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21 Cards in this Set
- Front
- Back
Relationship between B12 and Folate
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B12 deficiency leads to folate deficiency
B12 deficiency leads to increased folate derivatives |
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Megaloblastic anemia (re: B12 and folate)
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Caused by either B12 or folate deficiency
Reversed by large doses of folate (if caused by B12 deficiency) |
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Neurological symptoms (re: B12 and folate)
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B12 causes them, but not seen in patients with folate deficiency
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Megaloblastic anemia (signs)
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Low red blood cells
Large blood cell precursors (starting building up for division, but couldn't divide) Lots of RNA in precursor cells |
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Pernicious anemia
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Caused by B12 deficiency
Megaloblastic anemia with neurological signs (starts with sensory and then progresses to motor control) |
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Folates (use in cells)
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Used to transfer methyl groups
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THF
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Central intermediate in folate cycle
Folate derivative (tetrahydrofolate) N5 or N10 are the places that a methyl group is added |
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B12 and folate (interaction)
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B12 is used to convert N5-methyl-THF to THF
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Dihydrofolate reductase
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Reduces DHF to THF to allow it to enter the folate cycle again
DHF is produced in dUMP to dTMP |
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dUMP to dTMP
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Necessary for DNA synthesis
THF to DHF accomplishes the conversion |
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Sulfa drugs (re: folate)
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Antibiotics that stop synthesis of folate in bacteria
Don't affect humans, because we eat, rather than make, folate Increase oxidative stress |
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Anti-tumor drugs
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Starve tumors of folates (can't reproduce)
Methotrexate and aminopterin |
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Leucovorin rescue
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Give N5-THF
Solves problem of not working DHF reductase (from methotrexate) |
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Methotrexate
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Binds to DHF reductase
Starves cells of folates Normal cells aren't as affected, because they aren't dividing as much |
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SAM (synthesis)
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From ATP and methionine
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SAM and Folate
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After SAM transfers a methyl group somewhere, it needs to resynthesize methionine
N5-THF gives the methyl group to do that Converts N5-THF into THF; uses a B12 derivative to do so |
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B12 (structure)
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Have a cobalt and similar to hemoglobin (without Fe)
Also called cobalin |
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Cbl-IF
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Intrinsic factor is needed to absorb the vitamin in the ileum
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N2O and B12
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Nitrous oxide can oxidizes Cobalt to an unusable state
Can lead to B12 deficiency |
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B12 reactions
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Conversion of homocysteine to methionine (the one that uses N5-THF)
Conversion of malonyl-CoA to succinyl-CoA |
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Neurologic problems from B12
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No conversion of malonyl-coa to succinyl-coa
Leads to weird myelin |