Molecular Cell Biology Eighth Edition Test Bank

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2-12Chemical FoundationsTest BankSection 2.11. Covalent bonds between which of the following pairs of atoms are nonpolar?a. C–Cb. C–Hc. O–Hd.a and bAns:dQuestion Type:Multiple ChoiceChapter:2.1Blooms: RememberingDifficulty: Easy2. Which of the following is a noncovalent interaction?a. hydrophobic effectb. ionic interactionsc.vander Waals interactionsd. all of the aboveAns:dQuestion Type: MultipleChoiceChapter:2Blooms: RememberingDifficulty: Easy3. Which of the following is the strongest interaction?a. hydrogen bondb. ionic bondc. phosphoanhydride bondd.vander Waals interactionAns:cQuestion Type: Multiple ChoiceChapter:2Blooms: UnderstandingDifficulty: Easy4. Which of the following is the weakest interaction?a. hydrogen bondb. ionic bondc. phosphoanhydride bondd.vander Waals interactionAns: dQuestion Type: Multiple Choice

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2-2Chapter:2Blooms: UnderstandingDifficulty: Easy5. When two atoms differing in electronegativity are joined in a covalent bond, then the:a. electrons are shared equally between the atoms.b. bond is nonpolar.c. resulting compound is devoid of any dipole moment.d. atom with thegreater electronegativity attracts the bonded electrons morestrongly.Ans: dQuestion Type: Multiple ChoiceChapter:2Blooms: UnderstandingDifficulty: Moderate6. The interactions between two proteins such as an antibody and an antigen or ahormone and its receptor are quite strongdespite the fact that these interactions consist of relatively weak noncovalent bonds. How can this be?Ans: Two proteins can bind tightly because of molecular complementarity, in which multiple noncovalent bonds participate.Although each individual bond is weak, the cumulative effect of many noncovalent bonds is a relatively strong and highlyspecific interaction.Question Type: EssayChapter: 2Blooms: AnalyzingDifficulty: Moderate7.What produces the dipole of a water molecule?Ans: The dipole of a water molecule is caused by the difference in electronegativity between O and H. The oxygen atom has agreater electronegativity than the hydrogen atom.As a result, oxygen attracts the electrons in the O–H bond morestrongly,and the oxygen side of the bond has a slight net negative charge. This results in a dipole moment.Question Type: EssayChapter:2.1Blooms: UnderstandingDifficulty: ModerateSection 2.28. Which of the following is a negatively charged amino acid?a. alanineb. aspartatec. glutamined. histidineAns: bQuestion Type: Multiple ChoiceChapter: 2Blooms: RememberingDifficulty: Easy9. Which of the following is/area hydrophilic amino acid?a. aspartateb. serinec. tryptophand.aspartate and serine

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2-3Ans: dQuestion Type: Multiple ChoiceChapter: 2Blooms: RememberingDifficulty: Easy10. Adenosine is a:a. component of RNA.b.nucleoside.c.pyrimidine.d.a and bAns:dQuestion Type: Multiple ChoiceChapter: 2Blooms: RememberingDifficulty: Moderate11. Which of the following is a monosaccharide?a. fructoseb. galactosec. glucosed. all of the aboveAns: dQuestion Type: Multiple ChoiceChapter: 2Blooms: RememberingDifficulty: Easy12.Based on what you know about hydrophobic interactions, which of the following is/arecomposed of a bilayer?a.acell’smembraneb.spontaneously aggregated phospholipids surrounding an aqueousinteriorc.lipid vesicles that have budded off the cell’s membraned.all of the aboveAns: dQuestion Type: Multiple ChoiceChapter: 2Blooms: RememberingDifficulty: Easy13. You discover that you suffer from a deficiency in the amino acid tryptophan. At the pharmacy, you find bothD-tryptophanandL-tryptophan supplements. Which do you purchase? Why?Ans: You should chooseL-tryptophan. All amino acids can exist as one of two stereoisomers (DorL) because of asymmetryaround theαcarbon. Proteins consist of theLform of amino acids, and as these stereoisomers possess distinct biologicalproperties and are not readily interconverted, you should choose the form that is normally utilized by cells.Question Type: EssayChapter: 2ApplicationDifficulty: Moderate14. Cysteine often plays an important role in stabilizing protein structure. Explain how this works.

