5. Iron metabolism Flashcards
how much iron is active
80%
either:
Hb bound
myoglobin bound
enzyme bound
how much bound to Hb
65%
how much bound to myoglobin
10%
storage of iron
- 20% is stored
- either as ferritin, or haemosiderin
transport of iron
- 0.1-0.2%
transported as transferrin
what type of iron is insoluble/soluble
- ferric (Fe3+) insoluble
- ferrous (Fe2+) = soluble
which iron is easier to absorb in diet
haem iron
rich in meats
where does transferrin go
delivers iron to tissues that have tranferrin receptors
which cells in the liver is iron stored in as ferritin
hepatocytes
why is iron storage in the bone marrow important
erythroblasts = make Hb for RBCs
how come low iron absorption is okay
is recycled in body anyway after RBCs are broken down
how much absorbed and where
through duodenum
0.5-2mg only
but changes according to bodies needs
name the ferrric reductase that converts from fe3+ to 2+
duodenal cytochrome B
what is uptake inhibited by
phytates, tannins (tea), tetracylcine (antibiotics)
what enhnaces iron uptake
vitamin C
how do we lose iron
sweating, shedding mucosal lining cells in GI tract, faeces
just general turnover
specific cell in duodenum where iron is absorbed
enterocyte
what transporte allows ferrous iron to move into enterocyte
divalent metal transporter (DMT)
what channel allows iron to exit the enterocyte
ferroportin
(transports as Fe3+ only, unlike DMT)
main regulator of ferroportin
hepicidin
how is hepicidin affected by inflammation
increases
which decreases iron aborption (decreased serum iron levels)
how many atoms of iron can transferrin carry at a time
2
process of transferrin delivering iron
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
how can serum ferritin be measured
ELISA test
valuable diagnostic
where is iron mainly stored
- liver
- bone marrow
- spleen
which out of ferritin and haemosiderin is insoluble
haemosiderin
how much iron stored as haemosiderin usually
35%
what is haemosiderin derived as
lysosomal digestion of ferritin aggregates
(so only happens when too much iron)
where is haemoseridin found
macrophages as pappenheimer bodies
how do haemoseridin get removed
by spleen
only takes part of cell off as to not break down the whole thing = blister cell
what times could additional iron be required
- growth in childhood
- menstrual periods
- pregnancy (3-4mg needed)
