<prompt> Which amino acid can protonate and deprotonate at neutral pH?HistidineLeucineGlycineArginine  <response>: Ans. A. HistidineAmino acid which can protonate and deprotonate means those which can act as buffer.Amino acid whose pKapH of the medium has maximum buffering capacity.pKa of imidazole group of histidine is 6.5 - 7.4.At pH7, Imidazole group of histidine can act as buffer. 