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Cards In This Set
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Which base is the substrate for the reaction that produces uric acid in purine degradation.
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Xanthine
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In the nucleotide form which base is the first purine formed in the de novo biosynthetic pathway.
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IMP
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Which base is formed by de novo synthesis attached only to a dexoyribose, not to a ribose sugar?
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Thymine
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In the nucleoside triphosphate form, which base feedback inhibits the control step in pyrimidine biosynthesis?
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CTP
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Are substrates for the control step in purine biosynthesis?
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PRPP, Gln
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The enzyme used to catalyze the conversion of dUDP to dUTP has specificity for which features of the nucleotide substrate:
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The number of phosphates, but neither the base nor the sugar.
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Which statement about ribonucleotide reductase is false?
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Its enzyme activity is stimulated by ATP and inhibited by TTP.
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Which can function as a substrate for ribonucleotide reductase?
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UDP
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Which is a product of thymidylate synthase?
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DTMP
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Statements concerning allopurinol...
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A. Allopurinol is a structural analog of the base hypoxanthine and is used to reduce body urate levels. b. Allopurinol (or its metabolite) irreversibly inhibits xanthine oxidase. c. Allopurinol can be converted to the nucleoside monophosphate form by orotate phosphoribosyl transferase. d. Allopurinol in the nucleoside monophosphate form can inhibit the control step in de novo purine biosynthesis.
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Adenosine deaminase
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May use either adenosine or deoxyadenosine as a substrate.
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All of the following statements concerning the structure of ribonucleotide reductase are true except for which one?
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For the enzyme to be active, the two sulfur atoms in the active site must be in a disulfide bond form.
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Production of which of the following deoxynucleotides would be least affected by the influences of methotrexate?
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DCDP, dUDP
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Several enzymes involved in normal pyrimidine nucleotide biosynthesis and/or salvage are needed for the successful use of the chemotherapy agent 5-FU. Which of the following sets of enzymes are most important in this metabolic activation?
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OPRTase, RiboRtase
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Which of the following oral drug combinations might be useful in increasing the uptake of 5-FU into the blood stream as an intact drug/prodrug?
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5FU + CDMP (CDHP?)
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