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Chemistry
Q:
A hydrophobic interaction might occur within a protein between which of the following amino acid pairs?
a. Ser/Ile
b. Val/Leu
c. Tyr/Cys
d. Lys/Asn
e. His/Val
Q:
____ between tightly packed amino acid side chains in the interior of the protein are a major contributionto protein structure.
a. Hydrogen bonds
b. Electrostatic interactions
c. Covalent ester bonds
d. Van der Waals interactions
e. All are true
Q:
An electrostatic interaction might occur within a protein between which of the following amino acid pairs at typical physiological pH?
a. Ser/Asn
b. Asp/Glu
c. Arg/Cys
d. Lys/Asp
e. Val/Ile
Q:
Electrostatic interactions among amino acid residues on proteins may be damped out by high concentrations of:
a. water.
b. organic solvents.
c. salts.
d. heat.
e. all of the above.
Q:
____ amino acids are almost never found in the interior of a protein, but the protein surface may consist of ____ amino acids.
a. Nonpolar, both polar and nonpolar
b. Nonpolar, mostly nonpolar
c. Polar, both polar and nonpolar
d. Polar, only polar
e. Polar, only nonpolar
Q:
Amino acid side chains capable of forming hydrogen bonds are usually located on the protein ____ and form hydrogen bonds primarily with the ____.
a. surface, water solvent
b. interior, water solvent
c. surface, other amino acid side chains
d. interior, other amino acid side chains
e. all are true
Q:
Which of the following IS NOT a characteristic of globular proteins?
a. Insoluble in water.
b. Roughly spherical.
c. Folded so that the hydrophobic amino acids are in the interior of the molecule.
d. Hydrophobic side chains are exposed to the water.
e. None, all are true.
Q:
Fibrous proteins, such as collagen, have which one of the following properties?
a. Highly soluble in water.
b. Their hydrophilic residues are directed into the interior of the protein.
c. Exhibit enzymatic activity.
d. Serve structural roles in the cell.
e. Monomeric.
Q:
Hemoglobin is an 2, 2 ____ whereas, glutamine synthatase from E. coliis an 12____.a. -homodimer, -homomultimerb. -heteromultimer, -homomultimerc. -homomultimer, -heterodimerd. -heterodimer, -monomeric proteine. -heterodimer, -homomultimer
Q:
Proteins with two different polypeptide chains are:
a. monomeric proteins.
b. trimeric proteins.
c. homodimeric proteins.
d. heterodimeric proteins.
e. none of the above.
Q:
A gene can be defined as:
a. the unique function that some cells have but other cells do not have.
b. a specific segment of nucleotide bases in DNA that encode for the synthesis of a particular protein.
c. a single strand of DNA that is designated as the sense strand.
d. a functional segment of a unique protein.
e. the segment of DNA that is changed in a mutation.
Q:
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
Q:
Which of the following amino acids occurs most frequently in proteins?
a. methionine
b. alanine
c. tryptophan
d. tyrosine
e. histidine
Q:
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
Q:
Which of the following reagents is correctly defined?
a. iodoacetic acid: reduces disulfide bonds
b. guanadinium hydrochloride: disrupts ionic interactions and hydrogen bonds
c. phenylisothiocyanate: reacts with free carboxyl groups
d. cyanogen bromide: reacts with internal cysteine residues
e. performic acid: reacts with free cysteine residues
Q:
The lac repressoris an example of a(n):
a. enzyme.
b. regulatory protein.
c. transport protein.
d. storage protein.
e. structural protein.
Q:
Collagen is an example of a(n):
a. enzyme.
b. regulatory protein.
c. transport protein.
d. storage protein.
e. structural protein.
Q:
Hemoglobin is an example of a(n):
a. enzyme.
b. regulatory protein.
c. transport protein.
d. storage protein.
e. structural protein.
Q:
Proteins that do NOT perform any obvious chemical transformation, but control the ability of other proteins to carry out their physiological functions are:
a. enzymes.
b. regulatory proteins.
c. transport proteins.
d. storage proteins.
e. structural proteins.
Q:
Proteins destined for an extracellular location are characteristically:
a. phosphoproteins.
b. glycoproteins.
c. lipoproteins.
d. nucleoproteins.
e. flavoproteins.
