Question

Which of the following statements about NADH and its effect on the citrate cycle are true? Choose one or more:

A. High concentrations of NADH will lead to an increased amount of acetyl-CoA being produced due to NADH activating the pyruvate dehydrogenase enzyme.

B. Increasing NADH concentrations will inhibit the citrate cycle.

C. Low concentrations of NADH will result in lower concentrations of a-ketoglutarate due to inhibition of the isocitrate dehydrogenase enzyme.

D. NADH will bind to the enzyme citrate synthase, and when there is significantly more NADH in the cell than NAD+, less citrate will be produced.

Answer 1

B and D

Step-by-step explanation:

Feedback inhibition. The concentration of the product serves to stop the reactions of the starter materials.

Acetyl-CoA + 3 NAD+ + UQ + GDP + Pi + 2 H2O → CoA-SH + 3 NADH + UQH2 + 3 H+ + GTP + 2 CO2

Products of the first turn of the cycle are one GTP (or ATP), three NADH, one QH2 and two CO2

Because two acetyl-CoA molecules are produced from each glucose molecule, two cycles are required per glucose molecule. Therefore, at the end of two cycles, the products are: two GTP, six NADH, two QH2, and four CO2.

Answer 2

Answer: B & D

Step-by-step explanation:

Increasing NADH concentrations inhibits the citrate cycle.

In the citrate cycle NADH binds to the enzyme citrate synthase, and when there is significantly more NADH in the cell than NAD+, correspondingly less citrate are produced.