Which of the following facilitates entry of iron
Iron absorption primarily occurs in the duodenum and upper jejunum. The key here is understanding the transport mechanisms. I remember that ferroportin is a protein that exports iron from cells into the bloodstream. Wait, but the question is about entry into the cells, not into the blood. Hmm. Wait, the entry into the enterocyte (intestinal cell) would involve a different transport protein. Divalent metal transporter 1 (DMT1) is responsible for transporting ferrous iron (Fe²+) into the enterocyte. So the correct answer should be DMT1.
Now, the options A to D are missing, but the correct answer is likely DMT1. Let's assume the options include DMT1 as one of them. The other options might be other proteins like hepcidin, ferritin, or transferrin. Hepcidin is a hormone that regulates iron absorption by inhibiting ferroportin, so it doesn't facilitate entry. Ferritin stores iron in cells, and transferrin transports iron in the blood. So if any of these are options, they're incorrect. The clinical pearl here is that DMT1 is crucial for iron absorption, and mutations can lead to iron deficiency anemia. The high-yield fact is that DMT1 is the key transporter for iron into the intestinal cells.
**Core Concept**
Iron absorption is regulated by specific transport proteins in the duodenum. The **divalent metal transporter 1 (DMT1)** facilitates the uptake of ferrous iron (Fe²⁺) into enterocytes, a critical step in dietary iron absorption. Hepcidin and ferroportin regulate systemic iron homeostasis but not direct intestinal uptake.
**Why the Correct Answer is Right**
DMT1 is a transmembrane protein expressed on the apical (luminal) surface of duodenal enterocytes. It imports Fe²⁺ from the intestinal lumen into the cell. This step is essential because dietary iron is primarily absorbed as Fe²⁺ after reduction from Fe³⁺ by duodenal cytochrome B. Without DMT1, ferrous iron cannot enter enterocytes, leading to iron deficiency anemia.
**Why Each Wrong Option is Incorrect**
**Option A:** *Ferritin* stores iron intracellularly but does not transport it.
**Option B:** *Hepcidin* inhibits ferroportin, reducing iron release from cells into the blood, not its uptake.
**Option C:** *Transferrin* binds and transports iron in plasma, not across cell membranes.
**Clinical Pearl / High-Yield Fact**
DMT1 mutations cause **hypochromic microcytic anemia** due to impaired iron absorption. Remember: **"D for DMT1, the iron gatekeeper in the gut."** Unlike ferroportin (which exports iron), DMT1 is strictly for intestinal uptake.
**Correct Answer: C. Divalent metal transporter 1 (DMT1)**