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59 Cards in this Set
- Front
- Back
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Where is most of the iron stored in the body? (more iron is in use, but wheres the primary storage site)
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in resident macrophages
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Can the body promote iron loss?
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no it cannot, the body can only lose iron by bleeding
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What is the scale of bioavailbility of iron, from its 4 forms
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Heme>>> Ferrous Fe2+>Ferric Iron Fe3+>elemental iron Fe0
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What is a major source of heme iron? how available is it?
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Heme iron is VERY bioavailable
it is found in meats, and fish, and seafoods |
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What is the major source of Non-heme iron?
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vegetables, fruits and egs
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What are the solubility properties and bioavailability of Ferric Iron Fe3+
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this is insoluble at biological pH, and is not very bioavailable
requires stomach acid to solubilize it |
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What are the solubility properties and bioavailability of Ferrous iron Fe2+
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this is bioavailable, and it IS soluble at biological PH
(contained in iron supplements) |
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What are the solubility properties and bioavailability of elemental iron?
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this is poor at both
needs acidic PH to solubilize |
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What 3 major groups of things increase Iron uptake?
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Reducing molecules
Amino Acids Acidic foods |
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How does vitamin C help with iron uptake?
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this converts ferric iron Fe3+ into ferrous iron Fe2+
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What form of iron can from complexes with Vitamin C, AA's, and glucose. how does this affect absorption?
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these bind Ferrous Iron Fe2+
this makes it MORE bioavailable |
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How do Phytates affect iron absorption?
what contains phytates? |
these inhibit iron absorption, by forming chelates with divalent cations
common in high cereal grains, legumes |
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how do polyphenols affect iron absorption? where are they found?
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these inhibit iron absorption, by forming chelates with divalent cations
common in Tannic acid, from tea and coffee. Decrease iron uptake by 40-60% respectively |
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how do phosphates and phosphoproteins affect iron absorption?
where are they found? |
These bind Ferrous Fe2+, and Ferric Fe3+
these are found in egg yolk |
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how does Oxalate affect iron absorption? where is it found?
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These chelates non-heme iron (Fe2+ and Fe3+)
found i spinach, (which makes the iron in spinach not available for uptake) |
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how do Calcium and Zinc affect iron uptake? in what concentrations?
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500mg or more of Calcium
or 5X the iron levels of Zinc both inhibit iron uptake |
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What does Transferrin do?
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this is a serum protein that Transports iron, in circulation
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How does Non-heme iron get absorbed into enterocytes?
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this is taken up by DMT1
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How is heme iron absorbed into enterocytes?
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this is directly taken up as heme, and once inside the cell, is broken down by Heme Oxygenase (HO-1)
this releases the iron in heme |
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in the enterocytes, what does mobilferrin do?
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this transports Fe trough the cell, for use in other processes
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in the enterocytes, what does ferritin do?
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this is an iron storage site....it can cause iron loss if this isnt used, and the entrocytes die off.
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How is iron exported from the enterocyte?
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this occurs on the basal side, via Ferroportin
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What cells contain Ferroportin?
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ONLY duodenal enterocytes, macrophages, hepatocytes, and trophoblasts of the placenta
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What is the Fenton reaction?
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this is a toxic reaction involving Ferrous Iron (Fe2+) , this splits Hydrogen Peroxide into two hydroxyl radicals (while converting itself into ferric iron Fe3+)
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What is Transferrin, what is it job, and where is it found
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This binds ferric iron outside the cell (Fe3+)
its job is to: Solubilize iron Stop reactivity deliver iron to usage and storage sites |
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What are the 3 states of transferrin?
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apo-transferrin (no iron bound)
monoferric transferrin diferric transferrin |
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what do all growing cells require?
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IRON yay!
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How does iron cross a lipid bilayer to enter a regular cell?
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this uses a transferrin receptor, and its process of endocytosis.
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what type of transferrin does the transferrin receptor have a high affinity for?
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diferrictransferrin
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How is iron released from transferrin once endocytosed?
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there is an H+ pump in the endosome that acidifys the interior. this releases the stored iron
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how much iron is in storage in a healthy person?
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about 25%
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What does Ferritin do, and where is it found?
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This is an intracellular protein found in all cells,
and it is used to store iron. |
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What forms does ferritin come in?
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this is a 24 subunit polypeptide
has H and L subunits, found in various ratios |
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how much iron can a single ferritin store?
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up to 4500 atoms of iron
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can the iron store inside ferritin participate in the fenton reaction?
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no it cannot
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What is the BEST test to assess body iron stores?
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measuring Serum Ferritin Levels
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What is hemosiderin?
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This is a form of ferritin, that has been partially degraded by lysosomes. contains 30% more stored iron than Ferritin
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what is hemosiderin a sign of?
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this is a sign of iron overload
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What is Ferroportin, where is it found?
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this move iron OUT of the cell, and into circulation, it is found only in
Macrophages- iron from RBC breakdown Hepatocytes- Iron from storage Duodenal Enterocytes- iron from diet Placental Trophoblasts- iron to embryo |
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What is Hepcidin?
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this is a 25aa peptide, this control iron absorption and mobiliztion
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How do hepcidin levels affect ferroportin?
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High levels of hepcidin, BIND to ferroportin, preventing the 4 cell types from releasing iron, AND absorption of iron
aka induces internalization and degradation of ferroportin |
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What kinds of things induce hepcidin production?
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Increased iron stores, increased plasma iron levels.
Infection and inflammation (this causes less iron to be released, by binding and degrading ferroportin) |
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what kinds of things inhibit hepcidin production?
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decreased iron stores
hypoxia increased RBC demand (this is an overriding signal- like in blood loss) |
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What are IRE's?
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these are stem-loop structures in the mRNA, that code for Iron-regulated proteins
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What IRE's are in the 5'-UTR?
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ferritin and ALA-S2
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what IRE's are in the 3' UTR?
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Transferrin receptor, or DMT1
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what are IRPs?
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these are cytosolic proteins that bind to IRE, with high affinity, but have an even higher affinity for Iron
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What does an IRP bound to a 3' IRE do?
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this stabilizes the mRNA, increasing the level of protein synthesis
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what does an IRP bound to the 5' IRE do?
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this prevents DNA translation, decreasing protein synthese
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how do IRP's function?
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IRP's are sensitive to iron, so in LOW iron- IRP's are avtive, and bind the IRE's on the mRNA.
When iron is High, all IRP's are bound by iron, and the its ability to bind IRE's is impaired |
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What happens to the IRE's, IRP's and their gene products when iron is high?
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IRE's are unbound
Ferritin synthesis is increased increases iron storage transferrin synthesis is decreased |
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What happens to the IRE's, IRP's and their gene products when iron is low?
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IRE's are bound by IRP's
ferrtin synthesis is decreased increased export transferrin receptor is produced |
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how does iron affect infection?
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this makes infections WORSE in high levels
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What is lactoferrin? what makes it, and when is it used?
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this is a natural defense iron binding protein. it is similar to transferin.
synthesized by neutrophils, released during infection and inflammation VERY high affinity for iron, more than transferrin |
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What does IL-1 stimulate?
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-This encourages nutrophils to produce lactoferrin.
- increases RBC phagocytosis - slows down erythropoiesis |
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what does IL-6 do?
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this stimulates liver to release hepcidin, which lowers ferroprotin levels, and decreases overall iron in the blood
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what causes anemia of chronic disease?
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chronic high levels of hepcidin
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How much iron does 1 ml of blood contain?
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.5mg iron/1ml blood
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what is the most common cause of iron deficiency in the US?
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acute or chronic blood loss
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