<prompt> Hb is a good buffer because ofHistidine residuesProtein natureAcidic natureIron molecules  <response>: Ref Robbins 9e p650 Haemoglobin also functions in CO2 and proton transpo from tissues to lungs . Release of O2 from Oxy Hb at the tissue is accompanied by uptake of proton due to lowering of the pKa of histamine residues 