Biochemistry Eighth Edition Test Bank

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Chapter 1Biochemistry: An Evolving ScienceMultiple-Choice Questions1)DNA is made from the building blocks adenine, guanine, cytosine and _____.A)uridineB)thymineC)inosineD)riboseE)None of the answers is correct.Answer: BSection: 1.22)The DNA backbone is made from repeating _____.A)monosaccharide unitsB)amino acid unitsC)sugar-phosphate unitsD)fatty acidE)None of the answers is correct.Answer: CSection: 1.23)The number of hydrogen bonds formed between A and T is _____.A)1B)2C)3D)4E)2 if in DNA, 3 if in RNAAnswer: BSection: 1.24)The number of hydrogen bonds formed between G and C is _____.

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A)1B)2C)3D)4E)2 if in RNA, 3 if in DNAAnswer:CSection: 1.25)The fundamental groups of organisms include Eukarya, Bacteria,and _____.A)PlantaeB)AnimaliaC)ProtistaD)ArchaeaE)FungiAnswer: DSection: 1.16)Which of the following are the strongest bonds in molecules?A)covalent bondsB)ionicbondsC)hydrogen bondsD)metallic bondsE)None of the answers is correct.Answer:ASection: 1.17)Which of the following describes the relationship between the strengths of hydrogen andcovalent bonds?A)Hydrogen bonds are always stronger than covalent bonds.B)Hydrogen bonds and covalent bonds have equivalent strength.

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C)Hydrogen bonds are always weaker than covalent bonds.D)With a few exceptions, most hydrogen bonds are stronger than covalent bonds.E)With a few exceptions, most covalent bonds are stronger than hydrogen bonds.Answer: CSection: 1.38)The matter within a defined region of space is referred to as the _____.A)universeB)systemC)outer spaceD)wormholeE)None of the answers is correct.Answer: BSection: 1.39)For a spontaneous reaction,theGmust be _____.A)positiveB)negativeC)greater than 1D)between 1 and 0E)0Answer: BSection: 1.310)The term _____ is used to indicate Gibbs free energy.A)HB)EC)SD)GE)T

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Answer: DSection: 1.311)Which of the following is considered a metabolite, a substance that is chemicallytransformed in a biochemical process?A)deoxyribonucleic acidB)glycerolC)proteinD)ribonucleic acidE)polysaccharideAns:BSection: 1.112)The structure of DNA described by Watson and Crick includedA)a double helix.B)the sugar phosphate backbone aligned in the center of the helix.C)thebase pairs that are stacked on the inside of the double helix.D)both a double helix and the sugarphosphate backbone aligned in the center of the helixE)a double helixandthe base pairs that are stacked on the inside of the double helixAns: ESection: 1.213)What did Watson and Crick suggest to be significant about the base pairing found in thehelix?A)It allowed the DNA to twist in a helix.B)The DNA could be circular.C)It was a mechanism for copying.D)All of the answers are correct.E)None of the answers is correct.Ans: CSection: 1.3

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14)Approximately what percentage of the human genome encodes proteins?A)50%B)90%C)20%D)3%E)None of theanswers is correct.Ans: DSection: 1.415)What gives proteins such a dominant role in biochemistry?A)the rigidity of the peptide backboneB)the ability to act as a blueprintC)the ability to self-replicateD)the ability to spontaneously fold into complex three-dimensional structuresE)All of the answers arecorrect.Ans: DSection: 1.416)If the whole chain is used in a nonoverlapping frame, how many amino acids are definedby this DNA sequence: ATGTTTGGACTA?A) twoB) three C) four D) sixE) twelveAns: CSection: 1.417)What is the [H+] concentration in a urine sample that has a pH of 6?A)10–6MB)10–8MC)106MD)10–14ME)6 MAns: ASection 1.318)Which is the correct order of decreasing bond strengths?

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A)hydrogenbonds, covalent bonds, van der Waals interactionsB)hydrogen bonds, electrostatic interactions, covalent bondsC)van der Waals interactions, covalent bonds, hydrogen bondsD)covalent bonds, hydrogen bonds, van der Waals interactionsE)hydrophobic interactions, hydrogen bonds, electrostatic interactionsAns: DSection: 1.319)The energies for hydrogen bonds are approximatelyA)400 kJmol–1.B)100–240 kJmol–1.C)4–20 kJmol–1.D)200 kJmol–1.E)None of the answers iscorrect.Ans: CSection: 1.320)Which of the following is a hydrogen bond donor?A)the N in N—HDB)the H in S—HC)the O in P—OD)the H in O—HE)None of the answers is correct.Ans: DSection: 1.321)Typical van der Waals energies are aboutA)4–20 kJmol–1.B)2–4 kJmol–1.C)200 kJmol–1.D)500–1000 kJmol–1.E)None of the answers is correct.

