Which statement about ferric iron (Fe3+) is true?

Which statement about ferric iron (Fe3+) is true?

• A. Ferric (Fe3+) Is Insoluble in Aqueous Solutions and Not Absorbed
• B. Ferrous (Fe2+) Is Insoluble and Not Absorbed
• C. Heme Iron Is the Primary Form Absorbed in the Duodenum
• D. Ferric Iron Is Readily Converted to Heme Iron During Digestion

Answer: (A)

Ferric iron (Fe3+) is poorly soluble in the intestinal environment and does not cross the intestinal lining in meaningful amounts. In the duodenum, Fe3+ tends to form insoluble hydroxides, so it must be reduced to ferrous iron (Fe2+) to stay soluble and be absorbed. This reduction is carried out by mucosal ferrireductases (such as Dcytb) before Fe2+ is transported into enterocytes via the DMT1 transporter. Inside the enterocyte, iron can be stored as ferritin or exported by ferroportin after being oxidized back to Fe3+ for transport in the bloodstream. Because of this, ferric iron itself is not readily absorbed, which is why the statement about ferric iron being insoluble and not absorbed is the best description. Ferrous iron is soluble at intestinal pH and is the form predominantly taken up by the enterocytes, so the claim that ferrous iron is insoluble and not absorbed is not accurate. Heme iron has its own absorption pathway and is absorbed more efficiently than non-heme iron, but the idea that ferric iron is readily converted into heme iron during digestion isn’t correct.

Ferric iron (Fe3+) is poorly soluble in the intestinal environment and does not cross the intestinal lining in meaningful amounts. In the duodenum, Fe3+ tends to form insoluble hydroxides, so it must be reduced to ferrous iron (Fe2+) to stay soluble and be absorbed. This reduction is carried out by mucosal ferrireductases (such as Dcytb) before Fe2+ is transported into enterocytes via the DMT1 transporter. Inside the enterocyte, iron can be stored as ferritin or exported by ferroportin after being oxidized back to Fe3+ for transport in the bloodstream. Because of this, ferric iron itself is not readily absorbed, which is why the statement about ferric iron being insoluble and not absorbed is the best description.

Ferrous iron is soluble at intestinal pH and is the form predominantly taken up by the enterocytes, so the claim that ferrous iron is insoluble and not absorbed is not accurate. Heme iron has its own absorption pathway and is absorbed more efficiently than non-heme iron, but the idea that ferric iron is readily converted into heme iron during digestion isn’t correct.