Haemoglobin oxygen dissociation curve

Goodford PI, St-Louis J, Wootton R. A quantitative analysis of the effects of 2,3-diphosphoglycerate, adenosine triphosphate and inositol hexaphosphate on the oxygen dissociation curve of human haemoglobin. J Physiol 1978 283 397. 

The partial pressure, Pq, of the oxygen in the blood (oxygen tension) is related to Sq by the oxygen dissociation curve (Fig. 2.11). The shape and position of this sigmoidal curve depend on the temperature, the hydrogen ion concentration and the concentration within the red cells of other ligands of haemoglobin... 

Figure 25.8 Oxygen dissociation curves for haemoglobin and myoglobin, showing how haemoglobin is able to absorb O2 efficiently in the lungs yet transfer it to myoglobin in muscle tissue.

Fig. 1 Oxygen dissociation curves for fetal and maternal haemoglobin.

Figure 25.1 Oxygen dissociation curves for myoglobin (A) and haemoglobin at Pcoj values of 40 mmHg(B) and 80 mmHg (C)...

Adair, G., 1925, The haemoglobin system. VI. The oxygen dissociation curve of haemoglobin, J. Biol. Chem., 63 529. 

Fig. 1 Dissociation curves—the relationship between PO, and oxygen binding to haemoglobin (a) The normal oxygen-haemoglobin dissociation curve, (b) The effect of MWr CO.

One can obtain an idea of the affinity of a particular haemoglobin for oxygen by noting the position of its dissociation curve at the Pio value, i.e. the partid pressure of oxygen corresponding to 50% oxygenation. 

Hence the shape and position of die dissociation curve are adapted to the respiratory needs of the organism. The slightest decrease in the pg, would immediately bring about a loss of oxygen from the haemoglobin. The fact that one is not justified in considering, even in aquatic animals, that the arterial Po is equal to the external Pq has been verified by the observations of H. M. Fox (see Table XVII). 

E. The shift in the carbon dioxide dissociation curve by oxygenation of the blood is because of altered affinity of haemoglobin for hydrogen ions. 

An alteration in the affinity of haemoglobin for oxygen. Decreases in blood pH or increases in PCOi cause the haemoglobin dissociation curve to move to the right. Alternatively an increase in blood pH or a decrease in PCO2 cause the curve to move to the left. 

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