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75 Cards in this Set
- Front
- Back
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The ratio of enzyme activity relative to total protein is called _____ |
specific activity |
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The first step in protein purification from a homogenate is usually _____ |
centrifugation |
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A type of purification that is based on the attraction of the protein for a particular chemical group |
affinity chromatography |
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_____ can be added prior to gel electrophoresis to denature the proteins |
SDS |
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Sedimentation coefficients are described as _____ units |
Svedberg |
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Proteins with different sedimentation coefficients can be separated by _____ |
zonal |
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In order to sequence a whole protein, ______________ are used. |
overlap peptides |
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Proteins can be separated from small molecules and ions through a semi-permeable membrane by __________________. |
dialysis |
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__________________ gels are often used as the media for electrophoretic techniques such as SDS-PAGE and isoelectric focusing. |
polyacrylamide |
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Exclusion gel or gel-filtration chromatography separates molecules on the basis of ______. |
size |
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__________is a chemical reagent that is often used to detect the presence of amino acids. |
ninhydrin |
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In the Edman procedure for peptide sequence, phenyl isothiocyanate is used to selectively remove the ____________residue as a PTH-derivative. |
N-terminal |
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Polypeptides can be fragmented into smaller peptides by cleavage with chymotrypsin, which hydrolyzes the peptide bond at the C-terminal side of _________________________ residues.
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leucine, methionine, tryptophane, tyrosine, phenylalanine |
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Mass spectrometric techniques are critical in _____________research because it is possible to analyze constituents of large macromolecular assemblies. |
MALDI-TOF |
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The advantage to ______________protein synthesis is that the desired product is bound to beads and excess reagents can be easily removed at each step |
solid-phase |
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Proteins that are not catalystsare often probed or assayed using a.antibody binding assays b.catalytic activity c.genomic analysis d.none of the above e.all of the above |
a. antibody binding assays |
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The following methods are useful for cell homogenization: a. sonication b. freezing and thawing c. detergents d. enzymes e. all of these are correct |
e. all of these |
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Membrane proteins differ from globular proteins in that: a. membrane associated amino acids usually have polar side chains b. membrane proteins are much more soluble in detergents than water c. globular proteins are water insoluble d. all are true |
b. membrane proteins are much more soluble in detergents than water *
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he typical order of differential centrifugation fororganelles is (from slowest speed/lowest g to fastest speed/highest g): a. nuclei, microsomes, mitochondria & chloroplasts, cytosol, whole cells b. whole cells, nuclei, mitochondria & chloroplasts, microsomes, cytosol c. cytosol, microsomes, nuclei, mitochondria & chloroplasts, whole cells d. nuclei, mitochondria & chloroplasts, whole cells, cytosol, microsomes e. whole cells, cytosol, microsomes, nuclei, mitochondria & chloroplasts |
b. whole cells, nuclei, mitochondria & chloroplasts, microsomes, cytosol |
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The typical order for the major steps of enzyme isolation would be (from first to last): a. homogenization, salt fractionation, electrophoresis, column chromatography b. homogenization, column chromatography, salt fractionation, electrophoresis c.homogenization, electrophoresis, salt fractionation, column chromatography d. salt fractionation, homogenization, electrophoresis, column chromatography e. homogenization, salt fractionation, column chromatography, electrophoresis |
e. homogenization, salt fractionation, column chromatography, electrophoresis
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The purity of an enzyme at various stages of purification is best measured by a. total protein b. total enzyme activity c. specific activity of the enzyme d. percent recovery of the protein e. percent recovery of the enzyme |
c. specific activity of the enzyme
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When enzymes are purified, the assay is often based on a.light absorbance b.temperature changes c.catalytic activity d.mRNA levels e.pH. |
c.catalytic activity
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Salting out with ammonium sulfate is based upon proteins interacting with other proteins via
a. hydrogen bonds b. ionic bonds c. hydrophobic interactions d. disulfide bonds |
c. hydrophobic interactions * |
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Ammonium sulfate is useful in protein purification because a. it contains nitrogen and sulfur, both of which occur in proteins b. it is sparingly soluble in water, causing proteins to co-precipitate with it c. very pure proteins are obtained when it is used d. it forms ion-dipole interactions with water, making proteins less soluble and more likely to precipitate |
d. it forms ion-dipole interactions with water, making proteins less soluble and more likely to precipitate
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In chromatography the experimental setup always requires a. a stationary phase and a mobile phase b. a spectrophotometric detecting device c. a sample in which components differ in charge d. a sample in which components differ in polarity |
a. a stationary phase and a mobile phase *
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Which of the following is not a commonly used technique for protein isolation and purification? a. gaschromatography b. ion exchange chromatography c. electrophoresis d. solubility ("salting in" and "salting out") e. affinity chromatography |
