Lecture 10 Flashcards
What is another name for Vitamin B12?
Cobalamin
What is the structure of cobalamin?
- Consists of a Corrinoid ring (4 pyrrole rings)
- Cobalt atom in the middle
Describe how B12 and folate work together
B12 and folate work synergistically in the methylation pathway. B12 (coenzyme) helps attachment of methyl group. Allows conversion of homocysteine to methionine and back. In cells, folate is trapped in its inactive form. To activate folate, vitamin B12 removes and keeps the methyl group, which activates B12. Both the folate coenzyme and the vitamin B12 coenzyme are now active and available for DNA synthesis.
What are the dietary sources of vitamin B12?
Milk products, eggs, animal flesh, shellfish, fortified grain
What makes Vitamin B12?
Bacteria
What is the RDI for B12?
2.4 micrograms per day
Why are such small amounts of B12 needed?
Because it is stored in the liver for about 7 years.
What does B12 deficiency have a similar blood film to?
Folate deficiency
What does B12 deficiency lead to?
- Megaloblastic/macrocytic anaemia: enlarged RBC’s irregular due to poor production of DNA
- Neuropathy: sub-acute combined degeneration of the spinal cord. Not seen in folate deficiency.
What leads to microcytic anaemia?
Iron deficiency
Give an example of a malabsorption syndromes of B12. What is it usually treated with?
Pernicious anaemia
Treated with intra-muscular injections
What does a low haemoglobin level indicate?
Anaemia
What does elevated mean cell volume indicate?
Macrocytic anaemia (B12 or folate deficiency
What can reticulocyte numbers increase in response to? If the numbers are low, what does this imply?
Reticulocytes can increase in response to anaemia because the body responds to low blood count by producing more reticulocytes. If low, implies that the bone marrow is unable to respond to the usual stimulus of anaemia.
Describe the blood film of a person wth B12 deficiency
Hypersegmented neutrophils present