Hvor absorberes jern i fordøjelsessystemet?
tolvfingertarmen
Human iron metabolism
Ligesom de fleste mineralske næringsstoffer absorberes størstedelen af det jern, der optages fra fordøjet mad eller kosttilskud, i tolvfingertarmen af enterocytter i tolvfingertarmens slimhinde. Disse celler har særlige molekyler, der gør det muligt for dem at flytte jern ind i kroppen. For at blive optaget kan jern fra kosten optages som en del af et protein, f.eks. hæmprotein, eller jern skal være i sin jernholdige Fe2+-form. Et jernreduktaseenzym på enterocytternes børstekant, duodenal cytochrom B (Dcytb), reducerer jernholdigt Fe3+ til Fe2+. Et protein kaldet divalent metal transporter 1 (DMT1), som kan transportere flere divalente metaller gennem plasmamembranen, transporterer derefter jern gennem enterocyttens cellemembran ind i cellen.
duodenum
Human iron metabolism
Like most mineral nutrients, the majority of the iron absorbed from digested food or supplements is absorbed in the duodenum by enterocytes of the duodenal lining. These cells have special molecules that allow them to move iron into the body. To be absorbed, dietary iron can be absorbed as part of a protein such as heme protein or iron must be in its ferrous Fe2+ form. A ferric reductase enzyme on the enterocytes’ brush border, duodenal cytochrome B (Dcytb), reduces ferric Fe3+ to Fe2+. A protein called divalent metal transporter 1 (DMT1), which can transport several divalent metals across the plasma membrane, then transports iron across the enterocyte’s cell membrane into the cell.
Human iron metabolism