Question

Short note on :

Chloride shift or Hamburger’s phenomenon.

Answer 1

1. About 70% of CO₂ is transported in the form of sodium bicarbonates/potassium bicarbonates from tissue cells to lungs. 

2. In the RBCs, CO₂ combines with water in the presence of a Zn containing enzyme, carbonic anhydrase to form carbonic acid. This action is rapid in RBCs as compared to that in the plasma. 

3. Carbonic acid being unstable, immediately dissociates into HCO₃^- and H⁺ in the presence of same enzyme, leading to large accumulation of HCO₃^- inside the RBCs. It thus moves out of RBCs. This can bring about imbalance of the charge inside the RBCs.

4. To maintain the ionic balance between the RBCs and the plasma, Cl^- diffuses into the RBCs. This movement of chloride ions is known as chloride shift or Hamburger’s phenomenon. 

5. HCO₃^- that comes in the plasma joins to Na⁺ /K⁺ forming NaHCO₃ /KHCO₃ which can maintain pH of blood. The remaining H⁺ ions in the RBCs are buffered by haemoglobin by the formation of oxyhaemoglobin. 

6. At the level of lungs, due to the low partial pressure of carbon dioxide of the alveolar air, hydrogen ion and bicarbonate ions combine to form carbonic acid and under the influence of carbonic anhydrase again yields carbon dioxide and water.