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
Coenzyme in carboxylation reactions: 
Select and explain. 
A. Pyridoxine, B. Thiamine, C. Biotin, D. Cyanocobalamin
C: Biotin
Answer: C: Biotin 
Explanation: 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.