Biochem Sappling
What is the net charge of histidine at ph=1? a. +2 b. +1 c. 0 d. -1 e. -2
a. +2
Which of the following correctly identifies the priority of common substituents in the RS system? a. -OH > -COOH > -CH2OH > -H b. -H > -CH2OH > -COOH > -OH c. -COOH > -OH > -CH2OH > -H d. -COOH > -CH2OH > -OH > -H e. none of the above
a. -OH > -COOH > -CH2OH > -H
What is the total number of possible peptide pentamers that could be formed from five different amino acids? (Assume that each amino acid is present only once per peptide.) a. 120 b. 50 c. 25 d. 125 e. 100
a. 120
What is the pH of a 0.150 M solution of acetic acid at 25 °C? (pKa = 4.75) a. 2.8 b. 0.8 c. 4.75 d. 5.2
a. 2.8
At which pH would the net electric charge of tyrosine be zero, given that its -COOH group has a pKa of 2.20, its -NH3+ group has a pKa of 9.11, and its R group has a pKa of 10.07? a. 5.66 b. 6.14 c. 7.13 d. 9.59 e. 12.27
a. 5.66
Which of the following statements is false regarding DNA libraries? a. A clone of a transformed yeast or bacteria cell in a genomic library generally contains the complete genome of the organism of interest in a cloning vector. b. A genomic library is formed when fragments of a genome are cut with restriction endonucleases and inserted into cloning vectors. c. To generate a cDNA library, a researcher first extracts mRNA from an organism. d. A cDNA library only includes sequences of DNA that are expressed.
a. A clone of a transformed yeast or bacteria cell in a genomic library generally contains the complete genome of the organism of interest in a cloning vector.
Which of the following statements about antibodies is incorrect? a. A preparation of monoclonal antibodies will recognize multiple epitopes of an antigen, whereas a preparation of polyclonal antibodies will recognize a single epitope of an antigen. b. Antibodies are important components of ELISA assays. c. Polyclonal antibodies can be produced in animals. d. Antibodies can be used for protein purification.
a. A preparation of monoclonal antibodies will recognize multiple epitopes of an antigen, whereas a preparation of polyclonal antibodies will recognize a single epitope of an antigen.
Which amino acid repeat is present in collagen? (X is often Pro; Y is often 4-Hyp) a. Gly-X-Y b. Ala-Lys-X c. Gly-Ala-Y-X d. X-X-Y
a. Gly-X-Y
Which of the following is true regarding troponin C? a. It has 2 calcium-binding domains. b. It has 2 amino and 2 carboxyl termini. c. It has quaternary structure. d. It has many protein fibers cross-linked together.
a. It has 2 calcium-binding domains.
Which of the following correctly matches the enzyme class with the type of reaction it catalyzes? a. Oxidoreductase: transfer of electrons b. Ligase: cleavage of C—C, C—O, C—N, or other bonds by elimination, leaving double bonds c. Hydrolase: group transfer reaction d. Lyase: formation of C—C, C—S, C—O, and C—N bonds by condensation reactions
a. Oxidoreductase: transfer of electrons
Consider two proteins 100 amino acids long. Protein A is a fibrous protein in one continuous α-helix. Protein B is globular and its entire length comprises a β-α-β loop, and amino acids 20 and 86 form a salt-bridge. Neither requires a chaperone. Which statement is most likely? a. Protein A folds faster due to lack of long-range intramolecular interactions. b. The folding time for the two proteins should be nearly identical since they are of the same length. c. Protein B folds faster because the salt-bridge formation is extremely fast. d. All proteins, regardless of length, fold in nearly the same amount of time.
a. Protein A folds faster due to lack of long-range intramolecular interactions.
Suppose a hypothetical Hb protein had a Hill coefficient of 4.5. What could we say about this protein? a. The Hb must contain more than four subunits. b. The Hb could carry a maximum of four oxygen molecules. c. The Hb binds O2 noncooperatively. d. The O2 binding curve would be hyperbolic in shape. e. The O2 affinity would be higher than for the corresponding Mb.
a. The Hb must contain more than four subunits.
Which is false about the structure of DNA? a. The planes of the purine and pyrimidine base rings are parallel to the helix axis. b. The deoxyribose is in the C-2' endo conformation. c. It is a right-handed helix. d. The hydrophilic deoxyribose and phosphate groups are on the outside.
a. The planes of the purine and pyrimidine base rings are parallel to the helix axis.
If the equilibrium constant, Keq, for the reaction shown is 0.080, which statement is true when the concentrations of A, B and C are 0.20 M, 0.40 M and 0.10 M, respectively? 2A + B ⇄ 3C a. The reaction will shift toward the product, C. b. The reaction will increase rates equally in both directions. c. The reaction is at equilibrium. d.The reaction will shift toward the reactants, A and B.
a. The reaction will shift toward the product, C.
Which of the following statements regarding the intrinsic pathway is false? a. Tissue factor is a major component of the intrinsic pathway. b. The intrinsic pathway is also known as the contact activation pathway. c. The intrinsic and extrinsic pathways are interlinked and lead to the formation of active fibrin. d. All components of the intrinsic pathway are found in the blood plasma.
a. Tissue factor is a major component of the intrinsic pathway.
How is Vmax found on a Lineweaver-Burk plot? a. Vmax is the reciprocal of the y-intercept. b. Vmax is the asymptotic maximum of the hyperbolic curve. c. Vmax is equal to the y-intercept. d. Vmax is equal to the slope of the line.
a. Vmax is the reciprocal of the y-intercept.
In the protein hemoglobin, which is an oxygen carrier protein found in blood, a histidine side chain can find itself in two distinct sites within the protein. The pKa of the imidazole group on the histidine changes from 6.0 when occupying one site (we'll call this the R-form of hemoglobin) to 8.1 when occupying the other (this we will call the T-form of hemoglobin). Based on this, what statement can be made about this histidine? a. When the protein shifts from the R-form to the T-form at pH 7.0, the histidine goes from its neutral to ionic form. b.When hemoglobin is in the R-form at pH 7.0, the histidine would be ionized. c. When in the T-form at pH 7.0, the histidine unprotonated. d. When in the T-form at pH 7.0, the histidine is neutral. e. When in the R form at pH 7.0, the histidine is protonated.
a. When the protein shifts from the R-form to the T-form at pH 7.0, the histidine goes from its neutral to ionic form
How do A− and Z−form DNA differ from the B-form DNA, which was described by Watson and Crick? a. Z form appears more slender and elongated than B form. b. There is evidence of short tracts of A−DNA in bacteria and eukaryotes, but it is uncertain whether or not Z−DNA occurs in cells. c. A form is a left-handed double helix, while Z form is a right-handed double helix. d. The plane of the base pairs in Z−DNA is tilted about 20° relative to B−DNA.
a. Z form appears more slender and elongated than B form.
