Test Bank for Biochemistry A Short Course 5th Edition 2025. By Justin Hines, Catherine Reinke, John

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Chapter 1 1. What underlies the unity of biochemistry? a. Some organisms are highly uniform at the molecular level. b. All living beings are highly uniform at the organismal level. c. Organisms are highly uniform at the cellular level. d. All organisms are highly uniform at the molecular level. e. Some living beings are highly uniform at the cellular level. ANSWER: d 2. How many times more carbon is contained in organisms than in Earth's crust? a. 60 times b. 50 times c. 9.5 times d. 10 times e. 100 times ANSWER: b 3. Why is carbon preferable to be the chemical base for life? a. Carbon dioxide is essentially insoluble in water. b. It escapes the biochemical circulation once it is utilized. c. The stability and strength of the carbon–carbon bonds make it a good base for larger molecular complexes. d. By reacting with hydrogen, it can undergo combustion, which provides organisms with energy. e. Carbon dioxide is a strong construction material. ANSWER: c 4. What is NOT a primary function of proteins? a. signal receptors b. energy storage c. signal molecules d. structural units e. defensive agents ANSWER: b 5. What does being a catalyst mean? a. slowing down the rate of reactions to increase control over them b. being fully utilized in the course of a reaction; causing no unnecessary change in the reaction components c. repeatedly enhancing the rate of chemical reactions without being consumed d. repeatedly decreasing the rate of chemical reactions without being affected by enzymes e. enhancing the rate of chemical reactions being permanently affected during their course to control the environmental changes .. Powered by Cognero.

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Chapter 1 ANSWER: c 6. Which structure CANNOT be a nucleotide? a. a five-carbon sugar attached to a base and at least one phosphoryl group b. a five-carbon sugar attached to a heterocyclic ring structure and one phosphoryl group c. a five-carbon sugar attached to a base and two phosphoryl groups d. a five-carbon sugar attached to a base and four phosphoryl groups e. a five-carbon sugar attached to a heterocyclic ring structure and three phosphoryl groups ANSWER: d 7. What determines the nature of an organism? a. the information stored in proteins b. the information contained in deoxyribonucleotides c. the information stored in the deoxyribonucleic acid d. the information stored in biological polymers e. the information contained in the ribonucleic acid ANSWER: c 8. What is NOT a nucleotide? a. adenine b. thymine c. uracil d. cytosine e. adenosine ANSWER: e 9. Which statement about compositional differences between DNA and RNA is TRUE? a. Ribonucleotides contain an additional hydroxyl group. b. Ribonucleotides exploit three different bases, while deoxyribonucleotides exploit four. c. Deoxyribonucleotides contain an additional hydroxyl group. d. Deoxyribonucleotides contain a five-carbon sugar, whereas RNA bases contain a six-carbon sugar. e. Ribonucleotides exploit four different bases, while deoxyribonucleotides exploit three. ANSWER: a 10. What is the molecular basis for establishing intracellular compartments? a. the formation of membranous barriers due to ability of proteins to form extended linear structures b. the ability of lipids to form barriers due to their dual properties regarding solubility in water c. the formation of lipid barriers due to the small size of lipids d. the development of lipid barriers due to hydrophilic interactions within lipid molecules e. the formation of lipid barriers due to the dual nature of lipids regarding their interactions with proteins .. Powered by Cognero.

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Chapter 1 ANSWER: b 11. What can serve as sites of cell-to-cell interactions? a. molecules of glycogen b. branched chains of carbohydrates c. branched proteins d. hydrophobic tails of lipids e. hydrophilic heads of lipids ANSWER: b 12. Choose the CORRECT statement about functions of lipids and proteins. a. They both can be involved in signal transduction. b. They both form a cell skeleton. c. They both act as receptors for signal molecules. d. They both can provide large amounts of cellular energy upon combustion. e. They both are involved in the transfer of biological information. ANSWER: a 13. What determines the function of a cell or tissue? a. information contained in the genome b. selective transcription of RNA c. translation of RNA d. replication of DNA e. selective expression of genes ANSWER: e 14. What is the central dogma? a. the flow of information across all biomolecules of a cell b. the scheme proposed by Francis Crick to describe complex cell-to-cell interactions c. the basic scheme of the flow of information in the cell for eventual rendering of the genetic information into a functional form d. the scheme proposed in 1958 to describe the genome e. the basic scheme of selective replication of DNA ANSWER: c 15. What is the basic unit of life? a. DNA b. protein c. RNA d. cell e. biomolecular complexes .. Powered by Cognero.

