chloride shift

The chloride shift is a crucial process in the transport of carbon dioxide within the blood. When carbon dioxide enters the blood in the body's tissues, it combines with water to form carbonic acid (H₂CO₃). This acid then dissociates into hydrogen ions (H⁺) and bicarbonate ions (HCO₃⁻).

To facilitate the transport of bicarbonate ions, an enzyme called carbonic anhydrase, found within red blood cells, speeds up this reaction. The chloride shift occurs when a bicarbonate ion moves out of the red blood cell into the plasma, and a chloride ion moves into the red blood cell in exchange. This process allows the blood to carry more carbon dioxide as bicarbonate without altering the electrical charge of the plasma or red blood cells. This mechanism is vital for maintaining blood pH and efficiently transporting carbon dioxide from tissues to the lungs for exhalation.12