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45 Cards in this Set
- Front
- Back
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Where are the 2 major locations of iron in the body? Relative percentages?
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25% in storage(mostly macrophages)
75% in use in varous proteins |
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How does the body rid itself of excess iron?
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No mechanism, except blood loss.
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What must iron absorbtion offset each day?
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Loss from skin and intestinal sloughing
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What are the 4 forms of iron in order of decreasing bioavailibility?
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Heme>>Ferrous iron(2+)>Ferric iron(3+)>elemental iron
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Where is heme usually obtained in the diet?
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Meat
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Where is non-heme iron usually obtained?
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Fruits and vegetables
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How is ferric iron absorbed and what conditions diminish absorbtion?
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it is solubilized in an acidic environment then chelates with other macronutrients to be absorbed in the duodenum
-Achlorhydia(low HCL) in stomach and antacid use diminish solubility of ferric iron |
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Can meal composition affect the absorbtion of heme iron? Why not?
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No only non-heme iron is affected because heme iron is shelterd by poryphrin ring
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What are 3 things that enhance absorbtion of iron?
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Reducing agents ie Vitamin C and sorbitol
Amino acids Acidic foods |
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What are the 2 ways that vitamin C enhances iron absorbtion?
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Complexes with iron and reduces Ferric to ferrous iron
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What are the 6 compounds that inhibit iron absorbtion?
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COPPPZ!!!
Calcium Oxalate phytates Polyphenols Phosphates\phosphoproteins Zinc |
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What are some foods that are sources of phytates, polyphenols, and oxalate?
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Phytates in fruits and veg
polyphenols in tea and coffe Oxalate in spinach |
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How do the majority of iron absorbtion inhibitors stop iron absorbtion?
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By forming insoluble chelates
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What is the function of transferrin?
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Transfers iron in the blood to be used or stored
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What protein stores iron in cells?
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ferritin
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What 2 proteins function to mobilize iron stores in cells?
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hepcidin and ferroportin
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What does mobiliferrin do?
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Transports iron through cytosol of enterocytes during process of absorbtion
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What protein takes up heme iron at apical surface of enterocytes?
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Heme Oxygenase
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What protein takes up non-heme iron at apical surface of enterocytes?
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DMT1
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What protein transfers iron out of enterocyte basolateral surface?
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Ferroportin
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What are the only cell types that contain ferroportin?
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PET HiM
Placental cells enterocytes Trophoblast cells Hepatocytes Macrophages |
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What forms is iron usually transported in?
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Usually in ferric form attached to protein, unbound form is ferrous
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What is the Fenton reaction and how does this explain why iron usually transported on proteins?
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When ferrous iron reacts with hydrogen peroxide to form hydroxyl radical and ferric iron
Protein binding prevents this |
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What are the 3 functions of transferrin and what are its 3 conformations?
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Solubilize iron, attenuated reactivity of iron, delivery of iron to sites of usage
apotransferrin monoferric transferrin diferric transferrin |
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What form of iron does transferrin bind?
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Fe 3+
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What protein allows iron bound to tranferrin in the blood to enter cells?
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Transferrin receptor
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What form of transferrin does the transferrin receptor have the highest affinity for?
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Diferric transferrin
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What are the 3 steps of iron uptake from the blood?
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Tfr binds transferrin
Endosome is formed with proton pumps to acidify the contents Tfr and apotransferrin are returned to the plasma mem. or ECF |
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What is the general form of ferritin and in what form does it store iron?
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24 subunit protein with hollow core that fills up with iron. Fe2+ is converted to Fe 3+ upon entering but is stored as a mineralized from of iron not ferrous or ferric
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How can bodies iron stores be assessed?
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looking at serum ferritin levels
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what is hemosiderin?
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A partially degraded ferritin like protein that exists in lysosomes
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How does hepcidin regulate iron metabolism?
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Hepcidin decreases activity of ferroportin. So high hepcidin decreases iron release
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What are the positive regulators of hepcidin levels?
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High iron stores, infection
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What are the negative regulators of hepcidin?
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Low iron stores\plasma levels, hypoxia, increased erythroid demand
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How do IRP and IRE's act together to mount a response to iron levels?
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IRP are iron sensor proteins that bind iron if it is there so it doesn't bind IRE mRNA loops and vice versa
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What gene products have IRE at the 5' end and which have them at 3' end?
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ferretin, ALA-S2=5' end
Transferrin receptor, DMT-1=3' end |
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Are 5' IREs inhibitory of stabilitzing?
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inhibitory
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When and how is hypoferremia caused normally?
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During infection, transferrin scavenges iron from plasma and neutrophils secrete lactoferrin to scavenge iron from exocrine secretions
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What are 2 reasons that hypoferremia is induced during infection?
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limits bacterial growth, reduces probability of Fenton reaction due to higher levels of H2O2 used to fight infections
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What are the functions of IL-1 and IL-6 in inflammatory response?
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IL1- stimulates lactoferrin release from neutrophils, decreases RBC life span, and slows erythropoesis
IL6 stimulates hepcidin release so iron is held in macrophages IL-6 |
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What can high hepcidin levels cause in chronic infection?
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anemia of chronic disease caused by lack of iron delivery to bone marrow
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How much iron does one ml of blood contain?
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0.5mg
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What is the most common cause of iron deficiency in the US?
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Chronic blood loss due to ulcers
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What 3 groups of people are at increased risk of iron deficiency?
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Toddlers, women due to menstration, pregnant women due to increased demand
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When do hemosiderin levels increase?
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Usually in response to iron overload
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