Which molecule binds to hemoglobin with an affinity 240 times that of oxygen?

The molecule that binds to hemoglobin with an affinity 240 times that of oxygen is carbon monoxide. This affinity is significant because carbon monoxide competes with oxygen for binding sites on hemoglobin, which can lead to detrimental effects on oxygen transport in the body. When carbon monoxide binds to hemoglobin, it forms carboxyhemoglobin, preventing oxygen from being effectively transported to tissues and organs. This high affinity is one reason why carbon monoxide is considered extremely toxic; even low levels of exposure can be harmful or lethal because it impairs the body’s ability to carry oxygen.

Other molecules mentioned do interact with hemoglobin, but none have the same level of affinity as carbon monoxide. For example, carbon dioxide does bind to hemoglobin, but it does so at a much lower affinity compared to oxygen and carbon monoxide. Nitrogen is generally inert in this context and does not have a direct significant binding interaction with hemoglobin. Hydrogen sulfide can have biological activity but does not bind to hemoglobin in the same manner as carbon monoxide, and its physiological effects are quite different.

The extreme affinity of carbon monoxide for hemoglobin is a critical aspect of understanding not only its biochemical interaction but also the clinical implications regarding carbon monoxide poisoning.