Module 5- Respiration

Question 1

2 marks

Describe how acetylcoenzyme A is formed in the link reaction

Answer 1

1. Oxidation of pyruvate and CO2 released
2. Addition of coenzyme A

Question 2

Give ways in which the properties of ATP make it a suitbale source of energy in biological processes

Answer 2

• Immediate source of energy
• Soluble
• Involves in a simple reaction
• Energy released in small amounts

Question 3

2 marks

Explain why it is necessary for humans to synthesise a large amount of ATP

Answer 3

• Immediate source of energy
• ATP only releases a small amount of energy at a time

Question 4

3 marks

Describe the part played by the inner membrane of a mitochondrion in producing ATP

Answer 4

• Electrons transferred down electron transport chain
• Electrons transfer energy to proteins which actively trasnport protons from matrix to intermemembrane space
• Protons diffuse down proton gradient and back into matrix via ATP synthase
• Energy used to combine ADP + Pi to produce ATP

Question 5

6 marks

Describe how ATP is made in mitochondria

Answer 5

1. Substrate level phosphorylation
2. Krebs cycle produces reduced coenzyme- reduced NAD and reduced FAD
3. Electrons released from reduced coenzymes
4. Electrons pass along electron transport chain
5. Energy released
6. ADP+Pi –> ATP
7. Protons move to intermembrane space via ATP synthase

Question 6

5 marks

Explain why it is important for plants to produce ATP during respiration in addition to during photosynthesis

Answer 6

1. In the dark no ATP production in photosynthesis
2. Some tissues unable to photosynthesise —> produce ATP
3. ATP cannot be stored
4. Plants uses more ATP than produced in photosynthesis
5. ATP for active transport

Question 7

4 marks

Describe process of glycolysis

Answer 7

1. Glucose is phosphorylated using Pi from ATP
2. NAD is reduced
3. As TP is oxidised to form pyruvate
4. Net gain of 2 ATP molecules- 4 ATP molecules are produced

Question 8

2 marks

Malonate inhibits the Krebs cycles
Explain why malonate would decrease the uptake of oxygen in a respiring cell

Answer 8

1. Less reduced NAD and reduced FAD made
2. Less oxidative phosphorylation
3. Less oxygen is used as a final electron acceptor

Question 9

2 marks

At the end of a sprint race, a runner continues to breathe rapidly for some time. Explain the advantage of this.

Answer 9

1. Lactate has built up
2. Oxygen used to break down lactate to pyruvate

Question 10

2 marks

Mitochondria in muscle cells have more cristae than mitochondria in skin cells. Explain the advantage of mitochondria in muscle cells having more cristae.

Answer 10

• More cristae = larger surface area for electron transport chain –> more enzymes for ATP production / oxidative phosphorylation
• Muscle cells use more ATP than skin cells

Question 11

Explain glycolysis

Answer 11

1. Glucose is phosphorylated using Pi from ATP
2. NAD is reduced
3. As TP is oxidised to form pyruvate
4. Net product of 2 ATP & 4 ATP produced

Question 12

Anaerobic respiration in plants/yeasts and animals

Answer 12

Plants/ yeast: pyruvate–> ethanol +CO2—> ethanol
Animals: pyruvate–> lactic acid
Reduced NAD is oxidised

Question 13

Anaerobic respiration ATP production

Answer 13

1. Only ATP produced comes from glycolysis
2. The oxidised NAD can be used in glycolysis again

Question 14

Explain link reaction

Answer 14

1. Pyruvate enters mitochondrial matrix by active transport
2. Pyruvate oxidised to acetate
3. Acetate + coenzyme A–> acetylcoenzyme A

Question 15

Explain Krebs cycle

Answer 15

1. Acetlycoenzyme A + 4C–> 6C + coenzyme A
2. Series of redox reactions= coenzymes (to be used in oxidative phosphorylation)
3. Carbon dioxide is released
4. ATP generated by substrate level phosphorylation
5. Other respiratory substrates- aa+ lipid breakdown products can fuel krebs cycle
6. Products from one glucose: 2 ATP, 6 reduced NAD, 6 reduced FAD, 6 CO2

Question 16

Explain oxidative phosphorylation

Answer 16

1. Electrons donated from coenzymes
2. e- transferred down ETC- releasing energy- series of redox reactions
3. Protons (H+) pumped across inner mitochondrial membrane
4. Conc gradient of H+ established- H+ diffuse through ATP synthase
5. ADP + Pi–> ATP (chemisosmotic theory)
6. Oxygen is the final electon acceptor–> H2O is formed

