The Student Room Group
Reply 1
Iron in the diet is in one of two forms: ferrous (Fe2+) or ferric (Fe3+).

The mechanism we've been taught is for 'free' iron abroption from the gut.... that is, iron which has formed salts with anions or iron which has been made more soluble by the presence of Vit C.

-Ferric iron is reduced to ferrous iron by extracellular apical membrane protein DCytb
-All ferrous iron is transported across the apical membrane at a protein known as DCT1 (DCT = Divalent Cation Transporter) which cotransports H+ with Fe2+ (apparantly a 1:1 ratio). It's actually driven by the H+ gradient, rather than the ferrous iron gradient
-In the cytoplasm ferrous iron is almost immediately bound to Mobilferrin. This is a small protein responsible for taking the Fe2+ to the basolateral membrane
-Ferrous iron is transported across the membrane by 'ferroportin' (IREG1)
-In the plasma haephaestin oxidised the ferrous iron to ferric iron
-Ferric iron then binds to transferrin in the plasma
-Iron is off loaded at cells throughout the body, primarily hepatocytes, where it is stored bound to apoferritin forming a complex called ferritin

Heme iron can also be absorbed, and apparantly is done so more readily. Saying that, all I could find was that Heme iron is ferrous but something oxidises it to ferric iron in the cytoplam before it's reduced to ferrous iron again and then follows the same pathway.
Reply 2
corkskrew
Iron in the diet is in one of two forms: ferrous (Fe2+) or ferric (Fe3+).

The mechanism we've been taught is for 'free' iron abroption from the gut.... that is, iron which has formed salts with anions or iron which has been made more soluble by the presence of Vit C.

-Ferric iron is reduced to ferrous iron by extracellular apical membrane protein DCytb
-All ferrous iron is transported across the apical membrane at a protein known as DCT1 (DCT = Divalent Cation Transporter) which cotransports H+ with Fe2+ (apparantly a 1:1 ratio). It's actually driven by the H+ gradient, rather than the ferrous iron gradient
-In the cytoplasm ferrous iron is almost immediately bound to Mobilferrin. This is a small protein responsible for taking the Fe2+ to the basolateral membrane
-Ferrous iron is transported across the membrane by 'ferroportin' (IREG1)
-In the plasma haephaestin oxidised the ferrous iron to ferric iron
-Ferric iron then binds to transferrin in the plasma
-Iron is off loaded at cells throughout the body, primarily hepatocytes, where it is stored bound to apoferritin forming a complex called ferritin

Heme iron can also be absorbed, and apparantly is done so more readily. Saying that, all I could find was that Heme iron is ferrous but something oxidises it to ferric iron in the cytoplam before it's reduced to ferrous iron again and then follows the same pathway.


Cheers v helpful... I have to write an essay on this so I do need to know a lot of detail, so thanks...

Btw, approx 2/3 of the Fe2+ ions form ferritin in enterocytes - you made it sound as though all of the Fe2+ is absorbed into the blood
Reply 3
Revenged

Btw, approx 2/3 of the Fe2+ ions form ferritin in enterocytes - you made it sound as though all of the Fe2+ is absorbed into the blood


Probably made it sound like that because I didn't realise!
But I am correct in thinking the majority of transferrin is dumped in the liver?
Reply 4
corkskrew
Probably made it sound like that because I didn't realise!
But I am correct in thinking the majority of transferrin is dumped in the liver?


Yeah, liver is normally the right answer for everything! :wink:

It is stored mainly in the liver, spleen and bone marrow... a very small proportion of this is in the form of transferrin...

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