Vitamins Flashcards
What is the function of tetrahydrofolate?
Tetrahydrofolate receives one-carbon fragments from donors such as serine, glycine, and histidine and transfers them to intermediates in the synthesis of amino acids, purines, and thymine monophosphate (TMP).
Vitamin B-12 (Cobalamin) is required for two enzymatic reactions, which are?
The remethylation of homocysteine to methionine (done by methionine synthase) and the isomerization of methylmalonyl CoA.
How is B-12 synthesized?
B-12 (Cobalamin) is synthesized only by microorganisms; it is not present in plants. Animals obtain the vitamin preformed from their natural bacterial flora or by eating food derived from other animals. Cobalamin is present in appreciable amounts in liver, whole mils, eggs, oysters, fresh shrimp, pork, and chicken.
How Vitamin B-12 causes symptoms of megaloblastic anemia?
In vitamin B12 deficiency , the utilization of N5-methul form of tetrahydrofolate is impaired. Because the methylated form cannot be converted directly to to other forms of tetrahydrofolate, folate is trapped in the N5-methyl form, which accumulates.
The levels of other forms decreases, thus colabamin deficiency is hypothesized to lead to a deficiency of the tertrahydrofolate forms needed in purine andTMP synthesis, resulting in the symptoms of megaloblastic anemia.
