Question

Krebs cycle is called aerobic because

• A. Some of the enzymes require oxygen.
• B. All of the enzymes require aerobic media.
• C. Oxygen is released during this cycle.
• D. Some of the products of this cycle have to be oxidized.

Answer 1

The correct option is D Some of the products of this cycle have to be oxidized.

Kreb cycle produces 8 molecules of NADH plus 2 molecules of $FAD{H}_2$ (via succinate dehydrogenase) in the mitochondrial matrix. During electron transport through the inner mitochondrial membrane, NADH and $FAD{H}_2$ pump electrons through a series of electron transport proteins to final acceptor oxygen. This electron transport chain ensures availability of NAD and FAD for next round of Kreb cycle. Nonavailability of these reducing powers results in entry of pyruvate in anaerobic respiration pathway. So, to maintain continuity of Kreb cycle, oxidation of NADH and $FAD{H}_2$ by oxygen is prerequisite and the cycle is considered aerobic. Thus, the correct answer is option D.