What happens during CO2 unloading in relation to H+ and HCO3-?

During CO2 unloading in the body, the partial pressure of carbon dioxide (PCO2) decreases as CO2 diffuses from the blood into the alveoli for exhalation. This process affects the reversible reaction that occurs in red blood cells, where carbon dioxide is converted to bicarbonate (HCO3-) and hydrogen ions (H+) through the action of the enzyme carbonic anhydrase.

When CO2 is unloaded from hemoglobin (Hb), bicarbonate ions (HCO3-) shift back into the red blood cells in exchange for chloride (Cl-), a process known as the chloride shift. In this context, the H+ ions, which were previously buffered by hemoglobin during CO2 loading, begin to dissociate from hemoglobin due to the decrease in CO2 levels and a corresponding decrease in H+ concentration. As H+ dissociates from hemoglobin, it liberates the hemoglobin to bind with oxygen, promoting oxygen unloading to tissues.

The H+ ions, which were released from hemoglobin due to the lower CO2 concentration, can then interact with bicarbonate ions. However, predominantly what happens is that H+ dissociates from hemoglobin and does not directly bind with bicarbonate. The bicarbonate