Short notes on the transport of CO2 in blood

Short notes on the transport of CO2 in blood

Transport of CO₂:

With the result of various metabolic activities CO₂ is evolved which diffuses into the blood. The total amount of CO₂ in the venous blood is about 60nk / 100ml of blood and the arterial blood con­tains about 50ml CO₂ per 100ml. Thus, a relatively small amount of CO₂ is carried in the blood, yet blood reaction does not become acidic. This proves that in C0₂ transport the blood buffers play a very important role. CO₂ is carried in the following 3 ways.

(i) Transport of C0₂ in Physical solution:

Under normal temperature and pressure only 2.7 ml of C0₂ is carried in physical solution as H₂C0₃. As C0₂ enters the blood, it combines with H₂O of Plasma forming carbonic acid.

CO₂ + H₂O H₂CO₃ (Carbonic acid)

(ii) Transport of CO₂ as Bicarbonates:

Nearly 85% of the total C0₂ is carried as bicarbonates in both plasma and RBC’s.

NaHC0₃ in Plasma Arterial Blood = 33.1% Venous Blood =35.2%

KHC0₃ in RBC’s Arterial Blood = 9.8% Venous Blood = 10.5%

As CO, enters the blood cells from the tissues, it combines with H₂O to form H₂CO₃ which dissociates to hydrogen ions and bicarbonate ions. The latter diffuses into the plasma forming sodium and potassium bicarbon­ates.

H₂CO₃ H⁺ + HCO₂ Na+ +HCO₃–> NaHCO₃ K + HCO₂ -> KHCO₃

(iii) Transport of CO₂ as Carbamino Compounds:

About 10% of CO₂ is transported as carbamino compounds

Carbino-Haemoglobin in RBCs Carbinoproteins in plasma

Arterial Blood = 2% Arterial blood = 1 %

Venous blood =2.6% Venous blood =1.1.%

CO₂ + HbNH₂ -> HbNHCOOH Carbohaemoglobin

CO₂ Dissociation curve:

By plotting on the ordinate the total amount of CO₂ in the blood and on the abscissa the various CO₂ partial pressures, a curve is obtained, this is called CO₂ dissociation curve.