Biochemistry: A Short Course, Second Edition Test Bank

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Chapter 1Biochemistry and the Unity of LifeMatching QuestionsUse the following to answer questions 1–10:Choose the correct answer from the list below. Not all of the answers will be used.a) uridineb) cytoplasmc) proteind) thyminee) carbohydratef) sugar–phosphate unitsg) cell wallh) transcriptioni) glycogenj) lipidk)threel) twom) endoplasmic reticulumn) translationo) prokaryotesp) eukaryotesq) lysozome1.DNA is made from the building blocks adenine, guanine, cytosine, and ____________.Ans:dSection:1.22.____________:Unbranched polymer that, when folded into its three-dimensional shape,performs much of the work of the cell.Ans:cSection:1.23.____________:The number of hydrogen bonds formed between A and T.Ans:lSection:1.24.____________:The number of hydrogen bonds formed between G and C.Ans:kSection:1.25.The transfer of information from DNA to RNA is called ____________.Ans:hSection:1.36.____________ are cells which are composed of multiple specialized compartments.Ans:pSection:1.4

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Chapter 1Biochemistry and the Unity of Life27.____________:Class of biological macromolecules with many functions such as formingbarriers between cell organelles, serving as a metabolic fuel,and cell-to-cell signaling.Ans:jSection:1.28.____________:Highly organized region of the cell whereglycolyticmetabolism occurs.Ans:bSection:1.49.____________:Responsible for protein processing and xenobiotic metabolism.Ans:mSection:1.410.____________:Filled with proteases and other digestive enzymes.Ans:qSection:1.4Fill-in-the-Blank Questions11.Organisms are known to be highly uniform at the _______________ level.Ans:molecularSection:Introduction12.After hydrogen and oxygen, the next most common element in living systems is_______________.Ans: carbonSection:1.113.A chemical that can dissolve in water is said to be _______________.Ans:hydrophilicSection:1.214.A nucleotide consists of one or more _______________groups, a5-carbonribose sugar,and a nitrogen-containing aromatic ring group.Ans:phosphateSection:1.215.The most common carbohydrate fuel is _______________.Ans:glucoseSection:1.216.Heritable information is packaged into discrete units called _______________.Ans:genesSection:1.317.A group of enzymes called _______________ catalyze replication.Ans:DNA polymeraseSection:1.318.Although all cells in an organism have the same DNA, tissues differ due to selective_______________.Ans:expressionSection:1.319.The basic unit of life is considered the _______________.Ans:cellSection:1.420.Large particles of extracellular materialaretaken into the cell via:Ans:phagocytosisSection:1.4

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Chapter 1Biochemistry and the Unity of Life3Multiple-Choice Questions21.The structure of DNA described by Watson and Crick included:A) a double helix.B) the sugar–phosphate backbone aligned in the center of the helix.C) the base pairs that are stacked on the inside of the double helix.D) A and B.E) A and C.Ans:ESection:1.222.In higher organisms, which of the following is composed of a polymer with double-stranded phosphodiester-linked monomers?A) RNAB) DNAC) proteinD) carbohydrateE) None of the above.Ans:BSection 1.223.What gives proteins such a dominant role in biochemistry?A) the variation in protein sizesB) the ability to act as a blueprintC) their ability to self-replicateD) their ability to spontaneously fold into complex three-dimensional structuresE) All of the above.Ans:DSection:1.224.Proteins are chiefly composed of which of the following?A)carbohydrate and amino acidsB)long unbranched amino acid polymersC)peptide bonds formed between lipid moietiesD)aggregated amino acidsE)A and BAns:BSection 1.325.How a protein folds is determined by:A)whetherthe environment is hydrophobic or hydrophilic.B)the location in the cellin whichthe protein is located.C)the pH of the cytoplasm.D)the order of the amino acids found in the sequence.E)All of theabove.Ans:DSection:1.2

