Explain how partial pressure of oxygen affects how oxygen binds to haemoglobin in different areas of the body.

In the lungs, the partial pressure of oxygen is high therefore haemoglobin readily binds to the oxygen. This causes the haemoglobin to undergo a conformational change and increase its affinity for oxygen so that more oxygen can bind to the haemoglobin. In respiring cells the partial pressure of oxygen is low and haemoglobin readily dissociates the oxygen so that it can be delivered to the working tissues.