What occurs when HCO3 diffuses back into RBC in exchange for Cl?

The process of HCO3 (bicarbonate) diffusing back into red blood cells (RBC) in exchange for chloride (Cl) is known as the Reverse Chloride Shift. This occurs primarily in the lungs, where carbon dioxide is being expelled.

During the transport of carbon dioxide from tissues to the lungs, CO2 enters RBCs and is converted to bicarbonate, which then diffuses into the plasma. To maintain electrical neutrality, chloride ions move into the RBCs from the plasma; this is known as the Chloride Shift. When the blood reaches the lungs, bicarbonate needs to re-enter the RBCs so that it can be converted back to CO2 for exhalation. In this stage, Cl ions exit the RBCs and bicarbonate ions enter, hence the term Reverse Chloride Shift. This exchange is vital for facilitating the efficient removal of CO2 from the bloodstream as we breathe.

This process is critical for maintaining acid-base balance within the blood and facilitating respiration, linking the functions of the circulatory and respiratory systems effectively.