Which derivative of hemoglobin leads to irreversible changes in red blood cells?

Sulfhemoglobin is the derivative of hemoglobin that leads to irreversible changes in red blood cells. This compound is formed when sulfur is incorporated into the hemoglobin molecule, resulting in a stable and nonfunctional form of hemoglobin. Sulfhemoglobin cannot effectively transport oxygen, and its presence in the bloodstream represents a toxic state. Furthermore, the formation of sulfhemoglobin is generally irreversible, meaning that once it is formed, it does not return to normal hemoglobin.

In contrast, oxyhemoglobin is the normal compound formed when hemoglobin binds to oxygen, facilitating oxygen transport in the body. Methemoglobin, while also unable to transport oxygen effectively due to the iron in the heme group being in the ferric state (Fe3+), can be converted back to functional hemoglobin through enzymatic reduction. Carboxyhemoglobin results from the binding of carbon monoxide to hemoglobin, which reduces its oxygen-carrying capacity; however, like methemoglobin, it can revert back under certain conditions. Therefore, sulfhemoglobin is distinct as it creates permanent changes in red blood cells' ability to function.