5. Iron metabolism

Question 1

how much iron is active

Answer 1

80%
either:
Hb bound
myoglobin bound
enzyme bound

Question 2

how much bound to Hb

Answer 2

65%

Question 3

how much bound to myoglobin

Answer 3

10%

Question 4

storage of iron

Answer 4

• 20% is stored
• either as ferritin, or haemosiderin

Question 5

transport of iron

Answer 5

• 0.1-0.2%
  transported as transferrin

Question 6

what type of iron is insoluble/soluble

Answer 6

• ferric (Fe3+) insoluble
• ferrous (Fe2+) = soluble

Question 7

which iron is easier to absorb in diet

Answer 7

haem iron
rich in meats

Question 8

where does transferrin go

Answer 8

delivers iron to tissues that have tranferrin receptors

Question 9

which cells in the liver is iron stored in as ferritin

Answer 9

hepatocytes

Question 10

why is iron storage in the bone marrow important

Answer 10

erythroblasts = make Hb for RBCs

Question 11

how come low iron absorption is okay

Answer 11

is recycled in body anyway after RBCs are broken down

Question 12

how much absorbed and where

Answer 12

through duodenum
0.5-2mg only
but changes according to bodies needs

Question 13

name the ferrric reductase that converts from fe3+ to 2+

Answer 13

duodenal cytochrome B

Question 14

what is uptake inhibited by

Answer 14

phytates, tannins (tea), tetracylcine (antibiotics)

Question 15

what enhnaces iron uptake

Answer 15

vitamin C

Question 16

how do we lose iron

Answer 16

sweating, shedding mucosal lining cells in GI tract, faeces

just general turnover

Question 17

specific cell in duodenum where iron is absorbed

Answer 17

enterocyte

Question 18

what transporte allows ferrous iron to move into enterocyte

Answer 18

divalent metal transporter (DMT)

Question 19

what channel allows iron to exit the enterocyte

Answer 19

ferroportin
(transports as Fe3+ only, unlike DMT)

Question 20

main regulator of ferroportin

Answer 20

hepicidin

Question 21

how is hepicidin affected by inflammation

Answer 21

increases
which decreases iron aborption (decreased serum iron levels)

Question 22

how many atoms of iron can transferrin carry at a time

Answer 22

2

Question 23

process of transferrin delivering iron

Answer 23

binds to transferrin receptor
transferrin-receptor complex gets internalised
iron released in cell and the complex is recycled to the cell surface
- receptor and transferrin are recycled

Question 24

how can serum ferritin be measured

Answer 24

ELISA test
valuable diagnostic

Question 25

where is iron mainly stored

Answer 25

• liver
• bone marrow
• spleen

Question 26

which out of ferritin and haemosiderin is insoluble

Answer 26

haemosiderin

Question 27

how much iron stored as haemosiderin usually

Answer 27

35%

Question 28

what is haemosiderin derived as

Answer 28

lysosomal digestion of ferritin aggregates
(so only happens when too much iron)

Question 29

where is haemoseridin found

Answer 29

macrophages as pappenheimer bodies

Question 30

how do haemoseridin get removed

Answer 30

by spleen
only takes part of cell off as to not break down the whole thing = blister cell

Question 31

what times could additional iron be required

Answer 31

• growth in childhood
• menstrual periods
• pregnancy (3-4mg needed)