The oxygen dissociation curve is a graphical representation of the percentage of saturation of haemoglobin with oxygen at various partial pressures of oxygen.
In the lungs, the partial pressure of oxygen is very high. Hence, haemoglobin binds to oxygen and forms oxyhaemoglobin. Tissues or cells have a low oxygen concentration. Therefore, at the tissues or cellular level, oxyhaemoglobin releases oxygen to form haemoglobin.
The sigmoid shape of the oxygen dissociation curve is because of the binding of oxygen to haemoglobin. After the first oxygen molecule binds to the haemoglobin molecule, it increases the affinity for the second and subsequent molecule of oxygen to bind. Subsequently, haemoglobin attracts more oxygen.
Final answer
The oxygen dissociation curve is a graphical representation of the percentage of saturation of haemoglobin with oxygen at various partial pressures of oxygen.
The sigmoid shape of the oxygen dissociation curve is because of the binding of oxygen to haemoglobin. After the first oxygen molecule binds to the haemoglobin molecule, it increases the affinity for the second and subsequent molecule of oxygen to bind. Subsequently, haemoglobin attracts more oxygen.