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2-4Ans: Two adjacent sulfhydryl (SH) groups can oxidize to form a covalent disulfide (S–S) bond. Disulfide bonds can stabilizethe structure of folded peptides or sometimeslinktwo separate peptide chains together.Question Type: EssayChapter: 2Blooms: UnderstandingDifficulty: Easy15.Triacylglycerol and cholesterol esters are nonpolar; in contrast, phospholipids are amphipathic molecules. Biomembranesare based on phospholipids rather than on triacylglycerols. Why?Ans: Biomembranes are based on phospholipids rather than on triacylglycerols because phospholipids as amphipathicmolecules can form planar lipid bilayers, whereas the nonamphipathic nonpolar triacylglycerols cannot.Theiramphipathicproperty, the presence of a polar and nonpolar domain at opposite ends of the same molecule, allows phospholipids to formhydrophilic associations with water at the same time as forming hydrophobic associations with each other through theirhydrophobic tails. Triacylglycerols are strictly hydrophobic in nature and hence in an aqueous environment tend to associatewith one another to form lipid droplets. This minimizes the contact of triacylglycerol with water. Recall the old adage: oil andwater do not mix.Question Type: EssayChapter: 2Blooms: EvaluatingDifficulty: Difficult16. A nucleotide can vary in _____.a. the baseb. the sugarc. the phosphate groupd. the sugar and the baseAns: dQuestion Type: Multiple ChoiceChapter: 2Blooms: UnderstandingDifficulty: Moderate17. Which of the following is NOT one of the ways RNA differs from DNA?a. Ribonucleotides have a hydroxyl group on the 2 carbon of their sugar subunit.b. Ribonucleotides can have enzymatic activity.c. Ribonucleotides contain a phosphate group.d. Ribonucleotides can contain the base uracil.Ans: cQuestion Type: Multiple ChoiceChapter: 2Blooms: RememberingDifficulty: Moderate18. What is the major structural difference between starch and cellulose?a. the types of monosaccharide subunits in the moleculesb. the amount of branching that occurs in the moleculec. that humans can only ingest starchd. the type of glycosidic linkages in the moleculeAns: dQuestion Type: Multiple Choice

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2-5Chapter: 2Blooms: UnderstandingDifficulty: Moderate19. How do phospholipids interact with water molecules?a. The polar heads interact with water; the nonpolar tails do not.b. Phospholipids don't interact with water because water is polar and lipids are nonpolar.c. The polar heads avoid water; the nonpolar tails attract water (because water is polar and opposites attract).d. Phospholipids dissolve in water.Ans: aQuestion Type: Multiple ChoiceChapter: 2Blooms: RememberingDifficulty: Easy20. Which of the following is the BEST explanation for why vegetable oil is a liquid at room temperature while animal fatsare solid?a. Vegetable oil has fewer double bonds than animal fats.b. Animal fats have no amphipathic character.c. Vegetable oil has longer fatty-acid tails than do animal fats.d. Vegetable oil has more double bonds than do animal fats.Ans: aQuestion Type: Multiple ChoiceChapter: 2Blooms: UnderstandingDifficulty: EasySection 2.321.A 1-mL solution of 0.05 M H2SO4is diluted to 100 mL at 25°C. What is the pH of the resulting solution?a. 1b. 2c. 3d. 4Ans: cQuestion Type: Multiple ChoiceChapter: 2Blooms: ApplyingDifficulty: Moderate22. An Archaea cell living in an abandoned mine is found to contain a very high concentration of protons. It is likely that thiscell:a. has a high ph and is acidic.b. has a high ph and is alkaline.c. has low ph and is acidic.d. has a low pH and is alkaline.Ans: cQuestion Type: Multiple ChoiceChapter: 2Blooms: UnderstandingDifficulty: Easy

