Q7 / 200 · MHT CET - Medical 2026 (23 April Shift 2) · Biology
Which of the following coenzyme is NOT directly required in any of the steps of the Kreb's cycle?
- ANAD
- BFAD
- Correct answerCCoenzyme Q
- DCo A
Solution
The Krebs cycle involves a series of oxidation-reduction and substrate-level phosphorylation reactions.
NAD$^+$ is required as a coenzyme for the enzymes isocitrate dehydrogenase, $\alpha$-ketoglutarate dehydrogenase, and malate dehydrogenase.
FAD is required as a coenzyme for succinate dehydrogenase.
Coenzyme A (CoA) is required by the $\alpha$-ketoglutarate dehydrogenase complex to form succinyl-CoA.
Coenzyme Q (Ubiquinone) is a mobile electron carrier in the electron transport chain (ETC) located in the inner mitochondrial membrane and is not directly involved in any of the steps of the Krebs cycle.
Answer: Coenzyme Q
NAD$^+$ is required as a coenzyme for the enzymes isocitrate dehydrogenase, $\alpha$-ketoglutarate dehydrogenase, and malate dehydrogenase.
FAD is required as a coenzyme for succinate dehydrogenase.
Coenzyme A (CoA) is required by the $\alpha$-ketoglutarate dehydrogenase complex to form succinyl-CoA.
Coenzyme Q (Ubiquinone) is a mobile electron carrier in the electron transport chain (ETC) located in the inner mitochondrial membrane and is not directly involved in any of the steps of the Krebs cycle.
Answer: Coenzyme Q
Hence, the correct answer is option: 'C'.