a. gaschromatography
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In gel filtration chromatography a. materials are separated based on their size, the smaller ones eluting first b. materials are separated based on their size, the larger ones eluting first c. materials are separated based on their hydrophobic nature, the more hydrophobic ones eluting first d. materials are separated based on their hydrophobic nature, the less hydrophobic ones eluting first |
b. materials are separated based on their size, the larger ones eluting first
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Which substance would you expect to be eluted first from a gel filtration chromatographic column with a suitable degree of crosslinking? a. hemoglobin b. myoglobin c. 2,3-bisphosphoglycerate d. all would elute at the same rate |
a. hemoglobin *
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The degree of separation in gel filtration (molecular sieve) chromatography depends on a. the polarity of the mobile phase b. the pKa of the buffer material in the mobile phase c. the chemical nature of the sieve material d. the size of the pores in the sieve material |
d. the size of the pores in the sieve material
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Which separates based on the ionic charge on a protein? a. gel filtration b. affinity chromatography c. cation exchange d. anion exchange e. cation or anion exchange |
e. cation or anion exchange
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Which would be best to separate positively charged proteins? a. gel filtration b. affinity chromatography c. cation exchange d. anion exchange e. cation or anion exchange |
c. cation exchange
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In ion-exchangechromatography, compound A which interacts more strongly with the stationary phase than the compound B: a. compound A interacting more strongly will elute earlier than one with weaker interactions. b. compound A interacting more strongly will elute later than one with weaker interactions. c. the order of elution has nothing to do with interactions with the stationary phase, but with interactions with the mobile phase. |
b. compound A interacting more strongly will elute later than one with weaker interactions.
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In a sample consisting of lysine, leucine, and glutamic acid, which will be eluted last from an anion exchange resin at pH 7? a. all three will be eluted at the same time b. lysine c. leucine d. glutamic acid |
d. glutamic acid
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Elution of proteins by means of a pH gradient would work best with this type of column:
a. gel filtration b. affinity chromatography c. cation exchange d. anion exchange e. cation or anion exchange |
e. cation or anion exchange **
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In affinity chromatography a. there is nonspecific binding of proteins to column material b. there can be molecule specific ligands or group specific ligands c. themobile phase is always pure water d. the ligand is alwayse specific for one type of protein to be bound e. only minor purifications can be obtained |
b. there can be molecule specific ligands or group specific ligands |
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A chromatography technique where a solution of nonpolar compounds is put through a column that has a nonpolar liquid immobilized on an inert matrix is which type of chromatography? a. gel filtration b. ion exchange c. affinity d. HPLC e. Reverse Phase HPLC |
e. Reverse Phase HPLC |
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Which of the following is not an example of column chromatography? a. ammonium sulfate fractionation b. ion-exchange separation c. HPLC d. affinity separation |
a. ammonium sulfate fractionation
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In the SDS-PAGE (sodium dodecylsulfate -polyacrylamide gel electrophoresis) method, separation takes place on the basis of a. charge only, because all particles have different charges, but the same mass b. the sieving action of the gel, because all particles have the same charge, but different masses c. the sieving action of the gel, because all particles have approximatelythe same charge/mass ratio, but different masses d. the chemical nature of the buffer used as the electrolyte |
c. the sieving action of the gel, because all particles have approximatelythe same charge/mass ratio, but different masses
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When electrophoretic separations are done based on molecular weight, the distance that a molecule moves can be graphed as a straight line when compared to: a.the MW of the proteins b.the negative of the MW of the proteins c.the log of the MW of the proteins d.none of these |
c.the log of the MW of the proteins
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Two-dimensional electrophoresis usually exploits these 2 different properties of proteins: a. molecular weight and shape b. molecular weight and net charge c. molecular weight and isoionic pH(isoelectric pH or isoelectric point) d. isoionic pH and shape e. isoionic pH and net charge |
c. molecular weight and isoionic pH(isoelectric pH or isoelectric point)
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In electrophoresis experiments a. the separation must be carried out in bright light b. the polarity of substances to be separated is more important than their charge or size c. the sample can be badly degraded as a result of the separation d. an electric field must be applied to the mixture to be separated |
d. an electric field must be applied to the mixture to be separated
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Two dimensional separation methods a. lead to unreliable results b. are not widely used because of their complexity c. do not improve separation d. consist of two separation methods (isoelectric focusing and SDS-PAGE) appliedin sequence |
d. consist of two separation methods (isoelectric focusing and SDS-PAGE) appliedin sequence
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Which of the following happens as a protein is purified? a. the percent recovery and the fold purification both increase b. the percent recovery and the fold purification both decrease c. the percent recovery increases and the fold purification decreases d. the percent recovery decreases and the fold purification increases |
d. the percent recovery decreases and the fold purification increases
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Even though acid hydrolysis of proteins is favored over basic hydrolysis, with acid hydrolysis ____ is destroyed and must be estimated by other means.
