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Hematology > Ch. 11 - Iron Metabolism > Flashcards

Ch. 11 - Iron Metabolism Flashcards

0
Q

2 storage forms of iron

A
  • ferritin

- hemosiderin

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1
Q

The oxygen transport molecule in muscles

A

Myoglobin

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2
Q

Amount of iron in an average American diet

A

10-20 mg of iron/day

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3
Q

Amount of iron absorbed from the average American diet

A

1-2 mg of iron/day

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4
Q

2 form of iron that is absorbed by the body

A
  • heme

- nonheme

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5
Q

Type of iron that is absorbed more efficiently

A

Heme-bound iron

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6
Q

What type of food is heme-bound iron mostly from?

A

Meat

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7
Q

5-35% of heme iron is absorbed as _________

A

Hemin

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8
Q

What type of food is nonheme iron found?

A

Nonmeat sources (legumes and leafy vegetables)

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9
Q

Type of iron that accounts for 90% of dietary iron

A

Nonheme iron

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10
Q

Formation of this substance by organic acids and amino acids (ascorbate and citrate) enhances the absorption of nonheme iron

A

Soluble chelates

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11
Q

2 substances that produce soluble chelates

A
  • organic acids (ascorbate & citrate)

- amino acids

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12
Q

5 substances that decrease nonheme iron uptake

A
  • phytates
  • polyphenols
  • phosphates
  • oxalates
  • calcium
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13
Q

2 sites of maximal iron absorption

A
  • duodenum

- upper jejunum

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14
Q

Iron must be in the ________ form for transport of oxygen in Hb

A

Ferrous

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15
Q

Iron must be in the __________ form to be absorbed from food

A

Heme iron

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16
Q

Converts ferric nonheme iron to the soluble ferrous form

A

Duodenum-specific cytochrome b-like protein (DCYTB)

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17
Q

Protein where uptake of heme iron takes place

A

Heme carrier protein 1

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18
Q

Enzyme that degrades the heme iron in the apical membrane of the duodenal enterocyte

A

Heme oxygenase

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19
Q

3 products after heme iron is degraded by heme oxygenase in the apical membrane of the duodenal enterocyte

A
  • ferrous iron
  • carbon monoxide
  • bilirubin-IXa
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20
Q

Transports the ferrous iron across the duodenal epithelium

A

Divalent metal transporter 1 (DMT1)

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21
Q

A basolateral transport protein that carries the ferrous iron to the basolateral membrane, from which the ferrous iron is exported to the portal circulation

A

Ferroportin

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22
Q

Copper-containing iron oxidase that may facilitate iron egress by reoxidation of ferrous iron to ferric iron

A

Hephaestin

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23
Q

An antimicrobial peptide that seems to act as a negative regulator of intestinal iron absorption.

A

Hepcidin

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24
Q

When does hepcidin synthesis rise?

A

When transferrin is carrying its maximum capacity of iron

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25
Q

Substance that binds to the ferroportin receptor, causing degradation of ferroportin and trapping iron in the intestinal cells

A

Hepcidin

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26
Q

Transports ferric iron to hematopoietic and other tissues

A

Transferrin

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27
Q

Type of iron that transferrin transports

A

Ferric iron

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28
Q

2 kinds of cells with large amounts of transferrin receptors

A
  • normoblasts

- rapidly dividing cells

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29
Q

Process where transferrin is taken into the cell

A

Endocytosis

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30
Q

pH of acidification of the endosome causing the release of iron from transferrin

31
Q

Transports iron across the endosomal membrane to be used in the synthesis of iron-containing proteins

32
Q

How do humans regulate iron?

