QBM Final Exam Questions And Answers With Complete Solutions

QBM Final Exam Questions And Answers With Complete Solutions What is the best representation of DNA/protein if you could see it? - answerMolecular surface model OSHA - answerOccupational Safety and Health Association - Must inform employees of potential hazards MSDS - answerMaterial Safety Data Sheet - Lists chemical's physical and chemical properties, toxic, carcinogenic - Describes proper handling Biosafety levels - answerBSL-1 = minimal hazards BSL-2 =potential hazardous organisms, requires PPE - QBM LAB BSL-3 = pathogenic organisms that can cause serious disease, proper ventilation, special PPE, lab resctirctions (TB, etc) BSL-4 = no vaccines or treatments Accurate liquid transfers for pipettes - answerGraduated cylinder - 25 ml - 2L Glass/plastic pipette = 1ml-25ml (Mohr is finer - think "more" than serological) Transfer/Pasteur pipette = quick transfer/non-accurate Micropipette - 0.1microliter to 1 ml accuracy - tip should be in 1 cm of liquid Centrifugation separates samples based on ____, ___, and ___ - answerMass, shape, and density Analytical centrifugation - answerFor analytical purposes - Sucrose/CsCl gradients to study sedimentation - Can determine sample's purity/molecular weight Small bench top centrifuge - answer1.5 ml tube - must be within 0.25 g Large capacity - answerUsed for large volumes (1L) for separation of bacteria from media High speed centrifuge - answerLarge volumes, high speeds Ultracentrifuges - answerSamples that require *alot of force* like purifying viruses from a sample - performed under vacuum to reduce heat friction - Max: 80,000rpm and 600,000g - Must be balanced within 0.1g Sucrose gradients can separate samples based on ___, and they are used in ____ - answerDensity; swinging bucket rotors Types of rotors - answer1) Fixed angle - most common - *pelleting* 2) Swinging bucket - *does not create tight pellets*, used for sample analysis, cesium gradients, separatation by density Two types of bottles used in labs - answer1) Polycarbonate (clear) = see better, but more susceptible to chemicals/cracks 2) Polypropylene (opaque) = more resistant Spectroscopy - answerThe study of radiation interacting with matter - can analyze molecular structure - Can be electromagnetic or not electromagnetic Spectrometry - answerMeasurement of the spectroscopy interactions allowing to determine molecular structures/concentratiosn Spectrophotometer - answerMeasures light intensity of a specific wavelength as it passes through a sample and compares it to a blank 5 components: light source (tungsten - visible (400-1000nm) or deuterium(UV - 200/400nm)), monochromator, prism, sample compartment, detector Plate readers quickly read ____ volumes of hundreds of samples from ____ plate (s) - answermicroliter volumes from single plate 260nm - answerMaximum wavelength for DNA 280nm - answerMaximum wavelength absorbance for proteisn 340nm - answerUsed in CDNB Assay for enzyme activity 560nm - answerUsed in the *BCA* Assay for protein concentration 595nm - answerUsed in Bradford Assay for protein concentration 600nm - answerUsed for to measure bacterial growth in LB Media - During exponential growth phase 750nm - answerUsed in the Lowry/DC Protein Assay (protein concentration) Absorbance equations - answerA = εcb (b = 1 cm ) A = log (1/T) or A = -log (T) (Beer's Law) Transmittance = - answerT (%) = 10^-A Concentration of a sample is ___ proportional to the absorbance, and ____ proportional to transmittance - answerDirectly; indirectly DNA quantification equation - answerA260 of 1.0 = 50 *micrograms/MILLIliter* DNA purity ratio - answerA260/A280 is greater than 1.5 Which amino acids are the reason proteins absorb at 280nm - answerThe ringed amino acids tryptophan and tyrosine (protein concentration) The most accurate way to determine protein concentration is ____ - answerAmino acid analysis Bradford Assay - answer- Coomasie Brilliant Blue Dye - changes color from 495nm to 595nm as it forms *strong, noncovalent* complexes with proteins - high variability - DOES NOT detect free amino acids/DNA - DOES NOT bind to proteins below 3000 Da - CAN be used without standard curve - FASTEST Biuret Method - answer- Cu2+ binds to *peptide bond* N of proteins and absorbs at 550nm Lowry/DC Method - answer- Cu2+ binds to peptide bond, - Cu2+ is reduced to Cu+ and *FOLIN REAGENT* isa dded that becomes reduced by Cu+ and turns blue and is measured at *750nm* - cheap and easy DC: Uses detergent-compatible - low variability, more accurate, longer than bradford BCA Method - answer- Similar to Lowry method, but instead of Folin reagent, *BCA* is used and measured at *560nm* - Fast and stable - Low variation Standard curve - answerY axis = absorbance X axis = concentration - Accounts for variation in absorbance between different concentrations of samples Active sites generally show ... - answerConservation among species in the amino acid sequence - Substrates often interact with active sites with electrostatic, H bonding, Van der waals, hydrophobic, *occasional reversible covalent bonds* Competitive and non-competitive inhibitors of enzymes - answer- Competitive: bind to same site on enzyme (active site) - requries more substrate to overcome, can reach Vmax - Non-competitive: binds to second site causing allosteric changes preventing enzyme-substrate interaction = can't be overcome, can't reach Vmax Enzyme assay - answerDetermine's enzyme's rate - CDNB at 340nm Kinase assay - answerStudy enzymes that hydrolyze ATP to ADP and detect phosphorylation Cofactors vs coenzymes - answerCofactors = metals Coenzymes = organic molecules Unit of restriction enzyme - answer1 unit = amount of enzyme required to cleave 1 microgram of DNA in 1 hour in 50microliters of total volume 1 Dalton = - answer1 g/mol "1-12th the mass of a C-12 atom" 1 kDa = ___ amino acids - answer9 amino acids 1 amino acid = ____ Da - answer~112 Da! mM or microM - answermilliomoles/LITER micromoles/LITER Percent composition (v/v and w/v) - answerv/v = 30% v/v ethanol is 30 ml ethanol and 70 ml water (same volume units) w/v = solute is in *grams* and solvent is *ml* = 30% w/v NaOH is 3 grams/10 mL Solute needed = - answermolarity desired (mol/L) x volume desired (L) x molecular weight (g/mol) = solute needed (g) Stock solutions of Tris with a given pH can skip the titration of acid step - answerTrue When making a buffer, if you pass the desired pH while titrating with (Tris-HCl) for instance, you can add NaOH to bring it up - answerFalse! you cannot