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Step 1: Biochemistry
| Question | Answer |
|---|---|
| Heterochromatin | Condensed, transcriptionally INACTIVE, sterically inaccessible |
| Euchromatin | Less condensed, transcriptionally ACTIVE, sterically accessible |
| Methylation | Makes DNA MUTE |
| Acetylation | Makes DNA ACTIVE |
| Carbamoyl phosphate involved in... | De novo purine synthesis, Urea cycle. Ornithine transcarbamoylase deficiency leads to an accumulation of carbamoyl phosphate, which is then converted to orotic acid. |
| Hydroxyurea | Inhibits ribonucleotide reductase |
| 6-Mercaptopurine | Blocks de novo purine synthesis |
| 5-Fluorouracil | Inhibits thymidylate synthase |
| Methotrexate | Inhibits DHFR (dihydrofolate reductase) |
| Trimethoprim | Inhibits bacterial DHFR (dihydrofolate reductase) |
| Orotic aciduria | Inability to convert orotic acid to UMP (de novo pyrimidine synthesis pathway); autosomal recessive; will see increase orotic acid in urine, megaloblastic anemia, and failure to thrive; tx = oral uridine administration |
| Adenosine deaminase deficiency (ADA) | Think SCID!!! (one of the causes) Excess ATP and dATP imbalances nucleotide pool via feedback inhibition of ribonucleotide reducatase -> prevents DNA synthesis and thus decreases lymphocyte count . "Bubble boy" |
| Lesch-Nyhan syndrome | X linked. Defective purine salvage due to absence of HGPRT which converts hypoxanthine to IMP and guanine to GMP. Results in EXCESS URIC ACID production and de novo purine synthesis. Findings: retardation, self-mutilation, aggression, hyperuricemia, gout |
| Fluoroquinolones | Inhibit DNA gyrase - prokaryotic topo II (topos create a nick in the helix to relieve supercoils created during replication) |
| Prokaryotic only | DNA polymerase III (proofreads) and I (excises RNA primer) |
| Mutated in xeroderma pigmentosum | Nucleotide excision repair |
| Mutated in hereditary nonpolyposis colorectal cancer (HPNCC) | Mismatch repair |
| Mutated in ataxia telangiectasia | Nonhomologous end joining |
| a-amanitin | Found in death cap mushrooms, inhibits RNA polymerase II; causes liver failure if ingested |
| Pts w/ this disease make antibodies to spliceosomal snRNPS | Lupus |
| Explain the lac operon concept | When active, E. coli can metabolize lactose. Lactose inhibits the repressor. Glucose inhibits the activator. |
| Introns vs Extrons | Introns = noncoding, regulatory; Extrons = coding, are expressed |
| Tetracyclines | Bind 30S subunit, preventing attachment of aminoacyl-tRNA ("T"etracycline; "T"-RNA) |
| Aminoglycosides | Bind 30S subunit, inhibit the formation of the initiation complex and cause misreading of mRNA |
| Chloramphenicol | Inhibit 50S peptidyltransferase |
| Macrolides | Block translocation |
| Clindamycin and Chloramphenicol | Block peptide bond formation |
| I cell disease (inclusion cell disease) | Inherited lysosomal storage disease; failure of addition of mannose-6-phosphate to lysosome proteins (enzymes are secreted outside the cell instead of being targeted to the lysosome) Coarse facial features, clouded corneas, restricted joint movement |
| Drugs that act on microtubules | 1. Mebendazole/Thiabendazole (antihelminthic) 2. Griseofulvin (antifungal) 3. Vincristine/Vinblastine (anti-cancer) 4. Paclitaxel (anti-breast cancer) 5. Colchicine (anti-gout) |
| Chediak - Higashi syndrome | Microtubule polymerization defect resulting in decreased FUSION of phagosomes and lysosomes - results in recurrent pyogenic infections, partial albinism, and peripheral neuropathy |
| Kartagener's syndrome | Immotile cilia due to a DYNEIN arm defect -- results in male and female infertility (sperm immotile), bronchiectasis, and recurrent sinusitis; associated w/ situs inversus |
| Stain: Vimentin | Cell type: connective tissue |
| Stain: Desmin | Cell type: muscle |
| Stain: Cytokeratin | Cell type: Epithelial cells |
| Stain: GFAP | Cell type: Neuroglia |
| Cardiac glycosides (digoxin, digitoxin) | Directly inhibit the Na+/K+ ATPase which leads to indirect inhibition of Na+/Ca++ exchange. Increase Ca++ --> increase cardiac contractility. |
| Type I-IV Collagen | Type I: BONE, Type II: CARTILAGE, Type III: Reticulin, Type IV: Basement membrane or basal lamina |
| Defective in Ehlers Danlos syndrome | Type III collagen |
| Defective in Alport Syndrome | Type IV collagen |
| Osteogenesis Imperfecta | Genetic bone disease (brittle bone) Type I is aut dom, abnormal Type I collagen (BONE). See multiple fractures, blue sclera, hearing loss, dental imperfections. Type II is fatal in utero. |
