Carbon Dioxide Transport

Carbon dioxide (CO₂) is one of the main end products of metabolism. The body contains approximately 120 L of CO₂. The CO₂ formed in the cells diffuses through the interstitial space to enter the venous circulation. Reaction between CO₂ and H₂O is slow in the plasma but fast within the red blood cell (RBC) due to the intracellular presence of the enzyme carbonic anhydrase (CA). CO₂ dissociation curve is influenced by the state of oxygenation of the Haemoglobin (Hb) where oxyhaemoglobin carries less CO2 than deoxyhaemoglobin for the same partial pressure of carbon dioxide. Haldane effect describes how CO₂ transport is affected by the state of oxygenation of Hb. This is because deoxyhaemoglobin is better than oxyhaemoglobin in: combining with CO₂ to form carbamino compounds and combining with H+ ions. CO₂ dissociation curve is more linear than the oxyhaemoglobin dissociation curve which is sigmoid in shape.