Transport of Gases - Carbon dioxide

Description:

Transport as Carbamino-haemoglobin

• CO₂ is carried as carbamino-haemoglobin.

• When pCO₂ is high and pO₂ is low in tissues more binding of carbon dioxide occurs.

• When  pCO₂ is low and pO₂ is high as in alveoli, dissociation of CO₂ from carbamino-haemoglobin takes place. CO₂ bound to haemoglobin from the tissues is delivered at the alveoli.

Transport as Bicarbonate ions

• Carbonic anhydrase enzyme is present in large quantities in the RBCs. The enzyme is also present in minute quantities in plasma.

• Carbonic anhydrase can perform the following reaction −

• At tissues the pCO₂ is high due to catabolism so CO₂ diffuses into blood and forms HCO^-₃ and H⁺

• At alveoli, pCO₂ is low so the reaction proceeds in the opposite direction. This leads to the formation of CO₂ and H₂O. So CO₂ is transported in the form of bicarbonate and released out.

• Every 100 ml of deoxygenated blood delivers about 4 ml of CO₂ to the alveoli.