Lecture #18 - Cobalamin (Vitamin B12) Flashcards
What are the five groups attached to the Cobalt atom in Vitamin B12?
1.Cyanocobalamin
2. Hydroxycobalamin
3. Aquo- or hydrocobalamin
4. 5’-deoxyadenosylcobalamin
5. Methylcobalamin
Which forms of Vitamin B12 are active as coenzymes in humans?
Only 5’-deoxyadenosylcobalamin and methylcobalamin are active as coenzymes in humans
what is the name of the nucleus that forms Cobalamin (Vitamin B12)
Formed by corrin nucleus with the cobalt atom in the centre and the whole structure is built around this
Structure in DOCS
How is Vitamin B12 absorbed in the body?
- Must be released from proteins
- protected from acid degradation in the stomach and bacterial usage by binding to protein R
3.freed in the small intestine
4.binds to intrinsic factor for absorption.
Humans lacking IF have very low ability to absorb vitamin B12 and excrete all of it in the feces, as opposed to 30-60% of fecal excretion in persons with adequate IF. TRUE or FALSE
TRUE
Can Vitamin B12 be stored in the body?
Vitamin B12, unlike other water-soluble vitamins, can be stored in the body for years and signs of deficiency can take a long time (3-5 years) to manifest
what organ in the body contains the largest amount of stored vitamin B12
The liver contains the largest amount of stored vitamin B12 in the body (~50% of the total)
where is Vitamin B12 exclusively found
Exclusive in animal products
What are the physiological roles of Vitamin B12?
- Coenzyme in converting homocysteine to methionine
- synthesis and degradation of amino acids
- important for DNA synthesis and cell differentiation.
what can the absence of vitamin B12 cause
In the absence of vitamin B12, there is a delay or failure of normal cell division and arrested DNA synthesis leading to the formation of enlarged cells (megaloblastic anemia)
