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Flashcards in Iron and Heme Deck (60):
1

What is the form of iron found in veggies?

Fe 3+

2

Why can't Fe be found in the free form in the circulation?

forms ROS

3

What are the two storage forms of Fe?

Ferritin
hemosiderin

4

The appearance of hemosiderin molecules in tissues is a sign of what?

Fe overload

5

What is the form of Fe found in the blood when it is being shuttled from the enterocytes?

Transferrin

6

Where does Fe go to be made into heme?

Erythroid precursors

7

Where is ferritin found (in what cells)?

Phagocytes
Hepatocytes

8

What are small erythrocytes indicative of?

Fe deficiency anemia

9

What are the two problems when Fe is oxidized in the body?

Fe 3+ is useless
superoxide is created

10

What is the most damaging ROS?

hydroxide radical

11

Why is meat a better source of Fe than plants?

In heme and Fe2+ form

12

How is Fe regulated?

Uptake (there is no loss through urine)

13

What are the only two ways in which you can lose Fe?

Sloughing off of enterocytes
Blood loss

14

What percent of the Fe in the body is active?

80%

15

What is the dynamic storage form of Fe?

Ferritin

16

What is the degenerated, long-term storage form of Fe?

Hemosiderin

17

What happens to the Fe in RBCs when the RBCs die?

Taken up by splenic macrophages, added to transferritin, and exchanged with the liver

18

What is the protein that transports Fe into enterocytes?

DMT1

19

What is the protein that takes up heme?

Heme carrier protein HCP1

20

How is non-heme iron (Fe3+) taken up into enterocytes?

First, reduced to Fe2+ by duodenal p4500. Then DMT1 takes it up

21

The uptake of Fe is not dependent on how much Fe the body has. How, then, do we not have a constant accumulation of Fe in the blood?

Enterocytes can keep the Fe, and it will be lost when the enterocytes are sloughed off

22

What is the protein channel on the blood side of the enterocytes that allows ferritin to travel out?

Ferroportin 1

23

What is the kep protein that regulates how much Fe is released into the blood? What organ produces this?

Hepcidin
Produced by the liver if there is too much Fe

24

How do cell signal that the need Fe?

Transferrin receptor upregulated.

25

How is Fe brought into cells?

Transferrin binds it, endocytosis, acidification, release

26

What happens to Fe when it enter the circulation? What about when it enters a cell?

Turns to Fe3+ in the circulatuion

2+ in the cell

27

What is the protein that acidifies the endosome that contain the tranferrin receptor?

ATPase

28

What is the protein on the lysosome containing Fe, that allows for Fe to escape into the cell?

DMT1

29

Inside the cell, Fe is stored as what?

Ferritin

30

What are the three organs in the body where ferritin is held?

Liver
Spleen
Bone marrow

31

Ferritin denature into what?

Hemosiderin

32

Low hepcidin means Fe uptake is low or high?

high

33

What is the basis for hemochromatosis?

mutations in HFE (Fe upstream regulator) resulting in low hepcidin

34

What are the two physiologic consequences of hepcidin release?

Low release of Fe by enterocytes

Macrophages do not release Fe into the blood

35

What is the part of the DNA that regulates Fe? How is this regulated?

Iron response element (IRE)

Iron regulatory proteins bind to the mRNA (that is always there) and prevent transcription.

36

What are the three proteins that are encoded on the IRE?

Ferritin
delta-ALA synthase
Transferrin receptor

37

What is the role of delta-ALA synthase?

Produces heme

38

What is serum Fe used to test for?

Fe poisoning or overload

39

What is total iron binding capacity used for?

Tests transferrin saturation, which is usually around 30%. Lower = anemia

40

What complicates the total iron binding capacity values?

Hypoproteinemia

41

What is the value of the serum ferritin?

Best measure of Fe body stores

42

What is the value of red cell protoporphyrin?

Fe-free precursor of heme. Elevation = shortage of iron to complete heme synthesis

43

What cytokine stmulates the production of hepcidin? Why?

IL-6--reduces Fe available to bacteria

44

What is the first stage of Fe deficiency anemia?

Fe depletion

45

What is the second stage of Fe deficiency anemia?

Deficient erythropoiesis with normal [Hb]

46

What is the third and final stage of Fe deficiency anemia?

Hb production is inadequate, resulting in microcytic anemia

47

What are two iatrogenic causes of Fe overload?

transfusion
Inappropraite parenteral nutrition

48

Draw the heme synthesis pathway

Draw

49

What enzyme is the reguatory point for heme synthesis? What is the regulator?

ALA synthase
Heme or Fe will inhibit it

50

What intermediate of the heme synthesis pathway is susceptible to UV light?

UPG III

51

Where is ALA synthase located?

Membrane of the mitochondria

52

What is x-linked sideroblastic anemia?

Defective ALA synthase means not enough heme is produced

53

What are diseases that involve defects in heme synthesis called?

Porphyrias

54

What is the problem with how the heme synthesis is regulated, and porphyrias?

Since no heme is produced d/t porphyrias, ALA synthase is upregulated, generating more defective intermediates

55

What is the most common presentation of a porphyria?

Abdominal pain

56

What is the effect of EtOH consumption on porphyrias?

induces the synthesis of cytochrome p450s, which require heme

57

What is acute intermittent porphyria? Symptoms?

Deficiency in porphobilinogen deaminase (PBG deaminase)

Dark red urine

58

What is porphyria cutanea tarda? Symptoms?

Deficiency of uroporphyrinogen decarboxylase.

Fluorescent urine
Photosentivity of the skin

59

What are the two enzymes that Pb affects in the heme synthesis pathway?

ALA synthase
Ferrochelatase

60

Which is the photosensitive porphyria?

PCT since UPG III absorbs UV light