a. Lys b. Leu c. Asp d. Cys e. Trp |
e. Trp |
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Which of the following would not bea useful procedure for dissociating the subunits of a multimeric protein in order to sequence the individual subunits? a. exposure to pH extremes (ie, pH 1 or pH 13). b. high salt concentrations. c. 6 N HCl at 110oC for 24 hours. d. 8 M urea. e. 6 M guanidinium chloride |
c. 6 N HCl at 110oC for 24 hours. |
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In all forms of chromatography one way of identifying eluted substances is by
a. fluorescence spectroscopy b. comparison with standards c. radioactive labeling d. treating fractions with a reagent that will cause a color change |
b. comparison with standards
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47. It is frequently possible to bypass the determination of the identity of the N-terminal amino acid of a protein because a. this information is already available from the amino acid analysis b. the Edman method sequences the peptide from the N-terminal end c. N-terminal amino acids are always chemically modified d. this information is not needed |
b. the Edman method sequences the peptide from the N-terminal end *
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Generally speaking, sequence techniques have become so sensitive that if you are able to isolate the protein on a gel, there is enough of it to get a significant amount of its sequence. a. True b. False |
a. True |
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Cyanogen bromide cleaves the peptide bond at a.the carboxyl side of Arg and Lys residues b.the carboxyl side of Met residues to become a homoserine lactone at the C-terminal end of cleaved peptide fragments c.the amino terminus d.none of the above e.all of the above |
b.the carboxyl side of Met residues to become a homoserine lactone at the C-terminal end of cleaved peptide fragments *
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t is impossible to sequence a protein if you do not have overlapping sequences to work with.3
a. true b. False |
a. true |
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Determination of the sequence of amino acids in a peptide is done by
a. x-ray crystallography b. Edman degradation c. treatment with cyanogen bromide d. trypsin hydrolysis |
b. Edman degradation
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Methods for breaking proteins into smaller peptides include all of the following except: a. digestion with chymotrypsin b. cyanogen Bromide treatment c. digestion with Trypsin d. Edmann degradation e. all of the above create short peptides suitable for sequencing |
d. Edmann degradation
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If a protein with the sequence PQRKYPIG is treated with trypsin, what will the products be?
a. PQR KYPIG b. PQRK YPIG c. PQR K YPIG d. PQ R KPIG0 |
c. PQR K YPIG
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When end-group analysis was done on the protein insulin, the results indicated that both glycine and phenylalanine were N-terminal amino acids and both asparagine and alanine were C-terminal amino acids. Theseresults indicate that
a. the experiment was done incorrectly b. no conclusions can be drawn c. there were impurities in the sample d. insulin consists of two polypeptide chains |
d. insulin consists of two polypeptide chains |
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Which of the following protease enzymes is correctly identified with its specificity? a. trypsin: cleaves on C-side of acidic amino acids b. chymotrypsin: cleaves on C-side of aliphatic amino acids c. staphylococcal protease: cleaves on C-side of acidic amino acids d. clostripain: cleaves on C-side of lysine e. none of the above are correct |
c. staphylococcal protease: cleaves on C-side of acidic amino acids *
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Reaction of the peptide, ala-met-lys-ser, with phenylisothiocyanate (PITC) at pH 8.0 followed by mild acidification (first cycle of Edman method) would release:
a. the labeled peptide ala-met-lys-ser-PTH b. PTH-ala, PTH-ser,PTH-lys and PTH-met c. PTH-ser and the peptide ala-met-lys d. PTH-ala and the peptide met-lys-ser e. all of the above. |
d. PTH-ala and the peptide met-lys-ser
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Insulin is a polypeptide hormone that contains two short polypeptide chains linked by two interstrand disulfide bonds.The most logical order of events to perform in order to sequence this protein would be: A. the peptides are reduced with mercaptoethanol. B. the peptides are sequenced using Edman chemistry. C. the peptides are separated by chromatography techniques. D. the peptides are alkylated with iodoacetamide. a. A, D, C, B b. C, A, D, B c. C, B, A, D d. A,B,C,D e. A, C, D, B |
d. A,B,C,D * |
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The C-terminal residue of a polypeptide can be determined by first cleaving the polypeptide with: a. chymotrypsin b. carboxypeptidase c. trypsin d. CNBr e. none of the above |
b. carboxypeptidase
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____ is specific in hydrolyzing only peptide bonds in which the carboxyl function is contributed by an arginine or a lysine residue. a. chymotrypsin b. carboxypeptidase c. trypsin d. CNBr e. none of the above |
