Hb is a good buffer because of: (A) Histidine residues, (B) Protein nature, (C) Acidic nature, (D) Iron molecules
Answer is A. Ref Robbins 9/e 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