In deriving the Michaelis-Menton equation for enzyme kinetics, the steady-state assumption is applied. Specifically, what is assumed here? a. [ES] is constant. b. The formation of ES is the rate-limiting step. c. The maximum velocity has been reached. d. Rate is independent of [S].
a. [ES] is constant
When a peptide bond is formed, _____. a. a product of the reaction is water b. the amino group of one amino acid reacts with the amino group of another c. the amide backbone is readily ionizable at or around pH = 7 d. there is free rotation about the amide bond that is formed e. none of these are true
a. a product of the reaction is water
Which amino acid would provide stabilization at pH=7 if near the amino-terminal end of an α helix? a. aspartate b. arginine c. asparagine d. glycine
a. aspartate
Which of the following is not water soluble? a. butane b. glyceraldehyde c. glucose d. ethanol
a. butane
A study on pitcher plants in New Caledonia concluded that morphological variation among populations was the result of geographical isolation. Which experiments could most easily demonstrate this? a. comparison of chloroplast haplotypes b. a DNA microarray analysis comparison of seeds versus mature plants c. determination of the percent transposons in the genome d. a yeast two-hybrid analysis with seed coat fusion proteins
a. comparison of chloroplast haplotypes
The double helix that is formed after DNA replication _____. a. contains one parental strand of DNA and one newly synthesized strand of DNA b. contains one parental strand of DNA and one newly synthesized strand of RNA c. contains either two parental DNA strands or two newly synthesized strands of DNA d. contains two strands of DNA, each consisting of material from both the parental and newly synthesized strand e. none of the above
a. contains one parental strand of DNA and one newly synthesized strand of DNA
A protein that binds to glutathione can be purified using an affinity column where the solid phase is a cellulose matrix covalently attached to the molecule glutathione. What should be included in the elution buffer for this experiment to remove the protein from the column? a. glutathione b. β-mercaptoethanol c. high salt d. imidazole e. strong acid
a. glutathione
Hydrolysis of a peptide bond ______. a. is a thermodynamically favorable process b. results in formation of an amide and a carboxylic acid c. is thermodynamically unfavorable and requires energy input d. is the same thing as a condensation reaction e. None of these are correct.
a. is a thermodynamically favorable process
One way to compare the relatedness of different species is to examine genes that are __________ and to look for __________, which is conserved gene order on the chromosomes. a. orthologs; synteny b. paralogs; synteny c. paralogs; comparative mapping d. orthologs; comparative mapping
a. orthologs; synteny
The first step of the permanent waving of hair involves the ____. a. reduction of natural disulfides b. breaking of hydrogen bonds c. dissociation of hair protofibrils d. all of the above
a. reduction of natural disulfides
Pyrimidine has a __________ ring system containing ______ nitrogens. a. single; 2 b. double; 2 c. double; 3 d. single; 3
a. single; 2
What is an apoenzyme? a. the protein part of an enzyme, not including the cofactors or coenzymes b. a precursor protein that is chemically modified by phosphorylation to yield an active enzyme c. a non-amino acid unit that must be tightly bound to an enzyme and is essential for catalytic activity d. a protein that assists in the folding of an enzyme to its native conformation
a. the protein part of an enzyme, not including the cofactors or coenzymes
A regular secondary structure occurs in a protein chain segment when _______. a. the φ and ψ angles are the same, or nearly so, throughout the segment b. the dihedral angle ω is near 0° c. the pH is near 7.0 d. the segment is primarily composed of aromatic amino acids
a. the φ and ψ angles are the same, or nearly so, throughout the segment
What is the absorbance of a sample that transmits 70% of incident light? a. 0.300 b. 0.155 c. 0.700 d. 0.523 A= log (I(initial)/I)
b. 0.155
If a protein is composed of 100 amino acids, what would its approximate molecular weight be? a. 1.1 (kilodaltons) b. 11 (kilodaltons) c. 110 (kilodaltons) d. 11,000 (kilodaltons)
b. 11 (kilodaltons)
If a double-stranded DNA sample contains 21% thymidine residues, approximately what percent of guanine residues would you expect the sample to have? a. 21% b. 29% c. 42% d. 58%
b. 29%
Calculate the osmotic pressure of a solution at 300 K that is 0.500 M in sucrose and 0.500 M in KCl. (Note: 1 J/L = 1000 Pa = 1 kPa). a. 2500 kPa b. 3750 kPa c. 624 kPa d. 3.750 kPa
b. 3750
What is the pI of proline, given that its -COOH group has a pKa of 1.99 and its -NH3+ group has a pKa of 10.96? a. 1.99 b. 6.48 c. 8.97 d. 10.96 e. 12.95
b. 6.48
Which of the following statements is false regarding the binding of 2,3-BPG to hemoglobin? a. It is an example of heterotropic allosteric modulation. b. BPG blood levels decrease in individuals shortly after they move from sea level to high altitudes. c. BPG binds to hemoglobin in the cavity between the β subunits in the T state. d. It reduces the affinity of hemoglobin for oxygen.
b. BPG blood levels decrease in individuals shortly after they move from sea level to high altitudes.
Which of the following best defines a signature sequence? a. An amino acid sequence consisting of the residues that most commonly occur at each position in a set of similar sequences b. Certain segments of a protein sequence that are found in the organisms of one taxonomic group but not in other groups c. The random sequence that results when the amino acids of a known sequence are shuffled by a common computerized test d. The regions of a protein sequence that are identical in the organisms within one taxonomic group
b. Certain segments of a protein sequence that are found in the organisms of one taxonomic
What would you expect for the electrophoresis of DNA at pH 7? a. DNA migrates toward the negative electrode because the nitrogenous bases are protonated and carry a positive charge. b. DNA migrates toward the positive electrode because the phosphates carry negative charges. c. The charge on DNA depends on the sequence of the bases and therefore could go toward either electrode. d. DNA migrates to its pI because it is neutral. The positive charges on the nitrogenous bases balances with the negative charges on the phosphates.
b. DNA migrates toward the positive electrode because the phosphates carry negative charges.
Which of the following best describes the order of events that occurs during gene expression? a. DNA → RNA → natively folded protein → unfolded protein b. DNA → RNA → unfolded protein → natively folded protein c. RNA → DNA → natively folded protein → unfolded protein d. RNA → DNA → unfolded protein → natively folded protein e. none of the above
b. DNA → RNA → unfolded protein → natively folded protein
Which statement is true regarding an acid dissociation reaction in water? a. An acid dissociation reaction does not involve ionization. b. For a carboxylic acid, the conjugate base is the ionized form. c. The un-dissociated acid is always ionized. d. The conjugate base form will always be the ionized species. e. For an amino group, the conjugate base is the ionized form.
b. For a carboxylic acid, the conjugate base is the ionized form
Why does Gly occupy every third position in the collagen triple helix? a. Glycine is the most hydrophobic amino acid. b. Glycine is the smallest amino acid. c. Glycine has the highest propensity to form helices. d. Glycine is the strongest amino acid. e. Glycine is the most flexible amino acid.
b. Glycine is the smallest amino acid.
Sometimes, the body elicits an immune response against allergens like pollen that it would normally reserve for pathogens. Which of the immunoglobulins is known for its role in the allergic response? a. IgD b. IgE c. IgA d. IgG
b. IgE
Which of the following classes of immunoglobulins is the first to be made by B lymphocytes and the major antibody to be produced in the early stages of a primary immune response? a. IgE b. IgM c. IgG d. IgA
b. IgM
One method of effectively transferring protons from one place to another is called proton hopping. Why is this a much faster process than proton delivery by diffusion in an aqueous environment? a. Hopping is faster because it requires the breaking of fewer hydrogen bonds between water molecules. b. In hopping, a single proton does not traverse the entire distance, but only the distance to the next neighboring water, and this continues quickly in a chain-like fashion. c. Diffusion causes too much of a charge gradient, which slows proton transfer compared to hopping. d. Diffusion has to work against the osmotic pressure, whereas hopping does not.
b. In hopping, a single proton does not traverse the entire distance, but only the distance to the next neighboring water, and this continues quickly in a chain-like fashion.
Which statement is true about the binding of the heme iron to its protein? a. The nitrogens of histidine, arginine or glutamine coordinate to the iron. b. It binds through a coordinate bond to nitrogen on the side-chain of a highly conserved histidine. c. The iron ion has no direct coordinate bonds to its protein; the porphyrin ring links to the protein. d. Since the iron is a cation, either of the anionic amino acids (aspartate or glutamate) bind to the iron.
b. It binds through a coordinate bond to nitrogen on the side-chain of a highly conserved histidine.
