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IHN BIOCHEMISTRY FINAL > Quiz 5: Iron > Flashcards

Quiz 5: Iron Flashcards

1
Q

__ people have IDA

A

0.5 billion people have IDA

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2
Q

anemia is a disease of __

A

anemia is a disease of poverty

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3
Q

anemia = problems delivering __ and reabsorbing __

A

anemia = problems delivering O2 and reabsorbing CO2

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4
Q

iron deficiency causes

A
  1. abnormal cognitive and psychomotor development (altered NT metabolism)
  2. increased rates of premature delivery and perinatal mortality
  3. decreased work performance, decreased effort
  4. impaired immune response and thermogenesis
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5
Q

why does iron deficiency cause abnormal cognitive and psychomotor development

A

altered NT metabolism

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6
Q

iron is essential in physiology due to its capacity to exist in

A

several oxidation states

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7
Q

2 oxidation states of iron

A

ferrous (Fe2+)
ferric (Fe3+)

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8
Q

iron is a constituent of many proteins involved in transport and metabolism of __

A

iron is a constituent of many proteins involved in transport and metabolism of oxygen

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9
Q

iron is a __ mineral

A

iron is a trace mineral

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10
Q

main iron in circulation

A

ferric (Fe3+)

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11
Q

absorbable form of iron

A

ferrous (Fe2+)

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12
Q

iron solubility problem
__ soluble at neutral pH + reactive with oxygen
__ not soluble at neutral pH, forms ferrihydroxides with water

A

iron solubility problem
Fe2+ (ferrous) soluble at neutral pH + reactive with oxygen
Fe3+ (ferric) not soluble at neutral pH, forms ferrihydroxides with water

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13
Q

what does ferric iron require to move

A

transferrin (carrier protein)

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14
Q

body iron compartments

A
  1. most in circulation as hemoglobin
  2. 95% bound with ferritin (stored iron)
  3. rest = iron-containing enzymes or bound to transferrin
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15
Q

hemoglobin
myoglobin
ferritin
transferrin

A

hemoglobin: transport O2 in blood
myoglobin: muscle
ferritin: storage
transferrin: transfer to cells

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16
Q

food source

A

oysters
beans
chocolate
fortified cereals
lentils
spinach

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17
Q

RDA increased in

A

females bc menstruation
pregnancy (baby needs blood and circulatory system)

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18
Q

iron supplements should be taken with

A

orange juice bc vit C

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19
Q

iron UL

A

causes GI side effects (nausea and constipation)
bc iron is insoluble in gut secretions

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20
Q

3 determinants of iron absorption

A
  1. iron content in diet
  2. bioavailability
  3. absorption capacity of enterocyte
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21
Q

3 forms of dietary iron

A
  1. heme iron
  2. non-heme
  3. supplements
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22
Q

largest component of dietary iron is

A

non-heme iron (plants)

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23
Q

non-heme iron is usually found

A

attached to protein

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24
Q

non-heme iron
plant sources
animal sources
other sources

A

non-heme iron
plant sources: metalloproteins (ferritin), soluble iron, non-functional iron (structure or storage with phytates)
animal sources: ferritin and hemosiderins (meat), phosphoritin (egg yolk), lactoferrin (milk)
other sources: contaminants (ferric oxides and hydroxides)

