ABSTRACT
One mole of oxygen at STP occupies 22400 ml and so, under the same conditions, 1 mol Hb can carry 89600 ml oxygen. By calculation 1 g Hb can carry 1.34 ml and, as there are 150g Hb per litre of blood, when fully saturated with oxygen each litre can carry approximately 200 ml. We know that the PVO2 is around 40mmHg because Hb does not give all its oxygen up to the tissues as a result of its sigmoid dissociation curve. This equates to about 30% remaining bound to the Hb, despite the right shift in the dissociation curve brought about by carriage of CO2 and the resultant acidification of the imidazole radicals of the histidine molecule of Hb (see ‘Buffers’ and Figure 26.3).
