This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Proteins and Amino Acids, Subject name: Biochemistry
[{'content': 'Which amino acid can protonate and deprotonate at neutral pH? \nSelect and explain. \nA. Histidine, B. Leucine, C. Glycine, D. Arginine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. A. HistidineAmino acid which can protonate and deprotonate means those which can act as buffer.Amino acid whose pKa=pH of the medium has maximum buffering capacity.pKa of imidazole group of histidine is 6.5 - 7.4.At pH=7, Imidazole group of histidine can act as buffer.', 'role': 'assistant'}]