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Theme 2.2

Theme 2.2

Question 1 of 50

1

Proteins are synthesized in vivo by the translation of

Select one of the following:

  • cDNA

  • tRNA

  • rRNA

  • exons

  • mRNA

Explanation

Question 2 of 50

1

Since there are 20 standard amino acids, the number of possible linear polypeptides of length N can be expressed as:

Select one of the following:

  • n x 20

  • 20^n

  • 20 × 10^n

  • 10^20

  • n x 10^20

Explanation

Question 3 of 50

1

Natural proteins most commonly contain linear polypeptides between 100 and 1000 residues in length. One of the reasons

Select one of the following:

  • larger polypeptides would likely be insoluble.

  • smaller polypeptides do not form stable folded structures.

  • smaller polypeptides typically assemble into prion-like aggregates.

  • amide linkages are not strong enough to keep larger polypeptides intact.

  • ribosomes are unable to synthesize larger polypeptides.

Explanation

Question 4 of 50

1

The vast majority of polypeptides contain between ______ amino acid residues.

Select one of the following:

  • 10 and 50

  • 50 and 100

  • 100 and 1000

  • 1000 and 2000

  • 2000 and 34,000

Explanation

Question 5 of 50

1

Which of the following has the most dramatic influence on the characteristics of an individual protein?

Select one of the following:

  • the amino-acid sequence

  • the amino-acid composition

  • the location of its encoding gene within the genome

  • the stereochemistry at the alpha-carbon

  • the sequence of tRNA molecules involved in its translation

Explanation

Question 6 of 50

1

Which statement about insulin is correct?

Select one of the following:

  • Insulin is composed of two polypeptides, the A chain and the B chain.

  • Insulin contains an intrachain disulfide bond.

  • Insulin contains interchain disulfide bonds.

  • The A chain and the B chain of insulin are encoded by a single gene.

  • All of the above are correct.

Explanation

Question 7 of 50

1

The salting in of proteins can be explained by:

Select one of the following:

  • salt counter-ions reducing electrostatic attractions between protein molecules.

  • salt ions reducing the polarity of the solution.

  • salt ions increasing the hydrophobic interactions.

  • releasing hydrophobic proteins from nonpolar tissue environments.

  • hydration of the salt ions reducing solubility of proteins.

Explanation

Question 8 of 50

1

The quantitation of proteins due to their absorbance at ~280 nm (UV region) is due to the large absorbtivity of the ________ amino acids

Select one of the following:

  • anionic

  • dansylated

  • cleaved

  • polar

  • aromatic

Explanation

Question 9 of 50

1

Which of the following ‘assays’ would be most specific for a particular protein?

Select one of the following:

  • Bradford assay

  • UV absorptivity

  • radioimmunoassay

  • molar absorptivity

  • amino acid analysis

Explanation

Question 10 of 50

1

An enzyme-linked immunosorbent assay requires

Select one of the following:

  • a radioactive substrate.

  • a radioactive standard for binding to the antibody.

  • aromatic amino acids.

  • an antibody that binds the protein of interest.

  • a catalytic antibody.

Explanation

Question 11 of 50

1

ELISA is an example of a(n):

Select one of the following:

  • enzyme assay.

  • biological assay.

  • binding assay.

  • immunological assay.

  • none of the above

Explanation

Question 12 of 50

1

You are purifying a nuclease by affinity chromatography. To determine which fractions contain the protein of interest, you test samples of all fractions for their ability to break down DNA. This is an example of

Select one of the following:

  • a binding assay.

  • a biological assay.

  • an enzyme assay.

  • an immunological assay.

Explanation

Question 13 of 50

1

A radioimmunoassay requires

Select one of the following:

  • an enzyme-linked antibody.

  • a coupled enzymatic reaction.

  • a radiolabeled antibody.

  • a catalytic antibody.

  • a radiolabeled standard protein that is used to compete for binding to the antibody.

Explanation

Question 14 of 50

1

Five graduate students prepare extracts from 5 different tissues. Each student measures the total amount of alcohol dehydrogenase and the total amount of protein in his or her extract. Which extract has the highest specific activity?

