Which compound has a greater affinity for hemoglobin?

The compound with the greatest affinity for hemoglobin is carbon monoxide. This is due to the molecular structure and bonding characteristics of carbon monoxide, which can bind to the heme group of hemoglobin much more tightly than oxygen. In fact, carbon monoxide can inhibit the binding of oxygen by occupying the same binding site, leading to a significantly reduced ability of hemoglobin to transport oxygen in the blood.

The reason carbon monoxide's binding is so strong lies in its ability to form a stable covalent bond with the iron atom in the heme. The binding affinity of carbon monoxide is more than 200 times that of oxygen. This high affinity is what makes carbon monoxide a dangerous gas; even at low concentrations, it can displace oxygen from hemoglobin, leading to tissue hypoxia and potentially fatal outcomes.

Oxygen does bind to hemoglobin but with a considerably lower affinity compared to carbon monoxide. While carbon dioxide does have some binding interactions with hemoglobin, it primarily interacts via different mechanisms, such as through the formation of carbamino compounds and does not compete directly at the same binding site as oxygen or carbon monoxide. Nitrogen is inert and does not significantly bind to hemoglobin at physiological levels, which makes it irrelevant in this context. Therefore, carbon monoxide