Absorption Of Iron

cgeorge's version from 2016-02-23 18:15


Question Answer
Hereditary haemochromatosis isIron overload
Explain the processing of ironMajority of iron absorbed is used to make haemoglobin. After 100 days RBC's become engulfed by macrophages which recycle the iron out of the haemoglobin, releasing it into a plasma iron pool.
How can we lose iron (although noactive mechansim)Via sloughed off cells
How much iron do we absorb from the diet1-2mg/day
Inorganic iron is... and .... Insoluble ... Not very bioavailable
Haem iron is... and ...Soluble .. More bioavailable
Explain process of iron being absorbed into enterocyte and what happensFerric (poorly absorbed) can be reduced to ferous iron via Dcytb. Once in ferous form, absorbed via DMT1 transporter.
Once ferous is inside enterocyte what happens to it?It can either be stored in cell via ferritin, used by cell, or effluxed out via ferroportin into the blood
Once feroportin is out of the cell what happens?Ferous ion is reoxidised by helphaestin and iron binds to transferrin in the blod
How does a cell capture transferrin bound iron?Via transferrin receptor mediated exocytosis
Dyctb is a ferric reductase or oxygenase?Reductase
DMT1 is a transporter responsible for the uptake of Ferous (II)
Ferritin is responsible for Iron storage
Ferroportin is responsible for Iron efflux
Hephaestin is a reductase or oxidase?Iron oxidase
How is haem iron absorbed into enterocytes? And what happens after this?Via haem carrier protein 1. When haem is in cell, its broken down by haem oxygenase > Biliverdin & Free iron. This free iron can either bind to ferritin/be used by cell/effluxed.
What happens to the heme produced when RBC break down?The heme is captured by carrier protein hemopexin. This is then directed to liver > Binds to CD91 receptor, complex internalised. Then haemoxygenase 1 breaks haem > Biliverdin and iron
What does Haeme carrier protein 1 do?Transports haem iron into enterocytes
What is the CD91 receptor responsible for?Transporting hemopexin (heme bound to carrier potein) into the liver
When biliverdin is reduced is forms?Bilirubin
The 2 raw materials to make heme iron isGlycine and succinyl cOA
3 stores of ironLIver,spleen and bone marrow
What hormone regulates absorption of ironHepcidin
What does hepcidin do?Inhibits iron absorption
How can hepcidin be stimulated?Inflammation/infection
How does hepcidin work?Binds to feroportin (efflux protein) and degrades it so iron cant get out cells
Erythropoiesis would cause increase in hepcidin or decrease?Decrease, you need iron to make RBC, so you would switch off hepicin so free iron is available
Infection/inflammation via IL6 switches ... hepcidin. Why? And what happens?Switches on hepcidin. If you have infection, they need iron to proliferate. Hepcidin also binds to feroportin on the macrophage, keeping all the Fe in the macrophage
Whats the cause of anaemia?All the iron is locked up and not available due to an infection
If your ferritin levels are low does this indicate IDA or Anemia?Iron deficiency anemia
Heretidary haemochromatosis is caused byMutations in enzymes involved in making hepcidin. Cant switch it on, so you carry on absorbing iron into blood.
Coeliac disease is aAutoimmune disorder of the small bowel. Caused by a reaction to gliadin.