Iron Use and Cycle

Question 1

Which form of Iron is absorbed? How is it transported into enterocyte?

Answer 1

Ferrous (2+), via DMT1 (divalent metal transporter)

Question 2

What are the two sources of iron coming into enterocyte?

Answer 2

Iron from food we eat and free iron coming in as heme molecule

Question 3

This molecule stores excess mineral iron and has an outside protein coat

Answer 3

Ferritin (ferr, tin = a tin to store iron)

Question 4

This green bile pigment is a result from the breakdown of heme of hemoglobin in erythrocytes

Answer 4

Biliverdin

Question 5

This molecule transports iron out of cell

Answer 5

Ferroportin

Question 6

After leaving the enterocyte via ferroportin, ferrous iron gets converts to ferric form via this protein

Answer 6

Hephaestin

Question 7

The name of this transport glycoprotein when not bound to iron

Answer 7

Apo-transferrin

Question 8

Transport protein when bound with 2 irons

Answer 8

Transferrin

Question 9

What is every cell using heme for?

Answer 9

Electron transport chain! Every ETC protein has heme in them. Used to transport electrons

Question 10

Endocytosis of transferrin relies on this receptor in which type of cell?

Answer 10

TfR (Transferrin receptor), in erythroblast

Question 11

What state of iron binds to transferrin?

Answer 11

Ferric state (3+), two irons per transferrin

Question 12

What happens to transferrin after endocytosis in erythroblast?

Answer 12

Tranferrin molecule gets released via TfR, and now called “Apotransferrin” gets reused

Question 13

Once transferrin binds to TfR receptor on erythroblast, how does it enter cell?

Answer 13

Endocytosis

Question 14

Once in erythroblast, Fe3+ gets converted to Fe2+ and is mainly used to make

Answer 14

Makes heme for hemoglobin

Question 15

Why does macrophage need iron?

Answer 15

serves as internal storage of extra iron for body

Question 16

What are macrophage’s two sources of iron?

Answer 16

Engulfing RBCs (that contain iron in heme to make up hemoglobin), and uptake of transferrin via TfR

Question 17

If other parts of body need iron, iron leaves the macrophage via this transporter

Answer 17

ferroportin

Question 18

Hepatocytes (liver cells) store iron as

Answer 18

Ferritin

Question 19

Iron in hepatocyte (liver cell) can be moved out via

Answer 19

Ferroportin

Question 20

Where is apotransferrin made?

Answer 20

in liver cells! Livers contain nucleus and so can do transcription and translation to make apotransferrin that can bind to iron.

Question 21

Why is it a problem if you’re absorbing too much iron?

Answer 21

No way of regulating it. Only way to get rid of excess iron is shedding of epithelial cells in GI tract and skin. Can be a problem if you have too much, because can damage bodily organs

Question 22

What are there iron complications in sickle cell anemia?

Answer 22

Patients need RBCs so get frequent blood transfusion. Often times can become iron overloaded. Need RBCs but not iron!

Question 23

Where is the “thermostat” located that evaluates the corresponding amount of iron out in circulation?

Answer 23

Hepatocyte (liver cell)

Question 24

This peptide hormone is the master regulator of iron hemostasis. Where is it made?

Answer 24

Hepcidin, made in liver

Question 25

How does Hepcidin work when thermostat senses iron excess? What does it bind to?

Answer 25

Hepatocytes produce and excrete hepcidin>> hepcidin binds to ferroportin on hepatocytes, enterocytes, and macrophages>>internalization and destruction of ferroportin>>inhibits iron export

Question 26

ferrous iron gets converted to ferric form via this protein after leaving either macrophages or hepatocytes

Answer 26

Ceruloplasmin

Question 27

Enteroctyes help regulate iron levels by inhibiting this transporter

Answer 27

DMT1

Question 28

This element regulates iron levels within the mRNA coding for DMT1, Tfr, and apo-ferritin

Answer 28

Iron response elements (IREs)

Question 29

when there are low apotransferrin iron levels, IRE+IRP increase/decrease DMT1 and Tfr levels

Answer 29

increases (up regulates DMT1 because you want enterocytes to take in more iron, and up-regulate Tfr because you want erythroblasts, macrophages, and hepatocytes to take in more iron)

Question 30

Cytoplasmic iron in the corresponding cell binds to this protein that then binds to IREs to help regulation

Answer 30

Iron response proteins (IRPs)

Question 31

What amount of all body iron exists within hemoglobin?

Answer 31

2/3

Question 32

If you lose blood, iron levels will (increase/decrease) in circulation

Answer 32

decrease

Question 33

if you lose iron, serum iron will (increase/decrease)

Answer 33

decrease

Question 34

If you lose iron, ferritin levels (inside ~ correlate with serum levels) increase/decrease

Answer 34

decrease. if iron drops, macrophages and hepatocytes in response will move iron out of ferritin, into iron pool, and into circulation for what's being lost

Question 35

If iron levels decrease, apo-transferrin levels (increase/decrease)

Answer 35

increase. When macrophages and haptocytes move iron out of ferritin and into circulation pool, hepatocytes will increase the amount of apotransferin, hoping that more iron is coming in through GI tract

Question 36

If iron levels decrease, serum transferrin (increases/decreases)

Answer 36

increases. More iron released out into circulation

Question 37

Total iron binding capacity (TIBC) is an indirect measure of?

Answer 37

Transferrin

Question 38

If iron levels decrease, TIBC (total iron binding capacity) increases/decreases

Answer 38

increase

Question 39

Overall: Decreasing serum iron causes ____ in serum ferritin, ____ in serum transferrin, and ____ in total iron binding capacity

Answer 39

decrease in serum ferritin, increase in serum trasnferrin, an increase in TIBC

Question 40

Chronic inflammatory cytokines can cause an increase leakage of what out of cells?

Answer 40

Ferritin. This is important because inflammatory cytokines block release of iron from ferritin. Iron can be stored, but doesn't get released. So ferritin leaks out, and serum ferritin levels appear to be normal (which is an indication of iron levels), but iron is trapped.

Question 41

Which cell doesn't contain a TfR (transferrin receptor) on membrane?

Answer 41

Enterocyte (duodenum). Transporter for iron in heme is unidentified and Fe2+ enters via DMT1.

Question 42

This amount of iron is absorbed daily by GI and lost daily from shedding of epithelial cells

Answer 42

1-2 mg

Question 43

Daily RBC/hemoglobin production and other use of iron requires how much iron per day? What does this suggest?

Answer 43

25 mg. The majority of body iron is recycled

Question 44

low ph and iron chelators (i.e. Vitamin C) increase/decrease iron absorption

Answer 44

increase iron absorption