What is the role of intrinsic factor in digestion?

• A. It emulsifies fats in the stomach.
• B. It binds vitamin B12 in the stomach to enable absorption in the ileum.
• C. It neutralizes stomach acid.
• D. It digests proteins in the stomach.

Answer: (B)

Intrinsic factor is a glycoprotein produced by the stomach’s parietal cells that binds vitamin B12 in the stomach, forming a stable complex. This IF–B12 complex is protected as it moves to the terminal ileum, where specific receptors on intestinal cells absorb B12 into the bloodstream. This absorption step is essential for making vitamin B12 available for red blood cell formation and DNA synthesis. Without intrinsic factor, B12 cannot be efficiently absorbed, leading to pernicious anemia. The other descriptions refer to different digestive roles—emulsifying fats is done by bile salts, neutralizing stomach acid involves bicarbonate, and protein digestion happens via pepsin in the stomach—none of which involve intrinsic factor.