True about active absorption of iron is: March 2009
**Core Concept:** Iron is an essential element for red blood cell formation, which carries oxygen in the blood. Iron is absorbed in the small intestine, specifically in the duodenum, by a process called active absorption. This process involves binding of iron to specific proteins and transporters for efficient transport.
**Why the Correct Answer is Right:** Iron absorption occurs mainly in the duodenum due to the presence of specific cells called enterocytes, which secrete the iron-binding protein, Transferrin. Intestinal ferric reductase (encoded by the SLC11A2 gene) is responsible for reducing ferric iron (Fe3+) to ferrous iron (Fe2+). This ferrous iron is then transported through the basolateral membrane by divalent cation transporter protein (DMT1) and stored in ferritin or transported to the liver for storage or to bone marrow for incorporation into hemoglobin.
**Why Each Wrong Option is Incorrect:**
A. Absorption of iron involves passive diffusion, which is not the case for active transport.
B. Active transport is not limited to a specific part of the small intestine, making this option incorrect.
C. Ferrous iron (Fe2+) is not directly transported through the basolateral membrane, as ferric iron (Fe3+) is reduced and transported instead.
D. The liver is not directly involved in the process of iron absorption, which makes this option incorrect.
**Clinical Pearl:** Iron absorption is crucial for maintaining the body's iron balance and preventing iron deficiency anemia. Malabsorption syndromes, such as celiac disease or inflammatory bowel disease, can lead to iron deficiency anemia due to impaired iron absorption. Adequate iron intake and absorption are essential for optimal health, especially in growing children and pregnant women.