This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
[{'content': 'Coenzyme in carboxylation reactions: \nSelect and explain. \nA. Pyridoxine, B. Thiamine, C. Biotin, D. Cyanocobalamin', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Biotin/ Vitamin H/ Coenzyme RIt is a water-soluble B-vitamin (vitamin B7).It is composed of a ureido (tetrahydroimidizalone) ring fused with a tetrahydrothiophene ring.A valeric acid substituent is attached to one of the carbon atoms of the tetrahydrothiophene ring.Biotin is a coenzyme for carboxylase enzymes, involved in the synthesis of fatty acids, isoleucine, and valine, and in gluconeogenesis.', 'role': 'assistant'}]