Question

Consider a liver cell carrying out the oxidation of glucose under aerobic conditions. Suppose that we added a very potent and specific inhibitor of the mitochondrial ATP synthase, completely inhibiting this enzyme. Indicate whether each of the following statements about the effect of this inhibitor is true or false; if false, please explain in detail why it is false.

(a) ATP production in the cell will quickly drop to zero.

(b) The rate of glucose consumption by this cell will decrease sharply.

(c) The rate of oxygen consumption will increase.

(d) The citric acid cycle will speed up to compensate.

(e) The cell will switch to fatty acid oxidation as an alternative to glucose oxidation, and the inhibitor will therefore have no effect on ATP production.

Answer 1

Mitochondrial ATP synthase helps in the synthesis of ATP during aerobic respiration. It moves proton form intermembrane space to matrix. If ATP synthase activity is blocked then it can no longer transfer proton form intermembrane space to the matrix, thus building the concentration of proton in the intermembrane space.

The cell still produces ATP by anaerobic inspiration, so ATP production will not reduce to zero. So option A is false.

Since there is blockage of ATP synthesis via oxidative phosphorylation, the cell will start producing ATP anaerobically. anaerobic respiration generates less amount of ATP as compared to aerobic respiration, so glucose consumption will increase to match the ATP required by the cell.

So, option B is False.

During electron transport chain proton are pumped from matrix to intermembrane space by complex I and III and IV. Due to the inhibition of ATP synthase activity, proton concentration in the mitochondrial matrix will be less and the electron transport chain will not function. Oxygen is the terminal electron acceptor, due to no function of electron transport chain, oxygen consumption will drop to zero.

So, (c) The rate of oxygen consumption will increase is wrong.

Citric acid produces NADH and FADH, which donates their electrons to the electron transport chain. Since the electron transport chain is blocked, the citric acid cycle will also be inhibited. So option D is also false.

During Beta-oxidation, NADH and FADH are produced along with acetyl Co-A. NADH and FADH donate their electrons to the electron transport chain. Since the electron transport chain is blocked so, beta-oxidation will also be inhibited.

So option E is also wrong.

All options are wrong.