What is formed when the ferrous iron of hemoglobin is oxidized?

When the ferrous iron (Fe2+) of hemoglobin is oxidized, it converts to ferric iron (Fe3+), resulting in the formation of methemoglobin. In this state, hemoglobin can no longer effectively bind to oxygen, impairing its ability to carry oxygen throughout the body. This condition commonly occurs due to various factors, such as exposure to certain chemicals or drugs, which can oxidize the iron in hemoglobin.

Oxyhemoglobin, on the other hand, is formed when hemoglobin binds with molecular oxygen (O2) and represents the normal functional state of hemoglobin while delivering oxygen to tissues. Carboxyhemoglobin is the result of hemoglobin binding with carbon monoxide, and sulfhemoglobin occurs when sulfur is incorporated into the hemoglobin molecule. These forms, while relevant, are not the direct result of the oxidation of ferrous iron. Therefore, when discussing the specific process of iron oxidation in hemoglobin, methemoglobin is the product of interest.