The four commonly recognized types of hemoglobin are oxyhemoglobin, deoxyhemoglobin, methemoglobin, and hemichromes.
Here's a breakdown of each type:
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Oxyhemoglobin (Oxy-Hb): This is hemoglobin bound to oxygen. It is the form of hemoglobin present when red blood cells are carrying oxygen from the lungs to the tissues. The binding of oxygen changes the conformation of the hemoglobin molecule, increasing its affinity for more oxygen.
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Deoxyhemoglobin (Deoxy-Hb): This is hemoglobin without any oxygen bound to it. It is the form of hemoglobin that exists after oxygen has been released to the tissues. Deoxyhemoglobin has a lower affinity for oxygen compared to oxyhemoglobin.
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Methemoglobin (Met-Hb): In this form, the iron in hemoglobin's heme group is in the ferric (Fe3+) state instead of the ferrous (Fe2+) state. Methemoglobin cannot bind oxygen effectively. Normally, only a small percentage of hemoglobin exists as methemoglobin, as enzymes within red blood cells work to convert it back to functional hemoglobin. Elevated levels of methemoglobin can lead to hypoxia.
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Hemichromes: Similar to methemoglobin, hemichromes also contain iron in the Fe3+ state. They represent a further denatured state of hemoglobin. They are formed under conditions of oxidative stress or denaturation. Eventually, methemoglobin and hemichromes are enzymatically cleaved into smaller fragments within the cell.