Q:
The diversity in hemoglobin mutants indicates that:
a. any amino acid change is relatively important.
b. any amino acid change is lethal to the organism.
c. specific amino acid changes drastically alter one or more functions of a protein.
d. any amino acid change will have the same effect on the protein function.
e. All are true.
Q:
Although they have very different functions, hen egg white lysozyme and ____ share similar sequence homology and similar tertiary structure.
a. trypsin
b. ï¡-lactalbumin
c. thrombin
d. hemoglobin
e. chymotrypsin
Q:
Homologous proteins such as hemoglobin from different organisms do NOT:
a. have nearly identical lengths.
b. share little sequence homology with other proteins with similar function (e.g., myoglobin).
c. share a significant degree of sequence similarity.
d. perform the same function in different organisms.
e. have sequence identity in direct correlation to the relatedness of the species from which they were derived.
Q:
The preponderance of 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.
Q:
Which of the following would be a possible amino acid sequence for an oligopeptide given the experimental data below? 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.6.Chymotrypsin digestion yields a dipeptide and a tetrapeptide.a. trp-lys-met-cys-met-alab. lys-met-cys-phe-ala-trpc. trp-ala-phe-cys-met-lysd. lys-ala-cys-phe-met-trpe. lys-met-cys-ala-phe-trp
Q:
All of the statements 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 tripeptide by chymotrypsin.
Q:
What is the overall net charge on the peptide lys-lys-ser-glu at pH 7.0?a. +2b. +1c. 0d. -1e. -2
Q:
The advantage of treating separate samples of a protein with two or more enzymes when sequencing a protein is that the products are:
a. more homogeneous.
b. sequenceable without further chromatography.
c. fragments with the same N- and C-terminal amino acids.
d. fragments with sequence overlaps.
e. all are true.
Q:
____ 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.
Q:
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.
Q:
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
Q:
Which of the following would not be a 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 110°C for 24 hours.d. 8 M urea.e. 6 M guanidinium chloride.
Q:
What is the product formed from the acid hydrolysis of a simple amide?
a. acid & base
b. aldehyde & alcohol
c. acid & amine
d. ester & alcohol
e. amine & aldehyde
Q:
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.
Q:
After treating a protein with trypsin, which of the following techniques could be used to determine its identity by peptide mass fingerprinting?
a. NMR
b. MALDI-TOF mass spectrometer
c. HPLC
d. gel electrophoresis
e. none of the above
Q:
Edman degradation will:
a. determine the C-terminal amino acid by using a carboxypeptidase.
b. cleave the protein into a multitude of smaller peptides.
c. compare overlapping sets of peptide fragments.
d. determine the N-terminal amino acid.
e. generate two different, but overlapping sets of peptide fragments.
Q:
The amino acid sequence is NOT:
a. a distinctive characteristic of a polypeptide.
b. encoded by the nucleotide sequence of DNA.
c. a form of genetic information.
d. read from N-terminal end to C-terminal end.
e. constant for proteins with the same function from different organisms.
Q:
Amino acid analysis of a protein gives:
a. the sequence of the protein.
b. the number of residues of each amino acid in the protein.
c. the molecular weight of the protein.
d. the percentage or ratio of the various amino acids in the protein.
e. an identification of the N-terminal and C-terminal amino acids.
Q:
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
Q:
Which of the following is not a commonly used technique for protein isolation and purification?
a. gas-liquid chromatography.
b. ion exchange chromatography.
c. electrophoresis.
d. solubility ("salting in" and "salting out").
e. affinity chromatography.
Q:
Which of the following levels of protein structure is correctly defined?
a. primary: interaction between subunits of a protein
b. secondary: hydrogen bond arrangement of polar R-groups
c. tertiary: three dimensional arrangement of all atoms in a single peptide
d. quaternary: order of amino acid residues in the peptide chain
e. none of the above are correct
Q:
Which of the following IS NOT a characteristic of a protein's overall conformation?
a. The overall three-dimensional architecture of the protein.
b. Achieved by breaking and reforming covalent bonds.
c. Achieved by rotations about each single bond along the peptide backbone.
d. The result of amino acid side-chain interactions.
e. None, all are true.
