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Step 1: Biochemistry

QuestionAnswer
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
Created by: 092309