respiration exam qs

Question 1

describe the process of glycolysis (4 marks)

Answer 1

M1 : phosphorylation of glucose using ATP
M2: oxidation of triose phosphate to pyruvate
M3: net gain of ATP
M4: NAD reduced

Question 2

Malonate inhibits a reaction in the Krebs cycle
Explain why malonate would decrease the uptake of oxygen in a respiring cell (2 marks)

Answer 2

M1: less/no reduced NAD
M2 : oxygen is the final electron acceptor

Question 3

In muscles, pyruvate is converted to lactate during prolonged exercise
Explain why converting pyruvate to lactate allows the continued production of ATP by anaerobic respiration (2 marks)

Answer 3

M1: regenerates NAD
M2: so glycolysis can continue

Question 4

suggest one reason why it was importantly that the student left the apparatus for one hour after the Yeats culture reached a constant temperature (1 mark)

Answer 4

so the oxygen is used

Question 5

During her investigation, the coloured liquid moved to the right
Explain why it moved to the right (2 marks)

Answer 5

M1: anaerobic respiration produced carbon dioxide
M2: increase in pressure of gas

Question 6

explain why a log scale is used to record the number of cells (1 mark)

Answer 6

large range in numbers

Question 7

many yeast cells die during the death phase
suggest one reason why (1 mark)

Answer 7

increase in acidity

Question 8

Using the diagram above, explain the benefit of activation of AMPK during exercise (3 marks)

Answer 8

M1: less malonyl coA
M2: more fatty acids moved into mitochondria
M3: respiration of fatty acids provides ATP

Question 9

For the first ten minutes, the tap attached to tube A was left open and the syringe from tube B was removed
Suggest three reasons why the apparatus was left for 10 minutes (3 marks)

Answer 9

M1: equilibrium reached
M2: allow for pressure change in apparatus
M3: allow respiration rate of seeds to stabilise

Question 10

Suggest and explain why the chosen temperature was 20°C for this experiment (2 marks)

Answer 10

M1: optimum temperature for normal growth of seeds
M2: optimum temperature for enzymes involved in respiration

Question 11

During the experiment, the coloured liquid in the tubing moved towards tube B
Explain what caused this (3 marks)

Answer 11

M1: oxygen is taken up by the seeds
M2: CO2 is absorbed by the KOH solution
M3: pressure in B decreases

Question 12

describe the advantage of the Bohr effect during intense exercise (2 marks)

Answer 12

M1: increases dissociation of oxygen
M2: for aerobic respiration at the tissues

Question 13

An increase in the intensity of exercise produces an increase in the volume of carbon dioxide produced.
However, the graph above shows that the pCO2 in air breathed out did not show a large increase during the exercise.
Suggest one physiological change that would cause this result. Explain how the physiological change would allow for the removal of the increase in the volume of carbon dioxide produced (2 marks)

Answer 13

M1: increase in breathing rate
M2: same pCO2 per breath but more breaths

Question 14

At more than 80% of maximum muscle effort ATP can only be made for a limited time.
Use the diagram above to suggest one reason why.

a) ATP cannot move into muscle fibres at a fast enough rate
b) muscle fibres have a limited amount of phosphocreatine
c) muscle fibres produce too much lactate
d) muscle fibres quickly run out of ADP

Answer 14

b

Question 15

GW1516 is a performance enhancing drug, GW1516 activates AMPK and develops slow muscle fibres at rest.
Use diagram above the justify why professional athletes are not allowed to take GW1516
Do not include details of chemiosmotic theory in your answer (4 marks)

Answer 15

M1: more acetylcoenzy,e A would enter the Krebs cycle
M2 : so the Krebs cycle generates more reduced coenzymes
M3: so more ATP would be produced
M4: athletes could build slow muscle fibres without exercising