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Chapter 1Biochemistry and the Unity of Life426.The half-life of which of the following is likely to be shortest?A)proteinB)lipidC)carbohydrateD)DNAE)RNAAns:ESection:1.227.The central dogma describes:A)the formation of cells from individual components.B)the selective expression of genes.C)the flow of information between DNA, RNA,and protein.D)the work of polymerases on RNA and DNA.E)All of the above.Ans:CSection:1.328.Translation takes place on/inthe:A)ribosomes.B)smooth endoplasmic reticulum.C)nucleus.D)DNA polymerases.E)DNA parent strand.Ans:ASection:1.329.Which of the following organelles has a double membrane?A)nucleusB)endoplasmic reticulumC)mitochondriaD)plasma membraneE)A and CF)All of the above.Ans:ESection:1.430.The main function of the plasma membrane is to:A)provide the interior of the cell an enclosed environment which no molecules may cross.B)provide a selectively permeable barrier with the aid of transport proteins.C)give eukaryote and prokaryote cells structural strength.D)allow only the free passage of water in and out of the cell.E)None of the above.Ans:BSection:1.431.The structural components (filaments and tubules) are organelles calledthe:A)chloroplast.B)cytoplasm.C)cytoskeleton.D)cell wall.E)B and D.Ans:CSection:1.4

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Chapter 1Biochemistry and the Unity of Life532.Poisons that kill an organism as a result of a loss of high-energy ATP molecules are mostlikely totarget which organelle?A)mitochondriaB)cytoskeletonC)cytoplasmD)endoplasmicreticulumE)nucleusAns:ASection:1.433.A secreted protein would be processed through organelles in the following order:A)nucleus; secretoryvesicle; GolgicomplexB)cytoplasm; Golgi complex; cytosol;secretoryvesicleC)endoplasmic reticulum; cytoplasmic reticulum; Golgi complexD)nucleus; cytoplasm; endoplasmic reticulum; Golgi complex; secretory vesicleE)None of the above.Ans:ESection:1.434.Extracellular material is taken into the cell via which process?A)endocytosisB)phagocytosisC)lysosome-mediatedindocytosisD)reverse secretory mechanismE)phago-cytosolic internalizationAns:BSection 1.435.The rigid material which provides structural support to a plant cell is/arecalledthe:A)plant cytoskeletonB)plasma membraneC)cell wallD)chloroplast anchor proteinsE)microfilaments and microtubulesAns:CSection:1.4Short-Answer Questions36.What are the four key classes of biomolecules?Ans:Proteins, DNA/RNA,lipids,carbohydrates.These are the larger, monomer or biopolymermolecules which perform many functions to maintain cellular life.Each has a differentbiochemical make-up.Section:1.237.How do eukaryotic cells differ from prokaryotic cells?Ans:The simplest answer is defined by the existence of organelle.Eukaryotic cells containorganelles including a nucleus, while prokaryotic cells do not have such compartments.Section:1.4

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Chapter 1Biochemistry and the Unity of Life638.Describe the central dogma and why itisimportant for cell life.Ans:This is the phrase coined by Francis Crick and is the overview of how a cell uses theinformation from DNA to produceRNA, protein, andmore DNA.Much of the fate of acell (metabolism, survival, growth, movement,and cell differentiation) is based on thecontrol of the central dogma.Which genes are transcribed andtranslateddefinesthefunction of a cell.Section:1.339.Define an organelle.Ans:An organelle is often,but not always,enclosed by a membrane.Examples include thenucleus, mitochondria,and chloroplasts.However, the cytoplasm is defined as that areasurrounded by the plasma membrane, excluding the organelles.Section:1.440.What is the role of the endoplasmic reticulum(ER)?Ans:The endoplasmic reticulum is series of membrane tubes or sacs.Whenstudded withproteins (ribosomes),the endoplasmic reticulum is considered rough ER and is involvedwith the processing of nascent protein.Smooth ER is involved in maturing proteinsandcarbohydrates,and is responsible for xenophobic metabolism of foreign compounds.Section:1.441.Of the biochemical macromolecules, which class is chiefly responsible for catalysis of cellularprocesses?Ans:Proteins.Section:1.242.DNA and RNA are composed of what basic biochemical compounds?Ans:Both RNA and DNA are nucleotides.Central to nucleotides is a carbohydrate moleculecalled a riboseor deoxyribose.Bonded to the ribose is one of several aromatic nitrogen-containing organic compounds which are generically called “bases.”One or morephosphate groups are also bonded to the riboseor deoxyribose.Section:1.243.What are the important functions of carbohydrates?Ans:Structural, energy storage, modify proteins, cell–cell recognition, lipid modification.Section: 1.244.What is significant about the base pairing found in the helix?Ans:It provides a mechanism for copying the DNA from one generation to the next.Section: 1.445.Which property of lipids drives the formation of membranes?Ans:The dual chemical nature of lipids allows them to self-organize intomembranes.Section:1.2

