Question

1a) Explain what effect an accumulation of ADP has on the citric acid cycle? How is this linked to the oxidative
phosphorylation pathway?

b) Explain the effect of excess NADH on the CAC and how this is linked to the oxidative phosphorylation
pathway?

2) Although oxygen does not participate directly in the citric acid cycle, the cycle operates only when oxygen is
present. Is this also true with beta-oxidation? With glycolysis? Explain each of your answers.

Answer 1

1.a.

Accumulation of ADP will act as allosteric activator. So the rate of citric acid cycle will increase due to ADP.

Rate of cellular respiration is determined by need for ATP in the cell. So if a cell has more ATP, the rate of oxidative phosphorylation will decrease. If there is more ADP, the rate of phosphorylation will increase.

b.

More NADH is an indication of higher energy levels in the cell . As NADH is mostly produced in CAC, higher the NADH, lower the rate of CAC.

More NADH will increase the speed of Oxidative phosphorylation because NADH is immediately converted in to ATP by oxidative phosphorylation.

2.

Betaoxidation is a process which occurs in mitochondria. It is an aerobic process needing O2.

Glycolysis does not require O2. It occurs in the absence of O2 producing 2 NADH and 2 ATP molecules.