Total protein (mg) Total alcohol dehydrogenase activity (units)
A 300 60,000
B 200 80,000
C 3000 96,000
D 5000 100,000
E 1000 200,000

Select one of the following:

  • a

  • b

  • c

  • d

  • e

Explanation

Question 15 of 50

1

Which physical characteristic is not commonly used in protein separation?

Select one of the following:

  • solubility

  • stereochemistry

  • size

  • charge

  • polarity

Explanation

Question 16 of 50

1

Adding additional salt to a protein solution can cause:

Select one of the following:

  • an increase in solubility called ‘salting in’.

  • a decrease in solubility called ‘salting out’.

  • protein precipitation from solution.

  • all of the above

  • none of the above

Explanation

Question 17 of 50

1

A first step in purifying a protein that was initially associated with fatty substances would be

Select one of the following:

  • Coomassie Brilliant Blue dye staining.

  • analytical ultracentrifugation.

  • ELISA.

  • Western blotting.

  • hydrophobic interaction chromatography.

Explanation

Question 18 of 50

1

The acronym HPLC stands for

Select one of the following:

  • hydrophobic protein liquid chromatography.

  • high performance liquid chromatography.

  • hydrophilic partition liquid chromatography.

  • high priced liquid chromatography

  • hydrostatic process liquid chromatography.

Explanation

Question 19 of 50

1

A technique that can be used to separate proteins based primarily on the presence of non-polar residues on their surface is called

Select one of the following:

  • ion-exchange chromatography

  • gel filtration chromatography

  • affinity chromatography

  • gel electrophoresis

  • hydrophobic interaction chromatography

Explanation

Question 20 of 50

1

A technique that can be used to separate proteins based primarily on their pI is called

Select one of the following:

  • ion-exchange chromatography.

  • gel filtration chromatography.

  • affinity chromatography

  • isoelectric focusing.

  • hydrophobic interaction chromatography.

Explanation

Question 21 of 50

1

Which of the following amino acids would be last to elute at pH 8.0 from an anion-exchange column?

Select one of the following:

  • lysine

  • alanine

  • glutamic acid

  • asparagine

  • glycine

Explanation

Question 22 of 50

1

Which of the following amino acids would be first to elute at pH 8.0 from an anion-exchange column?

Select one of the following:

  • lysine

  • alanine

  • glutamic acid

  • asparagine

  • glycine

Explanation

Question 23 of 50

1

The pK1, pK2, and pKR of the amino acid lysine are 2.2, 9.1, and 10.5, respectively. The pK1, pK2, and pKR of the amino acid arginine are 1.8, 9.0, and 12.5, respectively. A student at SDSU wants to use ion exchange chromatography to separate lysine from arginine. What pH is likely to work best for this separation?

Select one of the following:

  • 1.5

  • 2.5

  • 5.5

  • 7.5

  • 10.5

Explanation

Question 24 of 50

1

The pK1, pK2, and pKR of the amino acid histdine are 1.8, 9.3, and 6.0, respectively. The pK1, pK2, and pKR of the amino acid arginine are 1.8, 9.0, and 12.5, respectively. You have a mixture of histidine and arginine, how would you try to separate these two amino acids?

Select one of the following:

  • anion exchange chromatography at pH 2

  • anion exchange chromatography at pH 4

  • cation exchange chromatography at pH 2

  • cation exchange chromatography at pH 4

  • cation exchange chromatography at pH 9

Explanation

Question 25 of 50

1

What can be done to increase the rate at which a protein of interest moves down an ion-exchange chromatography column?

Select one of the following:

  • reduce the ion concentration in the eluant

  • add a small amount of a non-ionic detergents to the eluant

  • change the pH of the eluant

  • add a protease inhibitor to the eluant

  • reduce the temperature of the eluant

Explanation

Question 26 of 50

1

Hydrophobic interaction chromatography can be used to separate proteins based on differences in

Select one of the following:

  • ionic charge

  • solubility

  • size

  • polarity

  • binding specificity.