What is the role of a polylinker in a cloning vector? a. It encodes for a gene product that provides antibiotic resistance. b. It provides multiple recognition sequences for restriction endonucleases. c. It is the site marking the origin of replication sequence. d. It allows for blue-white selection in transformed cells.
b. It provides multiple recognition sequences for restriction endonucleases.
Which of the following statements is false with regard to specific activity? a. It increases during the purification of an enzyme. b. It refers to the total units of enzyme in a solution. c. It refers to the number of enzyme units per milligram of total protein. d. It is a measure of the purity of an enzyme.
b. It refers to the total units of enzyme in a solution.
How do monoclonal antibodies differ from polyclonal antibodies? a. Monoclonal antibodies bind to only one protein. b. Monoclonal antibodies are produced in cultured B cells. c. Polyclonal antibodies all bind to the same antigen site of a protein. d. Polyclonal antibodies are produced from identical B lymphocytes. e. Only the first two answers are correct.
b. Monoclonal antibodies are produced in cultured B cells.
Which statement is false about the nitrogenous bases in DNA and RNA? a. The purines and pyrimidines are aromatic. b. The 6-membered rings are predominantly in the chair configuration. c. The nitrogenous bases are hydrophobic under neutral pH conditions. d. The purines and pyrimidines absorb UV light near 260 nm.
b. The 6-membered rings are predominantly in the chair configuration.
Kinetic studies frequently use the initial rate method. Which statement does not apply to this method? a. The [S] is high enough that it changes little during the rate measurement. b. The length of the pre-steady state is evaluated. c. The [S] at which saturation occurs can be determined. d. How the rate depends on [S] can be evaluated when [E] is held constant.
b. The length of the pre-steady state is evaluated.
What can be said about a single polypeptide containing: 5 Ala, 2 Glu, 1 Lys, 1 Gly, and 1 Cys? a. The peptide contains two carboxylic acid groups. b. The peptide will be charged at pH 7. c. The peptide is not redox active. d. The peptide contains three amino groups. e. All of these are true.
b. The peptide will be charged at pH 7.
In an SDS-PAGE experiment, a protein migrates much faster than expected relative to protein standards, based on its known molecular weight. What could cause this? a. The electrophoresis wasn't run long enough. b. The protein had a very high intrinsic negative charge. c. The buffer ionic strength was too low. d. The current was too high. e. The voltage was too high.
b. The protein had a very high intrinsic negative charge.
Which statement does not apply to intrinsically disordered proteins? a. They lack a hydrophobic core and have a high density of charged amino acids. b. They are usually all α structures. c. Some serve as scavengers. d. They can interact with many protein partners.
b. They are usually all α structures.
Which of the following statements is false about enzymes? a. They have the ability to discriminate between reactants. b. They change the Keq of a reaction. c. They are not consumed in the process of chemical reactions. d. They catalyze reactions by lowering the activation barrier
b. They change the Keq of a reaction.
Of the 20 common amino acids, only one lacks a chiral α-carbon. Likewise, there is one amino acid that has a second chiral carbon within its side chain. Which amino acid is it? a. Leu b. Thr c. Arg d. Ser e. Pro
b. Thr
During muscle contraction the ____________. a. length of the thick filaments shorten b. Z disks move closer to each other c. A bands convert into I bands d. M line disappears
b. Z disks move closer to each other
Circular dichroism measures the difference between _____. a. the dipole moment of the amino end of an α-helix vs. the carboxyl end b. absorption of right circular polarized light vs. left circular polarized light c. visible light absorption vs. ultraviolet light absorption d. absorbance by a linear peptide vs. absorbance by a circular peptide e. total light absorbed by an α-helix vs. total light absorbed by a β-sheet
b. absorption of right circular polarized light vs. left circular polarized light
In the cation exchange chromatography of amino acids where the elution buffer is applied as a gradient from low pH to high pH, what is the order of elution (first to last) of a mixture of glycine, aspartate and arginine? a. arginine; glycine; aspartate b. aspartate; glycine; arginine c. glycine; arginine; aspartate d. glycine; aspartate; arginine
b. aspartate; glycine; arginine
To serve as an effective regulatory mechanism, phosphorylation must _____. a. lead to enzyme activation b. be reversible c. lead to enzyme inhibition d. occur on a serine, but not a threonine, residue
b. be reversible
The process stimulated by helper T cells that selectively stimulates the proliferation of cytotoxic T cells and B cells that can bind to a particular antigen is called ________. a. mediated immune response b. clonal selection c. T-B activation d. the antigen cascade
b. clonal selection
Which of the following is true of both a nucleoid and a nucleus? a. the location where DNA is stored, but not replicated b. contains the genome of the cell c. is enclosed within a single membrane d. is enclosed within a double membrane e. the first two answers are correct
b. contains the genome of the cell
Which of the following refers to the aqueous solution inside of the cell, excluding organelles? a. cytoplasm b. cytosol c. all of the above d. none of the above
b. cytosol
What effect would decreasing the column length have in column chromatography? a. increased resolution and separation of proteins b. decreased resolution and separation of proteins c. no effect on the resolution and separation of proteins d. not enough information to tell
b. decreased resolution and separation of proteins
Autophagy of amyloid fibers includes _______. a. the action of heat shock proteins to refold the proteins b. degradation by encapsulation followed by docking with a lysosome c. elongation of the fibers and the formation of additional disulfide links d. aggregation to form larger insoluble structures.
b. degradation by encapsulation followed by docking with a lysosome
Circular dichroism spectroscopy can do all of the following except _____. a. determine whether proteins are properly folded b. determine primary structure of proteins c. monitor transitions between folded and unfolded states d. estimate the fraction of the protein that is folded in either of the common secondary structures
b. determine primary structure of proteins
Consider the following atoms commonly found in chemical reaction mechanisms. Rank them from least to most electronegative. a. hydrogen, nitrogen, carbon, oxygen b. hydrogen, carbon, nitrogen, oxygen c. oxygen, carbon, nitrogen, hydrogen d. oxygen, nitrogen, carbon, hydrogen
b. hydrogen, carbon, nitrogen, oxygen
Numerous weak interactions are responsible for stabilizing protein conformation. Of the following, ____ are the major contributors to stabilizing the conformation of most soluble proteins. a. hydrogen bonds b. hydrophobic interactions c. van der Waals interactions d. ionic interactions
b. hydrophobic interactions
The dimerization of cysteine to cystine is an example of __________. a. reduction b. oxidation c. hydrolysis d. single displacement
b. oxidation
Classify the enzyme that catalyzes the following reaction: CH3CH2OH → CH3CHO + H2O a. transferase b. oxidoreductase c. isomerase d. hydrolase
b. oxidoreductase
Paralogs are _____. a. different conformations of a protein b. proteins from one species with the same function c. genes transferred from one species to another d. proteins with different signature sequences
b. proteins from one species with the same function
What is the name reserved for RNA with catalytic activity? a. mRNA b. ribozyme c. rRNA d. tRNA
b. ribozyme
The following reagents can all be used to modify the cysteine thiol group in a protein except _____. a. maleimide b. sodium dodecyl sulfate c. iodoacetamide d. benzylbromide e. bromomethyl ketone
b. sodium dodecyl sulfate
Below is a list of components necessary to construct a YAC vector. What is necessary but missing? One endonuclease site Centromere sequence Origin of replication Two selectable marker genes a. lacZ gene b. telomere sequences c. a second endonuclease site d. polylinker DNA
b. telomere sequences
The major finding of the experiment by Christian Anfinsen in the 1950s with ribonuclease A was that _____. a. when ribonuclease A is denatured, it completely loses its catalytic activity b. the information required to fold ribonuclease A into its native structure is present in its amino acid sequence c. it is an enzyme that degrades RNA d. urea and a reducing agent will denature the enzyme
b. the information required to fold ribonuclease A into its native structure is present in its amino acid sequence
In a bi-substrate reaction that is said to occur via a "Ping-Pong" mechanism, _____. Please choose the correct answer from the following choices, and then select the submit answer button. a. the substrates can bind in either order, and a "ternary complex" may or may not form b. the substrates bind in a specific order and no "ternary complex" is formed c. the substrates can bind in either order to form a "ternary complex" d. the substrates must bind in a specific order to form a "ternary complex" e. the substrates can bind in either order, but no "ternary complex" is formed
b. the substrates bind in a specific order and no "ternary complex" is formed
What is a major advantage of a Lineweaver-Burk plot over a Michaelis-Menten plot? a. The Lineweaver-Burk plot is independent of total enzyme concentration, [Et] b. The Lineweaver-Burk plot displays more orders of magnitude of [S]. c. It is easier to determine Vmax from a y-intercept than from an asymptote. d. Lineweaver-Burk plots relate more directly to the reaction mechanism.
c. . It is easier to determine Vmax from a y-intercept than from an asymptote.
