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5 Written questions

5 Matching questions

  1. Second Step in Pyrimidine biosynth ATCase
  2. Other drugs related to nucleotides and nucleotide metabolism
  3. Anti virals, Acyclovir, AraA
  4. Purine Biosynthesis IMP to GMP
  5. Lesch-Nyhan Syndrome
  1. a IMP uses NAD+ and H20 to oxidize and add carboxyl O to bottom left carbon making base xanthine

    Glutamine and ATP needed to replace carboxyl O with N. Forming GMP
  2. b Signs and Symptoms young with hematuria, megaloblastic anemia, hyperuricemia, crystals in urine, mental retardation, decreased gross motor function, and self mutilation, gout in early 20s

    is a Rare X linked disorder 1/400000 males, milder form = 8% kelly-seegmiller syndrome

    Cause = near total deficiency of HGPRT about 2% of activity

    biochemical consequenses
    Overproduction or urate
    Elevated PRPP concentrations
    Marked increase in rate of de novo purine biosynth
  3. c Committed Step, and an allosteric enzyme

    Using Aspartate Transcarbamoylase, ATCase takes Carbamoyl Phosphate to N-carbamoyl aspartate adding aspartate
  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 Acyclovir, used to treat HSV infections, and is converted to triphosphate by enzymes including a viral nucleoside kinase with broad substrate specificity, and interferes with DNA synthesis in infected cells

    AraA tx for herpes related viral encephalitis. this is converted to triphosphates interferes with DNA synthesis, and is deaminated rapidly in vivo by ADA so is sometimes administered with a ADA inhibitor

5 Multiple choice questions

  1. UMP plus two ATP becomes UTP
  2. this is a way to use biofeedback high GTP means AMP should be formed Low GTP means GMP should be formed
  3. CTP synthetase takes Nitrogen from Glutamine and ATP and makes CTP the base Cytosine with ribose and three phosphates.
  4. some discussed earlier
    araC, triphosphate interferes with DNA synthesis
  5. high conc of dATP stops the enzyme and other dNTPs are not made

5 True/False questions

  1. Anti Leukemics6 mercaptopurine
    6 thiaguanine
    These compounds compete with hypoxanthine and guanine for the salvage enzyme HGPRT.
    They are converted by HGPRT into respective ribonucleotides, they inhibit the committed step of de novo purine biosynthesis pathway catalyzed by Gln PRPP amidotransferase, an effect similar to allopurinol
    They are also incorporated into DNA and RNA


  2. Nucleoside PhosphorylasesClinical use of nucleotide analogs usually is restricted to bases and nucleoside since phosphorylated nucleotides are poorly transported into cells

    They rely on tricking cellular or viral enzymes into phosphorylating nucleosides into metabolically active nucleotide forms, or converting bases into nucleotides vis salvage pathways


  3. Other causes of mild orotic aciduriaammonia 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. Purine biosynthesis IMP to AMPIMP uses Aspartate and GTP to add N in place of carboxyl O at top

    Fumarate leaves leaving just NH2 and AMP is formed


  5. Defects in Pyrimidine BiosynthesisFamilial Orotic Aciduria are inherited deficincies in orotate phosphoribosyltrandferase OPRT and or OMP decarboxylase

    These slow the formation of OMP from orotate, and UMP from OMP.

    Signs and symptomes are growth retardation, megaloblastic anemia, crystalline orotate in urine

    Tx effectively by large doses of orally administered uridine


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