State the different modes of CO2 transpo | Class 11 Biology Chapter Breathing and Exchange of Gasses, Breathing and Exchange of Gasses NCERT Solutions

Carbon dioxide is carried by blood in three forms: physical solution, bicarbonate ions and carbamino- haemoglobin.

(i) Physical solution: A very small amount of carbon dioxide about 7% dissolved in the plasma and is carried as a physical solution.  

(ii) Bicarbonate ions: About 70 % of carbon dioxide released by respiring tissue cells diffuses into the plasma and then into the red blood corpuscles. Here, the carbon dioxide combines with water to form carbonic acid and make carbonic acid and this reaction is catalyzed by enzyme carbonic anhydrase. Then carbonic acid dissociated into hydrogen ion and bicarbonate ions. And these bicarbonate ions are transported in the RBCs where most of them diffuses into the plasma to be carried by it.  

(iii) Carbaminohaemoglobin: Approx. 23% of CO₂ enters the RBCs loosely combines with the amino group (- NH₂) of the reduced Haemoglobin to form Carbaminohaemoglobin and this reaction releases oxygen.