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Chapter 1 ANSWER: d 16. What constitutes the cell membrane? a. a lipid bilayer organized through interaction of lipid hydrophobic heads with each other and lipid hydrophilic tails with the environment b. the outer layer of a cytoplasm c. a lipid bilayer organized through interaction of lipid hydrophobic tails with each other and lipid hydrophilic heads with an aqueous environment d. the periplasmic space e. a lipid bilayer organized by interaction with membrane proteins ANSWER: c 17. How can one distinguish eukaryotic and prokaryotic cells? a. Eukaryotic cells do not have any membranous compartments. b. The cytoplasm is present only in eukaryotic cells. c. The DNA is free in the cytoplasm of eukaryotic cells. d. Membrane-enclosed compartments are absent in prokaryotes. e. Eukaryotic cells are surrounded by two membranes with the periplasmic space in between. ANSWER: d 18. What are two biochemical features that are obligatory for a cell to exist? a. plasma membrane and nucleus b. nucleus and cytoplasm c. storage for genetic information and a lipid bilayer d. plasma membrane and nucleoid e. plasma membrane and cytoplasm ANSWER: e 19. What is an example of the structural function of carbohydrates? a. formation of branched complexes involved in cell-to-cell interaction b. construction of a cell wall c. formation of glycogen polymers d. modification of proteins e. construction of starch in plants ANSWER: b 20. Which is an organelle? a. ribosome b. cytoskeleton c. plasma membrane d. secretory granule .. Powered by Cognero.

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Chapter 1 e. cell wall ANSWER: d 21. Which sequence of steps preceding DNA replication is TRUE? a. The DNA polymerase gene is transcribed in the nucleus → the DNA is translated into the enzyme on ER → the enzyme is translocated through nuclear pores into the nucleus. b. mRNA of the DNA polymerase gene is synthesized in the nucleus → the mRNA is transferred to the cytoplasm → the DNA polymerase is synthesized on the ribosome → the enzyme is translocated through nuclear pores into the nucleus. c. The DNA polymerase gene is translated in the nucleus → the mRNA is transferred to the cytoplasm → transcription takes place in the ribosome → the enzyme is translocated through nuclear pores into the nucleus. d. mRNA of the DNA polymerase gene is translated in the cytoplasm→ the enzyme is transferred to the nucleus → transcription takes place in the ribosome. e. mRNA of the DNA polymerase gene is synthesized in the cytoplasm → the mRNA is transferred to the nucleus → the DNA polymerase is synthesized on the ribosome → the enzyme is translocated through nuclear pores out of the nucleus. ANSWER: b 22. In which organelles is chemical energy generated? a. nucleus and mitochondrion b. chloroplast and nucleus c. mitochondrion and endosome d. mitochondrion and chloroplast e. nucleus and endosome ANSWER: d 23. What is the source of cellular energy? a. glucose b. mitochondrion c. adenosine triphosphate d. glycogen e. lipids ANSWER: c 24. The quantity of which organelle in liver cells can be markedly changed by increasing the ingestion of drugs by an organism? a. smooth ER b. zymogen granules c. rough ER d. the Golgi complex e. ER lumen .. Powered by Cognero.

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Chapter 1 ANSWER: a 25. What organelles is NOT surrounded by two membranes? a. nucleus b. chloroplast c. mitochondrion d. the Golgi complex e. chromoplast ANSWER: d 26. Which statement about a plant cell is TRUE? a. The conversion of sunlight into a form of energy useful for a cell takes place in the plant vacuole. b. The plant cell wall is constructed from linear polymers of amino acids. c. The conversion of sunlight into a form of energy useful for a cell takes place in the mitochondrion. d. Chloroplasts power the whole living world. e. The plant cell wall is constructed mostly from branched polymers of carbohydrates. ANSWER: d 27. How big is a human microbiome in relation to the number of human cells? a. relates as 0:1 b. relates as 2:1 c. relates as 13:1 d. relates as 1:2 e. approximately equal ANSWER: e 28. What is the role of DNA polymerase? a. It catalyzes the transcription of DNA. b. It structures the collection of genes. c. It is the catalyst of synthesis of new strands of DNA. d. It selectively expresses heritable information of an organism. e. It is the catalyst of separation of DNA strands. ANSWER: c 29. Where are secreted proteins modified? a. smooth ER and transport vesicle b. the Golgi complex and smooth ER c. rough ER and transport vesicle d. the Golgi complex and transport vesicle e. rough ER and the Golgi complex ANSWER: e .. Powered by Cognero.

