Describe the different ways in which carbon (IV) oxide is transported by blood.

• Carbon (IV) oxide diffuses out of the tissues into the red blood cells where it reacts with water in the presence of carbonic anhydrase enzyme to produce carbonic acid. The acid dissociates into hydrogen and  hydrogen carbonate ions   
• The hydrogen carbonate ions then diffuse out of the red blood cells into the plasma; where it further dissociates to produce carbon (IV) oxide on reaching the alveolar cavities of the lungs and diffuses into the alveoli.
• Some carbon (IV) oxide combines with the amine group in the  haemoglobin  molecule  forming carbaminohaemoglobin; which  dissociates  in  the lungs  producing  carbon (IV)  oxide.
• Some carbon (IV)  oxide dissolve in blood plasma forming carbonic acid which later dissociate to carbon (IV) oxide on reaching the lungs;