Question

Which of the following gases has the highest affinity to bind with haemoglobin?

• A. Carbon dioxide
• B. Carbon monoxide
• C. Nitrogen
• D. Oxygen

Answer 1

The correct option is D Oxygen

Both oxygen and carbon dioxide are transported by haemoglobin. But, only 20-25$\%$ of carbon dioxide is transported by binding to haemoglobin, about 70$\%$ of it is transported as carbonate ions and around 3$\%$ by simple diffusion. But haemoglobin has a higher affinity for oxygen because of which it can exchange gases at the alveoli. So, all of it is transported by haemoglobin. Nitrogen and carbon monoxide are not normally transported by the blood.