Question 16

EPO is another performance enhancing drug. It can increase haematocrit.
A heart attach is caused by lack of glucose and oxygen being delivered to cardiac muscle via the coronary arteries. The overuse of EPO can increase the risk of a heart attack
Suggest how (2 marks)

Answer 16

M1: EPO causes blood to thicken
M2: the thickened blood could block the coronary arteries

Question 17

The normal haematocrit for human males in 47%. For professional male cyclists the maximum haematocrit allowed is 50%
A student suggested that professional male cyclists should be allowed to use EPO until their haematocrit is 50%
Give two reasons why this suggestion is not valid (2 marks)

Answer 17

M1: some cyclists will gain a bigger advantage
M2: there are health risks associated with taking EPO

Question 18

explain how you could determine the total amount of carbon dioxide secreted at 30°C during the period of recording (1 mark)

Answer 18

Determine the area under the curve

Question 19

Suggest an explanation for the effect of temperature on the rate of carbon dioxide release (3 marks)

Answer 19

M1: enzymes faster
M2: higher rate of respiration and carbon dioxide production
M3: spiracles open more often to get rid of more carbon dioxide

Question 20

Describe how acetyl coenzyme A is formed in the link reaction (2 marks)

Answer 20

M1: oxidation of pyruvate and carbon dioxide release
M2: addition of coenzyme A

Question 21

Oxaloacetate is the first substrate to bind with the enzyme citrate synthase
This induces a change in the enzyme, which enables the acetylcoenzyme A to bind.
Explain how oxaloacetate enables the acetylcoenzyme A to then bind to the enzyme (2 marks)

Answer 21

M1: change in shape of active site
M2: so substrate now complementary

Question 22

Suggest how production of succinyl coenzyme A could control the rate of the reaction catalysed by citrate synthase (2 marks)

Answer 22

M1: is a competitive inhibitor
M2: prevents enzyme substrate complexes forming

Question 23

Explain why converting pyruvate to lactate allows the continued production of ATP during anaerobic respiration. (2 marks)

Answer 23

M1: regenerates NAD
M2: NAD used in glycolysis

Question 24

In muscles some of the lactate is converted back to pyruvate when they are well supplied with oxygen. Suggest one advantage of this. (1 mark)

Answer 24

Pyruvate used in aerobic respiration

Question 25

Explain the line between P and Q (2 marks)

Answer 25

M1: no aerobic respiration
M2: because nothing to respire

Question 26

Explain the line between Q and R (2 marks)

Answer 26

M1: oxygen concentration falls because aerobic respiration uses oxygen
M2: oxygen is final electron acceptor

Question 27

The respiratory substrate and ADP added after 5 minutes were part of a buffered isotonic solution.
What other substance would the buffer or solution have to contain? (1 mark)

Answer 27

phosphate

Question 28

Describe and explain the difference between line R to S and line R to T ( 4 marks)

Answer 28

M1: oxygen concentration continues to fall in plants but stays constant in animals
M2: oxygen concentration falls more slowly in plants than before cyanide added
M3: because aerobic respiration continues in plant mitochondria
M4: because electron transfer continues in plant mitochondria

Question 29

Explain why a layer of oil is required in this investigation. (1 mark)

Answer 29

Prevents oxygen being taken up

Question 30

suggest why the rate of gas production decrease between 50 and 60 minutes (1 mark)

Answer 30

glucose decreases

Question 31

Explain what would happen to the volume of gas in the syringe if the yeast were only respiring aerobically (2 marks)

Answer 31

M1: stays the same
M2: same volume of oxygen uptake and carbon dioxide release

Question 32

Respiration produces more ATP per molecule of glucose in the presence of oxygen than it does when oxygen is absent. Explain why. (2 marks)

Answer 32

M1: oxygen is final electron acceptor
M2: only glycolysis occurs without oxygen

Question 33

describe how acetylcoenzyme A is formed in the link reaction (2 marks)

Answer 33

M1: hydrogen removed from pyruvate and carbon dioxide released
M2: addition of coenzyme A