Vitamin B12 & Folate Flashcards
What synthesises B12?
- bacteria
How do humans obtain B12?
- through diet
- daily amount in mixed diet = 5ug
What does Vitamin B12 bind to ?
- 2 plasma transcobalamins
- TC I = increase affintiy for B12
- TC II= readily gives B12 to the tissues
Where is B12 stored?
-in the liver = plentiful supplies 3-5 mgs
- 2+ year supply
What is the loss rate of B12?
- rate of loss = 0.05-0.1% of body stores lost per day
What is the adult requirement for folate ?
100-200 ug/daily
Describe Folate
- found in foods of both plant & animal origin
- western diet = 400ug of folate
How does folate exist in the diet ?
Polyglutamate form
- in the intestine this is converted to monoglutamate by conjugase enzyme
What can cause a Vit B12 deficiency ?
inadequate intake - veganism
What can cause inadequate absorption of B12?
- gastrectomy
- gastric dysfunction
What can occur from diversion of Vit B12?
- abnormal intestinal bacterial flora
- intestinal strictures
- stagnant loops
What are some symtpons of Vit B12 deficiency?
- lethargy
- beefy tongue
- pins & needles –> neurological problems
What can cause a deficiency of folates?
- inadequate dietary intake
- malabsorption –> coeliac disease
- increased requirements -> pregnancy, preemies & malignant diseases
What are the 2 function forms of Vit B12?
- Methyl cobalamin
- Adenosyl cobalamin
What are Vit B12 & folate required for ?
- Thymidine synthesis
- if there is a deficiency of either then uracil is incorporated into replicating DNA instead of thymidine - this has to be repaired
- slows down maturation time of red cells
What are Megaloblasts ?
Giant precursors of red cells in bone marrow open stippled chromatin
