pKa

PO4

pKa for PO4

--> 2, 6.8, 12

Because intracellular pH is lower (6.8-7.1)
--> Phosphate more effective intracellularly (in addition to greater concentration)

Intracellular phosphate = 60 mmol/L

Hb

pKa for DeoxyHb = 8.2

pKa for OxyHb = 6.6

But average pKa for Hb = 6.8 [BK2:p25]

NB:

• Should be the same for protein since it's the same imidazole group in histidine that provides buffering