<prompt> Which of the following is not true about buffering action of haemoglobin Hb?Hb is technically intracellular bufferHb is functionally a plasma bufferHbs buffering action is due to its histidine contentOxygenated Hb is a strong base  <response>: Protein buffers in blood include haemoglobin 150gl and plasma proteins 70gl. Buffering is by the imidazole group of the histidine residues which has a pKa of about 6.8. This is suitable for effective buffering at physiological pH. Haemoglobin is quantitatively about 6 times more impoant than the plasma proteins as it is present in about twice the concentration and contains about three times the number of histidine residues per molecule. 