If Vmax is 100.0 µM/min using an enzyme concentration of 0.1 µM, what is kcat for the reaction? a. 1 x 10-3 min-1 b. 10 min-1 c. 1000 min-1 d. 1 min-1 e. 100 min-1
c. 1000 min-1
Which of the following correctly identifies the order of events that describe the mechanism of action of HIV protease? 1. Formation of a tetrahedral intermediate. 2. Attack of the carbonyl carbon by water. 3. Protonation of the amino acid leaving group a. 1, 2, 3 b. 1, 3, 2 c. 2, 1, 3 d. 3, 1, 2
c. 2, 1, 3
The complementarity between the two strands is useful for determining base composition. If guanine makes up 14% of the nucleotides in a DNA sample, what percentage of nucleotides in this sample will be adenine? a. 14 b. 28 c. 36 d. 43 e. 72
c. 36
Which of the following correctly identifies the order of events that take place during the generation of a genomic sequence? 1) Genomic sequences are PCR amplified. 2) Genomic sequences are immobilized on a solid surface. 3) Genomic sequences are ligated to synthetic oligonucleotide sequences. 4) Genomic sequences are broken at random places into smaller fragments. a. 2, 3, 4, 1 b. 4, 2, 3, 1 c. 4, 3, 2, 1 d. 2, 4, 3, 1
c. 4, 3, 2, 1
Which statement describes the relationship between absorbance (A) and solute concentration (c) that follows the Lambert-Beer Law for an absorbing layer of fixed path length? a. A and c do not have a quantifiable relationship. b. A and c have a sinusoidal relationship. c. A is directly proportional to c. d. A is inversely proportional to c.
c. A is directly proportional to c.
Which sequence maximizes ion-pairing for the stabilization of α helix formation at pH 7? a. DAAARVVVVEV b. AVISNRPYGGG c. ADVVKLIEVAR d. ADVKLEVRIDV
c. ADVVKLIEVAR
Which of the following peptides would have a +1 charge at pH = 7? a. Arg-Gln-Lys-Leu-Lys b. Ala-Glu-Arg-Leu-Pro c. Ala-Gly-Asn-Leu-Lys d. Ala-Gly-Asp-Leu-Lys e. Ala-Glu-Asn-Leu-Lys
c. Ala-Gly-Asn-Leu-Lys
If Hb and Mb both had the same P50, but Hb bound O2 with positive cooperativity, what can we say about the two proteins? a. At pO2 above P50, Hb has a lower Y than Mb. b. At pO2 equal to P50, Hb has a higher Y than Mb. c. At pO2 above P50, Hb has a higher Y than Mb. d. At pO2 above P50, Hb and Mb have the same Y. e. At pO2 below P50, Hb has a higher Y than Mb.
c. At pO2 above P50, Hb has a higher Y than Mb.
Ramachandran plots describe the combinations of Φ and Ψ dihedral angles that are or are not permitted in a peptide backbone. Which of the following statements is INCORRECT regarding Φ and Ψ angles? a. Steric hindrance between atoms in the polypeptide backbone and amino acid side chains limit the values of Φ and Ψ. b. Φ involves C-N-Cα-C bonds. c. Both angles are defined as +/- 90 degrees when the polypeptide is fully extended and all peptide groups are in the same plane. d. Ψ involves the N-Cα-C-N bonds.
c. Both angles are defined as +/- 90 degrees when the polypeptide is fully extended and all peptide
Rank the stability of the following nucleic acid duplexes: RNA−DNA; DNA−DNA; RNA−RNA a. RNA−RNA < RNA−DNA < DNA−DNA b. RNA−RNA < DNA−DNA < RNA−DNA c. DNA−DNA < RNA−DNA < RNA−RNA d. DNA−DNA < RNA−RNA < RNA−DNA
c. DNA−DNA < RNA−DNA < RNA−RNA
________ reactions require an input of energy and their ΔG values are ________. a. Exergonic; positive b. Exergonic; negative c. Endergonic; positive d. Endergonic; negative e. None of the above.
c. Endergonic; positive
Halophiles are a group of organisms that flourish in high salt conditions. Which of the following is not true of halophiles? a. Halophiles belong to the domain Archaea. b. Halophiles are more closely related to slime molds than to animals. c. Halophiles are eukaryotes. d. Halophiles are single-celled organisms.
c. Halophiles are eukaryotes.
What contributes to CO being responsible for more than half of yearly deaths due to poisoning? a. It is present in the atmosphere at dangerously high levels. b. It has approximately 1000x greater affinity for hemoglobin than oxygen. c. Hemoglobin bound to CO does not efficiently release O2 in the tissues. d. all of the above
c. Hemoglobin bound to CO does not efficiently release O2 in the tissues.
What is the purpose of the secondary antibody in immunofluorescence methods? a. It binds to the protein that is being detected and produces a fluorescent signal. b. It is used to precipitate the protein of interest. c. It binds to the primary antibody that is bound to the protein being detected and produces a fluorescent signal. d. It binds to the cDNA generated via reverse transcription and produces a fluorescent signal. e. It binds to mRNA and produces a fluorescent signal.
c. It binds to the primary antibody that is bound to the protein being detected and produces a fluorescent signal
What are the usual units for the molar extinction coefficient, ε? (M=molarity) a. M/cm b. M c. M-1/cm-1 d. M(cm)
c. M-1/cm-1
Which of the following statements is incorrect regarding the globular and fibrous proteins? a. Fibrous proteins generally consist of one type of secondary structure. b. Fibrous proteins have their polypeptide chains arranged in long strands or sheets. c. Most globular proteins provide support, shape, and external protection to vertebrates. d. Globular proteins often contain several types of secondary structure.
c. Most globular proteins provide support, shape, and external protection to vertebrates.
Which form of glycine predominates at very low pH? a. NH2-CH2-COOH b. NH3+-CH2-COO- c. NH3+-CH2-COOH d. NH2-CH2-COO-
c. NH3+-CH2-COOH
If artificial red blood cells that contained myoglobin instead of hemoglobin were made, could they be used effectively in blood transfusions? a. Yes, because the structures of myoglobin and hemoglobin are similar and bind oxygen similarly. b. Yes, but patients would also need to be infused with extra BPG to regulate O2 binding. c. No, because it is not possible for myoglobin to exhibit the cooperative binding of oxygen. d. No, because myoglobin could not bind oxygen as efficiently in the lungs.
c. No, because it is not possible for myoglobin to exhibit the cooperative binding of oxygen.
Which statement about the amino acid Cys is not true? a. The Cys side chain contains a redox active thiol group. b. The Cys side chain is a nucleophile in its unprotonated form. c. The Cys side chain can act as an acid in its unprotonated form. d. The Cys side chain is ionizable. e. All of these are true.
c. The Cys side chain can act as an acid in its unprotonated form.