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Ans: BSection: 1.322)What two properties of water are important for biological interactions?A)the polarity of waterB)the density of waterC)the cohesive properties of waterD)the polarity of waterandthe cohesive properties of waterE)the density of waterandthe cohesive properties of waterAns: DSection: 1.323)The First Law of Thermodynamics statesA)diversity is the result of gradual evolution.B)the total entropy of a system and its surroundings always increasesfor aspontaneousprocess.C)thetotal energy of a system and its surroundingsisconstant.D)light is both particle and wave.E)None of theanswers is correct.Ans: CSection: 1.324)The Second Law of Thermodynamics statesA)the total entropy of a system and its surroundings always increases for a spontaneousprocess.B)temperatures will always decrease in a spontaneous process.C)the total energy of a system and its surroundings is constant.D)diversity is the result of gradual evolution.E)None of the answers is correct.Ans: ASection: 1.325)Which of the following atoms commonly found in biological molecules are oftenhydrogen-bond acceptors?

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A) carbonB) oxygenC) nitrogenD)All of the answers are correct.E)oxygenand nitrogenAns: ESection: 1.326)Entropy is defined asA)a spontaneous reaction.B)the enthalpy of the system.C)the measure of randomness of a system.D)the amount of heat exchanged.E)None of the answers is correct.Ans: CSection: 1.327)If a particular reaction has anegativeG, is itlikely to occur?A)Not unless energy is added to the systemB)Yes, if it is coupled to another reactionC)Yes, it is spontaneous.D)No, it is not spontaneous.E)Yes, as long as the temperature increasesAns: CSection: 1.328)What happens to nonpolar molecules in water?A)They dissolve independently.B)They aggregate together.C)They precipitate.D)All of the answers are correct.E)None of the answers is correct.

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Ans: BSection: 1.329)What is the [A–]/[HA] ratio when a weak acid is in a solution one pH unit below its pKa?A)1:1B)1:10C)10:1D)2:1E)None of the answers is correct.Ans: BSection 1.330)Why does DNA denature when the pH is raised above 9?A)Protons dissociate from guanine bases disrupting the hydrogen bonding to the otherstrand.B)Protons bind to guanine residues giving them additional positive charges which disruptthe hydrogen bonding to theother strand.C)Protons bind to functional groups that serve as hydrogen-bond acceptors, thus disruptingthe hydrogen bonding to the other strand.D)Protons dissociate from the phosphate groups in the backbone, which disrupts thehydrogen-bonding pattern between strands.E)None of the answers is correct.Ans: ASection 1.331)The simplest way to depict stereochemistry is to useA)ball-and-stick models.B)ribbon diagrams.C)space-filling models.D)Fisher projections.E)None of the answers is correct.Ans: DSection: Appendix

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32)Using the Henderson–Hasselbalch equation, calculate the pH of a buffer solution madefrom 0.20 M CH3COOH and 0.050 M CH3COO–that has pKa= 4.7.A)5.3B)4.1C)2.5D)0.4E)None of the answers is correct.Ans: BSection 1.333)What are the primary chemical components present in a phosphate buffer at pH 7.4?A)H3PO4and PO43–B)H2PO4–and PO43–C)HPO42–and PO43–D)H2PO4–and HPO42–E)H3PO4and HPO42–Ans: DSection 1.3Short-Answer Questions34)What are some of the medical implications of the human genome project?Ans:The obvious use is in diagnosing disease and in developing methods to treat and curediseases. Physicians will be able to account for individual genetic differences in determining thebest medical treatment. Other answers may be correct.Section: Introduction35)What is the significance of hydrogen bonding in biochemical structures such as DNA?Ans:The bonds are weak enough to be easily disrupted; yet when many are present, theyprovide the stabilization necessary for larger structures such as DNA.Section: 1.236)Describe resonance structures.Ans:Resonance structures are ways of writing covalent bonds in which two or more alternatebonding patterns can be achieved. This is due to the sharing of electrons over several atoms.

