BC Iron Met #13.txt

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BC Iron Met #13.txt
2011-01-20 21:24:41
BC Iron Met

BC #13 Iron Met
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  1. Where is iron primarily stored?
  2. How much iron is in our RBCs?
    2500 mg
  3. What is the only way a human can lose iron?
  4. What is the order of bioavailable heme (4 types)?
    Heme>>Ferrous (2+)>Ferric (3+)>Elemental (Fe0)
  5. What is the most abundant non-heme iron?
    Ferric (Fe3+)
  6. How is ferric (Fe3+) absorbed?
    • Low pH of stomach to b/c soluble
    • After breakdown, binds to another soluble molecule to be carried and stay soluble
  7. What pH is required for Ferrous Iron absorption?
    • Physiological (not a low pH like Ferric iron)
    • ***highly soluble, which is why it is the most bioavailable non-heme iron
  8. Does diet effect heme iron or non-heme iron bioavailability?
    non-heme b/c the porphyrin ring blocks metabolism in heme
  9. What are three enhancers of iron absorption?
    • 1) Reducers: can reduce ferric to ferrous (2+)
    • 2) Amino acids
    • 3) acidic foods: lower pH to help speed up absorption of ferric and ferrous absorption
  10. What are the 5 inhibitors of iron absorption? Examples of each?
    • 1) Phytates: cereals and legumes
    • 2) Polyphenols: tea and coffee
    • 3) Phosphates: egg yolk
    • 4) Oxalate: spinach (only 5% bioavailable due to this)
    • 5) Calcium and Zinc: supplements
  11. What are the cells that contain ferroportin for mobilization?
    • 1) Macrophages
    • 2) Enterocytes
    • 3) Hepatocytes
    • 4) Placental trophoblasts
  12. What is the Fenton reaction and what iron is involved?
    • ***Ferrous iron involved = toxic
    • Fe2+ + H2O2 = Fe3+ + OH- +OH- (two hydroxyl radicals to destroy cells)
  13. What needs to bind iron in order to stop the Fenton rxn?
    A protein
  14. What are the three stages of Transferrin depending on binding sites? What is normal saturation?
    • 1) Apotransferrin (0 Fe3+bound)
    • 2) Monoferric transferrin (1 Fe3+)
    • 3) diferric transferrin (2 Fe3+)
    • *** 33%
  15. What binds transferrin when it is bound to Fe3+?
    • Transferrin receptor
    • endocytosed, endosome made more acidic with H+ pump, iron released through DMT1, and apotransferrin + TfR sent back to plasma membrane
  16. What is Hemosiderin and when is it found in the body?
    • **better storage of non-soluble iron than ferritin
    • **ferritin that was degraded in lysosome
    • found during iron overload
  17. How much iron is in 1ml of blood?
    0.5 mg
  18. What occurs when Hepcidin levels are low?
    • Ferroportin is not destroyed
    • More absorption and release of iron from M,E,H,PT
  19. What occurs when Hepcidin levels are high?
    • Ferroportin endocytosed
    • lack of iron absorption
    • lack of iron release = more iron stored
  20. Why does hepcidin deficiency cause hemochromatosis? What problems are caused (2)?
    • Low hepcidin causes lack of absorption and release of iron so more is stored in the M,E,H,PT
    • Iron overload and organ damage pursue
  21. Where are IREs found on mRNA?
    • 5' region for ferritin
    • 3' region for TfR and DMT1
  22. When iron is high, what happens to IRP?
    IRP will not bind the IRE loop b/c iron has changed the IRP conformation
  23. What happens to the 3' end with IRE when iron is high? low?
    • 1) High: IRP will not bind IRE and RNAse will degrade b/c you don't need more transferred
    • 2) Low: IRP will bind IRE and stabilize b/c you need to absorb and transfer more
    • **3' end involved with TfR and DMT1
  24. What happens to the 5' end and IRE when iron is high? Low?
    • 1) High: IRP will not bind and translation occurs b/c you need a storage unit
    • 2) Low: IRP binds and translation does not occur b/c there is no use to build a storage unit with nothing to store
    • ***occurs with ferritin
  25. What is the function of Lactoferrin and where is it produced?
    • function: transfer iron from transferrin into macrophages to cause hypoferremia so no Iron is available during infection and the fenton rxn cannot occu
    • produced: neutrophils and released in circulation
  26. When an infection occurs, what interleukins are released by macrophages?
    IL-1, IL-6
  27. What is the function of IL-1?
    cause neutorphils to produce Lactoferrin
  28. What is the function of IL-6?
    cause liver to release hepcidin
  29. What is a disease caused by hypoferremia?
    • anemia of chronic disease (due to extremely high levels of hepcidin and no iron to the bones for erythro.)
    • ***Caused by release of IL-6 from macrophages
  30. When are three times iron insufficiency occurs?
    • 1) nutritional insufficiency in toddlers
    • 2) Menstraution
    • 3) Pregnancy due to transfer to child