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11 Cards in this Set
- Front
- Back
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RBC daily requirement of iron |
25 mg (only 1-2mg intake per day --> mostly recycled) |
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absorption of iron |
-in the duodenum -can be: in heme (meat); ferrous; ferric -gastric acidity converts ferrous (Fe2+) to ferric -ferric iron is solublized by low pH and iron chelators such as vit C --> high pH and chemical inhibitors result in decreased absorption -ferric --> ferrous by DMT1 (enterocytle surface protein on lumenal side) -heme absorption is poorly understood -then can be used by enterocyte, stored with ferritin, or transported into circulation by ferroportin |
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ferritin |
-intracellular storage form of iron -consists of an outer shell of the apo-ferritin protein and an inner core where iron is held -sequesters storage iron in a non-toxic form |
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ferroportin |
-transport protein in enterocytes -transports iron into blood stream |
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circulation of iron |
-transported out the cells via ferroportin (ferrous) -converted to ferric by haephastin on enterocytes or ceruloplasmin on macrophages or hepatocytes -ferric iron is bound to transferrin |
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transferrin |
-transports virtually all iron in the circulation -one molecule carries two iron atoms -w/o iron is called apo-transferrin |
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utilization of iron |
-2/3 of all body iron is w/in Hb in RBCs -developing RBC precursors in bone marrow absorb iron by binding transferrin on their transferrin receptor (TfR) resulting in internalization -iron transported to mitochondria where it is incorporated into heme, which is then complexed with globin |
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storage of iron |
-excess circulating iron is absorbed by macrophages (or hepatocytes) via TfR -macropahges also ingest senescent RBCs and digest their Hb -store iron in ferrirtin (macrophage ferritin is major storage depot for body iron) -transported out of the macrophage via ferroportin
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TfR |
-transferrin receptor -binds transferrin -internalizes protein, receptor, and iron -iron released --> apo-transferrin is released and TfR is recycled -iron --> mitochondria to be incorporated into heme |
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erythroid islands |
-RBC precursors surrounding macrophages in bone marrrow -indicate direct movement of iron from macrophage to developing RBCs |
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regulation of iron metabolism |
-hepatocytes produce and excrete hepcidin with levels that increase with the amount of circulation iron -hepcidin binds ferrorportin on hepatocytes, enterocytes, and macrophages --> it is internalized and destroyed -IREs and IRPs --> down-regulate DMT1 and TfR; up-regulate apo-ferritin
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