5- Respiration =)

Question 1

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

Answer 1

• ↓ e- removed + passed to e- transfer chain // ↓ NADH
• O2 = final e- acceptor

Question 2

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)

Answer 2

• regenerates NAD
• glycolysis continues

Question 3

Explain why oxygen is needed for the production of ATP on the cristae of the mitochondrion. (3)

Answer 3

1. ATP formed as e- pass along transport chain
2. O2 = terminal e- acceptor
3. forms H2O/ oxidises NADH –> NAD

Question 4

Where exactly in a cell does electron transfer chain occur? (1)

Answer 4

inner mem of mitochondria

Question 5

Describe how NAD is regenerated in anaerobic respiration in yeast cells. (1)

Answer 5

NADH reduces pyruvate into ethanol

Question 6

Apart from respiration, give 3 uses of ATP in a liver cell. (3)

Answer 6

1. a.t.
2. source of energy/ phosphate
3. mitosis
4. synthesis of glycogen/ protein
5. bile prod
6. phagocytosis

Question 7

Human skeletal muscle can respire both anaerobically and anaerobically.
Describe what happens to pyruvate in anaerobic conditions and explain why anaerobic respiration is advantageous to human skeletal muscle. (4)

Answer 7

1. pyruvate reduced into lactate
2. using NADH
3. NAD regenerated
4. NAD reused to oxidise ↑ respiratory substrate –> glycolysis continues
5. still releases energy when O2 in short supply

Question 8

Lowering the temperature has very little effect on the LDR, but it slows down the LIR.
Explain why the LIR slows at low temperatures. (2)

Answer 8

1. enzymes involved
2. ↓ rate of enzyme reaction - ↓ ke + ↓ collisions

Question 9

Pyruvate is formed in the breakdown of glucose during respiration. When there is sufficient oxygen, this pyruvate is fully broken down.
Name 2 substances formed from pyruvate. (1)

Answer 9

1. CO2
2. water
3. ATP
4. NADH

Question 10

If there is a shortage of oxygen in muscle cells during exercise, some pyruvate is converted into lactate.
Explain why muscle become fatigued when insufficient oxygen is available. (2)

Answer 10

1. lactate lowers pH
2. enzymes inhibited

x denatured!!!!!!

Question 11

Some of the lactate is oxidised to pyruvate by muscles when they are well supplied with oxygen.
Suggest an advantage of the lactate being oxidised in muscles. (2)

Answer 11

1. pyruvate= energy source in aerobic resp.
2. muscles have ↑ ATP supply
3. restores pH levels

Question 12

Name 2 substances for which there would be net movement into the mitochondrion. (2)

Answer 12

1. pyruvate
2. ADP + Pi
3. NADH
4. O2

Question 13

Investigating the effect of wavelength on rate of photos- shining light at suspension of photosynthesising algal cells.
Other than temp and pH, give 2 factors which should be kept constant during this investigation. (2)

Answer 13

1. light intensity
2. no. / species of algal cells
3. CO2 conc
4. time

Question 14

Respiratory Qutient (RQ)
RQ = vol of CO2 produced in resp./ vol of O2 used in resp.
What would the RQ for aerobic respiration of glucose be? (1)
A student calculated that the RQ of germinating seeds was 1.8. Explain the result. (2)

Answer 14

• 1
• aerobic + anaerobic
• ↑ CO2 produced than O2 uptake

Question 15

Aerobic respiration produces more ATP per molecule of glucose than anaerobic respiration.
Explain why. (2)

Answer 15

• O2 = final e- acceptor
• oxidative phosphorylation in a. resp
• only glycolysis in an. resp

Question 16

Describe how acetylcoenzyme A is formed in the link reaction. (2)

Answer 16

• oxidation of pyruvate + CO2 released
• addition of coenzyme A