Respiration

Question 1

Why does aerobic respiration yield fewer molecules of ATP than theoretical maximum (2 marks)

Answer 1

1. Some ATP used to actively transport private into mitochondrion
2. Some ATP used to actively transport H+ from R.NAD formed in glycolysis into the mitochondrion

Question 2

Explain why the incomplete breakdown of glucose in anaerobic respiration produces less ATP than aerobic respiration (4 marks)

Answer 2

1. glycolysis occurs
2. 2 ATP molecules net gain
3. only substrate level phosphorylation occurs
4. oxidative phosphorylation doesn’t occur

Question 3

Suggest why parasites are adapted to respire anaerobically (2 marks)

Answer 3

1. Parasites have little access to oxygen

2. Little oxygen is dissolved in plasma so it’s inaccessible

Question 4

Explain why the anaerobic respiration pathway in animal cells can be reversed but the pathway in yeast cells cannot be reversed (4 marks)

Answer 4

IN ANIMALS
1. pyruvate makes lactate
2. can be reversed as lactate dehydrogenase available to reverse reaction
IN YEAST
1. pyruvate converted in ethanol and CO2
2. decarboxylase enzyme can’t be reversed in this reaction

Question 5

Suggest why lactate is converted into pyruvate by liver cells rather than by respiring cells in which it is produced (1 mark)

Answer 5

1. hepatocytes can tolerate lactate

2. hepatocytes have enzymes to metabolise lactate

Question 6

Explain what might happen to a person if the liver did not break down insulin (2 marks)

Answer 6

1. blood glucose would fall too low

2. glucose would continue to be taken up by cells

Question 7

Suggest the consequences for liver metabolism if a person has a regular high alcohol intake (2 marks)

Answer 7

1. build of lactate kills liver cells

2. lack of NAD for metabolic reactions

Question 8

Explain why an anaerobic pathway is important for a plant cell (2 marks)

Answer 8

1. releases NAD so glycolysis can continue

2. ATP available for active transport

Question 9

What is the final product in anaerobic respiration in mammalian cells (1 mark)

Answer 9

lactate

Question 10

How are reaction pathways able to work independently of each other in the same leaf cell (1 mark)

Answer 10

1. take place in different part of the cell

Question 11

Outline the consequence of an inefficient transfer of pyruvate into mitochondria (2 marks)

Answer 11

1. less pyruvate for link cycle

2. little oxidative phosphorylation

Question 12

Explain how emphysema could result in fatigue (2 marks)

Answer 12

1. less ventilation

2. so less oxygen for respiration

Question 13

Describe and explain the role of ATP in the cell (3 marks)

Answer 13

1. phosphate group can be removed by hydrolysis
2. energy release for metabolism
3. ADP can attach a phosphate during respiration

Question 14

Discuss the advantages and disadvantages of using yeast to make ethanol rather than using the chemical method (5 marks)

Answer 14

ADVANTAGES ;
1. less energy required
2. substrate is sustainable 
3. process does not use fossil fuels
DISADVANTAGES;
1. time consuming
2. is killed by product 
3. can only use batch method

Question 15

Describe the differences in the two pathways of animal cells and yeast cells anaerobic respiration (3 marks)

Answer 15

ANIMALS
1. pyruvate converted into lactate
2. it can be reversed
YEAST
1. pyruvate converted into co2 and ethanol
2. decarboxylase enzyme cannot reverse reaction

Question 16

describe the process of animal and yeast respiration

Answer 16

animal:
pyruvate ( lactate dehydrogenase + RNAD) —> lactate —> glucose
yeast:
pyruvate ( pyruvate decarboxylase +CO2) —> ethanal —> ( NAD ) ethanol