Haemoglobin oxygen saturation curves

Figure 2.19 Oxygen saturation curves for myoglobin and haemoglobin and different pH values. (Reproduced by permission of John Wiley Sons, Ltd).

Rg. 2 Comparison of oxygen saturation curves for haemoglobin and myoglobin. 

Irrespective of the interpretative approach, it is now widely recognised that many enzymes do show marked deviations from Michaelis-Menten behaviour, and the deviation is often interpretable in terms of regulatory function in vivo. Thus, for example, a number of enzymes, including threonine deaminase [30] and aspartate transcarbamylase [31] as textbook cases, show a sigmoid, rather than hyperbolic dependence of rate upon substrate concentration. This, like the oxygen saturation curve of haemoglobin, permits a response to changes in substrate concentration... 

Fig. 13. Typical oxygen equilibrium curves for haemoglobin (curve a) and myoglobin (curve b) curve c indicates a myoglobin-type (i.e., a non-cooperative oxygenation curve) with the same percentage saturation as haemoglobin at venous oxygen partial pressure.

The curve flattens at very high Po2 as the whole protein reaches saturation point . At rest, haemoglobin in the blood which enters the general circulation from the left side of the heart is about 98% saturated with oxygen and the venous return is approximately 75% saturated with oxygen. 

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