• The chloride shift is the?movement of chloride ions into red blood cells?that occurs when?hydrogen carbonate ions are formed
• Hydrogen carbobate ions are formed by the following process
  • Carbon dioxide diffuses into red blood cells
  • The enzyme?carbonic anhydrase?catalyses the combining of carbon dioxide and water to form?carbonic acid (H2CO3)

CO₂?+ H₂O?? H₂CO₃

• • Carbonic acid dissociates to form?hydrogen carbonate ions?and?hydrogen ions

H₂CO₃?? HCO₃^-?+ H⁺

• Negatively charged hydrogencarbonate ions formed from the dissociation of carbonic acid are?transported out of red blood cells?via a transport protein in the membrane
• To prevent an electrical imbalance,?negatively charged chloride ions?are?transported into the red blood cells?via the same transport protein
  • If this did not occur then red blood cells would become positively charged as a result of a buildup of hydrogen ions formed from the dissociation of carbonic acid