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Common examples are found in peptide bonds, and in some of the DNA/RNA bases.Adenine isshown in the text.Section: 1.337)What is significant about the fact that metabolic processes are common to manyorganisms?Ans:These metabolic processes are extremely old, geologically, originating in a commonancestor.Section: 1.138)How is water able to be a solvent for so many biological molecules?Ans:Many biological molecules have polar characteristics. Water is extremely polar and iscapable of competing with other polar molecules by weakening their electrostatic and hydrogenbonds. The oxygen atom can act as a hydrogen-bond acceptor, and the hydrogen can act as adonor.Section: 1.339)What is the net effect of many van der Waals interactions?Ans:At the interface of two large molecules, the numerous van der Waals interactions cansubstantially affect and stabilize the interaction.Section: 1.340)If most proteins are found surrounded by water in the cell, what type of functional groupswould you expect to find on the surface of a water-soluble protein?Ans:Polar and charged amino-acid residues would be present on the surface of the protein.Section: 1.341)How are electrostatic forces used in protein folding?Ans:The attraction of two oppositely charged functional groups would be one of the forceshelping to form the three-dimensional shape of the protein.Section: 1.342)If the First Law of Thermodynamics is true, how can biological processes be carried out?Ans:Although energy cannot be created or destroyed, it can take on different forms, such asheat or chemical energy. Thus, the energy can be stored as chemical bond energy, which can beused to do work.Section: 1.343)How can a cell exist if the Second Law of Thermodynamics is true?

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Ans:Entropy in a local area can be decreased, but only at the expense of increased entropy inthe larger area, or universe.Section: 1.344)Provide a simple example of a process in which the entropy of a system changes.Ans:Several examples can be provided, including the random mixture of atoms when twodifferent gases are mixed, or the creation of water molecules from energy gained following themixture of oxygen and hydrogen under certain conditions.Section: 1.345)When solutions containing complementary single strands of DNA are mixed, a loss ofentropy occurs. How is it that the Second Law of Thermodynamics is not violated?Ans:Heat must be released to the surroundings.Section: 1.346)What is the significance of usingGin biochemistry?Ans:Gibbsfree energy, also called the free-energy change, is used to describe the energeticsof a reaction. This symbol is used to determine if particular reactions will be spontaneous orbiologically feasible.Section: 1.347)What thermodynamic and free-energy changes participate in protein folding?Ans:A combination of hydrogen bonds and van der Waals forces affect enthalpy and theentropy associated with hydrophobic interactions.Section: 1.348)How do hydrophobic interactions aid in protein folding?Ans:Hydrophobic interactionscause some nonpolar amino acids to aggregate and form theinterior of the protein. This results in a net release of heat and a favorable change in the systementhalpy.Section: 1.449)What are the enthalpy and entropy changes that accompany the formation of DNA doublehelices from complementary single strands of DNA?Ans:There is a loss of entropy from the system because there are fewer degrees of freedom inthe double helix as compared to the single strands. Therefore, heat must be released when thetwo strands combine to form the double helix so as not to violate the Second Law ofThermodynamics.Section: 1.3

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50)Describe the shape of methane.Ans:Methane is tetrahedral, with bond angles of about 109°.Section: Appendix

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Chapter 2Protein Composition and Structure1)Which of the following is most often found in proteins?A)D-amino acidsB)L-amino acidsC)an equal amount of D-and L-amino acidsD)amino acids with the-carbonexclusively having an Rabsolute configurationE)amino acids with the-carbonexclusively having an S absolute configurationAnswer: BSection: 2.12)A term that describes a molecule that contains both positive and negative charges butoverall has a neutral charge is _____.A)enantiomerB)amino acidC)racemateD)zwitterionE)amphipathAnswer: DSection: 2.13)Which amino acid forms disulfide bonds?A)histidineB)methionineC)prolineD)serineE)cysteineAnswer: ESection: 2.1

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4)Which of the following amino acids has an ionizable R-group with apKanear neutralpH?A)histidineB)serineC)aspartic acidD)lysineE)tyrosineAnswer: ASection: 2.15)Formation of a peptide bond produces _____ as a byproduct.A)ammoniaB)carbon dioxideC)waterD)H+E)OH–Answer: CSection: 2.26)What type of plot allows one to investigate the likely phi and psi angles of the peptidebackbone?A)HillB)Lineweaver-BurkC)Hanes-WoolfD)RamachandranE)Michaelis-MentenAnswer: DSection: 2.27)What level of protein structure is composed ofhelices,sheets,and turns?

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