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Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
Which amino acid can protonate and deprotonate at neutral pH?
assistant
The correct answer is  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.