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25
heme iron major sources
hemoglobin and myoglobin
26
increase heme iron = __ bioavailability for non-heme iron (meat factor)
increase heme iron = **increased** bioavailability for non-heme iron (meat factor)
27
heme is rapidly released from __ during digestion
heme is rapidly released from **hemoglobin** during digestion
28
what factors interfere with heme absorption?
NONE
29
absorption of heme iron non-heme iron
heme iron = 10-35% non-heme iron = < 10%
30
absorption of iron steps Fe2+ and Fe3+ path
1. bound heme or non-heme iron digested to Fe3+ and Fe2+ 2. Fe3+ to Fe2+ (DcytB) 3. DMT1 brings Fe2+ and H+ in 4. H+ out via NHE
31
absorption of iron as heme
1. myoglobin + Hg = heme 2. heme absorbed by hcp1 3. heme --> Fe2+ (heme oxygenase) 4. Fe2+ bound by ferroportin
32
increased iron in blood = __ ferroportin
increased iron in blood = **decreased** ferroportin
33
what does hephaestin do
turn Fe2+ to Fe3+
34
we can't have Fe2+ in circulation how do we fix this
ferroportin is attached to hephaestin hepahestin turns Fe2+ to Fe3+ transferrin binds to carry Fe3+ around
35
hephaestin requires __
Cu
36
SO __ deficiency causes issues with iron
SO **Cu** deficiency causes issues with iron
37
enhancers of iron absorption
1. sugars 2. acids 3. low pH 4. mucin 5. meat 6. fish
38
inhibitors of absorption of iron
1. high pH 2. polyphenols (coffee) 3. oxalic acid (spinach) 4. phytic acid (grain) 5. phosvitin (egg yolk) 6. divalent cations (Ca, Zn, Ca)
39
DMT1 =
divalent metal transporter 1
40
what type of transporter is DMT1
symporter Fe2+, H+
41
low iron = __ trxn of DMT1 gene in enterocytes
low iron = **increased** trxn of DMT1 gene in enterocytes
42
release of iron from heme
heme --> iron (enzyme: heme oxygenase + cytochrome P450 reductase) requires NADPH, O2, releases biliverdin + carbon monoxide iron --> ferritin or to export biliverdin --> bilirubin (biliverdin reductase) carbon monoxide (VERY TOXIC) --> soluble guanylyl cyclase
43
heme degradation is higher in what tissues
macrophages in spleen Kupffer cells
44
3 types of iron-containing proteins
1. heme proteins 2. iron-sulfur proteins 3. non-heme, non-iron-sulfur proteins
45
iron containing heme proteins
hemoglobin myoglobin cytochrome c
46
iron-sulfur proteins
NADH dehydrogenase cytochrome c reductase
47
non-heme, non-iron-sulfur proteins
tyrosine hydroxylase fatty acid desaturases
48
biological functions of iron
1. binding site for gases 2. regulates enzyme activity 3. modulate gene trxn and post-trxn modifications
49
hemoglobin binds __ O2 myoglobin binds __ O2 hemoglobin transports O2 in __ where it exchanges O2 to myoglobin for transport in __
hemoglobin binds **4** O2 myoglobin binds **1** O2 hemoglobin transports O2 in **blood** where it exchanges O2 to myoglobin for transport in **muscle**
50
sickle cell disease is a mutation in B-globin gene that causes __
sickle cell disease is a mutation in B-globin gene that causes **hemoglobin protein aggregation**
51
4 proteins of iron transport
transferrin haptoglobin ferritin lactoferrin
52
transferrin is major __ protein for Fe transport made in __
transferrin is major **plasma** protein for Fe transport made in **liver**
53
__ of transferrin is normally saturated with iron
**1/3** of transferrin is normally saturated with iron
54
transferrin receptor requires __ Fe bound
transferrin receptor requires **2** Fe bound
55
transferrin receptor is 2 homodimers bound by __ bridge that binds 2 saturated __
transferrin receptor is 2 homodimers bound by **disulfide** bridge that binds 2 saturated **transferrin Fe3+**
56
2 transferrin receptors
Tfr1: iron uptake, expressed in ALL cells Tfr2: senses systematic iron status, liver and erythroid precursors
57
3 sites for storage of iron bound to ferritin
liver spleen skeletal muscle
58
storage form of iron
hemosiderins
59
endocytosis of iron complex + transferrin
1. each Tfr binds 2 Tf molecules 2. uptake, endocytosis, Fe3+ to Fe2+ (Steap3) 3. released Fe2+ to exit cytosol (DMT1), release Hg and ferritin 4. apotransferrin-Tfr complex recycled to cell surface 5. Apo-Tf released back into circulation
60
why is endocytosis of iron so complex?
bc iron can cause a lot of damage (it is very reactive) if not handled properly
61
2 types of iron regulation
1. cellular (trxn and post-trxn regulation) 2. systemic (hepcidin-ferroportin axis)
62
trxn regulation: low iron = increased __ and __ high iron = increased __
trxn regulation: low iron = increased **DMT1** and **Tfr** high iron = increased **ferritin**
63
iron responsive elements
nucleotides in ferritin mRNA that control post-trxn regulation
64
iron-regulatory proteins
cytosolic proteins that interact with IREs to modulate translation
65
low iron trxn modifications
1. in low Fe, 1 Fe binds 5' UTR --> blocks ferritin translation 2. 1 Fe binds 3' UTR --> increases transferrin receptor translation (Tfr)
66
high iron trxn modifictions
no binding ferritin made more fragile, low transferrin receptors
67
iron deficiency = __ transferring receptors
iron deficiency = **more** transferring receptors
68
iron overload = Tfr messenger __ = __ = decreased __
iron overload = Tfr messenger **weak** = **degraded** = decreased **Tfr**
69
iron concentration in diff body regions
GI tract > skin > urine
70
which cell defines iron homeostasis?
macrophages and enterocytes
71
ferritin mediated export of iron macrophages
1. macrophage processes RBC (tons) 2. Fe2+ leaves in ferroprotin 3. Fe2+ --> Fe3+ (cell linked ceruloplasmin) 4. circulation
72
ferritin mediated export of iron enterocyte
1. ferritin enters cell 2. Fe 2+ leaves through ferroportin 3. Fe2+ --> Fe3+ (hephaestin: on cell)
73
low iron sensing
1. Tfr2 in liver senses low iron 2. no hepcidin synthesis 3. decreased plasma iron (Fe-Tf)
74
high iron sensing
1. high iron sensed by Tfr2 2. increased plasma Fe-Tf 3. increased hepcidin released 4. hepcidin binds ferroportin in enterocyte + macrophage 5. destroy proteinn, no more ferroportin 6. Fe in enterocyte is stuck, stays 5 days then to feces 7. macrophage retains iron for as long as needed
75
iron deficiency affects __ capacity anemia affects __ capacity
iron deficiency affects **tissue oxidative** capacity anemia affects **oxygen carrying** capacity
76
BOTH iron deficiency and anemia cause
1. abnormal cognitive development (altered NT metabolism) 2. increased premature deliveries 3. decreased work performance 4. impaired immune response
77
groups at risk
1. infants 2. pregnant women 3. low SES 4. elderly 5. cancer pts 6. GI diseases
78
anemia = __ conc in blood is low = decreased __ capacity of __ also decreased circulating __
anemia = **hemoglobin** conc in blood is low = decreased **oxygen carrying** capacity of **RBC** also decreased circulating **RBC**
79
hypochromic microcytic anemia of iron deficiency =
small RBC with narrow rim of peripheral hemoglobin

IHN BIOCHEMISTRY FINAL (15 decks)

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