Q:
The formation of a disulfide bond would be an example of what level of protein structure?
a. primary
b. secondary
c. tertiary
d. quaternary
e. both c and d are correct
Q:
All of the information necessary for a protein to achieve its intricate architecture is contained within its ____ structure.
a. primary
b. secondary
c. tertiary
d. quaternary
e. all are true
Q:
-Helix and -strand are components of ____ structurea. primaryb. secondaryc. tertiaryd. quaternarye. all are true
Q:
The amino acid sequence is defined as ____ structure.
a. primary
b. secondary
c. tertiary
d. quaternary
e. all are true
Q:
A common reaction of two cysteine residues in proteins results in the formation of ____.
a. thioester bonds
b. disulfide bonds
c. dithiol bonds
d. thioether bonds
e. none of the above
Q:
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. membrane proteins usually have more hydrophobic amino acids.
d. globular proteins are water insoluble.
e. All are true.
Q:
Molecules of a given protein have all EXCEPT:
a. a fixed amino acid composition.
b. a defined amino acid sequence.
c. a sequence read from C-terminal end to N-terminal end.
d. an invariant molecular weight.
e. a nucleotide sequence from which they are encoded.
Q:
Which of the following atoms IS NOT contained within the amide plane of the peptide backbone?
a. Cï¡-carbon.
b. amide nitrogen.
c. side chain carbons.
d. carbonyl carbon.
e. none, all are included.
Q:
Which of the following IS NOT a result of resonance in peptide bonds?a. approximately 40% double bond (coplanar) character.b. restricted rotation in the peptide backbone at the N-C bond and C-Co bond.c. the coplanar six atoms of the peptide bond group of atoms.d. a C-carbon that is out of the coplanar group of atoms.e. Co-N bond distance that is shorter than normal, but longer than C=N bonds.
Q:
The peptide bond has partial ____ character.
a. hydrogen bond
b. double bond
c. triple bond
d. van der Waals bond
e. all of the above
Q:
Where Cis the ï¡-carbon, N represents the amide nitrogen and Co is the carbonyl carbon of amino acids in a peptide, the peptide backbone of a protein consists of the repeated sequence:a. -C-N-Co-b. -N-Co-C-c. -N-C-Co-d. -Co-C-N-e. none of the above
Q:
For the peptide Ala-His-Glu-Val-Asp-Cys-Lys-Leu, what is the net charge at pH 3?a. -1 b. 0 c. +1d. +2e. +3
Q:
Which of the following is classified as a neutral polar amino acid?a. Asp b. Leu c. Hisd. Sere. Trp
Q:
When using a strongly acidic polystyrene resin (Dowex-50) chromatography column, the separation is PRIMARILY by:
a. ion exchange chromatography.
b. gas-liquid chromatography.
c. partition chromatography.
d. liquid-liquid partition chromatography.
e. none of the above.
Q:
Using a cation exchange resin, a mixture of four amino acids is separated using an elution gradient of increasing NaCl solution. What would be the correct elution sequence?
a. Asp, Arg, Ser, Lys
b. Arg, Asp, Lys, Ser
c. Lys, Arg, Asp, Ser
d. Asp, Ser, Lys, Arg
e. Ser, Asp, Lys, Arg
Q:
All are true statements about L-isoleucine EXCEPT:
a. Its enantiomer is named D-isoleucine.
b. L-alloleucine would be its diastereomer.
c. It contains a total of two asymmetric or chiral carbons.
d. It can also be named as (2S,3S)-isoleucine using the (R,S) system.
e. Its diastereomer would be named D-leucine.
Q:
All are true for stereoisomers EXCEPT:
a. A diastereomer is a nonsuperimposable non-mirror image.
b. An enantiomer is a nonsuperimposable mirror image.
c. Diastereomers have different melting points.
d. Diastereomers rotate plane polarized light in equal but opposite directions.
e. None, all are true.
Q:
Which of the following amino acids absorbs light most strongly between 250 and 300 nm?
a. His
b. Phe
c. Trp
d. Tyr
e. None of the above absorb light in this range
Q:
Which of the peptides would absorb light at 280 nm?
a. Ala-Lys-His
b. Ser-Gly-Asn
c. Ala-Ala-Trp
d. Val-Pro-Leu
e. Ser-Val-Ile
Q:
All of the following react with the thiol group on cysteine EXCEPT:
a. N-ethylmaleimide.
b. iodoacetate.
c. acrylonitrile.
d. "Ellman's Reagent".
e. benzaldehyde.
