This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Vitamins, Subject name: Biochemistry
Which of the following vitamins does not participate in oxidative decarboxylation of pyruvate to acetyl CoA - 
Select and explain. 
A. Thiamine, B. Niacine, C. Riboflavin, D. Biotin
D: Biotin
Answer: D: Biotin 
Explanation: Ans. is 'd' i.e.. Biotin o Oxidative decarboxylation of pyruvate to acetyl CoA occurs only in mitochondria.o Pyruvate, formed in cytosol, is transported into the mitochondria by a proton svmporter. In side the mitochondria, it is oxidatively decarboxylated to acetyl CoA by a multienzyme complex, i.e., py ruvate dehydrogenase (PDH) complex.o PDH complex is located in the mitocondria! matrix.o PDH complex is made up of three enzymes and requires five coenzymes.o The enzymes are: (i) E : Pyruvate dehydrogenase or pyruvate decarboxylase, (ii) E,: dihydrolipoyl transacetyl as e, and (iii) E,: dihydrolipoy l dehy drogenase.o The coenzymes required are thiamine pyrophosphate (TPP), lipoic acid. FAD, NAD, and CoA.Coming to the questiono Niacin is used as NAD, Riboflavin is used as FAD and thiamine is used as TPP.