Iron Metabolism

Question 1

What is iron required for?

Answer 1

Oxygen carriers

• haemoglobin
• myoglobin

Co-factor

Question 2

Can the body excrete iron?

Answer 2

No

Question 3

What are the common states of iron?

Answer 3

Ferrous iron

Ferric iron

Question 4

What is the formula of ferrous iron?

Answer 4

Fe2+

Question 5

What is the formula of ferric iron?

Answer 5

Fe3+

Question 6

Which is the reduced form?

Answer 6

Ferrous iron (Fe2+)

Question 7

Which is the oxidised form?

Answer 7

Ferric iron (Fe3+)

Question 8

Where is iron absorbed?

Answer 8

Duodenum

Jejunum

Question 9

What are sources of haem iron?

Answer 9

Liver
Kidney
Beef
Chicken

Question 10

What are sources of non-haem iron?

Answer 10

Fortified cereals 
Raisins 
Beans 
Oats 
Rice

Question 11

How is dietary iron absorbed?

Answer 11

Fe3+ reduced to Fe2+ by reductase
Fe2+ absorbed into enterocyte by DMT1
Fe2+ travels through ferroportin into blood
Hephaestin converts Fe2+ into Fe3+

Question 12

How is iron stored in enterocytes?

Answer 12

As Fe3+ with ferritin

Question 13

What is the cofactor for reductase?

Answer 13

Vitamin C

Question 14

How is iron transported in the blood?

Answer 14

Fe3+ bound to transferrin

Question 15

What inhibits ferroportin?

Answer 15

Hepcidin

Question 16

Where is hepcidin produced?

Answer 16

Liver

Question 17

What can reduce absorption of non-haem iron?

Answer 17

Tannins (tea)
Fibre
Antacids

Question 18

What can increase absorption of non-haem iron?

Answer 18

Vitamin C

Citrate

Question 19

How is iron stored?

Answer 19

Ferritin (soluble)

Haemosiderin (insoluble)

Question 20

What is ferritin?

Answer 20

Globular protein complex with hollow core that has pores that allow iron to enter/leave

Question 21

What is haemosiderin?

Answer 21

Aggregates of clumped ferritin particles, denatured protein and lipids - accumulate in macrophages

Question 22

Where is haemosiderin found?

Answer 22

Liver
Spleen
Marrow

Question 23

How is iron taken up by cells?

Answer 23

1. Fe3+ bound to transferrin binds to transferrin receptor and is taken in by receptor-mediated endocytosis
2. Fe3+ released and reduced to Fe2+ by acidic environment in endosome
3. Fe2+ released from endosome by DMT1
4. Once in cytosol
   - stored in ferritin
   - exported by ferroportin
   - taken up by mitochondria

Question 24

How is iron recycled?

Answer 24

Old RBCs engulfed by macrophages (mainly splenic and Kupffer cells)
Macrophages catabolise haem from RBCs
Iron exported to blood or returned to ferritin

Question 25

What is the main regulator of iron absorption?

Answer 25

Hepcidin

Question 26

What increases hepcidin synthesis?

Answer 26

Iron overload

Question 27

What decreases hepcidin synthesis?

Answer 27

High erythropoietic activity

Question 28

How is excess iron stored?

Answer 28

Haemosiderin

Question 29

What is the problem with excess iron?

Answer 29

Promotes free radical formation

Question 30

What can cause iron excess?

Answer 30

Transfusion associated haemosiderosis

Hereditary haemochromatosis

Question 31

What is transfusion associated haemosiderosis?

Answer 31

Gradual accumulations of iron from repeated blood transfusions

Question 32

Where does iron tend to accumulate?

Answer 32

Liver
Heart
Endocrine organs

Question 33

How much iron is in 400ml blood?

Answer 33

200mg

Question 34

How can you delay transfusion associated haemosiderosis?

Answer 34

Desferrioxamine

Question 35

What is the inheritance pattern of hereditary haemochromatosis?

Answer 35

Autosomal recessive

Question 36

What is the gene effected by hereditary haemochromotosis?

Answer 36

HFE gene on chromosome 6

Question 37

How does hereditary haemochromatosis cause iron overload?

Answer 37

HFE protein normally interacts with transferrin receptor - reduces affinity for iron bound transferrin

Mutated HFE cant bind to transferrin

Too much iron enters cells

Question 38

How is hereditary haemochromatosis managed?

Answer 38

Venesection