Which statement is true about antibody-antigen binding? a. The binding involves formation of a covalent bond between the antigen and antibody, so the Kd for this process is very low. b. The binding involves formation of a covalent bond between the antigen and antibody, so the Kd for this process is very high. c. The binding involves many non-covalent weak interactions between the antigen and antibody, so the Kd for this process is very low. d. The binding involves many non-covalent weak interactions between the antigen and antibody, so the Kd for this process is very high.
c. The binding involves many non-covalent weak interactions between the antigen and antibody, so the Kd for this process is very low
Many common expression vectors contain the β-lactamase gene because it confers resistance to the antibiotic ampicillin. Suppose ampicillin were left out of the growth media during the expression stage of the experiment. What would the results look like? a. The cells would grow normally and maintain the expression vector and produce the desired protein. b. The cells would grow normally and would maintain the expression vector, but not produce the desired protein. c. The cells would grow normally, but without "positive pressure" to maintain the plasmid, most would not express the desired protein. d. The cells would grow much more slowly. e. The cells would not grow at all.
c. The cells would grow normally, but without "positive pressure" to maintain the plasmid, most would not express the desired protein.
For a polyprotic acid, which statement is true? Polyprotic acids are stronger acids than monoprotic acids. a.A polyprotic acid has a single associated pKa value. b. A polyprotic acid can only react with one equivalent of base. c. The conjugate base of a polyprotic acid can also act as an acid itself. d. All of these statements are true.
c. The conjugate base of a polyprotic acid can also act as an acid itself.
Which of the following statements regarding the use of mammalian cells for protein expression is false? a. Mammalian cells are generally used to test the function of a protein in vivo rather than to produce a protein in large amounts. b. Mammalian cells can properly post-translationally modify proteins to their active form. c. The growth of mammalian cells in tissue culture is relatively inexpensive. d. Viruses are often employed to deliver the cloned gene of interest to these host cells.
c. The growth of mammalian cells in tissue culture is relatively inexpensive.
Which statement is true about hydrogen bonds? The strength of a hydrogen bond is about 90% of a typical covalent bond. a. The lifetime of an individual hydrogen bond in liquid water is on the order of milliseconds. b. The hydrogen bond is purely an electrostatic attraction due to the presence of partial charges. c. There is overlap of orbitals between molecules in a hydrogen bond, which give the hydrogen bond some covalent character. d. The strength of a hydrogen bond is about 90% of a typical covalent bond.
c. There is overlap of orbitals between molecules in a hydrogen bond, which give the hydrogen bond some covalent character.
Reverse turns are classified as secondary structure because _____. a. They only occur at interior protein positions. b. They link together α-helices. c. They are stabilized by hydrogen bonds between backbone amide groups. d. They link together β-sheets. e. They are not as important as primary structure.
c. They are stabilized by hydrogen bonds between backbone amide groups.
A haplotype is best defined as ______. a. variations among individuals in a population in the length of certain restriction fragments in which certain genomic sequences occur b. a segment of double-stranded DNA produced by the action of restriction endonuclease on a larger DNA c. a combination of DNA sequences at adjacent loci on a chromosome that are transmitted together d. a genomic base-pair change that helps distinguish one species from another or some subset of individuals in a population
c. a combination of DNA sequences at adjacent loci on a chromosome that are transmitted together
What generally happens during a successful enzyme purification protocol (comparing crude extract to final product)? a. activity increases and specific activity decreases b. activity and specific activity increase c. activity decreases and specific activity increases d. activity and specific activity decrease
c. activity decreases and specific activity increases
Which of the following have resulted in the evolution of the organisms that are adapted to their own particular ecological niches? a. genetic variation b. natural selection c. all of the above d. none of the above
c. all of the above
Which does not apply to the most common kind of α helix? a. is stabilized by hydrogen bonding b. has about 3.6 amino acid residues per helix turn c. can be a mixture of L and D amino acids d. is right-handed
c. can be a mixture of L and D amino acids
Electroporation is a method for generating _____________. a. recombinant DNA b. small DNA fragments c. competent bacterial cells d. high plasmid copy number
c. competent bacterial cells
Nucleotides are linked together in nucleic acids by _______bonds called _______. a. noncovalent; peptide bonds b. covalent; glycosidic bonds c. covalent; phosphodiester linkages d. noncovalent; glycosidic bonds
c. covalent; phosphodiester linkages
β turns are generally found on the ____ of a protein and often consist of ____ residues. a. exterior; gly and ala b. interior; pro and gly c. exterior; pro and gly d. interior; gly and ala
c. exterior; pro and gly
What feature of a disease classifies it as a prion disease? a. if it affects the central nervous system b. if it results from protein aggregation c. if the infectious agent is a protein d. if the diseases are fatal e. none of these define prion diseases
c. if the infectious agent is a protein
A living organism is classified as an open system because _______. a. it can evolve through point mutations b. it can self-replicate c. it exchanges matter and energy with the surroundings d. it response to its environment
c. it exchanges matter and energy with the surroundings
Because human and mouse α-globin genes are thought to have evolved from a common ancestor, they are considered to be _____. a. homologs b. paralogs c. orthologs d. none of the above
c. orthologs
There are 20 amino acids commonly found in proteins, but over 300 different amino acids have been identified in cells. Which of the following is not created by a post-translational modification? a. 4-Hydroxyproline b. Desmosine c. Selenocysteine d. γ-Carboxyglutamate
c. selenocysteine
Cell fractionation separates particles based on _____. a. carbohydrates b. solubility c. size d. lipids
c. size
Which of the following factors is most likely responsible for setting the upper limit of cell size? a. the amount of DNA a cell has b. the minimum number of each type of biomolecules required by the cell c. the rate of diffusion of solute materials d. none of the above
c. the rate of diffusion of solute materials
Consider the use of a BAC that contains a single cloning site in the middle of a lacZ gene, and also contains an ampicillin resistance gene. Bacteria are transformed with recombinant BAC and screened on a medium containing ampicillin and X-gal. Which colonies contain the recombinant BAC? a. blue colonies b. yellow colonies c. white colonies d. fluorescent colonies
c. white colonies
Which term best describes the inactive precursor of an enzyme? a. cofactor b. apoenzyme c. zymogen d. holoenzyme
c. zymogen
When pH = pKa, what is the average charge for an acetic acid-acetate ion system? a. +1 b. 0 c. -1 d. -0.5
d. -0.5
Which of the following combinations of φ and ψ dihedral angles would be allowed in a poly-Alanine polymer? a. +120°, -120° b. +180°, -180° c. -120°, -120° d. -120°, + 120° e. +120°, +120°
d. -120°, + 120° (Fig 4-3)
Calculate the maximum velocity, Vmax, for an enzyme-catalyzed reaction that follows Michaelis-Menten kinetics if [S] is 6 mM, Km = 2 mM and V0 = a. 0.020 mM/min. b. 0.0067 mM/min c. 0.04 mM/min d. 0.027 mM/min e. 5.76 mM/min
d. 0.027 mM/min
Starting with 1 picogram of DNA (1.00 x 10-12 g), if you were to amplify this DNA by PCR using a cycle number of 20, how much DNA would you end up with? a. 4.0 x 10-10 g b. 2.0 x 10-11 g c. 1.05 x 10-3 g d. 1.05 x 10-6 g e. 1.00 x 10-8 g
d. 1.05 x 10-6 g
For the acid AH, if [A-]/[AH] is 4500 when pH is three times the pKa, what is the pKa for this acid? a. 7.3 b. 4.8 c. 5.1 d. 1.8 e. 3.7
d. 1.8
How many turns are in a B-form DNA fragment that is 714 nm long? a. 68 b. Cannot calculate from information given. c. 210 d. 20
d. 20
When was the first human genome sequence completed? a. 1982 b. 1995 c. 2012 d. 2001
d. 2001
What is the approximate ratio of product to substrate at pH 7.0 if ΔG'° at 298 K equals -1 kJ/mol? a. 1000:1 b. 2:1 c. 10:1 d. 3:2
d. 3:2
Imagine a reaction mixture favors only the formation of dipeptides. If the mixture contains ample amounts of glycine and alanine, how many different dipeptides can possibly be formed? a. 1 b. 2 c. 3 d. 4
d. 4
Using the Henderson-Hasselbalch equation, calculate the percentage of an ammonia solution that would be in the ionic form at pH 9.40, assuming a pKa for the ammonium ion of 9.25. a. 70.9% b. 1.41% c. 58.5% d. 41.5% e. 29.1%
d. 41.5%
Which of the following statements is false with regard to the concerted and sequential models of cooperative binding? a. The sequential model allows for individual subunits to assume different conformations. b. In the concerted model, successive binding of ligand molecules to the low-affinity conformation makes a transition to the high-affinity conformation more likely. c. In the concerted model, the subunits of a cooperatively-binding protein are functionally identical—no protein has individual subunits in different conformations. d. A protein whose cooperative binding is explained by the sequential model cannot also have its cooperative binding explained by the concerted model.