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2-623.A 1-mL solution of 0.1 M NaOH is diluted to 1 L at 25°C. What is the pH of the resulting solution?a. 1b. 7c. 10d. 13Ans: cQuestion Type: Multiple ChoiceChapter: 2Blooms: ApplyingDifficulty: Moderate24. The pKaof the weak base NH3is 9.25. When present in lysosomes, a subcellular organelle—ammonia—is almost totallyprotonated. Which of the pH values listed below is most likely to be that of the lysosome lumen?a. 1b. 5c. 8d. 14Ans: bQuestion Type: Multiple ChoiceChapter: 2AnalysisDifficulty: Difficult25.If the equilibrium constant for the reaction A→B is 0.5 and the initial concentration of A is 25 mM and of B is 12.5 mM,then the reaction:a. will proceed in the direction it is written, producing a net increase in the concentration of B.b. will produce energy, which can be used to drive ATP synthesis.c. will proceed in the reverse direction, producing a net increase in the concentration of A.d. is at equilibrium.Ans: dQuestion Type: Multiple ChoiceChapter: 2AnalysisDifficulty: Difficult26.For the binding reaction A + B→AB, the dissociation constant is equal to:a.(+)b. ([A] + [B])/[AB].c.Keqd.The first and third answers are correct.Ans: bQuestion Type: Multiple ChoiceChapter: 2Blooms: ApplyingDifficulty: Easy27. What is the effect of an enzyme on the end equilibrium concentration of reactants and products?

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2-7Ans: An enzyme has no effect on the end equilibrium concentration of reactants and products.Question Type: EssayChapter: 2Blooms: AnalyzingDifficulty: Easy28. The enzyme alcohol dehydrogenase is capable of catalyzing the oxidation of a number of different substances, includingethanol, ethylene glycol, and methanol, to an aldehyde.The metabolic products of both ethylene glycol and methanol arehighly toxicto humans.A standard medical treatment for prevention of ethylene glycol or methanol poisoning is theadministration of a dose of ethanol. Why is this treatment effective?Ans: The ethanol-like ethylene glycol and methanol are capable of binding to the enzyme, alcohol dehydrogenase, andcompetingwithitsother substrates. A sufficient dosage of ethanol can out-compete the other substrates, and hence the ethyleneglycol and methanol are not metabolized to toxic products. Gradually the ethylene glycol or methanol will be excreted fromthe body.Question Type: EssayChapter: 2Blooms: EvaluatingDifficulty: Moderate29.How do cells maintain a relatively constant pH despite the fact that many metabolic processes produce acids?Ans: All cells contain buffers such as phosphate ions that can absorb or release protons or hydroxyl ions to stabilize pH changesnear neutral pH.Question Type: EssayChapter: 2Blooms: EvaluatingDifficulty: DifficultSection 2.430.In a biochemical reaction in whichH< 0 andS> 0:a. the reaction is spontaneous.b. the reaction is endothermic.c. the reaction is endergonic.d.Gis positive.Ans: aQuestion Type: Multiple ChoiceChapter: 2Blooms: ApplyingDifficulty: Easy31. In the reaction NAD++ H++ 2e−→NADH, NAD+becomes:a. dehydrated.b. hydrolyzed.c. oxidized.d. reduced.Ans: dQuestion Type: Multiple ChoiceChapter: 2Blooms: UnderstandingDifficulty: Easy32. The ultimate source of chemical energy forall cells is:

