Respiration

Question 1

What is the difference between aerobic respiration and anaerobic respiration?

Answer 1

• Aerobic respiration is a series of enzyme catalysed reactions where large quantities of energy are made available as ATP, with oxygen as the final electron acceptor.
• Anaerobic respiration is a series of enzyme catalysed reactions where small quantities of energy are made available as ATP by substrate level phosphorylation.

Question 2

What are the four stages of aerobic respiration, and where do they take place?

Answer 2

• Glycolysis, in solution in the cytoplasm
• Link reaction, in solution in the matrix
• Krebs cycle, in solution in the matrix
• Electron transport chain, in the inner membrane of the mitochondria

Question 3

What are the three reactions that take place in glycolysis?

Answer 3

• Glucose combines with 2ATP to produce hexose biphosphate
• Hexose biphosphate splits into two triose phosphates
• These react with 2ADP + 2Pi and NAD each to produce two pyruvate molecules, along with 4ATP and 2 reduced NAD

Question 4

What are the two reactions that take place in the link reaction?

Answer 4

• Pyruvate reacts with NAD to produce acetate, along with reduced NAD and carbon dioxide
• Acetate combines with coenzyme A to become acetyl coenzyme A

Question 5

After coenzyme A splits to leave acetate for the Krebs cycle, how many carbon atoms are at each stage of the cycle?

Answer 5

-2, 6, 5, 4, 4, 4

Question 6

What are the products of the Krebs cycle?

Answer 6

• Carbon dioxide x2
• Reduced NAD x3
• Reduced FAD x1
• ATP x1

Question 7

How many molecules of ATP can be synthesised from:

a) one reduced NAD?
b) one reduced FAD?

Answer 7

a) 3 molecules

b) 2 molecules

Question 8

How many moles of ATP are produced from one mole of glucose?

Answer 8

-38

Question 9

In anaerobic respiration in vertebrate muscle cells, what happens to the pyruvate produced in glycolysis?

Answer 9

• The reduced NAD produced when making pyruvate is oxidised

- Therefore pyruvate is reduced to produce lactate

Question 10

In anaerobic respiration in higher plants and yeast, what happens to the pyruvate produced in glycolysis?

Answer 10

• A carbon dioxide is removed from the pyruvate, producing ethanal
• The reduced NAD produced when making pyruvate is oxidised
• Therefore ethanal is reduced to produce ethanol