Final answer:
Iron is indeed absorbed by enterocytes in the duodenum of the small intestine through active transport and binds to ferritin within mucosal cells. This absorption can be adjusted based on the body's requirements, especially during times of increased demand such as bleeding or menstruation.
Step-by-step explanation:
It is true that iron is absorbed by enterocytes in the duodenum of the small intestine. Iron absorption mainly occurs in the duodenum and the proximal jejunum. Iron in food, typically in ferric form (Fe³+), is more readily absorbed in the presence of an acidic pH which favors its conversion to the ferrous form (Fe²+). In the duodenum, the ionic iron necessary for hemoglobin production is absorbed into mucosal cells through active transport. Inside these cells, iron binds to the protein ferritin, forming iron-ferritin complexes that store iron until the body requires it. When needed, especially during conditions like acute or chronic bleeding or menstruation in women, there is an increased uptake of iron from the intestine and an accelerated release of iron to the bloodstream.
Vitamins, minerals, proteins, fats, and water are absorbed throughout the small intestine, with iron and vitamin B12 absorption being more site-specific in the duodenum and ileum, respectively. Dietary fats are emulsified by bile salts and lecithin into micelles, enabling their absorption in enterocytes, whereas proteins are often absorbed as amino acids via active transport mechanisms.
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