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5 Written questions

5 Matching questions

  1. Biochemical Consequenses of ADA deficiency
  2. Why IMP to AMP uses GTP
  3. how 5 fluorouracil FUra works
  4. Sixth step OMP decarboxylase
  5. Second Step in Pyrimidine biosynth ATCase
  1. a Removes CO2 and forms Uracil base on ribose P, UMP from OMP
  2. b ADA deficiency causes abnormal build up of Deoxyadenosine containing nucleotides including dATP

    dATP feedback inhibits ribonucleotide reductase, allosterically choking off production of other dNTPs

    Lack of dNTPs prevents DNA synthesis preventing proliferation of lymphocytes.
  3. c this is a way to use biofeedback high GTP means AMP should be formed Low GTP means GMP should be formed
  4. d it is similar to dUMP and acts as a suicide inhibitor or thymidylate synthetase TS. This kill rapidly dividing cells Tumors and immune cells
  5. e Committed Step, and an allosteric enzyme

    Using Aspartate Transcarbamoylase, ATCase takes Carbamoyl Phosphate to N-carbamoyl aspartate adding aspartate

5 Multiple choice questions

  1. 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
  2. this is a way to use biofeedback high ATP means GMP should be formed Low ATP means ATP should be formed
  3. OPRT takes orotate and PRPP and adds ribose P to make OMP
  4. Allopurinol is a suicide inhibitor of xanthine oxidase, because it is similar in configuration to hypoxanthine and it binds tightly to molybdenum in xanthine oxidase.

    Xanthine oxidase takes Hypoxanthine to xanthine and xanthine to uric acid
  5. Ring closure no ATP

    Forms Di hydroorotase

    after NAD+ forms to orotate

5 True/False questions

  1. Results of tx with allopurinalammonia 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.


  2. Glutamine PRPP amido transferaseThe most important step, most difficult thermodynamically, and committed step.

    goes from PRPP to PRA

    Takes nitrogen from Glutamine and places on ribose with a PPi leaving group and Glucose formed


  3. First Step in Pyrimidine biosynth CPS IIusing Carbamoyl phosphate synthetase II, CPS II takes CO2 and Glutamine to Carbamoyl phosphate using 2 ATP

    In mitochondria CPS I uses NH4+ as a nitrogen source, this is part of the urea cycle


  4. Phophoribosyl transferases PRTsUsed for salvage

    Hypoxanthine Guanine PRT or HGPRT catalyzes 2 rxns

    PRPP and hypoxanthine to IMP plus PPi

    or PRPP plus Guanine to GMP plus PPi

    Adenine PRT , APRT

    PRPP plus adenine to AMP plus PPi.


  5. Pyrimidine Synthesis Differences from PurinesIMP uses Aspartate and GTP to add N in place of carboxyl O at top

    Fumarate leaves leaving just NH2 and AMP is formed


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