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2-8a. electricity.b. heat.c. light.d. magnetism.Ans: cQuestion Type: Multiple ChoiceChapter: 2Blooms: ApplyingDifficulty: Moderate33. Hydrolysis of ATP:a. is endothermic.b. has a positiveGvalue.c. must be coupled to anenergetically favorable reaction.d. none of the aboveAns:dQuestion Type: Multiple ChoiceChapter: 2Blooms: UnderstandingDifficulty: Easy34. What is [P]/[R] whenG =G°´?a.–1b. 0c. 1d. 2.3Ans: cQuestion Type: Multiple ChoiceChapter: 2Blooms: ApplyingDifficulty: Moderate35. A reaction with a positiveGvalue can be made energetically favorable by increasing the:a.G.b. starting concentration of products.c. starting concentration of reactants.d.The first two answers are correct.Ans: cQuestion Type: Multiple ChoiceChapter: 2Blooms: AnalyzingDifficulty: Moderate36. Photosynthesis by plants and certain microbes traps the energy in light and uses it to:a.reduce glucose into carbon dioxide.b.synthesize ATP fromADP and inorganic phosphate.c.generate ATP from the oxidation of reduced inorganic compounds.d.none of the aboveAns: bQuestion Type: Multiple ChoiceChapter: 2

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2-9Blooms: UnderstandingDifficulty: Moderate37. NAD+and FAD are often referred to as:a.redox proteins.b.polymers.c.reduced dinucleotides.d.electron-carrying coenzymes.Ans: dQuestion Type: Multiple ChoiceChapter: 2Blooms: RememberingDifficulty: Easy38. A solution of 8 M urea is sometimes used in the isolation of protein molecules. When the solution is prepared by dissolvingurea in water at room temperature, it becomes cold. How should theGfor this process change if you tried to dissolve ureain the cold room, rather than at room temperature?Ans: Urea will be less soluble at cold temperatures than at room temperature because the decrease in temperature will decreasethe termTS, increasing the value ofG, becauseG=H−TS. The values ofHandSare relatively independent oftemperature.Question Type: EssayChapter: 2Blooms: AnalyzingDifficulty: Moderate39. Phosphoglucomutase converts glucose 1-phosphate, the product of the reaction catalyzed by glycogen phosphorylase, intoglucose 6-phosphate. TheKeqfor this reaction is 19 under standard conditions. What is theG°´ for the reaction?Ans: −1.741 kcal/mol,G°´ = −2.3RTlogKeq,G°´ = −2.3 (1.987) (298) logKeqQuestion Type: EssayChapter: 2ApplicationDifficulty: Moderate40. Under what conditions is theG for a reaction different from theG°´?Ans:G°´ is the Gibbs free energy of a reaction under standard conditions: pH 7.0, 1 M initial concentration of all reactantsand products except protons and water, 1 atm pressure, 298°K (25°C).Variation of any of these parameters from standardconditions, depending onthereaction, can produce a differentGvalue.Question Type: EssayChapter: 2Blooms: UnderstandingDifficulty: Easy41. The amount of free energy released when bonds are broken during a reaction is higher when the molecule has moreelectronegative atoms.Ans: FalseQuestion Type:True/FalseChapter: 2Blooms: ApplyingDifficulty: Moderate

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2-1042. Which of the following is true about an observed change in free energy (G)?a. Free energy was created when the Big Bang occurred.b. It can be calculated from the total change in energy, temperature, and change in entropy.c. If a reaction's free energy is greater than zero, it is likely to happen spontaneously.d. Free energy is comparable to unusable energy.Ans: bQuestion Type: Multiple ChoiceChapter: 2Blooms: UnderstandingDifficulty: Easy

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3-13Section 3.11. Which of the following is defined as the tertiary structure of a protein?a. the primary amino acid sequenceb. structural domains such as aDNA-binding domainc. folded structures such as an α helixd. structural features such as a turnAns: bQuestion Type: Multiple ChoiceChapter: 3Blooms: UnderstandingDifficulty: Easy2. Monomeric proteins do not contain a:a. primary structure.b. secondarystructure.c. tertiary structure.d. quaternary structure.Ans: dQuestion Type: Multiple ChoiceChapter: 3Blooms: UnderstandingDifficulty: Easy3. Which of the following isNOTpart of a zinc-finger motif?a. zinc ionb. proline residuec. cysteine residued. histidine residueAns: bQuestion Type: Multiple ChoiceChapter: 3Blooms: RememberingDifficulty: Easy4.Describe the types of bonds/interactions that hold together or stabilize the primary, secondary, tertiary, andquaternarystructures of proteins.Ans:The primary structure of a protein is linked by covalent peptide bonds.The secondary structure is stabilizedby hydrogen bonds between atoms of the peptide backbone.The tertiary structure is stabilized by hydrophobicProtein Structureand Function

