Which of the following coenzyme is NOT directly required in any of...

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$-ketoglutarate dehydrogenase, and malate dehydrogenase.<br><br>FAD is required as a coenzyme for succinate dehydrogenase.<br><br>Coenzyme A (CoA) is required by the$\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