Transport of Carbon Dioxide

Carbon dioxide is transported in the blood in 3 ways:

  1. 5% is dissolved directly in the plasma

  2. 10% is combined with Haemoglobin too from carbominohaemoglobin

  3. The rest travels as hydrogencarbonate ions

The transport of Carbon Dioxide as hydrogencarbonate ions:

  • CO2 diffuses into the RBC

  • It reacts with water & forms carbonic acid

    • This is catalyses by carbonic anhydrase

  • The carbonic acid dissociates to form H+ & HCO3- ions

  • The hydrogen carbonate ions diffuse out of the RBC down their concentration gradient and into the blood plasma.

    • To counter this loss of -vely charged ions move into the RBC cytoplasm.

    • This is the chloride shift

  • The H+ ions that were formed are taken by Haemoglobin to form Haemoglobinic acid.

    • The prevents a drop in pH and in this way the Haemoglobin acts as a buffer

  • When the Haemoglobin combines with H+ ions

    • Oxyhaemoglobin releases it's oxygen

      • The oxygen diffuse out into the plasma and eventually too the respiratory tissues

Effect of increased CO2