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3-2interactions between the nonpolar side groups and hydrogen bonds between polar side groups. The quaternarystructure is held together by noncovalent bonds between protein subunits.Question Type: EssayChapter: 3Blooms: UnderstandingDifficulty: Easy5.Many proteins contain one or more motifs built from particular combinations of secondary structure. Describe thethree common structural motifs discussed in this chapter.Ans: The three structural motifs described in this chapter include the coiled coil motif, the helix-loop-helix motif,and the zinc finger motif. The coiled-coil motif consists of two or morehelices wrapped around one another. Thehelix-loop-helix motif consists of two helices connected by a loop that contains certain hydrophilic residues atinvariant positions in the loop.The zinc-finger motif consists of anhelix and twostrands held together by azinc ion in a fingerlike bundle.Question Type: EssayChapter: 3ApplicationDifficulty: Moderate6.What types of bonds are apt to be more common in the nonaqueous, interior environment of a protein than in theaqueous, surface environment of a protein?Ans: Proteins are arranged so that hydrophilic amino acids are on the surface of the protein and hydrophobic aminoacids are in the interior. Hence, hydrogen bonding and ionic interactions with water are particularly common at theprotein surface; hydrophobic interactions are more common in the protein interior.Question Type: EssayChapter: 3Blooms: ApplyingDifficulty: Moderate7.There are many important roles for the dynamic nature of proteins in a cell. Which of the following isNOTlikelyto describe one such reason?a.A protein’s structure determines its function.b.Other moleculescould be needed to allow proteins to fold into their active (ordered) conformation.c.Quaternary structures are usually very transient (occur for short periods of time).d.Proteins are crucial for many cell functions.Ans: cQuestion Type: Multiple ChoiceChapter: 3Blooms: ApplyingDifficulty: Moderate9.You are studying an oligopeptide composed ofeightamino acids. The four amino acids nearest the C terminus arenonpolar. The two amino acids nearest the N terminus are charged. The middle two amino acids are polar. Whichamino acid is likely to be labeled as number 2?a.threonineb.phenylalaninec.glutamined.lysineAns: dQuestion Type: Multiple ChoiceChapter: 3

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3-3Blooms: ApplyingDifficulty: Moderate10.A protein containing several proline residues is:a.not likely to form quarternary structures.b.likely to beanintegral membrane protein.c.not likely to form alpha helices.d.likely to be found in beta turns.Ans: cQuestion Type: Multiple ChoiceChapter: 3Blooms:RememberingDifficulty: Moderate11.Which of the following is true about protein folding?a.Amino acids cluster in the primary sequence so that all the hydrophobic amino acids are near each other tofacilitate folding into the hydrophobic core of the tertiary structure.b.All known proteins have well-ordered conformations.c.Amino acids with hydrophobic, nonpolar side chains stabilize the tertiary structure through hydrogen bondingwith water molecules surrounding the proteins.d.Elements from thesecondary structure are maintained in the tertiary structure.Ans: dQuestion Type: Multiple ChoiceChapter: 3Blooms: UnderstandingDifficulty: Moderate12.When comparing domains and structural motifs, which of the following is NOT true?a.Motifs are found in secondary structures, while domains are found in tertiary structures.b.Helices are observed in motifs and domains.c.Structural domains appear in different proteins with similar functions, while structural motifs have been lessconserved over evolution.d.Adomain may be repeated in the same protein, but multiple copies of the same motif are rare.Ans: cQuestion Type: Multiple ChoiceChapter: 3Blooms: UnderstandingDifficulty: Moderate13.You disrupt all hydrogen bonds in aprotein. What level of structure will be preserved?a.secondary structureb.primary structurec.tertiary structured.quaternary structureAns: bQuestion Type: Multiple ChoiceChapter: 3Blooms: UnderstandingDifficulty: Easy14.Two proteinsthathave a similar function:a.will share similar amino acid sequences if they are homologs.