d. A protein whose cooperative binding is explained by the sequential model cannot also have its cooperative binding explained by the concerted model.
Which of the following steps is not involved in the control of muscle contractions? a. Troponin binds to Ca2+. b. Tropomyosin binds to actin, preventing its interaction with myosin. c. Troponin-tropomyosin complex changes conformation upon Ca2+ binding to expose myosin binding sites on actin. d. ATP hydrolysis by myosin blocks Ca2+ binding to troponin. e. Ca2+ is released by the sarcoplasmic reticulum in response to a nerve impulse.
d. ATP hydrolysis by myosin blocks Ca2+ binding to troponin.
The physiological effects of histamine include _____. a. increased permeability of blood vessels b. vasodilation c. increased movement of immune cells to sites of inflammation d. All of these are effects of histamine. e. None of these is an effect of histamine.
d. All of these are effects of histamine.
For which reason might a researcher choose a bacterial artificial chromosome (BAC) over a traditional cloning vector? a. BACs contain a selectable marker, whereas traditional cloning vectors do not. b. BACs contain a polylinker, whereas traditional cloning vectors do not. c. BACs contain a screenable marker, whereas traditional cloning vectors do not. d. BACs can accommodate very long segments of cloned DNA, whereas traditional cloning vectors do not.
d. BACs can accommodate very long segments of cloned DNA, whereas traditional cloning vectors do not.
Which of the following statements is false regarding bacterial and animal cells? a. Bacterial cells have their genetic material located in the cytoplasm, while animal cells have their genetic material in the nucleus. b. Animal cells have membrane-bound organelles, but bacterial cells do not. c. Bacterial cells are smaller than animal cells. d. Bacterial cells do not have a plasma membrane and have a cell wall instead.
d. Bacterial cells do not have a plasma membrane and have a cell wall instead.
Describe what is occurring in the following reaction: C6H12O6 + 6O2 → 6CO2 + 6H2O + energy. a. C6H12O6 and CO2 are oxidized. b. O2 is oxidized and CO2 is reduced. c. C6H12O6 is reduced and O2 is oxidized. d. C6H12O6 is oxidized and O2 is reduced.
d. C6H12O6 is oxidized and O2 is reduced.
G−G base-pairing is a common feature of what type of DNA structure? a. B-form DNA b. hairpin turns c. DNA triplex d. DNA tetraplex e. cruciforms
d. DNA tetraplex
A nonapeptide was determined to have the following amino acid composition: two Lys, two Gly, two Phe, one each of His, Leu, and Met. When the native peptide was exposed to cyanogen bromide, a heptapeptide and a dipeptide were recovered. Incubation of the native peptide with trypsin gave a pentapeptide and a tetrapeptide. Cyanogen bromide cleaves at Met (C); whereas trypsin cleaves at Lys and Arg (C). Which sequence is compatible with this data? a. Gly-Phe-Lys-Lys-Gly-Leu-Met-Phe-His b. Gly-Leu-Phe-His-Lys-Lys-Phe-Met-Gly c. His-Leu-Gly-Lys-Lys-Phe-Phe-Met-Gly d. Gly-Met-Leu-Lys-His-Phe-Gly-Phe-Lys
d. Gly-Met-Leu-Lys-His-Phe-Gly-Phe-Lys
Which statement is true about alanine? a. Only the zwitterion form provides buffering. b. It is a good buffer near neutral pH. c. It cannot buffer at any pH. d. It has two pH regions where it can act as a buffer.
d. It has two pH regions where it can act as a buffer.
An atom, "X", is involved in a hydrogen bond with the hydrogen of a water molecule. How does the geometry of the hydrogen bond between H and X affect the strength of the hydrogen bond? a. It will be stronger if X is at a right angle to the covalent O-H bond in the water. b. It will be stronger if the hydrogen bond is at an angle of about 109.5° relative to the covalent O-H bond. c. The strength of the hydrogen bond does not depend on the geometry. d. It will be stronger if X is aligned with the covalent O-H bond in the water.
d. It will be stronger if X is aligned with the covalent O-H bond in the water.
A post-doc is studying protein X. The gene for the protein has been cloned and expressed, but the post-doc would like to make purification of the protein simpler. Which might be an option? a. Add chloramphenicol to the cells when they are expressing the protein. b. Use RT-PCR to amplify the protein, then use a Ni2+ column for purification. c. Use site-directed mutagenesis to alter the protein to make it more easily purified. d. Make a fusion protein, adding a GST tag. Then purify with affinity chromatography.
d. Make a fusion protein, adding a GST tag. Then purify with affinity chromatography.
Which of the following would be the strongest base? a. H3PO4 b. H2PO4- c. HPO42- d. PO43- e. None of these act as bases.
d. PO43-
Which of the following statements is not true regarding the equation: ΔG = ΔH - TΔS? a. T is the temperature in Kelvin. b. The equation includes the change in the randomness of the system. c. If ΔH is negative in this equation, it means that heat is being released. d. The equation includes free-energy of the system, designated as H.
d. The equation includes free-energy of the system, designated as H.
Hydrolysis of which of the following bonds in nucleotides provides the most chemical energy to drive cellular reactions? a. the bond between the α and β phosphates b. the bond between the γ and β phosphates c. the bond between the ribose and the α phosphate d. The first two answers are correct. e. The second and third answers are correct.
d. The first two answers are correct.
Which statement is true about the binding of O2 or CO to free heme in comparison to the binding to heme associated with myoglobin? a. Both O2 and CO bind to heme with about the same affinity whether or not the heme is associated with myoglobin. b. The heme in Mb binds both O2 and CO more strongly than free heme. c. The heme in myoglobin has enhanced binding of CO as compared to free heme. d. The heme in myoglobin has enhanced binding of O2 as compared to free heme.
d. The heme in myoglobin has enhanced binding of O2 as compared to free heme.
An active protein was purified to homogeneity using gel filtration and analyzed for its amino terminal residue using dabsyl chloride as described in Chapter 3. After multiple tries, the researcher gave up because there appeared to be four different amino terminal residues in the protein. What would you conclude about this protein? a. The protein had not been purified properly. b. The protein had Lys, Arg, and His residues that were reacting in the dabsyl chloride. c. The protein had been degraded. d. The protein was made of four unique subunits. e. none of the above
d. The protein was made of four unique subunits.