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Chapter 1 30. What regions of the endoplasmic reticulum can lack ribosomes? a. rough ER and budding-off secretory vesicles b. smooth ER and transport vesicles budding off the rough ER c. smooth ER and secretory vesicles budding off the rough ER d. rough ER and transport vesicles budding off the smooth ER e. smooth ER and sequestered plasma membrane ANSWER: b 31. Which statement about the difference between endocytosis and phagocytosis is TRUE? a. Endosomes formed only in phagocytosis can be fused with lysosomes. b. Small amounts of material can be taken into the cell by phagocytosis but only large ones by endocytosis. c. Endosomes formed only in endocytosis can be fused with lysosomes. d. Large amounts of material can be taken into the cell by phagocytosis but only small ones by endocytosis. e. Only immune cells can endocytize cholesterol. ANSWER: d 32. Which process is similar to the formation of lysosomes? a. formation of secretory granules b. endocytosis c. phagocytosis d. formation of transport vesicles e. stacking of membranes ANSWER: a 33. Where does sorting of proteins take place? a. rough ER b. transport vesicle c. the Golgi complex d. smooth ER e. secretory vesicle ANSWER: c 34. What components can assist in protein folding? a. stacked membranes b. chaperons c. zymogens d. ribosomes e. lipids .. Powered by Cognero.

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Chapter 1 ANSWER: b 35. Which organelles are unique for plant cells? a. chloroplasts and plant vacuole b. chloroplasts c. cell wall and plant vacuole d. chloroplasts and filaments ANSWER: a 36. What characterizes the matrix of the mitochondria? a. membrane that is in touch with the cytoplasm b. highly invaginated membrane c. combustion of fuel molecules d. intermembrane space e. actin filaments ANSWER: b 37. Which is common between the biomolecules that contribute to the transfer of biological information? a. diverse three-dimensional structure b. dimerization c. dual chemical nature d. repeating units in the linear structure e. repeating units in the branched structure ANSWER: d 38. In higher organisms, what is a polymer with double-stranded phosphodiester-linked monomers? a. RNA b. DNA c. protein d. carbohydrate e. lipid ANSWER: b 39. What determines folding of a protein? a. hydrophobic or hydrophilic environment b. the location of a protein in the cell c. the pH of the cytoplasm d. the sequence of amino acids that constitute the protein e. interactions of proteins with lipids ANSWER: d .. Powered by Cognero.

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Chapter 1 40. The half-life of what molecule is likely to be the shortest? a. protein b. lipid c. carbohydrate d. DNA e. mRNA ANSWER: e 41. What is another function of a plasma membrane apart from its barrier function? a. providing to the interior of the cell an enclosed environment that no molecules may cross b. providing a selectively permeable barrier with the aid of transport proteins c. giving eukaryote and prokaryote cells structural strength d. allowing only a free passage of water in and out of the cell e. facilitated entrance of hormones ANSWER: b 42. Poisons that kill an organism as a result of a loss of high-energy ATP molecules are MOST likely to target which organelle? a. mitochondria b. cytoskeleton c. cytoplasm d. endoplasmic reticulum e. nucleus ANSWER: a 43. A secreted protein would be processed through organelles in what order? a. nucleus, secretory vesicle, Golgi complex b. cytoplasm, Golgi complex, cytosol, secretory vesicle c. endoplasmic reticulum, secretory vesicle, Golgi complex d. nucleus, cytoplasm, endoplasmic reticulum, Golgi complex, secretory vesicle e. endoplasmic reticulum, Golgi complex, secretory granule ANSWER: e 44. Extracellular material is taken into the eukaryotic cell via: a. exocytosis. b. phagocytosis. c. formation of zymogen granules. d. secretory pathway. e. diffusion. ANSWER: b .. Powered by Cognero.

