Term
| What are the biological function of nucleotides? |
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Definition
1. Energy Metabolism - ATP synthesis
2. Information - DNA and RNA subunits
3. Physiological Mediators - cAMP, cGMP
4. Compoenents of coenzymes
5. Intermediates for small molecule group transfer
6. Allosteric effectors that bind to enzymes |
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Term
| What are the three components of a nucleotide? |
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Definition
1. Nitrogenous base - purine or pyrimidine
2. Ribose or Deoxyribose sugar
3. Phosphate (that makes them acidic and negatively charged) |
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Term
| What two organic components are the functional groups of nucleotides and where are they located on the compounds? What is the exception to this rule? |
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Definition
1. amino or a carbonyl group
2. 12 oclock and 8 oclock positions
3. The exception is a 2 oclock methyl group that differentiates thymine from uracil |
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Term
| What is the difference between a nucleoside and a nucleotide? |
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Definition
Nucleoside = nitrogenous base + sugar
Nucleotide = nitrogenous base + sugar + phosphate |
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Term
| What is the difference between a ribose and a deoxyribos sugar backbone? |
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Definition
| Ribose sugars have a hydroxyl group on the 2 carbon, deoxy sugars dont |
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Term
| What are the two types of synthesis of nucleotides? |
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Definition
1. De novo - assembly from small building blocks
2. Salvage - intact bases put on a sugar phosphate
Note: Salvage is energy preferable, but different tissues use different pathways |
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Term
| What role does PRPP Synthetase play in nucleotide synthesis? |
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Definition
| It takes the Hydroxyl group off of the 1 carbon in ribose sugars and replaces it with 2 phosphates strung together, which is a preferable leaving group for later reactions |
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Term
| What is the major donator of nitrogen to purine rings? |
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Definition
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Term
| What is the process by which purines are de novo synthesized? What is the rate limiting, regulating, and committed step? What is the intermediate? What is the branch point? Where does this all take place? |
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Definition
1. Synthesis takes place by taking the activated sugar PRPP and adding glutamines side chain nitrogen by use of amido transferase, then single carbon and single nitrogen are added, many steps and you arrive at Inosine monophosphate
2. The addition of glutamine's nitrogen to PRPP is the rate limiting, committed, and regulated step
3. The intermedaite is IMP
4. IMP is the branch point that can go to either AMP or GMP
5. This all takes place in the cytoplasm |
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Term
| Describe the regulation of de novo synthesis of purines |
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Definition
1. Product inhibition: GMP and AMP inhibit IMP, IMP inhibits PRPP conversion
2. Feedback inhibition: GMP and AMP inhibit PRPP conversion
3. Increased PRPP leads to more conversion to nucleotides |
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Term
| Describe the de novo synthesis of pyrimidines. What part of this happens in the mitochondrion? |
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Definition
1. Amide from glutamine, single carbon source, energy (ATP) and carbamoyl phosphate synthase II make carbamoyl phosphate
2. This reacts with aspartate to make N-Carbamoyl aspartate
3. Ring closes yielding orotic acid
4. Orotic acid is put on sugar phosphate PRPP to give OMP
5. OMP is decarboxylated to give UMP
The closing of the ring and formation of double bond happen in the mitochondrion |
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Term
| How is CTP made from UTP? |
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Definition
| Substitution of an amino group for a carbonyl group at the 12 oclock position |
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Term
| How are tri phosphates formed from mono phosphates? |
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Definition
| Transfer of phosphate groups from ATP |
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Term
| What is the rate limiting and regulated step in pyrimidine synthesis? |
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Definition
| Conversion of glutamine and HCO3 to carbamoyl phosphate by CPSII |
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Term
| Describe the feedback of the pyrimidine synthesis pathway |
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Definition
| UTP and CTP inhibit the activity of carbamoyl phosphate synthase II |
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Term
| What enzyme makes deoxy sugars from ribose sugars? |
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Definition
| Ribonucleoside diphosphate reductase |
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Term
| How is TMP made from dUMP? |
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Definition
| Addition of a methyl group by thymidylate synthase |
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Term
| Describe the process of breaking down purines? |
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Definition
1. Nucleic acids are broken down to nucleotides
2. Nucleotides lose their phosphates and become nucleosides
3. Nucleosides lose their nitrogens on the ring
4. Sugars are chopped off by a phosphate |
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Term
| What problems arise from an incrase in uric acid concentration? |
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Definition
| Stones forming in the kidney and it can lead to gout |
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Term
| What steps in pyrimidine degradation are the same as purines? which are different? |
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Definition
The breakdown to the bases is the same (acid->nucleotide->nucleoside->lose nitrogen->sugar chopped by phosphate)
The bases, however can undergo further degradation |
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