In methemoglobinemia, the iron in hemoglobin is in which oxidation state?

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Multiple Choice

In methemoglobinemia, the iron in hemoglobin is in which oxidation state?

Methemoglobinemia involves iron in the ferric oxidation state, Fe3+. In this form, the iron in the heme cannot bind oxygen reversibly, so methemoglobin itself cannot carry oxygen. That reduces the blood’s overall oxygen-carrying capacity, leading to tissue hypoxia even when oxygen is available in the lungs. Additionally, the presence of ferric iron shifts the dynamics of the remaining ferrous hemes, often making oxygen binding tighter and delivery to tissues less efficient. Other iron states, like ferryl (Fe4+), are not the physiologic form responsible for methemoglobinemia, and a zero oxidation state is not typical in this context.

Methemoglobinemia involves iron in the ferric oxidation state, Fe3+. In this form, the iron in the heme cannot bind oxygen reversibly, so methemoglobin itself cannot carry oxygen. That reduces the blood’s overall oxygen-carrying capacity, leading to tissue hypoxia even when oxygen is available in the lungs. Additionally, the presence of ferric iron shifts the dynamics of the remaining ferrous hemes, often making oxygen binding tighter and delivery to tissues less efficient. Other iron states, like ferryl (Fe4+), are not the physiologic form responsible for methemoglobinemia, and a zero oxidation state is not typical in this context.

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