Respiration

Question 1

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

Answer 1

• Removal of hydrogen/dehydrogenation
• By enzymes/dehydrogenases
• H accepted by NAD/reduced NAD formed
• In Krebs cycle, FAD (used as well)

Question 2

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

Answer 2

• Oxygen is the final electron acceptor

- Combines with electrons and protons (to form water)

Question 3

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

Answer 3

• Oxidation of/removal of electrons and H+
• From pyruvate
• Acetyl CoA/6 carbon compound
• Substrate level production of ATP/ATP produced in Krebs cycle
• Production of reduced NAD/FAD (allow they take up hydrogen)
• In matrix of mitochondria
• Electrons fed into electron transport chain/used in oxidative
• (Electrons) pass along carriers/through electron transport chain/through series of redox reactions
• Energy released
• Protons move into intermembrane space
• ADP/ADP + Pi
• ATP synthase

Question 4

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

Answer 4

• NAD/FAD reduced
• H+ ions/electrons transferred from coenzyme to coenzyme/carrier to carrier (ETC on cristae of inner membrane)
• Energy released (from electrons) through series of redox reactions
• Energy released used to pump H+/protons into intermembrane space
• H+/protons flow back through ATP synthase to produce ATP from ADP and phosphate

Question 5

Describe the events of oxidative phosphorylation.

Answer 5

• NAD/FAD reduced
• H+ ions/electrons transferred from coenzyme to coenzyme/carrier to carrier (ETC on cristae of inner membrane)
• Energy released (from electrons) through series of redox reactions
• Energy released used to pump H+/protons into intermembrane space
• H+/protons flow back through ATP synthase to produce ATP from ADP and phosphate

Question 6

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

Answer 6

• Larger surface area for electron carrier system/oxidative phosphorylation
• Provide ATP/energy for contraction

Question 7

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

Answer 7

• Equilibrium reached
• Allow for expansion/pressure change in apparatus
• Allow respiration rate of seeds to stabilise

Question 8

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

Answer 8

• Large range/difference in numbers

- Accept reference to exponential (increase)

Question 9

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

Answer 9

• Regenerates NAD/oxidises reduced NAD

- (So) glycolysis continues