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

6 marks

Oxidative phosphorylation

Answer 11

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