Which vitamin requires intrinsic factor in order to be absorbed? A) B12 B) K C) A D) C
The correct answer and explanation is :
The correct answer is A) B12.
Explanation:
Vitamin B12 (also known as cobalamin) is unique in that it requires a specific protein called intrinsic factor (IF) for its absorption in the small intestine. Intrinsic factor is a glycoprotein produced in the stomach’s parietal cells. It plays a crucial role in facilitating the absorption of vitamin B12, which is vital for the formation of red blood cells, neurological function, and DNA synthesis.
Here’s how the process works:
- Stomach Digestion: When you consume vitamin B12 through food, it is typically bound to protein. In the acidic environment of the stomach, gastric enzymes help release B12 from the proteins it’s attached to. This free vitamin B12 then binds to a protein called R-binder, which protects it as it moves through the stomach.
- Intrinsic Factor Binding: Once the B12-R-binder complex reaches the small intestine (specifically the duodenum), pancreatic enzymes break down the R-binder. Vitamin B12 then binds to intrinsic factor (IF), which is produced in the stomach.
- Absorption in the Ileum: The vitamin B12-intrinsic factor complex travels to the ileum (the last section of the small intestine), where specific receptors recognize this complex. The vitamin B12 is then absorbed into the bloodstream through the ileum’s enterocytes (cells of the intestine lining).
If intrinsic factor is deficient or absent, vitamin B12 cannot be properly absorbed, leading to a condition known as pernicious anemia. Pernicious anemia is a type of megaloblastic anemia caused by vitamin B12 deficiency, and it results in symptoms like fatigue, weakness, neurological issues, and cognitive decline.
In contrast, vitamins A, C, and K do not require intrinsic factor for absorption. Vitamin A is absorbed with dietary fats in the small intestine, while vitamins C and K are absorbed directly by enterocytes without the need for a specific protein like intrinsic factor.