define absorption storage and elimination of

Question

Define Absorption, Storage and Elimination of cyanocobalamin?

Vitamin B₁₂ in food is bound to proteins and is only released by the action of a high 'Concentration of hydrochloric acid present in the stomach. Once released from foods, vitamin B₁₂ absorption involves contact with two proteins, intrinsic .factor (IF) and R binder. The glycoprotein, called R-binders (or haptoconins), protect vitamin B₁₂ from chemical denaturation in the stomach, IF is a glycoprotein synthesized by the gastric parietal cells and function in the small intestine.

Although the formation of the vitamin B₁₂- intrinsic factor complex was initially thought to happen in the stomach, it is now clear that this is not the case. At an acidic pH, (in the stomach) the affinity of the intrinsic factor for vitamin B₁₂ is low whereas its affinity for the R-binders is high. When the contents of the stomach enter the duodenum, the R-binders become partly digested by the pancreatic proteases, which in turn cause them to release their vitamin B₁₂. Because the pH in the duodenum is more neutral than that in the stomach, the intrinsic factor has a high binding affinity to vitamin B₁₂, and it quickly binds the vitamin as it is released from the R-binders.  The vitamin B₁₂ intrinsic factor complex then proceeds to the lower end of the small intestine, where it is absorbed by phagocytosis by specific ileal receptor. The absorbed cbl is processed into a complex transcobalamin-II-cbl (TCII-cbl), secreted into portal blood and delivered to the liver and ultinlately all tissues.

Vitamin B₁₂ is the only B vitamin our body can store. The average adult body contains 2 to 5 1ng of vitamin B₁₂ with 80 percent of this stored in the liver.