<prompt> All of the following vitamins play a key role in the Citric acid cycle exceptThiaminRiboflavinNiacinCobalamin  <response>: VITAMINS PLAY KEY ROLES IN THE CITRIC ACID CYCLE Four of the B vitamins are essential in the citric acid cycle and hence energy-yielding metabolism: 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. Thiamin vitamin B1, as thiamin diphosphate, the coenzyme for decarboxylation in the a-ketoglutarate dehydrogenase reaction, and Pantothenic acid, as pa of coenzyme A, the cofactor esterified to active carboxylic acid residues: acetyl-CoA and succinyl-CoA. Reference: Harper; 30th edition; Page no: 164 