Bicarbonate and CO2 Transport

CO2 diffuses down its concentration gradient out of tissues and into red blood cells (RBCs). Once inside the RBC, the enzyme carbonic anhydrase catalyses the conversion of CO2 into carbonic acid (H2CO3). Carbonic acid is then hydrolysed into H+ ions and ______.

The H+ ion is bound by haemoglobin which ______ the process.

The reverse occurs at the lungs where H+ dissociates from haemoglobin and combines with ______ to form carbonic acid which is then converted back to CO2 and water.

This reaction is again catalysed by ______.

Chloride shift refers to the exchange of ______ (HCO3−) and chloride (Cl−) across the membrane of red blood cells (RBCs).

CO2 diffuses freely into RBCs but as HCO3– ions are charged they cannot easily cross the cell membrane to leave the RBC. As a result, a carrier protein is utilised to allow ______ to leave the RBC in exchange for chloride ions.

This also allows the RBC to maintain its ______.

The majority of CO2 is transported via ______.

Figure 1. This equation shows the dissociation and formation of ______.