Question 17

6 marks

Oxidative phosphorylation

Answer 17

• Reduced NAD and reduced FAD are oxidised, and they donate electrons to membrane protein
• This forms protons, NAD and FAD
• Electrons move along along membrane proteins through a series of redox reaction along ETC, releasing energy
• Electrons transfer energy to the proteins, which is used to pump protons from the matrix to intermembrane space
• Protons in intermebrane space diffuse down proton gradient and back into matrix via ATP synthase
• ADP+Pi–> ATP, catalysed by ATP synthase/ ATPase
• Oxygen is final electron acceptor, combining with electrons and protons to form water
• Over 30 ATP molecules can be made

Question 18

6 marks

Describe how ATP is made in the mitchondria

Answer 18

1. Substrate level phosphorylation in the Krebs cycle
2. Krebs cycle produces reduced coenzymes e.g. reduced FAD and reduced NAD
3. Electrons released from FADH and NADH
4. Electrons pass along ETC, through a series of redox reactions
5. Energy is released
6. ADP+Pi—> ATP
7. Protons move into intermembrane space
8. ATP synthase

Question 19

5 marks

The concentration of carbon dioxide in the air at different heights above ground in a forest changes over a period of 24 hours. Use your knowledge of photosynthesis to describe these changes and explain why they occur.

Answer 19

1. High concentration of carbon dioxide at night as no photosynthesis is occurring as light required for light-dependent reaction.
2. In the dark plants still respire.
3. In the light uptake of carbon dioxide is greater than carbon dioxide produced.
4. Decrease in carbon dioxide concentration with light
5. Increase in carbon dioxide concentration closer to ground as at ground level less photosynthesising due to less light.

Question 20

2 marks

Describe the role of oxygen in aerobic respiration

Answer 20

1. Final acceptor for hydrogen
2. To form water

Question 21

2 marks

Explain why the scientist did not use glucose as the respiratory substrate for these isolated mitochondria.

Answer 21

1. Glucose is broken down during glycolysis in the cytoplasm
2. Glucose cannot cross mitochondrial membranes

Question 22

1 mark

A student investigated the rate of anaerobic respiration in yeast. She put 5 g of yeast into a glucose solution and placed this mixture in the apparatus shown in the figure below. She then recorded the total volume of gas collected every 10 minutes for 1 hour. Explain why a layer of oil is required in this investigation

Answer 22

Prevents O2 being taken up

Question 23

2 marks

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

Answer 23

1. Oxygen is final electron acceptor
2. Oxidative phosphorylation provides most ATP, only glycolysis without O2

Question 24

2 marks

What measurements would the scientists have made in order to calculate the rate of carbon dioxide production?

Answer 24

1. Volume of carbon dioxide given off
2. From known area / per m2 / m-2
3. In a set time

Question 25

# 2 marks The student repeated Experiment 1 using seeds which were respiring anaerobically. What would happen to the level of coloured liquid in the right-hand side of the manometer tube? Explain your answer.

Answer 25

1. Remains the same 2. No o2 uptake

Question 26

# 2 marks Explain why converting pyruvate to ethanol is important in allowing the continued production of ATP in anaerobic respiration.

Answer 26

1. Allows NAD to be recycled 2. So glycolysis can continue

Question 27

# 2 marks Give two ways in which anaerobic respiration of glucose in yeast is similar to anaerobic respiration of glucose in a muscle cell

Answer 27

1. Pyruvate is reduced 2. Reduced NAD is oxidised to NAD 3. ATP is formed

Question 28

# 2 marks Give two ways in which anaerobic respiration of glucose in yeast is different to anaerobic respiration of glucose in a muscle cell

Answer 28

1. CO2 released by yeast but not by muscle cell 2. Ethanol formed by yeast, lactate by muscle cell

Question 29

# 2 marks Explain one advantage of the high glycogen content of fast muscle fibres

Answer 29

1. Glycogen hydrolysed to glucose for glycolysis (anaerobic respiration) 2. Glycolysis- net gain of 2 ATP molecules- not very efficient

Question 30

# 2 marks Give two ways in which anaerobic respiration of glucose in yeast is (i) similar to anaerobic respiration of glucose in a muscle cell (ii) different from anaerobic respiration of glucose in a muscle cell.

Answer 30

1. (i) pyruvate reduced; 2. Reduced NAD is oxidised to form NAD 3. (ii) ethanol / alcohol formed by yeast, lactate by muscle cell 4. CO2 released by yeast but not by muscle cell