Co2 Transport | Anatomy2Medicine
Co2 Transport,Blood

Co2 Transport

Carbon Dioxide Transport in Blood

    • Forms of co2 in blood
      • CO2 is carried in the blood in three forms:
        • as dissolved CO2
        • as carbaminohemoglobin (CO2 bound to hemoglobin
        • as bicarbonate (HCO3-), which is a chemically modified form of CO2.
          • HCO3- is quantitatively the most important of these forms.
    • Dissolved CO2
      • Henry’s law,
        • concentration of CO2 in blood is the partial pressure multiplied by the solubility of CO2.
      • The solubility of CO2 is 0.07 mL CO2/100 mL blood/mm Hg;
      • concentration of dissolved CO2 in arterial blood, =  2.8 mL CO2/100 mL blood (40 mm Hg x  0.07 mL CO2/100 mL blood/mm Hg),
      • it  is approximately 5% of the total CO2 content of blood. (MCQ)
      • because of the lower solubility of O2, compared with CO2, dissolved O2 is only 2% of the total O2 content of blood(MCQ)
    • Carbaminohemoglobin
      • CO2 binds to terminal amino groups on proteins (e.g., hemoglobin and plasma proteins such as albumin).
      • When CO2 is bound to hemoglobin, it is called carbaminohemoglobin, which accounts for about 3% of the total CO2. (MCQ)
      • CO2 binds to hemoglobin at a different site than O2 binds to hemoglobin.
      • Bohr effect(MCQ)
        • CO2 binding to hemoglobin reduces its affinity for O2 and causes a right-shift of the O2-hemoglobin dissociation curve (Bohr effect).


  • Haldane effect(MCQ)


        • In turn, O2 bound to hemoglobin changes its affinity for CO2
        • when less O2 is bound, the affinity of hemoglobin for CO2 increases (the Haldane effect).
    • HCO3–
      • Almost all of the CO2 carried in blood is in a chemically modified form, HCO3– accounts for more than 90% of the total CO2.


  • The reactions that produce HCO3- from CO2


      • involves the combination of CO2 and H2O to form the weak acid H2CO3.
      • This reaction is catalyzed by the enzyme carbonic anhydrase(MCQ)
      • In turn, H2CO3 dissociates into H+ and HCO3-.
      • In the tissues,
        • CO2 generated from aerobic metabolism is added to systemic capillary blood, converted to HCO3-
        • transported to the lungs
      • In the lungs, HCO3- is reconverted to CO2 and expired.