Oxygen transport saturation curve

Fig. 3. Oxygen transport by perfluorocarbons versus hemoglobin (Hb) (a) In the case of PFCs, O2 dissolution is characterized by loose, nondirectional van der Waals interactions. Oxygen solubility follows Henry s law, that is, is directly proportional to the gas s partial pressure (curve c). (b) In the case of Hb, a strong, localized chemical bond is established with the iron atom of a heme. Successive binding of four O2 molecules to the four hemes of Hb is cooperative, and saturation occurs when all four iron atoms are bound. Hence, the sigmoid shape of the O2 uptake curve, which levels off when the partial pressure of O2 on earth is attained (curve d) [20].

Studies of oxygen transport in pregnant mammals have shown that the 02-saturation curves of fetal and maternal blood are markedly different when measured under the same conditions. Fetal erythrocytes contain a structural variant of hemoglobin, HbF, consisting of two a and two y subunits (a2y2), whereas maternal erythrocytes contain HbA (a2/32). 

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