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5 Written questions

5 Matching questions

  1. Why IMP to AMP uses GTP
  2. Important Enzymes in Pyrimidine Biosynth
  3. Why allopurinal decreases rate of purine biosynthesis
  4. Prokaryotic Regulation of Pyrimidine Biosynth
  5. Other drugs related to nucleotides and nucleotide metabolism
  1. a CTP inhibits the action of ATCase the committed step and addition of aspartate to carbamoyl P

    and UMP inhibits the action of CPSII the first step and formation of Carbamoyl p
  2. b this is a way to use biofeedback high GTP means AMP should be formed Low GTP means GMP should be formed
  3. c CPS II = takes CO2 and Gln to Carbamoyl P
    ATCase, committed step = take Carbamoyl P and Aspartate to N-Carbamoyl aspartate
    CTPS = takes UTP to CTP
  4. d Antivirals, acyclovir, Arabinosyladenine araA, for HSV and herpes related viral encephalitis
    Anti retrovirals, AZT, DDC, ddI for HIV
    Anti neoplastics, arabinosylcytosine araC
    Anti Leukemics, 6 mercaptopurin, 6 thiaguanine
  5. e It lowers the PRPP pool by binding and using HGPRT to form an allopurinol ribonucleotide

    This inhibits the action of glutamine PRPP amidotransferase

    and Thus there is less flux through the de novo purine pathway

5 Multiple choice questions

  1. AZT, DDC, ddI
    Used to treat HIV and AIDS
    Triphosphates inhibit retroviral reverse transcriptase
  2. ATP and GTP allosterically inhibit formation of PRPP from pentose phosphate pathway

    IMP, AMP and GMP allosterically inhibit PRPP amidotransferase, the committed step of the pathway with adds a N from Glutamine to PRPP

    AMP and GMP allosterically inhibit the first step in their own formation from IMP

    ATP and GTP are require for each others formation a non-allosteric type of biofeedback
  3. ammonia toxicity
    Ornithine transcarbamoylase def
    in both cases carbamoyl P accumulated in liver mitochondria, which enters cytoplasm, which drives overproduction of orotate via the pyrimidine biosynthesis pathway.
  4. this is a way to use biofeedback high ATP means GMP should be formed Low ATP means ATP should be formed
  5. Ring closure no ATP

    Forms Di hydroorotase

    after NAD+ forms to orotate

5 True/False questions

  1. How Methotrexate Mtx anti folate worksrather than directly inhibiting Thymidylate Synthetase TS is inhibits the cyclical production of the methyl donor N5N10 methylene THF

    It does this by inhibiting the enzyme DHFR dihydrofolate reductase. Stopping the reduction of Dihydrofolate to THF, which is a needed substrate for N5N10 methylene THF


  2. Primary Genetic basis of GoutStarting point with PRPP, and activated ribose

    Purine ring is built up step by step while attached to ribose sugar

    forming IMP a nucleotide intermediate that can form either AMP or GMP


  3. 7th step addition of two phosphates to UMPIMP uses Aspartate and GTP to add N in place of carboxyl O at top

    Fumarate leaves leaving just NH2 and AMP is formed


  4. Common threadElevated levels of Uric Acid, chronic elevation of blood uric acid, hyperuricemia from xanthine overproduction and formation of uric acid

    Also called Gouty arthritis and uric acid nephrophathy

    Uric acid has limited water solubility and precipitates under acidic conditions like collecting ducts eg kidney stones, a can lead to sodium urate that is most likely to precipitate at neutral pH synovial fluid of jointe eg gouty arthritis


  5. Defects in Pyrimidine BiosynthesisOPRT takes orotate and PRPP and adds ribose P to make OMP