Deoxygenated blood can carry increasing amounts of carbon dioxide, whereas oxygenated blood has a reduced carbon dioxide capacity.
The Haldane Effect describes the effect of oxygen on CO2 transport. The Haldane Effect (along with the Bohr Effect) facilitates the release of O2 at the tissues and the uptake of O2 at the lungs. This is represented by a right shift of the oxyhemoglobin dissociation curve and a left shift of the oxyhemoglobin dissociation curve respectively. The Haldane Effect results from the fact that deoxygenated hemoglobin has a higher affinity (~3.5 x) for CO2 than does oxyhemoglobin. Deoxygenated hemoglobin has a higher affinity for CO2 because it is a better proton acceptor than oxygenated hemoglobin. Therefore, when hemoglobin is deoxygenated (i.e., at tissues) there is a right shift of the carbonic acid-bicarbonate buffer equation to produce H+ which in turn increases the amount of CO2 which can be carried by the blood back to the lungs to be exhaled. Then, with oxygenation at the lungs CO2 dissociates more readily from hemoglobin.
CO2 + H2O ⇆ H2CO3 ⇆ H+ + H+CO3-
The following is the general equation of the Haldane Effect
H+ + HbO2 ←→ H+Hb + O2
In the end, the Haldane effect allows for approximately 50% of the CO2 excreted by the lungsand is physiologically much more important than its reciprocal counterpart, the Bohr effect (the effect of carbon dioxide on oxygen transport).
R A Klocke Mechanism and kinetics of the Haldane effect in human erythrocytes. J Appl Physiol: 1973, 35(5);673-81 [PubMed:4203704]