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Chapter 2Water, Weak Bonds, and the Generation of Order Out ofChaosMatching QuestionsUse the following to answer questions 1–10:Choose the correct answer from the list below. Not all of the answers will be used.a) ionic bonds or salt bridgesb) Brownian motionc) hydrophobicd) hydrogene) polarf) nonpolarg) van der Waalsh) entropyi) zwitterionj) amphipathick) positivel) dielectric constantm) negative1.____________:The typeof bond found between an oxygen on onewatermoleculeandhydrogen on a different water molecule.Ans:dSection:2.22.Movement of particles due to the random fluctuations of energy content of the environment isknown as____________.Ans:bSection:2.13.Electrostatic interactions between atoms with opposite electrical charges are also called____________.Ans:aSection:2.34.Waterweakens the electrostatic interaction of ions due to its high ____________.Ans:lSection:2.35.The distance when two atoms no longer repulse each other yet havethestrongest attraction isknown as the____________ radii or contact distance.Ans:gSection:2.3

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Chapter 2Water, Weak Bonds, and the Generation of OrderOut of Chaos26.____________:Thermodynamic force that drives hydrophobic interactions.Ans:hSection:2.47.____________:A molecule with two distinctive chemical properties or characteristics.Ans:jSection:2.48.Which type of amino acids are responsible for increasing entropy as a protein folds?Ans:fSection:2.49.____________:The charge of the side group ofaspartatewhen the pH is more than one pH unitabove the pKa.Ans:mSection:2.510.____________:The charge of an amino group when the pH is one pH unit below the pKa.Ans:kSection:2.5Fill-in-the-Blank Questions11.Molecules that are readily soluble in water are considered____________.Ans:polarSection 2.212.The force that is quantified by Coulomb’s lawis calledthe____________.Ans:ionic or electrostatic interactionSection 2.313.A solvent with a low dielectric constant would be a____________solvent for salts.Ans:poorSection 2.314.The transient force which,while weak, still has a large impact on how macromolecules interactisthe____________.Ans:Van der Waals interactionSection 2.315.Hydrophobic molecules are driven together by____________, not because theyhavean affinityfor each other.Ans:entropySection 2.416.Lipidsthatinteract withboththe water andthehydrophobic regionsof the membrane areconsidered____________.Ans:amphipathicSection 2.417.An acid ionizes to form a proton and its________________.Ans:base or conjugate baseSection 2.5

