Buffering action of haemoglobin is mainly due to
High-Yield Explanation
The buffering action of hemoglobin is due to the imidazole group of the hystadine residues. Hemoglobin molecule contains 38 histidine. imidazole group of deoxyhemoglobin dissociate less than those of oxyhaemoglobin. Ref: Page no 566 Textbook of physiology Volume 1 AK Jain 7th edition