Question

Haldane effect plays more important role in promoting carbon dioxide transport than that of the Bohr's effect in promoting oxygen transport because

• A. oxyhaemoglobin is a stronger acid which donates hydrogen ion $(H^+)$ which in turn displace carbon dioxide from blood
• B. carbaminohaemoglobin is a stronger acid which splits into hydrogen ion $(H^+)$ and bicarbonate $(HCO^-_3)$
• C. carbon dioxide reacts with water to form carbonic acid that lowers the $pH$ in tissue
• D. carbon dioxide is less soluble in venous blood than in arterial blood

Answer 1

Answer: (A)

The degree of oxygenation of blood markedly affects the amount of $CO_2$ transported in blood. The lower the $PO_2$ and the haemoglobin saturation with $O_2$, the more the $CO_2$ that can be carried in the blood. This phenomenon, is called the Haldane effect. It depicts the greater ability of reduced haemoglobin to form carbaminohaemoglobin and to buffer $H^+$ by combining with it. In the pulmonary circulation, uptake of $O_2$ facilitates the release of $CO_2$. As haemoglobin becomes saturated with $O_2$, the hydrogen ions released combine with $HCO_3^-$ helping to unload $CO_2$ from the pulmonary blood. The Haldane effect is quantitatively more important in promoting $CO_2$ transport than the Bohr effect in promoting $O_2$ transport. It results from the simple fact that combination of $O_2$ with haemoglobin causes the haemoglobin (oxyhaemoglobin) to become a stronger acid. This in turn displaces $CO_2$ from the blood.