| Ehlers Danlos syndrome | Faulty collagen synthesis causing: hyperflexible skin, tendency to bleed, hypermobile joints. Type III collagen most frequently affected. |
| Alport Syndrome | Abnormal Type IV collagen. Most common is X-linked recessive. Characterized by progressive hereditary nephritis and deafness. May be associated with ocular disturbances. (KIDNEY, EYE, EAR) |
| Marfan's syndrome | Caused by a defect in fibrillin |
| Emphysema or cirrhosis | Can be caused by a1-antitrypsin deficiency, resulting in excess elastase activity (elastase inhibits a1antitryp) |
| Southern blot | DNA |
| Northern blot | RNA |
| Western blot | Protein |
| X Linked Dominant Disorder | Hypophosphatemic rickets - increased phosphate wasting at proximal tubule |
| Mitochondrial Myopathies | Leber's hereditary optic neuropathy, myoclonic epilepsy, mitochondrial encephalopathy |
| Achondroplasia | defect on fibroblast growth factor receptor 3, associated w advancing paternal age |
| ADPKD | Always bilateral, PKD1 gene mutation, berry aneurysms, mitral valve prolapse |
| FAP | associated with chromosome 5 APC gene |
| Huntingtons disease | chromosome 4 CAG repeats |
| Marfans syndrome | fibrillin mutation |
| Neurofibromatosis Type 1 | cafe au lait spots, neural tumors, lisch nodules; long arm chromosome 17! |
| Neurofibromatosis Type 2 | Bilateral acoustic schwannomas, juvenile cataracts, NF 2 gene on chromosome 22 |
| VHL | Deletion of VHL gene (tumor suppressor) on chromosome 3, results in constitutive expression of HIF and activation of angiogenic growth factors |
| CF | deletion of Phenylalanine 508 |
| GAA repeat | Friedricks ataxia |
| CGG repeat | Fragile X |
| CAG repeats | Huntingtons |
| CTG repeats | Myotonic dystrophy |
| Edwards syndrome (trisomy 18) | micrognathia, clenched hands, low set ears, rocker bottom feet |
| Pataus syndrome (trisomy 13) | cleft lip/palate, holoprosencephaly |
| Excess Vit A | teratogenic - cleft palate, cardiac abnormalities |
| Ethanol metabolism causes what? | Increased NADH/NAD+ ration, "ethanol hypoglycemia" |
| Metabolism site: mitochondria | TCA cycle, oxidative phosp, Fatty acid oxidation, acetyl-CoA production |
| Metabolism site: cytoplasm | glycolysis, FA synthesis, HMP shunt, protein synthesis, steroid synthesis |
| Glycolysis | PFK-1 - phosphofructokinase-1 |
| Gluconeogenesis | Fructose-1,6-bisphosphatase |
| TCA cycle | Isocitrate dehydrogenase |
| Glycogen synthesis | Glycogen synthase |
| Glycogenolysis | Glycogen phosphorylase |
| HMP shunt | G6PD |
| De novo pyrimidine synthesis | Carbamoyl phosphate synthetase II |
| De novo purine synthesis | Glutamine PRPP amidotransferase |
| Urea cycle | Carbamoyl phosphate synthetase I |
| Fatty acid synthesis | Acetyl-CoA carboxylase (ACC) |
| Fatty acid oxidation | Carnitine acyltransferase I |
| Ketogenesis | HMG-CoA synthase |
| Cholesterol synthesis | HMG-CoA reductase |
| Von Gierke's disease | Severe fasting hypoglycemia, increase glycogen in liver, hepatomegaly Deficient: glucose-6-phosphatase |
| Pompe's disease | Cardiomegaly Deficient: Acid maltase (lysosomal alpha-1,4-glucosidase) |
| Cori's disease | Milder form of type I with normal lactate levels Deficient: Debranching enzyme (alpha-1,6-glucosidase) |
| McArdle's disease | Increase glycogen in muscle, painful muscle cramps, myoglobinuria with strenuous exercise Deficient: Skeletal muscle glycogen phosphorylase |
| Fabry's disease | Peripheral neuropathy of hands/feet, angiokeratomas, CV/renal disease; X LINKED Deficient: alpha-galactosidase A Accumulate: ceramide trihexoside |
| Gaucher's disease | Hepatosplenomegaly, aseptic necrosis of femur, bone crises, Gaucher's cells Deficient enzyme: Glucocerebrocidase Accumulation: Glucocerebroside |
| Niemann Pick disease | Progressive neurodegeneration, hepatosplenomegaly, cherry red spot on macula, foam cells Def enzyme: Sphingomyelinase Accum: Sphingomyelin |
| Tay Sachs | Progressive neurodegeration, developmental delay, cherry red spot on macula, no hepatosplenomegaly (vs Niemann Pick) Def: Hexosaminidase A Accum: GM2 ganglioside |
| Krabbe disease | Peripheral neuropathy, developmental delay, optic atrophy, globoid cells Def: Galactocerebrocidase Accum: Galactocerebroside |
| Hurler's syndrome | Developmental delay, accum heparan sulfate, dermatan sulfate |
| Hunters syndrome | Mild Hurlers + aggressive behavior; x linked |
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092309
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