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WILLIAM'S HEMATOLOGY > 43 Iron Metabolism > Flashcards

43 Iron Metabolism Flashcards

1
Q

Iron components in the average Person (mg/ % of total body iron)

Hemoglobin
Storage iron (ferritin , hemosidirin)
Myoglobin
Labile pool
Other tissue iron
Transport iron

A

Iron components in the average Person (mg/ % of total body iron)

Hemoglobin: 2000 (67%)
Storage iron (ferritin , hemosidirin): 1000 (27%)
Myoglobin: 130 (3.5%)
Labile pool: 80 (2.2%)
Other tissue iron: 8 (0.2%)
Transport iron: 3 (0.08%)

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2
Q

Hemoglobin, which is _____% iron by weight, contains approximately____ g of body iron in men and ____ g in women.

A

0.34%
2 g
1.5 g

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3
Q

One milliliter of packed erythrocytes contains approximately ____ mg of iron.

A

1 mg of iron

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4
Q

Storage forms of iron

A

Ferritin and hemosiderin

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5
Q

Water-soluble or Water-insoluble

Ferritin
Hemosiderin

A

Ferritin: Water-soluble
Hemosiderin: Water-insoluble

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6
Q

Subunit of ferritin that have ferroxidase activity, thereby enabling ferritin to take up or release iron quite rapidly.

Takes up iron more readily but retains it less avidly

A

H (heavy)

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7
Q

Much of the storage iron in the liver and spleen is in ferritin containing mostly______ subunits.

A

L subunits

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8
Q

TRUE OR FALSE

Except under conditions of inflammation, the plasma (serum) ferritin concentration usually correlates with total-body iron stores, making measurement of serum ferritin levels important in the diagnosis of disorders of iron metabolism.

A

TRUE

Except under conditions of inflammation, the plasma (serum) ferritin concentration usually correlates with total-body iron stores, making measurement of serum ferritin levels important in the diagnosis of disorders of iron metabolism.

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9
Q

The cargo protein_______, a ferritin receptor, is increased during iron deficiency and delivers ferritin to lysosomes.

A

NCOA4

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10
Q

Found predominantly in macrophages

Microscopically, in unstained tissue sections or marrow films, it appears as clumps or granules of golden refractile pigment.

A

Hemosiderin

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11
Q

Structurally similar to hemoglobin, but it is monomeric rather than tetrameric

It is present in small amounts in all skeletal and cardiac muscle cells

A

Myoglobin

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12
Q

Size of the labile iron pool

A

80–90 mg of iron

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13
Q

It is now sometimes considered to be equivalent to the chelatable iron pool.

A

Labile iron pool

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14
Q

Includes cytochromes and other iron-containing enzymes

Although a small compartment, it is vital and sensitive to iron deficiency.

A

Tissue iron

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15
Q

Amount of tissue iron

A

6–8 mg

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16
Q

The smallest but the most active of the iron compartments

A

Transport iron

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17
Q

Amount of transport iron

A

3 mg

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18
Q

A dumbbell-shaped glycoprotein with a molecular weight of approximately 80 kDa where each of the two globular domains contains a binding cleft for Fe3+

A

Transferrin

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19
Q

Normally, approximately ______of the transferrin iron-binding sites are occupied by iron.

A

One-third

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20
Q

Apotransferrin (transferrin devoid of iron) is synthesized by

A

Hepatocytes and cells of the monocyte macrophage system

21
Q

RDA for Iron

Male 19 and above
Female 19 - 50 years
Female 51 years and above
Pregnant
Lactation

A

RDA for Iron

Male 19 and above: 8 mg
Female 19 and above: 18 mg
Female 51 years and above: 8 mg
Pregnant: 27 mg
Lactation: 9 mg

22
Q

Increase or decrease iron absorption

Oxalates, phytates, and phosphates

Hydroquinone, ascorbate, lactate, pyruvate, succinate, fructose, cysteine, and sorbitol:

A

Oxalates, phytates, and phosphates: decrease iron absorption

Hydroquinone, ascorbate, lactate, pyruvate, succinate, fructose, cysteine, and sorbitol: increase iron absorption

23
Q

Iron normally enters the body through the gastrointestinal tract, mostly through the

A

Enterocytes of the duodenum

24
Q

The reduction of ferric iron to ferrous iron, in part by duodenal _____________________, ferrous iron is transported into the intestinal villus cell by the _________________.

