Receptor for vitamin B12-intrinsic factor complex is located in:
Correct Answer: Ileum
Description: Ref: W F Canong. Digestion. Absorption, & Nutritional Principles. In: Review of Medical Physiology. 24th ed. California: McGraw-Hill Companies: 2012, p485.Explanation:"Most vitamins are absorbed in the upper small intestine, hut Vitamin B12 is absorbed in the terminal ileum " (Ref: Ganong)Vitamin B12 AbsorptionProtein-bound vitamin B12 must be released from the proteins by the action of digestive proteases in both the stomach and small intestine.Gastric acid & Pepsin releases the vitamin from food particle.R-proteins (such as haptocorrins [aka transcobalamin 1) and cobalaphilin) are B12 binding proteins that are produced in the salivary glands.V itamin B12 then hinds to the R-Proteins to avoid degradation in acidic stomach environmentThe next binding protein is intrinsic factor (IF), a protein synthesized by gastric parietal cellsIn the duodenum, proteases digest R-proteins and release B12. which then binds to IF. to form a complex (IF/B12).Vitamin B12 must be attached to IF for it to be absorbed, as receptors on the enterocytes in the terminal ileum of the small bowel only recognize the B12-IF complexIF also protects the vitamin from catabolism by intestinal bacteria.Once the IF/B 12 complex is recognized by- specialized ileal receptors, it is transported into the portal circulation.The vitamin is then transferred to transcob- alaniin II (TC-II/BI2). which serves as the plasma transporter.
Category:
Physiology
Get More
Subject Mock Tests
Practice with over 200,000 questions from various medical subjects and improve your knowledge.
Attempt a mock test nowMock Exam
Take an exam with 100 random questions selected from all subjects to test your knowledge.
Coming SoonGet More
Subject Mock Tests
Try practicing mock tests with over 200,000 questions from various medical subjects.
Attempt a mock test now