True about active absorption of iron is: March 2009
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 Fe3+and 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.
Absorbed in distal ileum
Absorbed in stomach
Not absorbed in duodenum and proximal jejunum
Decreases following gastrectomy