In the circulatory system, bicarbonate leaves the red blood cells and enters the plasma through an exchange mechanism with ______ to maintain electroneutrality.

In the circulatory system, bicarbonate leaves the red blood cells and enters the plasma through an exchange mechanism with ______ to maintain electroneutrality.

• A. Chloride
• B. Carbonic acid
• C. Lactate
• D. Sodium

Answer: (A)

The transport of bicarbonate out of red blood cells in exchange for chloride maintains electroneutrality across the red cell membrane, a process known as the chloride shift. When carbon dioxide produced by tissues enters red blood cells, it is converted to bicarbonate by carbonic anhydrase. The bicarbonate ion then moves out into the plasma via an anion exchanger in the red cell membrane, and a chloride ion moves in to balance the negative charge. This exchange keeps the overall electrical charge stable while facilitating CO2 transport to the lungs. In the lungs, the process reverses as bicarbonate re-enters the red blood cells in exchange for chloride, aiding CO2 offloading. Thus, the partner that maintains electroneutrality is chloride.

The transport of bicarbonate out of red blood cells in exchange for chloride maintains electroneutrality across the red cell membrane, a process known as the chloride shift. When carbon dioxide produced by tissues enters red blood cells, it is converted to bicarbonate by carbonic anhydrase. The bicarbonate ion then moves out into the plasma via an anion exchanger in the red cell membrane, and a chloride ion moves in to balance the negative charge. This exchange keeps the overall electrical charge stable while facilitating CO2 transport to the lungs. In the lungs, the process reverses as bicarbonate re-enters the red blood cells in exchange for chloride, aiding CO2 offloading. Thus, the partner that maintains electroneutrality is chloride.