Question

As pyruvate is prepared for the TCA cycle, it undergoes a process of

A) reductive carboxylation.
B) oxidative decarboxylation.
C) oxidative carboxylation.
D) reductive decarboxylation.
E) CoQ reproduction.

Answer 1

Option B, oxidative decarboxylation, is the correct process that pyruvate undergoes before entering the TCA cycle, where it is converted to acetyl CoA, while releasing carbon dioxide and forming NADH.

Step-by-step explanation:

Before pyruvate enters the Tricarboxylic Acid (TCA) cycle (also known as the Krebs cycle), it undergoes a process classified as oxidative decarboxylation. This essential step converts the three-carbon pyruvate into a two-carbon acetyl group, while simultaneously releasing carbon dioxide and transferring electrons to the electron carrier NAD+ to form NADH. Specifically, the enzyme pyruvate dehydrogenase facilitates the removal of a carboxyl group (-COOH) from pyruvate, resulting in the production of carbon dioxide. Concurrently, the remaining two-carbon fragment is oxidized, and the enzyme complex transfers the resulting acetyl group to coenzyme A (CoA), forming acetyl CoA. This compound is then ready to enter the TCA cycle for further energy extraction.

The direct answer to the student's question is option B) oxidative decarboxylation.