Folate, Vitamin B12, and Anaemia Flashcards
What is vitamin B12 needed for?
Nuclear maturation. (It is essential as a cofactor for DNA and cell metabolism)
Where is vitB12 absorbed?
ileum (requires intrinsic factor)
Where do we get vitB12 for?
animal products
What kind of anaemia is caused by vitB12 and folate deficiency?
macrocytic anaemia
What reactions need vitB12?
Conversion of homocysteine to methionine which is important for methylation of DNA, RNA and proteins
Convert Methylmalonyl CoA to Succinyl CoA (important for breakdown of fatty acids and production of energy)
Why is DNA methylation so important?
It is a part of the synthesis of new DNA
How much vitB12 do we need each day?
1 microgram
How much vitB12 does Western diet contain?
10 - 15 micrograms/day
How much vitB12 does the human body store?
2 - 4 micrograms in the liver and this is sufficient for 3 - 4 years without further supply
What does the long storage time mean?
Deficient intake may take years to manifest
How is vitB12 detatched from the carrier protein in the meat consumed?
The acidic environment of the stomach
What is vitB12 bound to before being absorbed?
R-binder in the stomach then it passes into duodenum and pH change causes it’s release from R-binder
At duodenum intrinsic factor then binds to the vitB12
Where is intrinsic factor produced?
Parietal cells of the gastric mucosa
Where is the vitB12-intrinsic factor complex absorbed?
At the ileum where there is cubulin/amnion protein
What does vitB12 bind to in the ileum?
cubulin/amnion receptor
What does vitB12 bind to after passing through the wall of the ileum? Why?
Transcobalamine (TcI and TcII) which transport vitB12 to the liver
Which Tc receptor can bind to receptors in organs?
TcII (this is where vitB12 is said to be active)
What happens to vitB12 attached to TcI?
It is inactive
What causes vitB12 deficiency?
Vegans: no animal products in diet
Infants born to B12-deficient mothers and breasfed
Malabsorption problems (gastric causes (gastrectomy), intestinal causes (defects of the ileum), or crohn’s disease, or bacterial overgrowth)
What is pernicious anaemia?
Autoimmune gastritis resulting in reduced intrinsic factor secretion.
Whenever someone has vitB12 deficiency they are automatically tested for autoimmune antibodies
Who’s most likely to have pernicious anaemia?
Females and elderly
Someone with family history of autoimmune diseases