Chloride shift/Hamburger phenomenon

The greater proportion (70%) of carbon dioxide is transported in the form of bicarbonates.
The CO2 reacted with the water of the cytoplasm in the presence of enzyme carbonic anhydrase to form carbonic acid.
The carbonic acid (H2CO3) is a weak acid, which undergoes partial dissociation to yield hydrogen ion (H+) and bicarbonate ion (HCO3-).
The given reaction mostly occur inside RBCs, because the enzyme carbonic anhydrase is abundant there.

Fig. Diagrammatic representation of chloride shift.

In RBCs, CO2 combines with water to from carbonic acid which dissociates to gives H+ ion and bicarbonate (HCO3-) ion in the presence of enzyme carbonic anhydrase.
The bicarbonate ion then diffuses outside the RBC in the plasma and combines with Sodium ions to from Sodium bicarbonate (NaHCO3).
Loss of bicarbonate ions from RBC causes positive charge inside RBC which is balanced by diffusion of chloride (Cl-) ion from plasma into the RBC.
This exchange of Cl- ion and HCO3- ion between plasma and RBC is known as chloride shift.
This phenomenon of chloride shift maintain the electrical neutrality of cell.
This phenomenon is also known as Hamburger phenomenon.
Reverse of chloride shift occurs in tissues.