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23 Cards in this Set
- Front
- Back
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What is the fundamental process of information transfer in cells? |
The use of DNA and RNA. |
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What are the two ring systems used in nucleotides? What are the sizes of the rings? |
Pyrimidine: 6 member ring Purine: 6 member ring and 5 member ring. |
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Which nucleotides come from the pyrimidine rings? |
Cytosine, Uracil, Thymine |
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Which nucleotides come from the purine rings? |
Adenine and Guanine. |
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What is the difference between a nucleoside and a nucleotide? |
Nucleoside: Base + Sugar Nucleotide: Base + Sugar + Phosphate |
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What are the components of a nucleotide? |
The purine or pyrimidine base linked to a ribose or de-oxy ribose sugar with a phosphate group attached to the sugar. |
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What are the 2 pathways to build nucleotides? |
The De novo pathway and the Salvage pathway. |
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What are the main ideas behind the de novo pathway? |
1. begins with metabolic precursors (aa's, ribose 5 phosphate, and CO2) 2. The free bases (A, T, G, C, and U) aren't intermediates. 3. Present and identical in nearly all living organisms. |
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What are the main ideas behind the salvage pathway? |
1. The free bases and nucleosides released from nucleic acid breakdown are recycled. 2. The free bases (A, T, G, C, and U) are intermediates. |
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What are the sources of the atoms in the Purine ring? |
Aspartate, CO2, Glycine, Formate, and the Amide N of glutamine. |
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Which step is the committed step of purine de novo synthesis? What happens? |
Step 2: The acquisition of purine atom N9 and the synthesis of 5-phospho-beta-D-ribosylamine with the enzyme Glutamine PRPP amidotransferase. |
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What is a committed step and why is it important? |
It is an effectively irreversible reaction in the biosynthesis pathway that will lead to the continuation of the process. It is important to know because it is a good site for inhibitors/drugs. |
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What is the main enzyme to be regulated in the de novo synthesis of purines? How is it regulated? |
Glutamine PRPP amidotransferase: it is inhibited through feedback inhibition (from GMP, GDP, GTP, AMP, ADP, ATP at specific allosteric sites) and its irreversible inhibitor Azaserine (also an anti tumor agent) |
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Steps 4 and 10 of the de novo purine biosynthesis rely on what molecule? What is the importance of this? |
They rely on folic acid. This is important because antagonists of folic acid metabolism indirectly inhibit purine formation (therefore nucleic acid synthesis, cell growth and development). This is an excellent target for anti-tumor or infective bacteria drugs. |
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What are the feedback regulated enzymes of the de novo purine synthesis pathway? What are their inhibitors? |
1. Ribose-5-phosphate pyrophosphokinase ATP, ADP, AMP, GTP, GDP, GMP 2. Gln-PRPP amidotransferase ATP, ADP, AMP, GTP, GDP, GMP inhibit, alpha PRPP activates. 3. IMP dehydrogenase, GMP competitive inhibitor 4. Adenylosuccinate synthase, AMP competitive inhibitor. |
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What is the end product of purine catabolism? |
Uric acid, that can then be oxidized to different excretory products. |
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What is the purpose of HGPRT? |
It helps convert bases back to nucleotides. |
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True/False: PRPP is only involved in the de novo pathway. |
False: it is involved in both the de novo pathway and the salvage pathway. |
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Name 4 diseases associated with disorders in purine metabolism. |
1. Gout 2. Lesch Nyhan syndrome 3. SCID (severe combined immunodeficiency syndrome) 4. von Gierke's disease |
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What is defective with gout? What are the molecular results? |
PRPP synthase/HGPRT is defective. It results in hyperuricemia, an excess of uric acid. |
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What is defective with Lesch Nyhan syndrome? What are the molecular results? |
There is no HGPRT. It results in hyperuricemia. |
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What is defective with SCID? What are the molecular results? |
Adenosine deaminase (ADA). Results in high levels of dAMP. |
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What is defective with von Gierke's disease? What are the molecular results? |
Glucose-6-phosphate. Results in hyperuricemia. |