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Chapter 1 45. If substance X inhibits secretion of the labeled protein but fully synthesized, folded, and glycosylated protein is still found in the cell, where is the most likely site for substance X to act? a. nucleus during translation b. budding off the secretory granule c. translation on the ribosome d. enzyme modification in the Golgi complex e. nucleus during transcription ANSWER: b 46. Which match between the loss of a particular organelle with the associated disease is TRUE? a. hypercholesterolemia – smooth endoplasmic reticulum b. diabetes – endosome c. Tay-Sachs disease – lysosome d. muscle degeneration – mitochondria e. stroke – Golgi body ANSWER: c 47. What experiments would you perform to verify the existence of the endoplasmic reticulum in a strain of bacteria? a. determine whether the bacterium can synthesize ATP in the presence of fuel molecules and O2 b. determine whether the bacterium can synthesize proteins c. determine whether the bacterium generates CO2 in the presence of fuel molecules d. determine whether the bacterium has an internal membrane-enclosed compartment e. determine whether lipids can form a bilayer structure in the bacterial cell ANSWER: d 48. What is/are the rigid material(s) that provide(s) structural support to a plant cell? a. plant cytoskeleton b. plasma membrane c. cell wall d. outer membrane e. microfilaments and microtubules ANSWER: c 49. Filaments and microtubules are components of a network called the: a. chloroplast. b. cytoplasm. c. cytoskeleton. d. cell wall. e. mitochondrion. .. Powered by Cognero.

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Chapter 1 ANSWER: c 50. Translation takes place on/in the: a. ribosomes. b. smooth endoplasmic reticulum. c. nucleus. d. DNA polymerases. e. DNA parent strand. ANSWER: a 51. Which three elements make up the majority of organisms, listed in descending order of abundance (as a percentage) in humans? a. carbon, oxygen, hydrogen b. hydrogen, oxygen, carbon c. hydrogen, carbon, nitrogen d. nitrogen, hydrogen, oxygen e. hydrogen, oxygen, nitrogen ANSWER: b 52. The abundance of which element makes living organisms unique? a. hydrogen b. oxygen c. phosphorous d. nitrogen e. carbon ANSWER: e 53. When comparing carbon–carbon and silicon–silicon bonds, which is FALSE? a. Carbon–carbon bonds are stronger than silicon–silicon bonds and provide greater stability to large molecules. b. Carbon–carbon bonds release more energy when undergoing combustion, compared to silicon– silicon bonds. c. Molecules with carbon–carbon bonds are better construction materials compared to molecules with silicon–silicon bonds d. Carbon–carbon bonding leads to greater solubility in water compared to silicon bonding. e. Carbon-based molecules are better fuel sources than silicon-based molecules. ANSWER: d 54. The linear structure of proteins is constructed by linking ____ with _____ bonds. a. nucleotides; covalent b. amino acids; peptide .. Powered by Cognero.

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Chapter 1 c. amino acids; phosphodiester d. polypeptides; hydrogen e. amino acids; hydrogen ANSWER: b 55. Which is NOT a functional role of proteins? a. catalysis b. signal transduction c. cell-cell recognition d. cell mobility e. storage of genetic information ANSWER: e 56. Which three components make up the monomers that are put together to form DNA? a. ribose sugar, nitrogenous base, and three hydroxyl groups b. ribose sugar, nitrogenous base, and three phosphoryl groups c. deoxyribose sugar, nitrogenous base, and three phosphoryl groups d. deoxyribose sugar, nitrogenous base, and three amino groups e. deoxyribose sugar, nitrogenous base, and three hydroxyl groups ANSWER: c 57. Which statement regarding DNA and RNA is FALSE? a. DNA and RNA both contain pentose sugar backbones. b. DNA and RNA both consist of nucleotides connected by phosphodiester linkages. c. DNA and RNA both consist of four unique nucleotides, differing only in the nitrogenous base. d. DNA and RNA are both directional molecules. e. DNA and RNA are both helical structures composed of strands connected by hydrogen bonding. ANSWER: e 58. Which is a result of the hydrophobic and hydrophilic dual chemical nature of lipids? a. the ability to perform enzymatic functions and speed up biochemical reactions b. the ability to form barriers that delineate an “inside” and “outside” at a biochemical level c. the ability to act as signal molecules d. the ability to combust to provide large amounts of cellular energy e. the ability to store and transfer genetic information ANSWER: b 59. A particular mutation renders DNA polymerase nonfunctional. Which is MOST LIKELY to be affected by this mutation? a. replication of DNA b. transcription of DNA molecules to functional RNAs .. Powered by Cognero.