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3-4b.must have similar amino acid sequences.c.will have identical primary structures.d.belong in families together.Ans: aQuestion Type: Multiple ChoiceChapter: 3Blooms: RememberingDifficulty: ModerateSection 3.215. All the following statements about molecular chaperones are trueEXCEPT:a.they play a role in the proper folding of proteins.b.they are located in every cellular compartment.c.they are found only in mammals.d.they bind a wide range of proteins.Ans: cQuestion Type: Multiple ChoiceChapter 3.2Blooms: UnderstandingDifficulty: Easy16. Hsp90 family members are present in all organismsEXCEPT:a. archaea.b. bacteria.c.fungi.d.plants.Ans: aQuestion Type: Multiple ChoiceChapter 3.2Blooms: RememberingDifficulty: Easy17.Describe the mechanism by which the bacterialchaperonin GroEL promotes protein folding.Ans:The bacterial chaperonin GroEL forms a barrel-shaped complex of 14 identical subunits. A partially folded ormisfolded polypeptide is inserted into the GroEL barrel, where it binds to the inner wall and folds into its nativeconformation. In an ATP-dependent step, the GroEL barrel expands to a more open state, which results in release ofthe folded protein.Question Type: EssayChapter 3.2Blooms: UnderstandingDifficulty: Moderate18.What role doesaberrant protein folding play in the development of a disease such as Alzheimer’s disease?Ans:Misfolding of a protein marks it for degradation by proteolytic cleavage.In Alzheimer’s disease, misfoldingand subsequent proteolytic degradation of the amyloid precursor protein generates a short fragment called-amyloidprotein, which changes from an-helical to a-sheet conformation. This aberrant structure aggregates into highlystable filaments called amyloid plaques that accumulate in the brains of Alzheimer’s patients.Question Type: EssayChapter 3.2Blooms: Understanding

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3-5Difficulty: Easy19.Which of the following does NOT impose limits on protein folding?a.ability of side chains to form hydrogen and ionic bondsb.backbone sequence of the polypeptidec.rotations of the planes around the peptide bondsd.size of side chainsAns: bQuestion Type: Multiple ChoiceChapter 3.2Blooms: RememberingDifficulty: Easy20.Eggs are protein-rich foods. An uncooked egg can catalyze a reaction that breaks down bacterial cell walls. Aftercooking, this activity is almost abolished. This is likely because:a.the enzyme became denatured.b.bacteria can grow on cooked eggs.c.the cell membranes wereliquefied.d.cooking sped up chemical reactions.Ans: aQuestion Type: Multiple ChoiceSection 3.2Blooms: UnderstandingDifficulty: Moderate21.The correct order for molecular chaperone–mediated protein folding is:I–exchange of ATP for ADP on chaperoneII–chaperone undergoes conformational change, whichaffects protein foldingIII–chaperone binds to exposed hydrophobic residues on unfolded proteinIV–folded protein is releaseda.I, II, III, IVb.III, II, I, IVc.III, I, II, IVd.II, III, I, IVAns: bQuestion Type: Multiple ChoiceSection 3.2Blooms: UnderstandingDifficulty: EasySection 3.322. All the following statements about enzymes are trueEXCEPT:a.they function in an aqueous environment.b.they lower the activation energy of a reaction.c.they increase the rate of a reaction.d.a single enzymetypically reactswith many different substrates.Ans: dQuestion Type: Multiple ChoiceChapter 3.3Blooms: UnderstandingDifficulty: Easy

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