TRANSPORT of CO2

 Explain different ways of transport of CO2 from Cell? 

TRANSPORT OF CARBON DIOXIDE

Carbon dioxide is transported by the blood from cells to the alveoli.

It is transported by following four ways:

 1. As dissolved form (7%)

 • Carbon dioxide diffuses into blood and dissolve in the fluid of plasma forming a simple solution.

 2. As carbonic acid (negligible)

 • Few dissolved carbon dioxide in plasma combine with water to form carbonic acid.

 3. As bicarbonate (63%)

 • From plasma ,carbon dioxide enter the RBC.

 • In RBC, carbon dioxide combine with water to form carbonic acid.

 • Carbonic acid is very unstable, all carbonic acid dissociate into bicarbonate and hydrogen ion.

 • As concentration of bicarbonate ion increases in RBC, bicarbonate ions diffuses through the cell membrane in to plasma.

 Chloride Shift or Hamburger Phenomenon:

 • It is the exchange of chloride ion for bicarbonate ions across RBC membrane.

 • It occurs when carbon dioxide enter the blood from tissue.

 Reverse Chloride Shift

 • It is the process by which chloride ions are moved back into plasma from RBC shift.

 • It occurs in lungs. It helps in elimination of carbon dioxide from the blood.

 4. As carbamino compounds (30%)

 • Carbon dioxide combines with haemoglobin to form

  carbamino-hemoglobin AND it also combines with plasma protein to form carbamino protein.

 • Carbaminohemoglobin and carbamino protein together called carbamino compound.

Written by: RB Sah (MBBS)

Reference: K. Sembulimgan Physiology Book; Guyton and Hall Medical physiology