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MBC - Lecture 52
Purine Metabolism (Mock)
| Question | Answer |
|---|---|
| Lecture 52 | Purine Metabolism |
| ___ is the parent nucleotide for AMP and GMP. | IMP |
| ___ steps/reactions in IMP synthesis. | 11 |
| PRPP Synthetase | Catalyzes synthesis of 5-phosphoribosyl-1-pryophosphate (PRPP) from ribose 5-phosphate |
| Glutamine PRPP Amidotransferase | Catalyzes synthesis of 5-phosphoribosylamine from PRPP (nitrogen from glutamine) |
| IMP branches to ___ or ___ by two steps. | AMP or GMP |
| IMP, GMP, and XMP negative feedback at same site on ___. | glutamine PRPP amidotransferase |
| AMP negative feedback at a different site on ___. | glutamine PRPP amidotransferase (same enzyme, different site) |
| GMP and AMP negative feedback at respective: | respective IMP branch point |
| Feedback regulation of glutamine PRPP amidotransferase is the: | conversion from inactive to active state |
| IMP, GMP, and AMP promote the ___ state. | inactive |
| PRPP promotes the ___ state. | active (positive feedback) |
| PRPP pool size ___ purine nucleotide synthesis. | regulates |
| Purine ribonucleotides act as ___ for PRPP synthetase and glutamine PRPP amidotransferase. | allosteric regulators |
| Glucose-6-Phosphatase Deficiency (GSD Type I, Von Gierke’s Dsiease) | Increased flux through pentose phosphate pathway and adenine nucleotide pool degradation |
| Increased flux through pentose phosphate pathway yields: | Increased ribose-5-phosphate, PRPP, IMP/GMP/AMP, and uric acid production |
| Uric acid overproduction causes ___. | gout |
| Adenine Nucleotide Degradation | Type 1 GSD and fructose intolerance, F-1-P aldolase/aldolase B deficiency, triggered by decreased Pi |
| Purine bases and nucleosides can be salvaged to ___ form. | mononucleotide |
| Adenine Phosphoribosyl Transferase | Catalyzes phosphoribosylation of adenine forming AMP, using PRPP and releasing PPi |
| Hypoxanthine-Guanine Phosphoribosyl Transferase (HGPRTase) | Catalyzes phosphoribosylation of hypoxanthine or guanine forming IMP or GMP, using PRPP and releasing PPi |
| AMP Deaminase | Catalyzes deamination of adenine nucleotide to IMP, releasing NH4+ |
| Adenosine Deaminase | Catalyzes deamination of adenosine to inosine, releasing NH4+ |
| 5’-Nucleotidase is due to: | IBE increased 5’-nucleoside |
| 5’nucleotidase causes: | developmental delay, seizures, ataxia, language deficit, hyperactivity, short attention span, poor social interaction, increased infections, and anemia |
| 5’-nucleotidase is treated with ___ supplement. | uridine |
| Uricase | Catalyzes degradation of uric acid to allantoin |
| Uricase is ___ in humans. | absent (would prevent gout if present) |
| Rasburicase IV can prevent ___. | acute uric acid nephropathy |
| Allopurinol and alloxanthine are ___ that inhibit ___. | structural analogs, xanthine oxidase |
| Enzyme defects that can lead to excessive excretion of urate: | PRPP synthetase, HGPRTase, glucose-6-phosphatase |
| PRPP Synthetase Deficiency | “Gout", increased Vmax/inhibition resistance/low Km, purine overproduction and over excretion, X-linked recessive |
| HGPRTase (Partial Deficiency) | “Gout”, purine overproduction and over excretion, X-linked recessive |
| HGPRTase (Complete Deficiency) | “Lesch-Nyhan Syndrome”, purine overproduction and over excretion, self-mutilation |
| Adenine Phosphoribosyltransferase Deficiency | “Renal Lithiasis”, 2,8-dihydroxyadenine renal lithiasis, autosomal recessive |
| Xanthine Oxidase | “Xanthinuria”, xanthine renal lithiasis, hypouricemia, autosomal recessive |
| Urates are ___ soluble than uric acid. | more |
| Uric acid stones are reduced by ___ of urine. | alkalinization |
| Hypouricemia leads to __. | tophi |
| Tophi | Crystallization of sodium urate in soft tissues and joints |
| Tophi causes an inflammatory reaction, ___. | acute gouty arthritis |
| Adenosine Deaminase Deficiency | “Immunodeficiency”, T- and B-cell immunodeficiency (SCIDS), deoxyadenosinuria, autosomal recessive |
| Purine Nucleoside Phosphorylase Deficiency | “Immunodeficiency”, T-cell immunodeficiency, inosinura/deoxinosinuria/guanosinuria/deoxguanosinuria, hypouricemia, autosomal recessive |
| AMP Deaminase Deficiency | “Monoamine Deaminase Deficiency” (MADD), muscle pain/cramping/fatigue, autosomal recessive |
| Purine analogs block ___. | purine nucleotide biosynthesis |
| 6-mercaptopurine inhibits ___. | PRPP-amidotransferase |
| Azathioprine is a ___ analog, metabolized to ___. | purine, 6-MP |
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emyang
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