Vitamin B12 Absorption

Question 1

What are the sources of vitamin B12?

Answer 1

• Shell fish
• Meat
• Dairy products
• Eggs

Question 2

How is vitamin B12 absorbed?

Answer 2

1. Meat enters the stomach
2. B12 released in the acidic environment
3. For prevention of degradation, it forms a complex with haptocorrin
4. The stomach also has gastric parietal cells which release intrinsic factor
5. Haptocorrin then moves to the duodenum
6. IF arrives with B12 complex
7. B12 and haptocorrin separate
8. B12 forms a complex with IF
9. Arrives at the terminal ileum
10. The enterocytes have receptor cubulin which interacts with the complex and forms an endosome
11. Within the endosome, the IF separates from the colbalamin and is degraded
12. Colbalamin transported to a secretory vesicle where it forms with a third protein celled Transcobalamin II
13. TCII is transported to the blood where it is distributed around the body