This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of carbohydrate, Subject name: Biochemistry
All of the following are cofactors for the enzymes of the TCA cycle, except 
Select and explain. 
A. Niacin, B. Pantothenic acid, C. Biotin, D. Riboflavin
C: Biotin
Answer: C: Biotin 
Explanation: The following vitamins serve as cofactors for various enzymes of the TCA cycle - Riboflavin 1. Active form: FAD 2. Cofactor for: Succinate dehydrogenase Niacin 1. Active form: NAD+ 2. Cofactor for: Isocitrate dehydrogenase, a-ketoglutarate dehydrogenase, and Malate dehydrogenase complex Thiamin 1. Active form: Thiamin diphosphate 2. Cofactor for: decarboxylation step of alpha keto glutarate dehydrogenase complex Pantothenic acid 1. Active form : As a pa of Coenzyme A 2. Cofactor for: esterified to the carboxylic acid residues, i.e. acetyl-CoA and succinyl-CoA. Reference: Harper's Illustrated Biochemistry 30th Edition Page no: 164