<prompt> True about active absorption of iron is: March 2009Absorbed in distal ileumAbsorbed in stomachNot absorbed in duodenum and proximal jejunumDecreases following gastrectomy  <response>: Ans. D: Decreases following gastrectomyIn adults, the amount of iron lost from the body is relatively small. The losses are generally unregulated, and total body stores of iron are regulated by changes in the rate at which it is absorbed from the intestine.Various dietary factors affect the availability of iron for absorption; for example, the phytic acid found in cereals reacts with iron to form insoluble compounds in the intestine. So do phosphates and oxalates.Most of the iron in the diet is in the ferric Fe3 form, whereas it is the ferrous Fe2 form that is absorbed. Fe3 reductase activity is associated with the iron transpoer in the brush borders of the enterocytesNo more than a trace of iron is absorbed in the stomach, but the gastric secretions dissolve the iron and permit it to form soluble complexes with ascorbic acid and other substances that aid its reduction to the Fe2 form. The impoance of this function in humans is indicated by the fact that iron deficiency anemia is a troublesome and relatively frequent complication of paial gastrectomy.Almost all iron absorption occurs in the duodenum. Some is stored in ferritin, and the remainder is transpoed out of the enterocytes by a basolateral transpoer named ferropoin 1. A protein called hephaestin Hp is associated with ferropoin 1. It is not a transpoer itself, but it facilitates basolateral transpo.In the plasma, Fe2 is conveed to Fe3and bound to the iron transpo protein transferrin. This protein has two iron-binding sites. Normally, transferrin is about 35 saturated with iron.Intestinal absorption of iron is regulated by three factors: recent dietary intake of iron, the state of the iron stores in the body, and the state of erythropoiesis in the bone marrow. 