What is false regarding iron absorption?
Ans: b (It occurs in the distal jejunum) Ref: Ganong, 22nd ed, p. 477Physiology of iron absorptionIron metabolism is unique because homeostasis is maintained by regulation at the level of absorption and not by excretion.Almost all iron absoiption occurs in the duodenum and upper jejunum.Only about 6-10% of the dietary iron is absorbed.Factors that increase iron absorptionMeatAscorbic acidAcidsSH group containing amino acidFactors that decrease iron absorptionPhytates in dietOxalates in dietIron is absorbed from the intestine in the ferrous form (Fe2+). It is transported from the lumen into the enterocytes via DMT1. Some Fe2+ in enterocyte is converted to Fe3+ and stored as ferritin. Rest of the iron (Fe2+) is transported from the enterocyte into the plasma by ferroportin 1. Ferroportin 1 is associated with a protein hephaestin (Hp) which facilitates transport of iron.In the plasma Fe2+ is converted to Fe!+ and bound to the iron transport protein transferrin. Transferrin is the transport form of iron.Iron is stored in liver, spleen, bone marrow and mucosal cells as ferritin.
10% of dietary iron only is absorbed.
It occurs in the distal jejunum
Ascorbic acid increases iron absorption
Iron administration increases incidence of breath holding spells
Nutrition