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19 Cards in this Set
- Front
- Back
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What does THF do?
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It acts as a carrier of one-carbon units (e.g. formaldehyde, formate) in a variety of metabolic reactions.
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List the forms of THF.
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1. N10-formyl-THF
2. N5,N10-methylene -THF 3. N5-formimino-THF 4. Dihydrofolate 5. N5, methyl-THF |
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What is the only way to convert N5-methyl-THF to a more convenient form?
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The methionine synthase reaction.
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What is the methyl folate trap?
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A vitamin B12 deficiency will lead to a build up of N5-methyl-THF, leading to a shortage of other forms of folate and subsequent impairment in processes in which they are involved.
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What is N10-formyl-THF involved in?
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Purine biosynthesis; contributes C2 and C8 of the purine ring.
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What is N5,N10-methylene-THF involved in?
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Thymidylate synthase; it methylates dUMP to yield thymidylate.
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Of what are the sulfonamides analogs?
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They are analogs of p-aminobenzoic acid (PABA)
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What is the mechanism of the sulfonamides?
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The drug inhibits dihydropteroate synthetase which is a bacterial enzyme that synthesizes folic acid, thus making these and other compounds that inhibit bacterial folate synthesis excellent antibiotics.
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How are the fates of homocysteine, folate, and methionene linked?
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They are linked in one-carbon metabolism, and with the help of vitamins B6 and B12 participate in a cycle that continually produces donors of one-carbon units for use in essential biochemical reactions.
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How does a folic acid defiency manifest itself?
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it is manifested as megaloblastic anemia, whih is the insufficient generation of mature red blood cells.
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How is megaloblastic anemia treated?
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it is treated with vitamin B12 and folate
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a genetic defect in N5, N10-methylene-THF reductase can lead to ?.
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Hyperhomocyteinemia.
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What is the universal methyl donor?
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S-adenosylmethionine
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What are the three main one-carbon donors?
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THF, biotiin (CO2), and SAM (S-adenosylmethionine)
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Levels of ? in the blood mirror the efficiency of ? and is now used as a useful diagnostic target for a variety of disorders associated with methylation.
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Homocysteine, one-carbon metabolism
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Defects in which enzyme cause homocysteinuria?
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cystathione-β-synthetase
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Homocystein's reactive thiol group could lead to ?.
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Protein degradation
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What is another route for homocysteine toxicity?
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A descrease in the availability of (SAM)
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What are the effects of decrease SAM levels?
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it can cause hypomethylation and subsequent defects in gene expression, maintenance of DNA integrity and stability, mRNA processing, etc.
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