Carbon dioxide is transported from the tissues to the lungs in three primary forms: dissolved in plasma, as bicarbonate ions, and bound to hemoglobin. Approximately 7-10% of COâ is dissolved directly in the plasma. The majority (about 70%) is transported as bicarbonate ions (HCOââ»), formed through the reaction of COâ with water catalyzed by the enzyme carbonic anhydrase. The remaining COâ is bound to hemoglobin, forming carbaminohemoglobin.
