Iron Metabolism

Question 1

Oxygen can react with (blank) in one electron red-ox reactions.

Answer 1

iron

Question 2

Oxygen transport and storage are done via what two things?

Answer 2

myoglobin and hemoglobin

Question 3

Where do you find iron-containing proteins?

Answer 3

amino acid metabolism
inflammatory responses
Electron transport -cytochromes

Question 4

Iron and O2 generate (blank). There are many mechanisms in place to avoid excessive production of these.

Answer 4

free radicals

Question 5

(blank) is sequestered by binding proteins, protoporphyrins, and Fe-S centers

Answer 5

Iron

Question 6

Where do infants get iron from?

Answer 6

lactoferrin in mothers milk

Question 7

Where do you get absorption of iron?

Answer 7

upper small intestine (mostly duodenum)

Question 8

Heme-iron is taken up by a heme transporter (HT) protein. Once in cell, heme (blank) splits iron from heme

Answer 8

dioxygenase

Question 9

(blank) promotes Fe+2 to Fe+3

Fe+3 is reduced to Fe+2 by a ferric reductase: duodenal cytochrome b (Dcytb).

Answer 9

Gut environment

Question 10

What is the absorption of Iron in the gut?

Answer 10

Fe+2 then transported by DMT1 across apical membrane of enterocyte as Fe+2.
Ferroportin (FP) aided by hephaestin (Hp)(redox protein) makes the Fe2+ into Fe 3+ and transports it into the interstitial fluid then to plasma
Plasma Fe+3 binds to apo-transferrin to form transferrin
Some Fe+2 is stored as Fe+3-ferritin in cell

Question 11

What is the major storage protein of iron?

Answer 11

ferritin (4500 irons Fe3+ to one protein molecule)

Question 12

When do you see the aggregated form of ferritin?

Answer 12

in iron overload where it is hemosiderin (partially degraded)

Question 13

(blank) level is the most convenient laboratory test to estimate iron stores
Under steady state conditions, the serum ferritin level correlates with total body iron stores

Answer 13

serum ferritin

Question 14

Iron (III) is (blank) at physio pH, this is why transferrin is need to by Iron III to avoid precipitation in plasma

Answer 14

insoluble

Question 15

Is it healthy to have low conc. of free iron?

Answer 15

no it is damaging

Question 16

Essentially all plasma iron is bound to (blank). How many irons does this carry?

Answer 16

transferrin

2 Fe 3+

Question 17

What is the normal saturation % of transferrin with iron?

Answer 17

33%

Question 18

Describe iron uptake into the cell

Answer 18

transferrin bind iron-> transferrin iron complex binds to transferrin receptors (Tfr). the Tfr-diferric(2 irons)-Transferrin complex then gets sucked into an endosome and brough into the cell-> endosome becomes acidic and iron is released from complex-> iron is taken by mitochondria and put into heme by ferrochetolase-> apotransferrin is recycled back to plasma to get more iron.

Question 19

What is the primary storage site of iron?

Answer 19

liver

Question 20

What is the master control organ of iron homeostasis and produces the peptide hormone hepcidin?

Answer 20

liver

Question 21

What does hepicidin do?

What is the production of this stimulated by?

Answer 21

Inhibitor of processes that put iron into the blood
Directly interacts with ferroportin

Production is stimulated in:
Inflammation
Iron overload

Question 22

(blank) controls the main inflows of iron into plasma.

hepcidin binds directly to (blank) which is the hepcidin receptor.

Answer 22

hepcidin

ferroporFtin

Question 23

What happens when hepcidin is high?

Answer 23

hepcidin is internalized away from membrane, iron is trapped in enterocytes, macrophages, and hepatocytes, level of circulating iron goes down
(iron uptake is high)

Question 24

What happens when hepcidin is low?

Answer 24

iron enters plasma at high rates (iron uptake is low)

Question 25

What is the major site of iron absorption in the small intestine?

Answer 25

the duodenum

Question 26

``` What happens in each of these cells: villus cell or duodenal epithelial cell? liver parenchymal cell? reticuloendothelial macrophages? red blood cell precursor? ```

Answer 26

dietary iron absoprtion iron storage iron recycle heme synthesis

Question 27

Lots of ferritin is not needed in the face of low iron stores because ferritin is an (blank) storage protein.

Answer 27

intracellular

Question 28

Extracellular iron concentration is sensed through the interaction of (blank) with (blank). If you have a lot of iron what will be made?

Answer 28

holotrasnferrin and TFRI/TFR2 (transferrin receptors) | ferritin and hepcidin

Question 29

(blank) is the Inappropriate increase in intestinal iron absorption resulting in deposition of excessive amounts of iron in parenchymal cells with eventual tissue damage and impaired function of organs.

Answer 29

hemochromatosis

Question 30

You get (blank) when you have saturation of iron-binding proteins

Answer 30

hemochromatosis

Question 31

``` What does this describe? Deposition of hemosiderin in the tissues (aggregated ferritin) Primary affected tissues Liver - cirrhosis Pancreas - diabetes Skin – bronze; bronze diabete ```

Answer 31

hemochromatosis

Question 32

What are these primary causes of: Autosomal recessive allele Locus designated HFE Major histocompatibility complex (MHC) class-1 gene. Protein associates with b2-microglobulin.

Answer 32

hemochromatosis

Question 33

What is the mechanism of hemochromatosis/

Answer 33

messed up HFE/transferrin interaction resulting in increased uptake of iron

Question 34

What is the primary cause of hemochromatosis?

Answer 34

genetics

Question 35

Iron overload is reflected in serum (blank) concentrations

Answer 35

ferritin

Question 36

serum ferritin contains (blank) iron but tissue ferritin contain (blank) iron. HOw is it measured?

Answer 36

little to none A LOT of ug/L

Question 37

What happens to your serum ferritin levels as you age?

Answer 37

it increases

Question 38

What is the most common cause of poisoning of young children? What is the treatment?

Answer 38

iron poisoning (too many flinstones vitamins strong laxative, IV deferoxamine mesylate (Desferal) -Binds iron and excreted in urine

Question 39

What is this: Serum free iron not bound to transferrin Lipid peroxidation occurs, resulting in damage to blood vessels and Mitochondria

Answer 39

iron toxicity

Question 40

The most common cause of anemia is (blank)

Answer 40

iron deficiency

Question 41

In most adults, iron deficiency results from (blank)

Answer 41

blood loss (~5% of premenopausal women in US)

Question 42

Most functional defects in iron deficiency occur with the development of what three things? +

Answer 42

anemia Weakness and pallor Exercise intolerance

Question 43

Women who donate blood will develop (blank) more often than men

Answer 43

iron deficiency