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Chapter 1 c. transcription of DNA molecules to mRNA d. translation of mRNA molecules to proteins e. folding of functional RNAs ANSWER: a 60. Liver cells and heart cells contain the exact same genetic information. What is responsible for liver and heart cells having drastic structural and functional differences? a. DNA replication b. mutations c. protein sorting d. selective gene expression e. ribosomes ANSWER: d 61. An unusual accumulation of mRNA molecules is observed in the cytoplasm of a cell with low levels of protein. Which enzyme or cell structure is likely malfunctioning in this cell? a. DNA polymerase b. plasma membrane c. ribosomes d. RNA polymerase e. secretory granule ANSWER: c 62. You are a researcher studying the function of a protein called mastermind. This protein functions in neuronal cells to assist in the transmission of electrical signals. In one of your experiments, you notice that mastermind is present in the neuronal cells, but not functioning properly. Other cellular functions appear normal. Select the likely explanation for your observations. a. A mutation in the mastermind mRNA has occurred. b. Ribosomes are not functioning properly. c. RNA polymerase is not functioning properly. d. The mastermind gene is missing from the genome. e. DNA polymerase is not functioning properly. ANSWER: a 63. A nonfunctional RNA polymerase would MOST directly affect which biological process? a. folding of polypeptides into functional proteins b. conversion of mRNA into protein c. transfer of genetic information from DNA to RNA d. replication of genetic information e. exportation of mRNA from the nucleus to the cytoplasm ANSWER: c .. Powered by Cognero.

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Chapter 1 64. What is meant when scientists say DNA replication is semi-conservative? a. Half of an offspring’s genetic content comes from one parent and the other half comes from the other parent. b. DNA replication consumes energy to synthesize the first strand and synthesizes the second strand without expending additional energy. c. Each strand of a parent DNA molecule acts as a template strand to make two new daughter DNA molecules. d. DNA polymerase is only needed to synthesize one of the strands. e. Each strand of DNA is synthesized without a template. ANSWER: c 65. Which is an example of the selective permeability of cell membranes? a. oxygen diffusing freely across the plasma membrane b. proteins embedded in the plasma membrane facilitating entry of glucose c. free movement of water across a cell membrane d. phospholipids containing hydrophobic and hydrophilic regions. e. proteins associated with the plasma membrane transducing information ANSWER: b 66. Which of the following is NOT a biochemical process that occurs in the cytoplasm? a. mRNA synthesis b. glucose metabolism c. fatty acid synthesis d. protein synthesis e. endosome-lysosome fusion ANSWER: a 67. Which biological process occurs on rough endoplasmic reticulum (ER) but not on smooth ER? a. processing of exogenous chemicals b. transcription c. translation d. phagocytosis e. DNA replication ANSWER: c 68. What is a consequence of mutations in chaperone proteins in the lumen of the ER? a. improperly sorted proteins b. misfolded proteins c. untranslated proteins d. hyperactive proteins e. unmodified proteins .. Powered by Cognero.

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Chapter 1 ANSWER: b 69. The primary function of lysosomes is to: a. bring sorted proteins to the correct organelle or plasma membrane. b. engulf foreign microorganisms or exogenous agents. c. fuse with secretory granules to dump cargo into the extracellular environment. d. fuse with endosomes to digest extracellular material and damaged intracellular organelles. e. store water, ions, and various nutrients. ANSWER: d 70. Which is TRUE of both familial hypercholesterolemia and Tay–Sachs disease? a. Both diseases are the result of improper gene expression. b. Both diseases are the result of disruptions in the microbiome. c. Both diseases are the result of improper combustion of fuels. d. Both diseases are the result of malfunctions in specific cellular organelles. e. Both diseases are the result of an inability to store glucose molecules as glycogen. ANSWER: d

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Chapter 2 1. Molecules that are readily soluble in water are considered: a. nonpolar. b. polar. c. zwitterionic. d. volatile. e. dielectric. ANSWER: b 2. The interaction that is described by Coulomb's law is called: a. hydrophobic. b. weak. c. electrostatic. d. hydrogen. e. physical. ANSWER: c 3. What would be the solubility of a salt in a solvent with a low dielectric constant? a. excellent b. good c. suitable d. poor e. exclusive ANSWER: d 4. Hydrophobic molecules are driven together by: a. entropy. b. enthalpy. c. van der Waals interactions. d. affinity. e. hydrogen bonds. ANSWER: a 5. The protein that interacts with both water and the hydrophobic regions of the membrane is considered: a. polar. b. nonpolar. c. amphibious. d. anabolic. e. amphipathic. ANSWER: e 6. Protonation of a base yields its: .. Powered by Cognero.