Explanation

Question 27 of 50

1

You are trying to separate five proteins, which are listed below, by gel filtration chromatography. Which of the proteins will elute first from the column?

Select one of the following:

  • cytochrome c (12 kDa)

  • RNA polymerase (99 kDa)

  • glutamine synthetase (621 kDa)

  • interferon-y (34 kDa)

  • hemoglobin (62 kDa)

Explanation

Question 28 of 50

1

SDS-PAGE separates proteins primarily due to differences in

Select one of the following:

  • isoelectric point.

  • mass.

  • polarity.

  • solubility.

  • amino acid sequence.

Explanation

Question 29 of 50

1

Which of these techniques is used to separate proteins mainly based on mass?

Select one of the following:

  • polyacrylamide gel electrophoresis (in the absence of SDS)

  • SDS-PAGE

  • isoelectric focusing

  • immunoblotting

  • Western blotting

Explanation

Question 30 of 50

1

Which of these techniques uses antibodies to detect very small amounts of specific proteins following separation by SDS-PAGE.

Select one of the following:

  • immunoblotting

  • silverstaining

  • Coomassie Brilliant Blue staining

  • ELISA

  • RIA

Explanation

Question 31 of 50

1

Disulfide bonds can be cleaved using

Select one of the following:

  • iodoacetate.

  • dansyl chloride.

  • 2-mercaptoethanol (beta-ME).

  • trypsin

  • phenylisothiocyanate.

Explanation

Question 32 of 50

1

Which of these reagents is commonly used to determine the number of polypeptides in a protein?

Select one of the following:

  • iodoacetate

  • dansyl chloride

  • 2-mercaptoethanol (beta-ME)

  • cyanogen bromide

  • DEAE

Explanation

Question 33 of 50

1

Enzymes that hydrolyze the internal peptide bonds (not the peptide bonds of the terminal amino acids) of a protein are classified

Select one of the following:

  • oxidoreductases.

  • lyases.

  • endopeptidases.

  • nucleases.

  • exopeptidases.

Explanation

Question 34 of 50

1

Which of the following substances cannot be used to cleave peptide bonds in polypeptides?

Select one of the following:

  • trypsin

  • cyanogen bromide

  • endopeptidases

  • 2-mercaptoethanol

  • pepsin

Explanation

Question 35 of 50

1

Which of these are commonly used to cleave peptide bonds in polypeptides?

Select one of the following:

  • 2-mercaptoethanol

  • dansyl chloride

  • iodoacetate

  • sodium dodecyl sulfate

  • trypsin

Explanation

Question 36 of 50

1

The peptide Leu─Cys─Arg─Ser─Gln─Met is subjected to Edman degradation. In the first cycle the peptide first reacts with phenylisothiocyanate under basic conditions. The product of this reaction is incubated with anhydrous trifluoroacetic acid and subsequently with an aqueous acid. What are the products generated in the first cycle.

Select one of the following:

  • PTH─Leu, PTH─Cys, PTH─Arg, PTH─Ser, PTH─Gln, and PTH─Met

  • PTH─Leu─Cys─Arg─Ser─Gln─Met

  • PTH─Met and Leu─Cys─Arg─Ser─Gln─Met

  • PTH─Leu─Cys and PTH─Arg─Ser─Gln─Met

  • PTH─Leu and Cys─Arg─Ser─Gln─Met

Explanation

Question 37 of 50

1

Edman degradation can be used to

Select one of the following:

  • identify the N-terminal amino acid of a polypeptide.

  • identify the C-terminal amino acid of a polypeptide.

  • separate the subunits of a multi-subunit protein.

  • cleave a protein at specific sites.

  • cleave disulfide bonds within a protein so that the individual polypeptides can be separated.

Explanation

Question 38 of 50

1

Although a protein’s primary sequence can be inferred from the nucleotide sequence, modifications such as ______ can be determined most easily by tandem mass spectrometry followed by protein database searching.

