Transport fo CO2, in blood In dissolved state : 7% of CO3 gets dissolved in the blood plasma and is carried in solution to lungs or about 0.3 mL of CO3 is transported per 100 mL of blood in dissolved state in blood plasma. In the form of bicarbonate : About 70% of CO2 (about 2.5 mL per 100 mL of blood), received by blood from tissues, enters the RBCs where it reacts with water to form carbonic acid (H2CO3). As Carbaminohaemogloblin : About 23% of CO2 is transported in combination with haemogloblin and plasma proteins. CO2 reacts directly with amine radicals (NH2) of haemoglobin to form an unstable compound carbamino-haemogloblin (Hb.CO2). Sodium bicarbonate act as buffer of blood.