c. trypsin |
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All of thestatements about the peptide val-asp-trp-asn-ser are correct EXCEPT: a.this peptide would show a strong absorption band at 280 nm b.reaction with chymotrypsin would yield two peptides c.to synthesize this peptide using the solid phase method of Merrifield, the amino acid directly attached to the resin would be valine d.after the second round of Edman degradation using the reagent PITC, the PTH-amino acid residue released would be PTH-asp e.the peptide would be converted to a dipeptide and a tripeptideby chymotrypsin. |
c.to synthesize this peptide using the solid phase method of Merrifield, the amino acid directly attached to the resin would be valine |
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Which of the following would be a possible amino acid sequence for an oligopeptide given the experimental data below? 1. The amino acid composition is found to be [ala, lys, phe, met, cys, plus some decomposition products]. 2. the peptide has a molecular weight around 700 Da and absorbs at 280 nm 3. treatment with carboxypeptidase results in tryptophan and a peptide 4. CNBr treatment yields a tetrapeptide and a dipeptide 5. trypsin digestion produces an amino acid and a pentapeptide with met on the amino end a.trp-lys-met-cys-met-ala b.lys-met-cys-phe-ala-trp c.trp-ala-phe-cys-met-lys d.lys-ala-cys-phe-met-trp e.lys-met-cys-ala-phe-trp |
e.lys-met-cys-ala-phe-trp * |
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The predominanceof protein sequence information is now derived from: a. chemical sequencing (Edman method). b. mass spectrometry. c. mass spectrometry-mass spectrometry. d. translating the nucleotide sequence of genes into codons, and thus amino acid sequence. e. none of the above. |
a. chemical sequencing (Edman method). * |
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Although they havevery different functions, hen egg white lysozyme and ____ share similar sequence homology and similar tertiary structure. a. trypsin b. α-lactalbumin c. thrombin d. hemoglobin e. chymotrypsin |
b. α-lactalbumin |
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Which of the following mutations would probably be least likely to impact the function of the protein? a. Lys to Ser b. Ala to Asp c. His to Pro d. Val to Ile e. Phe to Tyr |
d. Val to Ile |
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What types of molecules can serve as antigens? a.proteins b.polysaccharides c.metal ions d.all of the above e.a and b |
e.a and b |
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An ELISA can be used for a.quantitative analysis b.size analysis c.absorbance measurements d.all of the above e.none of the above |
d.all of the above * |
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A technique used to identify proteins after gel electrophoresis, which employs antibodies in the detection process. a.Southern Blot b.Southwestern Blot c.Northern Blot d.Western Blot e. none of these |
d.Western Blot |
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Protein databases a.can identify proteins from small stretches of amino acid sequences. b.are not useful in proteomics studies due to the complexities of the proteome c.are determined from sequence data only, never deduced from genomic data d.none of the above e.all of the above |
a.can identify proteins from small stretches of amino acid sequences. |
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The use of synthetic peptides includes a.use as antigens for making antibodies b.drugs c.“hooks” used in purification d.all of the above e.a and c |
d.all of the above * |
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Matrix-Assisted Laser Desorption Ionization is a type of _______ technique. a. electrophoresis b. ion exchange chromatography c. affinity chromatography d. mass spectrometry |
a. electrophoresis |
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Which of the following techniques can be used to determine mass to charge ratio of a molecule? a.Edman degradation b.affinity chromatography c.MALDI-TOF d.SDS-PAGE e.diagonal electrophoresis |
c.MALDI-TOF |
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After treating a protein with trypsin, which of the following techniques could be used to determine its identity by peptide mass fingerprinting? a. NMR c. HPLC d. gel electrophoresis e. none of the above |
b. MALDI-TOF mass spectrometer |
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A technique that can be used to study three-dimensional protein structure. a.NMR spectroscopy b.fluorescent microscopy c.X-ray crystallography d.Western blotting e.ion-exchange chromatography |
c.X-ray crystallography |
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Techniques that can be used to obtain information about protein shape are a.x-ray crystallography b.NMR spectroscopy c.SDS-PAGE d.a and b e.a, b, and c |
d.a and b |
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Which technique cannot be used for quantitative analysis? a.x-ray crystallography c.absorbance spectroscopy d.all of the above e.none of the above |
a.x-ray crystallography |