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Chapter 2Water, Weak Bonds, and the Generation of OrderOut of Chaos318.When the pH is more than two pH units above the pKa of a carboxyl group, the acid is____________.Ans:unprotonatedSection 2.519.Buffers are critical in maintaining proper____________levels in biological systems.Ans:pHSection 2.520.The source of the key buffering component of blood is____________.Ans:carbon dioxideSection2.5Multiple-Choice Questions21.What is the H+concentration in a urine sample that has a pH of 6?A) 10−6MB) 10−8MC) 106MD) 10−14ME) 8 MAns: ASection: 2.522.Which of the following is considered a noncovalent bond?A) electrostatic interactionsB) hydrogen bondsC) van der Waals interactionsD) All of the above.E) Noneof the above.Ans:DSection:2.323.What charged group(s) are present in glycine at a pH of 7?A)–NH3+B)–COO−C)–NH2+D) A and BE) A, B, and CAns:DSection:2.524.Water can formhydrogen bondswith the___________ of another molecule.A) carbonyl groupsB) amine groupsC) aromatic ringsD) alcohol groupsE)A, B,and DAns:ESection:2.3& 2.4

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Chapter 2Water, Weak Bonds, and the Generation of OrderOut of Chaos425.What pairs of atoms in bases are involved in hydrogen bonds?A)N–H and O–HB)N–H and S–HC) O–H and P–OD)All of the above.E)None of the above.Ans: ASection: 2.326.Typical van der Waals energies are about:A)4–20 kJ/mol.B)2–4 kJ/mol.C)200 kJ/mol.D)All of the above.E)None of the above.Ans: BSection: 12.327.What two properties of water are important for biological interactions?A)the polarity of waterB)the density of waterC)the cohesive properties of waterD)A and CE)B and CAns: DSection: 2.228.List atoms commonly found in biological molecules that are often hydrogen-bond acceptors.A) carbonB) oxygenC) nitrogenD) B and CE) All of the above.Ans:DSection:1.329.What happens to nonpolar molecules in water?A)They dissolve independently.B)They aggregate together.C)They precipitate.D)All of the above.E)None of the above.Ans: BSection: 1.330.What is the [A−]/[HA] ratio when the weak acid is in a solution one pH unit above its pKa?A)1:1B)1:10C)10:1D)2:1E)None of the above.Ans: CSection 1.3

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Chapter 2Water, Weak Bonds, and the Generation of OrderOut of Chaos531.What are the primary chemical components present in a phosphate buffer at pH 7.4?A)H3PO4and PO4−3B)H2PO4−and PO4−3C)HPO4-2and PO4-3D)H2PO4−and HPO4−2E)H3PO4and HPO4−2Ans: DSection 1.332.Whatis the concentration of acetic acid in250 mlof a100 mM acetate buffer at pH 4.76?A)250 mMB)100 mMC)50 mMD)75 mME)There is not enough information to tell.Ans:CSection 2.5Short-Answer Questions33.Using Coulomb’s law, describe how water is an ideal solvent for the ions found in cells?Ans:The force which attracts two oppositely charged ions is measured by a constant akq1q2Kq1q2 divided the dielectric constant of the solvent×R.This means that a solvent suchas water, with a high dielectric constant,will result in a lowered attractive force.Section:2.434.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:2.335.What is an electrostatic interaction? Give an example.Ans:It is the attractive force of two oppositely charged atoms. Salts (such as NaCl) are acommon example.Section:2.336.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 andhydrogen bonds. The oxygen can act as a hydrogen-bond acceptor, and the hydrogen canact as a donor.Section:2.237.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:2.3

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Chapter 2Water, Weak Bonds, and the Generation of OrderOut of Chaos638.How is protein folding driven?Ans:Nonpolar amino acids associate with each other,forming the interior of folded proteins.This causes an increase in the entropy of water and thermodynamically drives proteinfolding.Section:2.439.If noncovalent bonds are so much weaker than covalent bonds, how do they stabilize largebiochemical structures?Ans:There is stability in numbers.Section:Introduction40.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:2.441.How do hydrophobic interactions aid in membrane formation?Ans:Hydrophobic interaction causesthenonpolartailsto aggregate and form the interior ofthemembrane. This results in a net release of heat and a favorable change in the systementhalpy.Section:2.442.Give examples of key functional groups found in biochemistry.Ans:Hydrophobic, hydroxyl, aldehyde, keto, carboxyl, amino, phosphoryl, sulfhydrylSection:2.5, Table 2.143.Draw a titration curve for the ionization of acetic acid.Ans:The curve should look likeFigure 2.12.Section:2.544.Why are conjugate acid–base pairs so important in biological systems?Ans:The conjugate acid–base pairs in biological systems act as buffers. Many metabolicactivities release protons, and these can combine with the conjugate baseand so havelittle effect on the pH.Section:2.5

