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Year 2 Hematology > Iron and heme > Flashcards

Iron and heme Flashcards

1
Q

small RBCs is a clue for what type of iron dysfunction?

A

uptake dysfunction

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2
Q

what is the mechanism of the Fenton reaction?

A
  1. oxygen picks up electron from iron or copper
  2. iron / copper oxidized
  3. superoxide anion or hydroxyl radical produced
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3
Q

what are the active forms of iron?

A

Hb, Mb, cytochromes

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4
Q

iron is transported by what protein?

A

transferrin

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5
Q

what is the inactive form of iron?

A

ferritin

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6
Q

what is the degenerated, long term storage of iron?

A

hemosiderin

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7
Q

what cells are the gatekeepers of iron uptake?

A

enterocytes

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8
Q

what is the role of divalent methyl transporter (DMT)?

A

uptake of iron 2+

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9
Q

what is the role of cytochrome B on the enterocyte?

A

reduces Fe 3+ to 2+ for uptake

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10
Q

inside the cell, iron is protected by what protein?

A

ferritin

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11
Q

what is the role of ferroportin?

A

determines how much iron will be released from enterocyte into circulation

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12
Q

what is the role of hepcidin?

A

downregulates activity of ferroportin - blocks uptake of iron

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13
Q

what is the role of hephaestin?

A

oxidizes iron 2+ to 3+ to be taken up by ferritin in the circulation

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14
Q

iron is taken up into other cells by what mechanism?

A

transferrin receptors

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15
Q

the presence of hemosiderin indicates what condition?

A

iron overload

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16
Q

in a hemolytic disorder involving destruction of RBCs inside macrophages, what happens to the ferritin?

A

accumulates then degrades to hemosiderin

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17
Q

what is the main regulator of iron uptake?

A

hepcidin

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18
Q

how does low hepcidin affect iron uptake?

A

high uptake

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19
Q

a defect in what enzyme results in hereditary hemochramotosis? how?

A
  1. human hemochromatosis protein (HFE)

2. low hepcidin production

20
Q

regulation of intracellular iron storage occurs at what level?

A

post transcription

21
Q

what is the role of iron response elements (IREs)?

A

forms hairpin loop on mRNA for ferritin that prohibits the placement of the ribosome at the start codon (prohibiting transcription of iron binding factors)

22
Q

what is the role of aconitase?

A

iron regulatory protein that is bound to the IRE in low iron conditions (do not need ferritin when there is already low iron)

23
Q

what is the result of free iron on the IREs?

A
  1. binds aconitase and removes it from the IRE

2. translation of ferritin can begin

24
Q

where are IREs found?

A
  1. ferritin RNA
  2. ALA synthase RNA
  3. transferrin receptor RNA
25
Q

what is the key enzyme for heme synthesis?

A

ALA synthase

26
Q

what is the function of the IRE on the transferrin receptor?

A

repression of translation (if cell is already full of iron then you want to shut down receptors so you are not taking up more)

27
Q

what does total iron binding capacity (TIBC) measure?

A

unoccupied transferrin

28
Q

how does a high TIBC level relate to iron stores?

A

high TIBC = low iron stores

29
Q

what does transferrin saturation measure?

A

occupied transferrin

30
Q

how does a high transferrin saturation relate to iron stores?

A

high saturation = high iron stores

31
Q

what is the best measure of iron body stores?

A

serum ferritin

32
Q

what is protoporphyrin?

A

iron-free precursor of heme

33
Q

what does a high protoporphyrin level indicate?

A

low iron stores (not enough to load all the heme)

34
Q

iron deficiency can develop into anemia via what mechanisms?

A
  1. iron depletion
  2. deficient erythropoiesis
  3. low Hb (hypochromia, microcytosis)
35
Q

iron overload is characterized by what findings?

A
  1. high transferrin saturation

2. hemosiderin deposits

36
Q

heme synthesis starts with what compounds?

A

succinyl CoA and glycine

37
Q

which compound in heme synthesis is photoactive?

38
Q

definition: porphyrias

A

heme synthesis disorders

39
Q

what is the precursor to UPG3? is it photoactive?

A
  1. porphobilinogen

2. no

40
Q

acute intermittent porphyria is a build up of what heme precursor? is it a photoactive disorder?

A
  1. porphobilinogen

2. no

41
Q

how does AIP affect the urine? blood?

A
  1. dark red urine (accumulation of PBG and ALA)

2. anemia (cannot make enough heme)

42
Q

porphyria cutanea tarda is a build up of what heme precursor? is it a photoactive disorder?

A
  1. UPG3

2. yes

43
Q

lead poisoning affects what steps of heme synthesis?

A
  1. PBG synthase (ALA to porphobilinogen)

2. ferrochelatase

44
Q

which porphyria is exacerbated by alcohol consumption (stress)?

A

AIP (acute intermittent porphyria)

45
Q

what regulates ALA synthase?

Year 2 Hematology (34 decks)

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