Respiration

Question 1

Describe the process of glycolysis (4)

Answer 1

1. Phosphorylation of glucose using ATP
2. Oxidation of triose phosphate to pyruvate
3. Net gain of ATP
4. NADH produced

Question 2

Describe how oxidation takes place in glycolysis and in the Krebs cycle. (4)

Answer 2

1. Removal of hydrogen
2. By dehydrogenase enzyme
3. NADH produced
4. In Krebs cycle, FAD used

Question 3

Water is a waste product of aerobic respiration. Describe how water is formed at the end of aerobic respiration. (2)

Answer 3

1. Oxygen is terminal/final electron acceptor
2. Combines with electrons and protons

Question 4

Explain how the amount of ATP is increased by reactions occurring inside a mitochondrion. (6)

Answer 4

1. Removal of electrons and protons
2. From pyruvate
3. Acetyl CoA
4. Substrate level production of ATP in Krebs cycle
5. Production of NADH and FADH
6. In matrix of mitochondria
7. Electrons fed into electron transport chain
8. Electrons pass through electron transport chain through series of redox reactions
9. Energy released
10. Protons move into intermembrane space
11. ADP + Pi
12. ATP synthase

Question 5

Describe the roles of the coenzymes and carrier proteins in the synthesis of ATP.

OR

Describe the events of oxidative phosphorylation

(5)

Answer 5

1. NADH and FADH produced
2. Protons and electrons transfer from coenzyme to coenzyme
3. Energy released through series of redox reactions
4. Energy released used to pump protons into intermembrane space
5. Protons move through ATP synthase to produce ATP from ADP and Pi

Question 6

The mitochondria in muscles contain many cristae. Explain the advantage of this. (2)

Answer 6

1. Larger surface area for electron carrier system
2. Provide MORE ATP

Question 7

Give two reasons why the respirometer was left for 10 minutes when it was first placed in the water bath. (2)

Answer 7

1. Equilibrium reached
2. Allow for expansion
3. Allow respiration rate of seeds to stabilise

Question 8

Explain why a log scale is used to record the number of cells/bacteria. (1)

Answer 8

1. Large range / increase in number of cells on y axis

Question 9

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

Answer 9

1. Regenerates NAD
2. Glycolysis continues

Question 10

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

Answer 10

1. Less NADH
2. Oxygen is final/terminal electron acceptor

Question 11

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

Answer 11

1. Oxidation of pyruvate and carbon dioxide released
2. Addition of coenzyme A

Question 12

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

Answer 12

1. Lactate causes muscle cramps

Question 13

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

Answer 13

1. ATP formed as electrons pass along electron transport chain
2. Oxygen combines with protons and electrons to produce water
3. Oxygen is final/terminal electron acceptor

Question 14

Describe how ATP is made in the mitochondria (6)

Answer 14

1. Substrate level phosphorylation of ATP / ATP produced in Krebs cycle
2. Krebs cycle produces NADH and FADH
3. Electrons released from NADH and FADH
4. Electrons pass through electron transport chain through series of redox reactions
5. Energy released
6. Protons pumped into intermembrane space
7. ADP + Pi
8. ATP synthase

Question 15

Explain why the scientist didn’t use glucose as the respiratory substrate for these isolated mitochondria (2)

Answer 15

1. Glucose broken down during glycolysis
2. Glucose can’t cross mitochondrial membrane

Question 16

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

Answer 16

1. Formed when NADH used to reduce pyruvate to ethanol