Question

In the presence of oxygen, the three-carbon compound pyruvate can be catabolized in the citric acid cycle. First, however, the pyruvate (1) loses a carbon, which is given off as a molecule of CO2, (2) is oxidized to form a two-carbon compound called acetate, and (3) is bonded to coenzyme A. Which of the following sets of products result from these reactions?
(A) acetyl CoA, O2, and ATP.
(B) acetyl CoA, FADH2, and CO2.
(C) acetyl CoA, FAD, H2, and CO2.
(D) acetyl CoA, NADH, H+, and CO2.
(E) acetyl CoA, NAD+, ATP, and CO2.

Answer 1

Answer:

(D) acetyl CoA, NADH, H+, and CO2.

Explanation:

The given explanation is about oxidative decarboxylation of pyruvate into acetyl CoA and carbon dioxide. The reactions are catalyzed by enzyme complex pyruvate dehydrogenase. During the reaction, pyruvate loses one of its carbon atoms in the form of CO2 and the rest of two carbons form the acetate which in turn combines with CoA to form the acetyl CoA.  

Since it is an oxidative decarboxylation, the released electrons are accepted by NAD+ which in turn is converted into NADH + H+.  

Overall, there is the formation of one molecule of acetyl-CoA, CO2 and NADH + H+ each from one molecule of pyruvate.