aerobic respiration

Question 1

Glycolysis: Phosphorylation

Answer 1

. Glucose is phosphorylated by added 2 phosphates from 2x ATP
. Makes 2x triose phosphate + 2x ADP

Question 2

Glycolysis: oxidation

Answer 2

. Triose phosphate is oxidised –> 2x pyruvate
. NAD takes H+ and becomes 2x reduced NAD
. Net gain of 2x ATP.

Question 3

Link reaction

Answer 3

. Pyruvate decarboxylated (co2 removed)
. NAD is reduced - changing pyruvate –> acetate
. Acetate + coenzyme A –> Acetyl Coenzyme A

Question 4

Krebs Cycle

Answer 4

. Acetyl CoA + oxaloacetate –> citrate, coenzyme A goes back to link reaction
. 6C citrate –> 5C molecule, decarboxylation + dehydrogenation occur, produces reduced NAD
. 5C –> 4C, decarboxylation and dehydrogenation occur, 1x reduced FAD, 2x reduced NAD
. ATP produced by substrate-level phosphorylation.
. Citrate –> oxaloacetate.

Question 5

Oxidative Phosphorylation

Answer 5

. reduced NAD + FAD are oxidised.
. Electrons move down electron transport chain, losing energy which is used to pump protons from mitochondrial matrix into intermembrane space
. This forms an electrochemical gradient, which protons move down via ATP synthase –> ATP produced.
. Movement of H+ ions across a membrane that generates ATP is chemiosmosis.
. In mitochondrial matrix protons + electrons + oxygen –> water.

Question 6

The outer mitochondrial membrane is not permeable to hydrogen ions (H+).
Explain the importance of this feature of the membrane.

Answer 6

. to stop H+ diffusing out (of mitochondrion) / into
cytoplasm (1)
• (therefore) maintaining a high concentration (of H+) in the intermembrane space (1)
• so {hydrogen ions / protons / H+} can move down {concentration / electrochemical} gradient (1)
• (by) chemiosmosis (1)
• to synthesise ATP (1)