A

By controlling absorption

33
Q

Relationship of the amount of iron absorbed to iron stores and the rate of erythropoiesis

A

Amount of iron absorbed is inversely proportional to iron stores and the rate of erythropoiesis

34
Q

Rate of iron absorption when there is decreased iron stores

A

3-4 mg/day

35
Q

Rate of iron absorption when there is iron overload

A

0.5 mg/day

36
Q

Amount of iron lost per day by way of feces

37
Q

Regulates transferrin, transferrin receptors and ferritin (ferrokinetics)

A

Iron-responsive protein (IRP)

38
Q

3 substances involved in ferrokinetics

A
  • transferrin
  • transferrin receptor
  • ferritin
39
Q

Cells that produce plasma transferrin

A

Hepatocytes

40
Q

Transports iron from the enterocytes of the duodenum to transferrin receptors on marrow normoblasts

A

Plasma transferrin

41
Q

A transferrin molecule that is a single-chain glycoprotein with no iron attached

A

Apotransferrin

42
Q

Chromosome where the transferrin gene is located

A

Chromosome 3 (3q21-qter)

43
Q

The only cells without transferrin receptors

A

Mature RBCs

44
Q

A major mechanism for regulation of iron metabolism

A

Control of transferrin receptor biosynthesis

45
Q

Induces transferrin receptor synthesis

A

Iron deficiency

46
Q

Accessible reserve form of iron that is stored

47
Q

A partially degraded or precipitated form of ferritin

A

Hemosiderin

48
Q

The protein component of the ferritin molecule without the iron which is an empty sphere that is composed of 24 light (L) and heavy (H) subunits

A

Apoferritin

49
Q

The chromosome containing the genes for the L chains

A

Chromosome 19

50
Q

The chromosome containing the genes for the heavy chains

A

Chromosome 11

51
Q

2 tissues that have large amounts of L subunits

A
  • liver
  • spleen

These are tissues with major iron storage deposits

52
Q

Tissue that has a high amount of H subunits

A

Heart tissue

These tissues do not normally store ferritin.

53
Q

Measure of Fe3+ bound to serum transferrin and does not include free serum Hb iron

A

Serum iron concentration

54
Q

Technique that measures serum iron concentration

A

Chromogen spectrophotometry

55
Q

Explain the diurnal variation of iron

A

Iron is at its highest concentration in the morning and at its lowest in the evening.

56
Q

Iron-binding sites that do not carry iron

A

Serum unsaturated iron-binding capacity (UIBC)

57
Q

The total of available sites for iron

A

Total iron-binding capacity (TIBC)

58
Q

Technique to measure UIBC

A

Chromogen spectrophotometer

59
Q

Direct measurement of TIBC

A

Immunoassay (Transferrin assay)

60
Q

Indirect measurement of TIBC

A

Chemical means

61
Q

3 values needed to diagnose iron deficiency

A
  • Serum iron concentration
  • TIBC
  • Percent transferrin saturation
62
Q

Percentage of sites available for carrying iron

A

Percent transferrin saturation

Computed by dividing seum iron level by TIBC and multiplying the result by 100

63
Q

When does plasma ferritin concentration decrease?

A

During early in the development of iron deficiency

64
Q

When is plasma ferritin concentration increased?

A

During inflammation

65
Q

A truncated form of the cell membrane receptor and circulates in bound to transferrin

A

Serum transferrin receptors (sTfR)

66
Q

Technique used to measure sTfR

A

Immunoassay

67
Q

When does the amount of sTfR increase?

A

When cells lack iron

68
Q

When does the amount of sTfR decrease?

A

Chronic diseases

69
Q

An intermediate product of hemoglobin synthesis that resides in RBCs

A

Erythrocyte protoporphyrin

70
Q

Assay for erythrocyte protoporphyrin

A

Free erythrocyte protoporphyrin

71
Q

How is tissue iron assessed?

A

Biopsy of bone marrow or liver

72
Q

Used to visually estimate the amount of iron in macrophages, nucleated RBCs, and reticulocytes

A

Prussian blue reaction

73
Q

Nucleated RBCs containing iron cells

A

Sideroblasts

74
Q

Granules of iron in nucleated RBCs

A

Siderosomes

75
Q

Reticulocytes in the bone marrow that contain iron

A

Siderocytes

Hematology (7 decks)

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