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Chapter 3Amino AcidsMatching QuestionsUse the following to answer questions 1–10.Choose the correct answer from the list below. Not all of the answers will be used.a)Lamino acidsb) waterc) protonsd) zwitterionse) leucinef) serineg) tyrosineh) cysteinei) glutamatej) histidinek) prolinel) asparaginem)Damino acids1.____________:Chiral type of amino acids found in proteins.Ans:aSection:3.12.____________:Another name for dipolar molecules.Ans:dSection:3.13.____________:Disulfide bonds are formed by pairs ofthisamino acid.Ans:hSection:3.24.____________:The amino acid with a pKanear neutral pH.Ans:jSection:3.25.____________:The aminoacid with whose side group has a terminal carboxamide.Ans:lSection:3.26.____________:The amino acid with an imidazole side chain.Ans:jSection:3.27.____________:An amino acidthatmust be supplied by the diet.Ans:jSection:3.3

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Chapter 3Amino Acids28.____________:The amino acid with a negativelycharged side chain at neutral pH.Ans:iSection:3.29.____________:The amino acid with a sulfhydrylside chain.Ans:hSection:3.210.____________:The amino acidwiththe abbreviation Ser.Ans:fSection:3.2Fill-in-the-Blank Questions11.The amino acid that contains a weakly acidic “phenolic” group is__________.Ans:tyrosineSection 3.212.__________areamino acidswith neutral R groupscontaining an electronegative atom thathoards electrons.Ans:Polar amino acidsSection 3.213.The amino acid with the smallest-size side chain allowing greatestflexibility in a proteinis__________.Ans:glycineSection 3.214.The charge of glycine when the pH is<2.0is __________.Ans:+1Section 3.115.Between the amino and the carboxyl functional group, the ________ has the lowest affinity for aproton.Ans:carboxylSection:3.116.The amino acid with an indol ring is__________.Ans:tryptophanSection:3.217.__________is an amino acid with a hydrophobic side chain containing a thioether.Ans:MethionineSection:3.218.The____________groupis the functional groupthatmakes an amino acid more reactive thannonpolar amino acids such as valine, alanine,and phenylalanine.Ans:hydroxylSection:3.219.The group of amino acids that can be supplied by an organism under a defined condition are the______ amino acids.Ans:NonessentialSection:3.320.____________ is often seen in a child with a protein-deficient diet.Ans:EdemaSection:3.3

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Chapter 3Amino Acids3Multiple-Choice Questions21.What chargedgroup(s) is/arepresent in glycine at a pH of 7?A)–NH3+B)–COO−C)–NH2+D) A and BE) A, B, and CAns:DSection:3.222.At a pH of 12, what chargedgroup(s) is/arepresent in glycine?A)–NH3+B)–COO−C)–NH2+D) A and BE) A, B, and CAns:BSection:3.223.In what pH range is zwitterionicalanine the predominate structure?A) 0–2B)9–14C) 8–10D) 2–4E) 2–9Ans: ESection 3.224.Which amino acids contain reactive aliphatic hydroxyl groups?A) serine and methionineB) serine and threonineC) methionine and threonineD) cysteine and methionineE) cysteine and threonineAns: BSection: 3.225.Name three amino acids that are positively charged at a neutral pH.A) lysineand arginineB) histidineand arginineC) cysteineand arginineD) lysineand prolineE) glutamineand histidineAns: ASection: 3.226.Interactions between side chains of and Aspartateand Arginineat neutral pH would be?A)hydrophobicB)ionicC)hydrogen bondingD)stericE)covalentAns: BSection: 3.2

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