The Role of Haemoglobin (AQA A Level Biology): Revision Note

Haemoglobin & red blood cells

• Haemoglobin is located within red blood cells, where its role is to transport oxygen around the body

• When oxygen binds to haemoglobin, oxyhaemoglobin is formed:

oxygen + haemoglobin  oxyhaemoglobin

4O₂ + Hb  Hb4O ₂

• Each molecule of haemoglobin contains four haem groups, each able to bond with a single molecule of oxygen (O₂)

  • Each molecule of haemoglobin can carry four oxygen molecules, or eight oxygen atoms

• Red blood cells have a specialised structure that maximises their ability to transport oxygen:

  • They have no nucleus to maximise the space available for haemoglobin

  • They have a biconcave shape to maximise the surface area for diffusion of oxygen

  • They are highly flexible to allow them to pass through narrow capillaries

  • Their diameter is approximately the same as that of the capillaries, slowing down the flow of blood to maximise time for diffusion