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19 Cards in this Set
- Front
- Back
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1. What is a nucleoside?
What is a nucleotide? |
Sugar + N base
Sugear + N base + Phosphate |
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2. Which bases are purines?
Which are pyrimidines? |
Adenine and Guanine
Cytosine and Thymine (Uracil) |
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3. Which AA contribute to form purines?
What else contributes to purines other than AA? |
1. Glycine
2. Glutamine (2) 3. Aspartate (provide N) FH4-C1 *comes from Ser and Gly |
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4. How do humans synthesize all purine and pyrimidines?
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De novo synthesis
Made from scratch using AA atoms as nucleotides |
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5. In de novo purine synthesis what is necessary to begin with?
What is this? What is the rate limiting step in de novo purine synthesis |
PRPP
Activated ribose 5-P that is the donor molecule PRPP synthase is rate limiting and controlled step |
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6. What is the first step in purine synthesis?
What is the enzyme used? |
Ribose 5-P --> PRPP
Use PRPP synthetase Also use 1 ATP |
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7. What is the pathway of de novo purine synthesis?
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1. Glutamine+ PRPP
2. Add glycine 3. FH4-C1 (add twice) 4. Glutamine 5. Asp (add N) 6. IMP |
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8. From IMP what happens?
What is a typically pathway from here? |
Form GMP and AMP
GMP ---> GDP (kinase) Then both 1. GDP --> GTP --> RNA 2. GDP --> dGDP --> dGTP --> DNA |
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9. Where did the FH4-C1 atoms come from?
What is the link between RNA and DNA? |
Either Ser or Gly
NDPs ***Only take NDPs to dNDPs which make DNA |
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10. What two AA are used in de novo pyrimidine synthesis?
What happens first in de novo pyrimidine synthesis? What enzyme is used? |
Aspartate (Asp) and Glutamine (Gln)
Gln + CO2 + 2ATP --> CP + Asp (CP = carbomyl phosphate) CPS II ( |
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11. What happens next?
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CP + Asp --> UMP
UMP --> UDP --> UTP --> RNA |
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12. What happens that is confusing in the de novo synthesis of pyrimidine?
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From UTP form CTP to form CDP
**only diphosphates can be made into deoxy riboses Eventually form dUMP --> dTMP to DNA |
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13. What is necessary to make dTMP?
What make NDP's and NTP's from NMP's? What makes dNDP's from NDP's? |
FH4-C1 (from Ser or Gly)
Kinases **kinase specificity is essential Ribonucleotide reductase |
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14. How are nucleobases salvaged or scavenged?
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1. Break down DNA
2. Free bases + PRPP 3. Form NMP |
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15. How is Xanthine formed?
Two ways.... |
1. From HX (hypoxanthine)
-use xanthine oxidase or 2. From Guanine (purine degradation) |
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16. What happens to xanthine when it is formed?
What can accumulation of this cause? |
Form uric acid
It's insoluble so it precipitates in joints and can cause gout |
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17. What do tumor and infection drug aim to do?
What do anticancer-anti-inflammatory drugs such as methotrexate target? |
Inhibit nucleotide formation or use nucleotide synthetic enzymes to make a toxic product
DHFR (dihydrofolate reductase) **inhibit nucleotide formation |
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18. How is the carbamoyl phosphate formed in de novo pyrmidine synthesis different from that formed in urea cycle?
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This CP is cytoplasmic and derived from glutamine
NOT derived from ammonia |
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19. How is CPS II in pyrimidine synthesis different from CPS I in the urea cycle?
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1. Cytoplasmic
2. Stimulated by PRPP 3. Inhibited by UTP |
