DISSOCIATION CURVE

OXYGEN DISSOCIATION CURVE

S-shaped (sigmoidal) curve that shows the partial pressures of oxygen (PO₂) in relation to the
% saturation of haemoglobin. At 50 % saturation (indicated on the curve by p50), half of the haemoglobin binding sites contain oxygen molecules.

Image adapted from Haemoglobin, BioNet
Permission granted by Dr J M Basford,
University of Cardiff

From the curve you can see that at high PO₂, as in the pulmonary capillaries, haemoglobin is nearly 100 % saturated. This point is shown by the red arrow.

You can also see that at low PO₂, as in exercising muscles, haemoglobin saturation is much lower and oxygen is released. This point is shown by the blue arrow.

The dissociation curve is sigmoidal in shape because binding of the 1st O₂ molecule increases the affinity of haemoglobin for oxygen, making it easier for the next oxygen molecule to bind.

Undergraduates click here for more information on the co-operative binding of oxygen and the sigmoidal shape of the dissociation curve

Undergraduates click here for information on the effect of pH, CO₂ & temperature on dissociation curves

Undergraduates click here for information on the oxygen dissociation curve for myoglobin