B12

Question 1

B12 can also function as

Answer 1

Methylcobalamin

Question 2

What’s an indicator of B12 deficiency

Answer 2

High levels of methylmalonic acid

Question 3

Enterohepatic circulation of B12 function

Answer 3

Creates 3-8ug of B12 which can bind to IF and be reabsorbed

Question 4

Why does a B12 deficiency develop more rapidly in individuals who malabsorb vs vegetarians

Answer 4

Cannot absorb B12, so stores are depleted

Question 5

What is required for the enzyme methylmalonyl CoA mutase

Answer 5

Adenosylcobalamin x2

Question 6

B12 functions mainly in what two forms

Answer 6

Adenosylcobalamin

Methylcobalamin

Question 7

3 Function of methylmalonyl CoA mutase

Answer 7

Conversion of methylmalonyl CoA to succinyl CoA

Oxidation of odd chain FA

Catabolism of ketogenic AA

Question 8

Explain 5 steps of B12 absorption

Answer 8

B12 is released from food

Binds to R proteins in saliva and gastric juice

In the small intestine R protein is digested to release B12

B12 binds to Intrinsic factor in small intestine

B12-IF complex binds to enterocyte receptors (cubulin) and gets internalized