Which of the following statements is incorrect regarding the use of bacteria for the expression of recombinant proteins? a. Many do not undergo the covalent modifications or proteolytic cleavage that may be necessary for their activity. b. They are difficult to grow in large amounts. c. They require expensive media for growth. d. The regulatory sequences that govern gene expression in E. coli and many other bacteria are not well understood.
d. The regulatory sequences that govern gene expression in E. coli and many other bacteria are not well understood.
Which of the following statements is false regarding the reaction catalyzed by lysozyme? a. Lysozyme cleaves the (β1→4) glycosidic C-O bond between NAM and NAG. b. The lysozyme reaction is a nucleophilic substitution, with -OH from water replacing the GlcNAc at C-1 of Mur2Ac. c. Lysozyme catalyzes a reaction in which the product has the same anomeric configuration as the substrate. d. There are two chemically reasonable mechanisms that could generate the observed product of lysozyme reaction, although recent data supports the SN1 model.
d. There are two chemically reasonable mechanisms that could generate the observed product of lysozyme reaction, although recent data supports the SN1 model.
Which statement does not apply to transition-state analogs with respect to enzymes? a. They are important in pharmaceutical drug design. b. They chemically resemble the transition state of the substrate. c. They bind at the active site more strongly than the substrate. d. They bind covalently to the enzyme.
d. They bind covalently to the enzyme.
Which of the following statements about allosteric enzymes is true? a. They are generally smaller than nonallosteric enzymes. b. They are generally less complex than nonallosteric enzymes. c. They function through irreversible, covalent binding of regulatory compounds. d. They have one or more regulatory sites for binding modulators.
d. They have one or more regulatory sites for binding modulators.
What is the purpose of inserting a polylinker into a plasmid vector? a. To increase the uptake of the plasmid by E. coli. (Enhance transformation efficiency.) b. To increase the frequency of transcription of a cloned gene in the vector. c. To increase the number of plasmids that E. coli will produce (copy number). d. To increase the number of restriction sites in the vector.
d. To increase the number of restriction sites in the vector.
Which statement about the titration curve for a weak acid is correct? a. It takes less base to fully titrate a strong acid than a weak acid. b. It takes more base to fully titrate a strong acid than a weak acid. c. A strong acid and a weak acid will have the same pH when the solution is 50% titrated. d. When a strong acid is 50% titrated, the pH of the solution is lower than for a weak acid. e. When a strong acid is 50% titrated, the pH of the solution is higher than for a weak acid.
d. When a strong acid is 50% titrated, the pH of the solution is lower than for a weak acid.
Amyloidoses are _________ characterized by _________. a. protein chaperones; their speed of folding b. a set of proteins; similar motifs and evolution c. complexes of proteins; the same SCOP2 classification d. a set of diseases; misfolded proteins
d. a set of diseases; misfolded proteins
BPG _________________________. a. is a heterotropic modulator of hemoglobin b. carries a negative charge at biological pH and binds in the central cavity between the hemoglobin subunits c. is present in relatively high concentrations in erythrocytes and stabilizes the T state of hemoglobin d. all of the above
d. all of the above
During muscle contraction___. a.sarcomeres become progressively shorter b. thick and thin filaments slide past each other c. Z disks in neighboring I bands draw closer together d. all of the above
d. all of the above
Myosin can best be described as _____. a. a contractile protein of the muscle b. an actin-binding protein c. an ATPase d. all of the above e. both a contractile protein of the muscle and an actin-binding protein
d. all of the above
The reaction catalyzed by enolase _____. a. demonstrates general acid-base catalysis b. demonstrates transition-state stabilization c. demonstrates metal ion catalysis d. all of the above
d. all of the above
What effect does the binding of CO2 and H+ to hemoglobin in the peripheral tissues have in the body? a. The tense form of hemoglobin is stabilized by the binding of CO2 and H+. b. Binding of H+ to hemoglobin serves as a buffer to regulate the pH of peripheral tissues. c. It facilitates the release of O2 in the peripheral tissues. d. all of the above
d. all of the above
Which of the following is true of using tandem affinity purification tags for protein purification? a. This technique minimizes false positives. b. Protein interactions that persist through both steps are likely to be functionally significant. c. Two consecutive purification steps help to eliminate any weakly bound contaminants. d. all of the above
d. all of the above
Which of the following properties of RNA suggest it or its related precursors may have been the first genes and catalysts? a. RNA-like molecules can form abiotically. b. RNA molecules can catalyze their own formation. c. The process of RNA self-replication is not perfect, enabling the formation of RNA variants. d. all of the above
d. all of the above
Which of the following statements about the structure of chymotrypsin is true? a. Chymotrypsin is made up of three peptides held together by five disulfide bonds. b. Chymotrypsin is synthesized as a zymogen called chymotrypsinogen. c. A serine residue is a key active-site residue in the enzyme. d. all of the above
d. all of the above
Why can the pKa value for an ionizable R group change when an amino acid becomes incorporated into a peptide? a. Environmental factors can influence pKa. b. Ionizable R groups can interact with other peptide R groups. c. There can be a loss of charge to alpha-carboxyl and alpha-amino groups. d. all of the above
d. all of the above
Which amino acid would most likely be found in the binding site of protein whose ligand is a cation? a. alanine b. lysine c. cysteine d. aspartate
d. aspartate
Which of the following types of proteins are exceptions to the two simple rules of protein folding: (1) Hydrophobic residues are found buried in the interior of a protein; and (2) the number of hydrogen bonds and ionic interactions within the protein are maximized? a. globular proteins b. transmembrane proteins c. proteins with intrinsically disordered segments d. both b and c
d. both b and c
Which molecule is a common second messenger produced by the activity of adenylyl cyclase? a. ATP b. cUDP c. ADP d. cAMP
d. cAMP
Mast cells are responsible for the production of _____. a. immunoglobulins b. haptens c. aterm-123ntibodies d. histamine e. insulin
d. histamine
Where in the body are lymphocytes and macrophages produced? a. in the pituitary gland b. in the blood c. in the pancreas d. in the bone marrow e. in the liver
d. in the bone marrow
Non-coding segments of DNA interspersed between coding segments in a gene are called ___________. a. spliceosomes. b. exons. c. intergenes. d. introns.
d. introns.
The resin used for cation exchange is _______ charged. If a solution of Val, Lys, and Glu at pH = 7 are loaded onto a column with cation exchange resin, what order would the amino acids elute from the column if eluted with salt? a. positively; Lys, Val, Glu b. negatively; Lys, Val, Glu c. positively; Glu, Val, Lys d. negatively; Glu, Val, Lys
d. negatively; Glu, Val, Lys
Transposons are DNA sequences that can transpose (move around) within the genome, and many carry genetic information required to _____. a. produce enzymes that replicate their own sequence b. produce proteins that inhibit transcription c. produce proteins that induce apoptosis d. produce enzymes that catalyze their transposition e. All of the above
d. produce enzymes that catalyze their transposition
If a disulfide bond connects two polypeptide chains in a protein, the highest level of protein organization this protein has is _____. a. primary structure. b. secondary structure. c. tertiary structure. d. quaternary structure.
d. quaternary structure.
