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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
When does hepcidin synthesis rise?
When transferrin is carrying its maximum capacity of iron
25
Substance that binds to the ferroportin receptor, causing degradation of ferroportin and trapping iron in the intestinal cells
Hepcidin
26
Transports ferric iron to hematopoietic and other tissues
Transferrin
27
Type of iron that transferrin transports
Ferric iron
28
2 kinds of cells with large amounts of transferrin receptors
- normoblasts | - rapidly dividing cells
29
Process where transferrin is taken into the cell
Endocytosis
30
pH of acidification of the endosome causing the release of iron from transferrin
pH 5.5
31
Transports iron across the endosomal membrane to be used in the synthesis of iron-containing proteins
DMT1
32
How do humans regulate iron?
By controlling absorption
33
Relationship of the amount of iron absorbed to iron stores and the rate of erythropoiesis
Amount of iron absorbed is inversely proportional to iron stores and the rate of erythropoiesis
34
Rate of iron absorption when there is decreased iron stores
3-4 mg/day
35
Rate of iron absorption when there is iron overload
0.5 mg/day
36
Amount of iron lost per day by way of feces
1 mg/day
37
Regulates transferrin, transferrin receptors and ferritin (ferrokinetics)
Iron-responsive protein (IRP)
38
3 substances involved in ferrokinetics
- transferrin - transferrin receptor - ferritin
39
Cells that produce plasma transferrin
Hepatocytes
40
Transports iron from the enterocytes of the duodenum to transferrin receptors on marrow normoblasts
Plasma transferrin
41
A transferrin molecule that is a single-chain glycoprotein with no iron attached
Apotransferrin
42
Chromosome where the transferrin gene is located
Chromosome 3 (3q21-qter)
43
The only cells without transferrin receptors
Mature RBCs
44
A major mechanism for regulation of iron metabolism
Control of transferrin receptor biosynthesis
45
Induces transferrin receptor synthesis
Iron deficiency
46
Accessible reserve form of iron that is stored
Ferritin
47
A partially degraded or precipitated form of ferritin
Hemosiderin
48
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
Apoferritin
49
The chromosome containing the genes for the L chains
Chromosome 19
50
The chromosome containing the genes for the heavy chains
Chromosome 11
51
2 tissues that have large amounts of L subunits
- liver - spleen These are tissues with major iron storage deposits
52
Tissue that has a high amount of H subunits
Heart tissue These tissues do not normally store ferritin.
53
Measure of Fe3+ bound to serum transferrin and does not include free serum Hb iron
Serum iron concentration
54
Technique that measures serum iron concentration
Chromogen spectrophotometry
55
Explain the diurnal variation of iron
Iron is at its highest concentration in the morning and at its lowest in the evening.
56
Iron-binding sites that do not carry iron
Serum unsaturated iron-binding capacity (UIBC)
57
The total of available sites for iron
Total iron-binding capacity (TIBC)
58
Technique to measure UIBC
Chromogen spectrophotometer
59
Direct measurement of TIBC
Immunoassay (Transferrin assay)
60
Indirect measurement of TIBC
Chemical means
61
3 values needed to diagnose iron deficiency
- Serum iron concentration - TIBC - Percent transferrin saturation
62
Percentage of sites available for carrying iron
Percent transferrin saturation Computed by dividing seum iron level by TIBC and multiplying the result by 100
63
When does plasma ferritin concentration decrease?
During early in the development of iron deficiency
64
When is plasma ferritin concentration increased?
During inflammation
65
A truncated form of the cell membrane receptor and circulates in bound to transferrin
Serum transferrin receptors (sTfR)
66
Technique used to measure sTfR
Immunoassay
67
When does the amount of sTfR increase?
When cells lack iron
68
When does the amount of sTfR decrease?
Chronic diseases
69
An intermediate product of hemoglobin synthesis that resides in RBCs
Erythrocyte protoporphyrin
70
Assay for erythrocyte protoporphyrin
Free erythrocyte protoporphyrin
71
How is tissue iron assessed?
Biopsy of bone marrow or liver
72
Used to visually estimate the amount of iron in macrophages, nucleated RBCs, and reticulocytes
Prussian blue reaction
73
Nucleated RBCs containing iron cells
Sideroblasts
74
Granules of iron in nucleated RBCs
Siderosomes
75
Reticulocytes in the bone marrow that contain iron
Siderocytes

Hematology (7 decks)

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