Select one of the following:

  • phosphorylation

  • disulfide crosslinks

  • glycosylation

  • acetylation

  • all of the above

Explanation

Question 39 of 50

1

The positive charge on proteins in electrospray ionization mass spectrometry is the result of

Select one of the following:

  • protons fired at the gas-phase protein molecules.

  • protonated side chains of Asp and Glu residues.

  • protonated side chains of Arg and Lys residues.

  • a high pH.

  • electrons fired at the gas-phase protein molecules.

Explanation

Question 40 of 50

1

______________ has emerged as a technique for protein sequencing.

Select one of the following:

  • NMR spectroscopy

  • Mass spectrometry

  • Gel electrophoresis

  • Phylogenetic analysis

  • Limited proteolysis

Explanation

Question 41 of 50

1

Protein sequences are customarily ‘reconstructed’ from sequenced fragments because

Select one of the following:

  • protein purification invariably results in the fragmentation of the protein of interest.

  • proteins are naturally and inevitably cleaved by proteolytic enzymes.

  • proteins are composed of multiple subunits.

  • large polypeptides cannot be directly sequenced.

  • all of the above

Explanation

Question 42 of 50

1

You have purified a new peptide hormone. To determine its amino acid sequence you have digested the polypeptide with trypsin and in a separate reaction you have cleaved the polypeptide with cyanogen bromide.

Cleavage with trypsin yielded 5 peptides that were sequenced by Edman degradation as shown in the following.
1. Ser─Leu
2. Asp─Val─Arg
3. Val─Met─Glu─Lys
4. Ser─Gln─Met─His─Lys
5. Ile─Phe─Met─Leu─Cys─Arg

Cleavage with cyanogen bromide yielded 4 peptides that were sequenced by Edman degradation:

1. His─Lys─Ser─Leu
2. Asp─Val─Arg─Val─Met
3. Glu─Lys─Ile─Phe─Met
4. Leu─Cys─Arg─Ser─Gln─Met

Determine the identity of the N-terminal amino acid after reconstructing the intact protein.

Select one of the following:

  • asp

  • ser

  • his

  • glu

  • ile

Explanation

Question 43 of 50

1

In two homologous proteins, which residue is most likely to replace a Glu residue as a conservative substitution?

Select one of the following:

  • asp

  • trp

  • met

  • ile

  • lys

Explanation

Question 44 of 50

1

A phylogenetic tree depicts ___________ of proteins.

Select one of the following:

  • folding patterns

  • hypervariable residues

  • invariable residues

  • evolutionary relationships

  • gene sequences

Explanation

Question 45 of 50

1

A protein that has had few changes in its amino acid sequence over evolutionary history is labeled

Select one of the following:

  • a fibrinopeptide.

  • evolutionarily conserved.

  • random.

  • a product of pseudogenes.

  • phylogenetic.

Explanation

Question 46 of 50

1

Paralogous genes are

Select one of the following:

  • genes that do not encode protein.

  • genes of slowly evolving proteins.

  • relics of genes that are not expressed.

  • genes of rapidly evolving proteins.

  • the results of gene duplication.

Explanation

Question 47 of 50

1

A fast way for nature to generate new proteins is:

Select one of the following:

  • generation of pseudogenes.

  • mutation by neutral drift.

  • shuffling protein domains or motifs.

  • hypervariable positions.

  • liberal substitution.

Explanation

Question 48 of 50

1

___________ is an example of a very slowly evolving protein.

Select one of the following:

  • Histone H4

  • Hemoglobin

  • Cytochrome c

  • Fibrinopeptides

  • none of the above

Explanation

Question 49 of 50

1

Proteins are often constructed from multiple segments of 40-200 amino acid residues, commonly called

Select one of the following:

  • pseudogenes.

  • hypervariable residues.

  • protolytic fragments.

  • domains.

  • subunits.

Explanation

Question 50 of 50

1

In a conjugated protein, a prosthetic group is:

Select one of the following:

  • a fibrous region of a globular protein.

  • a nonidentical subunit of a protein with many identical subunits.

  • a part of the protein that is not composed of amino acids.

  • a subunit of an oligomeric protein

  • synonymous with “protomer.”

Explanation

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