purine synthesis.txt

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Author:
kepling
ID:
43528
Filename:
purine synthesis.txt
Updated:
2010-10-21 15:27:40
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Purine synthesis
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Purine Synthesis
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  1. What is the counterion available when phosphate groups are added to nucleosides to make nucleotides?
    Mg2+
  2. What is one nucleoside that can be used in its nucleoside form and for what?
    • Adenosine = promote sleepiness
    • Adenosine receptors blocked by caffeine
  3. What do the terms -bis or -tris refer to?
    Phosphate groups being attached at different carbons on the nucleotide ring instead of to one another (that would be -di or -tri)
  4. What are the 6 functions of nucleotides? PESICR
    • 1) Precursor nucleic acids
    • 2) Energy currency (ATP, GTP)
    • 3) Second messengers (cAMP)
    • 4) Intermediates (UDP-)
    • 5) Cofactors (NAD, FAD, SAMe, CoA)
    • 6) Ribozymes
  5. What is required for formation of IMP (other than PRPP and Glutamine-PRPP)?
    • 1) 6 ATP
    • 2) Tetrahydrofolate
  6. What supplies energy to form AMP from IMP?
    GTP
  7. What supplies energy for GMP from IMP?
    ATP
  8. What percentage of purines are salvaged (recycled)?
    90%
  9. Why is the salvage pathway so important (2 reasons)?
    • 1) No ATP involved
    • 2) Faster (1 step compared to 12 for de novo synthesis)
  10. What pathway forms urea?
    Amino acid catabolism
  11. What pathway forms uric acid?
    Purine degradation
  12. What percentage of purines are degraded to uric acid?
    10% (since 90% are salvaged)
  13. What will happen to uric acid production if the purine salvage pathway drops to 70%?
    Purine degradation will rise to 30% b/c of de novo synthesis

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