Receptor for absorption of Vit-B12 intrinsic factor complex is located in
**Core Concept**
The vitamin B12 absorption process involves the binding of vitamin B12 to intrinsic factor, a protein produced in the stomach. This complex then binds to a specific receptor on the surface of enterocytes in the small intestine, facilitating the absorption of vitamin B12.
**Why the Correct Answer is Right**
The receptor for the vitamin B12 intrinsic factor complex is called cubilin. It is a transmembrane glycoprotein located on the apical surface of enterocytes in the small intestine. When the vitamin B12 intrinsic factor complex binds to cubilin, it triggers a series of intracellular signaling events that lead to the internalization of the complex and the subsequent release of vitamin B12 into the enterocyte cytoplasm. This process is essential for the absorption of vitamin B12, which is necessary for the synthesis of DNA, fatty acid metabolism, and the maintenance of the nervous system.
**Why Each Wrong Option is Incorrect**
* **Option A:** The ileal bile acid transporter (IBAT) is responsible for the absorption of bile acids in the ileum, not the absorption of vitamin B12.
* **Option B:** The folate receptor is involved in the absorption of folate, not vitamin B12.
* **Option D:** The glucose transporter (GLUT2) is responsible for the absorption of glucose in the small intestine, not the absorption of vitamin B12.
**Clinical Pearl / High-Yield Fact**
A deficiency in cubilin can lead to megaloblastic anemia, a condition characterized by the production of abnormally large red blood cells. This condition can be caused by a variety of factors, including a deficiency in vitamin B12, folate, or both.
**Correct Answer:** C. Cubilin.