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How is iron from old red blood cells reused to make new hemoglobin?
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blood
Blood sediment in test tubes, showing plasma (clear fluid), red blood cells (red), and the release of hemoglobin into the surrounding plasma (pink).
When red blood cells reach the end of their approximately 120-day life span, they are removed from circulation and destroyed by macrophages—specialized phagocytic cells found primarily in the spleen, liver, and bone marrow.12
The process of recycling iron occurs as follows:
- Extraction: Within these macrophages, the hemoglobin from the old red blood cells is broken down, freeing the iron.12
- Transport: The released iron is transported through the plasma by a protein called transferrin.13
- Utilization: Transferrin carries the iron to the bone marrow, where it is incorporated into new hemoglobin during the production of new red blood cells (erythropoiesis).134
- Storage: Any iron not immediately required for new hemoglobin synthesis is stored within the reticuloendothelial cells (often in the form of ferritin) and remains available for future use.15
This efficient system ensures that virtually all iron is conserved and reused by the body.1