Iron and heme Flashcards Preview

Year 2 Hematology > Iron and heme > Flashcards

Flashcards in Iron and heme Deck (45)
1

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

uptake dysfunction

2

what is the mechanism of the Fenton reaction?

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

3

what are the active forms of iron?

Hb, Mb, cytochromes

4

iron is transported by what protein?

transferrin

5

what is the inactive form of iron?

ferritin

6

what is the degenerated, long term storage of iron?

hemosiderin

7

what cells are the gatekeepers of iron uptake?

enterocytes

8

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

uptake of iron 2+

9

what is the role of cytochrome B on the enterocyte?

reduces Fe 3+ to 2+ for uptake

10

inside the cell, iron is protected by what protein?

ferritin

11

what is the role of ferroportin?

determines how much iron will be released from enterocyte into circulation

12

what is the role of hepcidin?

downregulates activity of ferroportin - blocks uptake of iron

13

what is the role of hephaestin?

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

14

iron is taken up into other cells by what mechanism?

transferrin receptors

15

the presence of hemosiderin indicates what condition?

iron overload

16

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

accumulates then degrades to hemosiderin

17

what is the main regulator of iron uptake?

hepcidin

18

how does low hepcidin affect iron uptake?

high uptake

19

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

1. human hemochromatosis protein (HFE)
2. low hepcidin production

20

regulation of intracellular iron storage occurs at what level?

post transcription

21

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

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

what is the role of aconitase?

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

23

what is the result of free iron on the IREs?

1. binds aconitase and removes it from the IRE
2. translation of ferritin can begin

24

where are IREs found?

1. ferritin RNA
2. ALA synthase RNA
3. transferrin receptor RNA

25

what is the key enzyme for heme synthesis?

ALA synthase

26

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

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

what does total iron binding capacity (TIBC) measure?

unoccupied transferrin

28

how does a high TIBC level relate to iron stores?

high TIBC = low iron stores

29

what does transferrin saturation measure?

occupied transferrin

30

how does a high transferrin saturation relate to iron stores?

high saturation = high iron stores

31

what is the best measure of iron body stores?

serum ferritin

32

what is protoporphyrin?

iron-free precursor of heme

33

what does a high protoporphyrin level indicate?

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

34

iron deficiency can develop into anemia via what mechanisms?

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

35

iron overload is characterized by what findings?

1. high transferrin saturation
2. hemosiderin deposits

36

heme synthesis starts with what compounds?

succinyl CoA and glycine

37

which compound in heme synthesis is photoactive?

UPG3

38

definition: porphyrias

heme synthesis disorders

39

what is the precursor to UPG3? is it photoactive?

1. porphobilinogen
2. no

40

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

1. porphobilinogen
2. no

41

how does AIP affect the urine? blood?

1. dark red urine (accumulation of PBG and ALA)
2. anemia (cannot make enough heme)

42

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

1. UPG3
2. yes

43

lead poisoning affects what steps of heme synthesis?

1. PBG synthase (ALA to porphobilinogen)
2. ferrochelatase

44

which porphyria is exacerbated by alcohol consumption (stress)?

AIP (acute intermittent porphyria)

45

what regulates ALA synthase?

heme