This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Vitamins, Subject name: Biochemistry
What is function of Intrinsic Factor - (NEET/DNB 
Select and explain. 
A. Increases cobalamin absorption Pattern), B. Increases folate absorption, C. Converts prothrombin to thrombin, D. Converts fibrinogen to fibrin
A: Increases cobalamin absorption Pattern)
Answer: A: Increases cobalamin absorption Pattern) 
Explanation: Ans. is 'a' i.e., Increases cobalamin absorption o Intrinsic factor is a small glycoprotein secreted by the parietal cells of the gastric mucosa.lt is essential for vitamin B12 absorption.o Gastric acid and pepsin release the vitamin from protein binding in food and make it available to bind to cobalophilin, a binding protein secreted in the saliva.o In the duodenum, cobalophilin is hydrolyzed, releasing the vitamin for binding to intrinsic factor,o Intrinsic factor binds only the active vitamin Bi: vitamers and not other corrinoids.o Vitamin Bn is absorbed from the distal third of the ileum via receptors that bind the intrinsic factor vitamin B12 complex, but not free intrinsic factor or free vitamin,o Vitamin Bi; is also called as ''extrinsic factor of castle".