Vit B12

Here are some high yield facts about vitamin B12.

• Only water soluble vitamin stored in the body.  (other only's of special mention)

•  Contains 2 C - Cobalt and Corrin ring  (other rings of biochemical importance) 

• Present only in foods of animal origin (Curd is of animal origin!) So, pure vegans are prone to B12 defeciency (think of Gandhi)

 Though Intrinsic factor of castle is secreted by parietal cells of stomach, it can not bind to   B12  in the stomach. Why ?   B12  in the food is released by gastric juice and  B12 binds to cobalophilin, a salivary protein. In the duodenum, cobalophilin is hydrolysed --> IF binds to   B12 . Both gets absorbed in distal ileum.  

•  Co-enzyme for 3 enzymes in the body - 1) Methyl malonyl CoA mutase 2)Methionine synthase  3) Leucine aminomutase.  (other 3's and 4's with exam point of view) 

• Deficiency results in methyl malonyl  aciduria  (Xanthurenic acid - B6; FIGLU - folate)

•  Folate is trapped in the form of  methyl THFA in B12  defeciency. 

• Megaloblasts are NOT seen in peripheral smears. seen in bone marrow examination. You can see macrocytes in peripheral smear. 

•  Cyanocobalamin is the synthetic form found in vitamin tablets. It releases negligible amounts of cyanide in the body.

I hope you know everything about pernecious anemia, blind loop syndrome etc.,

Injection  B12 is given for patients with diabetic neuropathy as it is important of myelin synthesis.

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