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
Imidazole ring is present in 
Select and explain. 
A. Tryptophan, B. Arginine, C. Histidine, D. Tyrosine
C: Histidine
Answer: C: Histidine 
Explanation: Ans. is 'c' i.e.,Histidine Some amino acids contain a special functional group in their side chain which provide some specific functions to that amino acids. These are : Hydroxyl group in serine and threonine - Indole ring in tryptophanAmide group in aspargine and glutamine - (3-Carboxyl in glutamic acidThioether in methionine - Imidazole in histidineSulphydryl in cysteine - Phenol in tyrosiney-carboxyl in glutamic acid - Pyrrolidine in prolineGuanidinium in arginine - c-amino in lysine