In blood, CO₂ is transported majorly as

• sodium carbonate

• carboxyhaemoglobin

• bicarbonate

• CO₂ as such

C.

bicarbonate

In dissolved state 7% of CO₂ gets dissolved in the blood plasma and about 0.3 mL of CO₂ is transported per 100 mL of blood in plasma.

In the form of bicarbonate about 70% of CO₂ is received by blood from tissues, enters the RBCs where it reacts with water to form carbonic acid (H₂CO₃).

As carbaminohaemoglobin about 23% of CO₂ is transported in combination with haemoglobin and plasma proteins. CO₂ reacts with NH₂ (amine radicals) of Hb to form an unstable compound cabamino- haemoglobin (Hb.CO₂).

Sodium bicarbonate acts as a buffer of blood.