A

Cytochrome b (Dcytb) reductase

Divalent metal transporter (DMT)-1

25
Q

Basolateral export of ferrous iron is mediated by ___________ in association with hephaestin and plasma ceruloplasmin to oxidize iron to the ferric state.

A

Ferroportin

26
Q

Ferric iron is taken up by plasma_______________.

A

Apotransferrin

27
Q

Destruction of aged erythrocytes and hemoglobin degradation occur within

A

Macrophages

28
Q

Approximately _____% of this iron is rapidly reincorporated into hemoglobin.

A

80%

29
Q

Thus, 20% to 70% percent of the hemoglobin iron of nonviable erythrocytes reappears in circulating red cells in _____ days.

A

12 days

30
Q

Regulates plasma iron concentrations by controlling the absorption of iron by the intestinal epithelial enterocytes and its release from iron-recycling macrophages and hepatocytes involved in iron storage.

A

Hepcidin

31
Q

Hepcidin is produced predominantly by

A

Hepatocytes

32
Q

The structural similarity of hepcidin and a class of antimicrobial peptides termed________ suggests that the hormone evolved from the latter to modulate iron homeostasis as a mechanism of body defense against microorganisms.

A

Defensins

33
Q

TRUE OR FALSE

Patients with iron overload and high plasma iron levels are susceptible to such infections, such as with Vibrio vulnificus and Yersinia enterocolitica

A

TRUE

Patients with iron overload and high plasma iron levels are susceptible to such infections, such as with Vibrio vulnificus and Yersinia enterocolitica

34
Q

Hepcidin exerts its iron-regulatory effect by binding to_________, a transmembrane iron-export protein expressed on enterocytes, macrophages, and hepatocytes.

A

Ferroportin

35
Q

Hepcidin production is stimulated by inflammatory cytokines such as interleukin ______, and the overproduction of hepcidin is an important factor in the pathogenesis of the anemia of chronic inflammation

A

(IL)-6

36
Q

Hepcidin transcription is regulated in an iron-dependent manner by the ___________ pathway.

A

BMP pathway

37
Q

Acts as an inhibitor of the interaction of BMP with the receptor

Autosomal recessive mutations cause a very severe form of hereditary hemochromatosis, serves as a coreceptor for the BMPs

A

Hemojuvelin

38
Q

A membrane serine protease that likely acts by proteolysis of hemojuvelin and perhaps also other proteins in the BMP receptor complex

Inhibitory effect of hepcidin transcription

A

Tmprss6 (also called matriptase 2)

39
Q

Humans with mutations of the Tmprss6 ortholog were shown to manifest this condition

IDA that does not improve with oral iron therapy and responds only partially to parenteral iron therapy.

A

Iron-refractory iron-deficiency anemia

40
Q

An erythropoietin-induced erythroblast-secreted glycoprotein that acts on hepatocytes to suppress their hepcidin production and is required for rapid suppression of hepcidin after hemorrhage or erythropoietin administration.

A

Erythroferrone

41
Q

TRUE OR FALSE

Within hours after the onset of systemic infection, plasma iron concentration increases.

A

FALSE

Within hours after the onset of systemic infection, plasma iron concentration decreases.

42
Q

The main human cytokine responsible for hepcidin induction

A

IL-6

43
Q

Plays a role in the binding and endocytosis of diferric transferrin

A major mechanism for regulation of iron metabolism

A

TfR1

44
Q

Also endocytic for holotransferrin, is not thought to be involved in delivering iron to cells but its hepatic expression is necessary for normal hepcidin expression and regulation.

A

TfR2

45
Q

The final steps of heme synthesis take place in____________, where iron is inserted into protoporphyrin by the enzyme__________________.

A

Mitochondria

Ferrochelatase

46
Q

Ringed sideroblast can be stained by

A

Prussian blue

47
Q

TRUE OR FALSE

In iron deficiency and in the anemia that accompanies chronic disorders, sideroblasts almost disappear from the marrow

A

TRUE

In iron deficiency and in the anemia that accompanies chronic disorders, sideroblasts almost disappear from the marrow

48
Q

In normal, iron-replete marrow, much smaller siderotic granules are also demonstrable, scattered in the cytoplasm of about___________of erythroblasts

A

One-third

49
Q

Most iron loss occurs by way of

A

Desquamated intestinal cells in the feces : 1 mg per day

WILLIAM'S HEMATOLOGY (89 decks)

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