Q:
Ninhydrin has all these properties EXCEPT:
a. It reacts with an amino acid by oxidatively deaminating its amino group.
b. It can be used to detect the location of amino acids following chromatography.
c. It produces a purple colored product upon reaction with alanine.
d. It produces a yellow product upon reaction with histidine.
e. It can be used to quantify most amino acids.
Q:
The pKaof the cysteine side chain ____ group is 8.32, so it is about 11% deprotonated at pH ____.
a. acid, 3.2
b. amino, 8.5
c. hydroxyl, 10.2
d. sulfhydryl, 7.4
e. none of the above
Q:
An amino acid + an aldehyde ï‚®water + ?
a. amide.
b. ester.
c. substituted amide.
d. hemiacetal.
e. Schiff base.
Q:
If the pI of a peptide is 4.6, ____ might be present while ____ would probably be absent.
a. Glu / Lys
b. His / Ser
c. Arg / His
d. Asp / Gly
e. Cys / Tyr
Q:
Glutamic acid has pKavalues of 2.2, 4.3 and 9.7. Calculate the isoelectric point for glutamic acid.
a. 3.25
b. 4.3
c. 5.4
d. 7.0
e. 8.6
Q:
What is the pH of a serine solution in which the amine group (pKa9.2) is 33% deprotonated?a. 8.7b. 8.9c. 9.0d. 9.5e. 9.8
Q:
At which of the following pH values would histidine (pKavalues of 1.8, 6.0 and 9.2) be found with a net negative charge?
a. 1.0
b. 4.0
c. 8.0
d. 11.0
e. none of the above
Q:
Which statement about these amino acids and amino acid derivatives is correct?a. GABA (-aminobutyric acid) is a potent inhibitory neurotransmitter derived from aspartic acid.b. Ornithine is an important metabolic intermediate found in the urea cycle.c. Epinephrine is a hormone derived from tryptophan.d. Serotonin is a neurotransmitter derived from tyrosine.e. Histamine is a neurotransmitter derived from glutamine.
Q:
The pKaof the -carboxyl group of an amino acid is ____ by the presence on the amine group.a. greatly increased (>2 pH units)b. greatly decreased (> 2 pH units)c. unchangedd. slightly increased (1-2 pH units)e. slightly decreased (1-2 pH units)
Q:
The amino acid with a side-chain pKanear neutrality and which therefore plays an important role as proton donor and acceptor in many enzyme catalyzed reactions is:
a. histidine.
b. cysteine.
c. proline.
d. serine.
e. methionine.
Q:
All of the amino acids EXCEPT ____ have both free -amino and free -carboxyl groups.a. aspartic acidb. prolinec. asparagined. lysinee. valine
Q:
Which of the listed amino acids is classified as a basic amino acid?
a. leucine
b. phenylalanine
c. aspartate
d. asparagine
e. lysine
Q:
Which of the following amino acids has more than one chiral carbon?
a. serine
b. lysine
c. threonine
d. cysteine
e. aspartic acid
Q:
The difference between serine and homoserine is the same as between cysteine and homocysteine. This change from the common amino acid is:a. one additional methylene (-CH2-) group.b. one additional carboxyl group.c. two additional amine groups.d. presence of a ring system.e. one additional amine group.
Q:
All of the statements about the classification of these amino acids are correct EXCEPT:
a. Aspartic acid and asparagine are acidic amino acids.
b. Alanine and valine are neutral, nonpolar amino acids.
c. Serine and glutamine are polar, uncharged amino acids.
d. Lysine and arginine are basic amino acids.
e. Tyrosine and phenylalanine are aromatic amino acids.
Q:
Because peptide bond formation is thermodynamically ____, biological systems must couple peptide bond formation to a thermodynamically ____ reaction.
a. favorable, favorable
b. unfavorable, unfavorable
c. favorable, unfavorable
d. unfavorable, favorable
e. none of the above
Q:
The amino and carboxyl groups of amino acids react in a head-to-tail fashion, eliminating water, and forming a covalent ____ linkage typically referred to as a(n) ____ bond.
a. ester, aromatic
b. anhydride, phosphoanhydride
c. amide, peptide
d. dehydration, hydrogen
e. none of the above
Q:
The intrinsic properties of the 20 amino acids include all EXCEPT:a. -Carbon is symmetric.b. The capacity to polymerize.c. Novel acid-base properties.d. Varied structure and chemical functionality in side chains.e. Chirality