The reaction shown is a single-step reaction. What happens to the rate if the concentrations of both A and B are doubled? A + B → C a. rate is halved b. rate doubles c. rate stays constant d. rate quadruples
d. rate quadruples
The C−N bond in the peptide backbone of a protein would have a bond that is ______ the C−N bond in CH3−NH3+. a. identical to b. longer than c. the same length as d. shorter than e. weaker than
d. shorter than
Which kinds of sequences are common in centromeres and telomeres? a. long interspersed nuclear elements (LINEs) b. transposons c. single nucleotide polymorphisms (SNPs) d. simple-sequence repeats (SSRs)
d. simple-sequence repeats (SSRs)
A single heavy chain of an immunoglobulin molecule has ________, whereas a single light chain of an immunoglobulin molecule has _______. a. six constant domains and two variable domains; two constant domains and two variable domains b. one constant domain and one variable domain; three constant domains and one variable domain c. two constant domains and one variable domain; one constant domain and two variable domains d. three constant domains and one variable domain; one constant domain and one variable domain
d. three constant domains and one variable domain; one constant domain and one variable domain
The quantity kcat is called the _______ and is a measure of the ______ at saturation. a. turnover time; maximum rate b. turnover time; minimum [S] c. turnover number; [ES] d. turnover number; amount of product produced
d. turnover number; amount of product produced
If a cell homogenate were subjected to centrifugation at increasingly higher speeds, in which order would you expect to see the following components in the pellet? a. microsomes, mitochondria, whole cells b. nucleus, microsomes, mitochondria c. mitochondria, whole cells, chloroplasts d. whole cells, chloroplasts, mitochondria e. none of the above
d. whole cells, chloroplasts, mitochondria
Which is a difference between γ and β turns? a. γ turns contain disulfide bonds; β turns have hydrogen bonds b. γ turns have trans proline; β turns have cis proline c. γ turns rarely contain glycine; β turns frequently contain glycine d. γ turns have three amino acids; β turns have four amino acids
d. γ turns have three amino acids; β turns have four amino acids
Forty-two percent of a propionic acid solution is in its acidic form at pH 5.5. What is the pKa of propionic acid? a. 3.2 b. 5.6 c. 2.3 d. 7.8 e. 5.4
e. 5.4
Which statement regarding the use of DNA microarray analysis is not correct? a. It can be used to monitor increases or decreases in gene transcription. b. It can be used to compare expression patterns at different developmental stages of an organism. c. It cannot be used to measure changes in protein levels in response to external cellular stimuli. d. It cannot be used to monitor formation of specialized RNA molecules like siRNA and miRNA. e. All of these are true statements.
e. All of these are true statements.
Which enzyme has the highest catalytic efficiency? a. Enzyme E: Km = 2.5 µM; Vmax = 100 µM/min b. Enzyme C: Km = 2.5 mM; Vmax = 100 mM/min c. Enzyme D: Km = 25 µM; Vmax = 100 mM/min d. Enzyme B: Km = 50 µM; Vmax = 1000 mM/min e. Enzyme A: Km = 2.5 µM; Vmax = 100 mM/min
e. Enzyme A: Km = 2.5 µM; Vmax = 100 mM/min
During the cloning process, what is the specific function of DNA ligase? a. It is used to stabilize the base-pairing between the sticky ends of the DNA fragments being linked. b. It adds a phosphate group to the 5'−end of a polynucleotide. c. It cuts DNA at very specific recognition sequences. d. It causes the circular DNA to twist into a supercoiled structure. e. It catalyzes the formation of a phosphodiester bond in the DNA.
e. It catalyzes the formation of a phosphodiester bond in the DNA.
Why are salt bridges much stronger when they occur at the interior of a protein as compared to its surface? a. There is no difference in strength between salt bridges at the surface and the core of a protein. b. Because a salt bridge neutralizes the charges on each ionic group and makes it very non-polar, so it also interacts by hydrophobic forces. c. Salt bridges become covalent at the core of a protein because there are no other charges around. d. A salt bridge inside a protein causes induced dipoles to interact with the ions. e. The interior of the protein has a much lower dielectric constant than the solvent so there is no shielding of the charges.
e. The interior of the protein has a much lower dielectric constant than the solvent so there is no shielding of the charges.
All of the common secondary structural elements fall within allowed combinations of φ and ψ dihedral angles except _____. a. α-helix b. β-helix c. triple helix d. antiparallel β-sheets e. They all have allowed angles.
e. They all have allowed angles.
Binding energy can be used to overcome _____. a. the need for proper alignment of catalytic functional groups on the enzyme b. the solvation shell of hydrogen-bonded water that surrounds and helps to stabilize most biomolecules in aqueous solution c. the entropy of molecules in solution, which reduces the possibility that they will react together d. the distortion of substrates that must occur in many reactions e. all of the above
e. all of the above
The ammonium ion has a pKa of 9.25, whereas acetic acid has a pKa of 4.76. What can we say about these weak acids based on these constants? a. At pH 9.25, NH4+ = NH3. b. At pH > 9.25, NH4+ < NH3. c. At pH 4.76, NH4+ > NH3. d. At pH 9.25, CH3COOH < CH3COO-. e.All of these are accurate statements.
e. all of these are accurate statements
Where do especially stable haplotypes occur within the human genome? a. X chromosome b. Y chromosome c. mitochondrial genome d. all of the above e. b and c
e. b and c
A researcher has isolated an enzyme with an optimal pH of 3 and needs to select a buffer to perform experiments with the enzyme. Which of the following would be the best buffer choice for the researcher? a. bicine, pKa 8.04 b. PIPES, pKa 6.6 c. HEPES, pKa 7.31 d. MES, pKa 5.97 e. none of the above
e. none of the above
DNA and mRNA are localized primarily in the ________ and _________, respectively. a. cytoplasm; mitochondria b. mitochondria; cytoplasm c. cytoplasm; nucleus d. nucleus; mitochondria e. nucleus; cytoplasm
e. nucleus; cytoplasm
The creation of a DNA library captures all genetic information that is present in the cell. Which two steps below are unique to the preparation of a specialized library to eliminate all the noncoding DNA that make up a large portion of many eukaryotic genomes? a. isolation of total mRNA from cells and cleavage of the mRNA sequences b. formation of duplex DNA from cDNA and transformation of bacterial cells with the cloning vector containing inserted DNA sequences c. partial digestion of the genomic DNA and reverse transcription of the fragments d. ligation of DNA fragments into a cloning vector and reverse transcription of mRNA to cDNA e. reverse transcription of the mRNA to cDNA, and degradation of mRNA with alkali
e. reverse transcription of the mRNA to cDNA, and degradation of mRNA with alkali
Simple sequence repeats (SSRs) are small sequences that are repeated many times (as many as 1 million/cell) in tandem in the chromosome. These sequences are a part of what regions of DNA? a. genes b. telomeres c. noncoding DNA d. promoters e. telomeres and noncoding DNA
e. telomeres and noncoding DNA
Which of the following uncommon amino acids is an essential component of vertebrate collagen?
4-Hyp
RT-PCR is _________ PCR and can be used to _________. A. reverse transcriptase; detect RNA produced by living cells B. reverse transcriptase; estimate the copy number of a sequence in a cell C. real time; estimate the copy number of a sequence in a cell D. real time; detect RNA produced by living cells
A. reverse transcriptase; detect RNA produced by living cells
What is free Gibbs equation?
Delta G= -RTlnK
The carbonyl of the first (#1) amino acid (amino end) of an α helix will hydrogen bond to the amine group of which amino acid? a. #5 b. #3 c. #2 d. #4
a. #5
The purpose of adding β-mercaptoethanol during a protein electrophoresis (SDS-PAGE) experiment is _____. a. to make sure all disulfides are reduced b. to prevent the hydrolysis of the peptide backbone c. to denature the protein d. to create cross-links in the acrylamide e. to make sure the protein is negatively charged so it will migrate in an electric field
a. to make sure all disulfides are reduced
The _______ is the collection of the protein coding regions in the genome. a. transcriptome b. exome c. codex d. proteome
b. exome
In covalent catalysis _____. a. metal ions are used to activate a nucleophile b. the transition state energy of the reaction is increased c. the ΔG°' for the reaction is always negative d. two substrates are linked together by a covalent bond e. during the reaction, a substrate is covalently attached to the enzyme, forming an intermediate
e. during the reaction, a substrate is covalently attached to the enzyme, forming an intermediate
