3. • Carbon dioxide is transported in the blood
in three ways
• Physically dissolved
• Bound to hemoglobin
• As bicarbonate ion
4. Physically Dissolved
• Part of the carbon dioxide released from
the tissues is dissolved in plasma. But
only a small amount, typically just 7 –
10%, is transported this way.
5. Bound to Hemoglobin
• 30% of the CO2 combines with Hb to form
carbamino hemoglobin (HbCO2)
• The unloading of O2 from Hb in the tissue
capillaries therefore facilitates the picking
up of CO2 by Hb
• 20-30% is transported by this route
6. As Bicarbonate (HCO3) Ion
• The most important means of CO2
transport is as bicarbonate (HCO3), with
60-70% of the CO2 being converted into
HCO3 by the following chemical reaction in
Erythrocytes by the help of enzyme
Carbonic Anhydrase
C.A
• CO2 + H2O » H+ + HCO3-
7.
8. Chloride Shift
• The red blood cell membrane has a HCO3
– Cl carrier that passively facilitates the
diffusion of these ions in opposite
directions across the membrane.
• Consequently, HCO3 efflux and Cl influx
occur, which is known as chloride shift
11. Haldane Effect
• binding of O2 with hemoglobin tends to
displace CO2 from the blood is known as
the Haldane effect
12. • The Haldane effect results from the fact that
• combination of O2 with hemoglobin in the lungs causes
the hemoglobin to become a stronger acid.
• This displaces CO2 from the blood and into the alveoli in
two ways.
• First, highly acidic hemoglobin has less tendency to
combine with CO2
• Second, the increased acidity of the hemoglobin also
causes it to release an excess of hydrogen ions.
• These bind with bicarbonate ions to form carbonic acid,
which then dissociates to CO2, and the CO2 is released
from the blood into the alveoli