Answer
A. Forming carbonic acid in the plasma of the RBC.
Work Step by Step
Carbon dioxide combines with cellular water inside red blood cells to form carbonic acid. Carbonic anhydrase, an enzyme, speeds the chemical reaction to form hydrogen ions and bicarbonate ions. The bicarbonate ions are carried in plasma and the hydrogen atoms bind to the globin in hemoglobin. When blood reaches lungs the chemical reaction is reversed and the carbon dioxide is reformed before being expelled from the body through exhalation.
