<prompt> Vitamin not required in TCA cycle ?NiacinRiboflavinThiamineFolic acid  <response>: Ans. is d i.e., Folic acid Four of the B vitamins are essential in the citric acid cycle : Riboflavin, in the form of flavin adenine dinucleotide FAD, a cofactor for succinate dehydrogenase. Niacin, in the form of nicotinamide adenine dinucleotide NAD the electron acceptor for isocitrate dehydrogenase, a-ketoglutarate dehydrogenase, and malate dehydrogenase. Thiamine vitamin B1, as thiamine diphosphate, the coenzyme for decarboxylation in a-ketoglutarate dehydrogenase reaction. Pantothenic acid, as pa of coenzyme A, the cofactor attached to active carboxylic acid residues such as acetyl-CoA and succinyl CoA. 