

Answer 7

1. Glucose is produced at the leaves and dissolved in the water of the leaves
2. This decreases the water potential of the source cell therefore water moves into the source cell via osmosis increasing the hydrostatic pressure at the source cell.
3. The sugars in the in the dissolved source cell trvel to the sink cell where the sugars are used and converted into insoluble starch
4. This causes an increase in water potential causing the water to leave via osmosis decreasing the hydrostatic pressure

Question 8

analyse the information to explain how the times shown in the diagram relate to the cardiac cycle

Answer 8

1. There is depolarisation at the SAN which sends and electrical impulse to both atria causing atrial systole
2. At the same time an imoulse is sent to the AVN where there is a delay so the ventricles can fill
3. The AVN sends the impulse down the bundle of his allowing atrial diastole then to the purkinje fibres
4. Purkinje fibres cause ventricle systole from the apex upwards so blood then is pushed out