1. Transport of Carbon Dioxide

2. Learning Intentions Describe the role of haemoglobin in carrying carbon dioxide. Describe and explain the significance of the dissociation curves of adult oxyhaemoglobin at different carbon dioxide levels (the bohr effect).

3. How is carbon dioxide transported? 5% in the plasma. 10% combined with haemoglobin (carbaminohaemoglobin) 85% as hydrogencarbonate ions (HCO 3 - )

4. Formation of Hydrogencarbonate ions Some carbon dioxide enters red blood cells. Combines with water to form carbonic acid catalysed by carbonic anhydrase. Carbonic acid dissociates to release hydrogen ions and hydrogen carbonate ions. Hydrogen carbonate ions diffuse out of the RBCs into plasma. Charge maintained by chloride entering RBC (chloride shift) Hydrogen ions combine with haemoglobin to form haemoglobonic acid.

5. Hydrogencarbonate ions

6. Releasing oxygen The partial pressure of oxygen (also called oxygen tension) of respiring tissues is lower than the lungs. Oxyhaemoglobin dissociates.

7. The Bohr effect (shift) Hydrogen ions compete with oxygen and displace oxygen on haemoglobin. Oxyhaemoglobin releases more oxygen.