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Chapter 2 a. conjugate molecule. b. conjugate base. c. conjugate acid. d. ionized derivative. e. ionized base. ANSWER: c 7. An organic acid ionizes to form a conjugate base and: a. hydrogen. b. water. c. a hydroxyl ion. d. a proton. e. hydrogen peroxide. ANSWER: d 8. Gastroesophageal reflux disease is a common example of a pathological change in: a. pKa of acetic acid. b. hydrogen bonds in a key digestive enzyme. c. protein structure. d. water content in cells. e. pH level. ANSWER: e 9. What is the pH of human blood? a. 5.5 b. 7.0 c. 9.4 d. 6.4 e. 7.4 ANSWER: e 10. Choose the functional group that CANNOT form a hydrogen bond with water. a. carbonyl group b. amino group c. aromatic ring d. alcohol group e. sulfhydryl group ANSWER: c 11. Which combination can associate to form a hydrogen bond? .. Powered by Cognero.

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Chapter 2 a. N–H and O b. N–H and S c. O–H and P d. C=O and S e. C=O and P ANSWER: a 12. What is the typical length of noncovalent bonds? a. 0.4 angstroms b. 4 angstroms c. 40 angstroms d. 4 nm e. 0.04 nm ANSWER: b 13. In a typical cell, the water content is about: a. 60%. b. 70%. c. 80%. d. 90%. e. 99%. ANSWER: b 14. Oxygen is an electronegative atom. That means that in a molecule of water the: a. electrons of covalent bonds spend more time near the oxygen atom than near the hydrogen atoms. b. electrons of covalent bonds spend more time near the hydrogen atoms than near the oxygen atom. c. electrons of bonds are located closely to the hydrogen atoms. d. electrons of bonds are located closely to the oxygen atom. e. bonds joining the hydrogen atoms to the oxygen atom are noncovalent. ANSWER: a 15. What does it mean that liquid water has a partly ordered structure? a. There are van der Waals interactions between water molecules. b. Hydrogen-bonded clusters of molecules are continually being formed and broken apart in liquid water. c. In the physiological range of temperatures liquid water can undergo phase transition to gas that is completely unordered and to ice that is completely ordered. d. There is Brownian motion of water molecules. e. Water molecules can form hydrogen bonds with polar molecules but not with nonpolar molecules. ANSWER: b .. Powered by Cognero.

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Chapter 2 16. How many neighboring water molecules are hydrogen-bonded on average to one water molecule in a sample of pure water? a. 1.4 b. 2.4 c. 3.4 d. 4.4 e. 5.4 ANSWER: c 17. What type of interactions is NOT a weak interaction? a. nuclear interactions b. salt bridges c. van der Waals interactions d. ionic bonds e. hydrogen bonds ANSWER: a 18. What is the amount of energy needed to apply a 1-newton force over a distance of 1 angstrom? a. 1010 J b. 10–10 J c. 1 J d. 10 J e. 1 kcal ANSWER: b 19. What is the amount of energy needed to raise the temperature of 2 kilograms of water from 14.5°C to 15.5°C? a. 2 J b. 2 kJ c. 2 cal d. 20 cal e. 2 kcal ANSWER: e 20. What factor does NOT affect electrostatic interaction according to Coulomb's law? a. the charges on the two interacting atoms b. a change in entropy if the interaction occurs c. the distance between the two interacting atoms d. the dielectric constant of the medium e. presence and concentration of other charged corpuscles in the medium .. Powered by Cognero.

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Chapter 2 ANSWER: b 21. How much weaker are hydrogen bonds as compared to covalent bonds? a. from 2 to 10 times b. from 20 to 50 times c. from 100 to 1000 times d. from 1000 to 10,000 times e. from 10,000 to a million times ANSWER: b 22. What is the difference in length between a typical hydrogen bond and a covalent bond? a. They are equal in length. b. A hydrogen bond is somewhat shorter than a covalent bond. c. A hydrogen bond is much shorter than a covalent bond. d. A hydrogen bond is somewhat longer than a covalent bond. e. A hydrogen bond is much longer than a covalent bond. ANSWER: d 23. What group in nucleotide bases is a hydrogen-bond donor? a. N–H b. S–H c. P–O d. C=O e. C–H ANSWER: a 24. Van der Waals interactions do not depend on: a. the distance between the two interacting atoms. b. the distribution of electrons around the nuclei. c. the presence of other charged corpuscles in the medium. d. a transient asymmetry in electrical charge of atoms. e. the geometry of the large molecules. ANSWER: c 25. What amino acids are most likely to be found in the core of a water-soluble globular protein? a. nonpolar b. polar but uncharged c. positively charged d. negatively charged e. random ANSWER: a .. Powered by Cognero.

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Chapter 2 26. Choose the molecule around which in an aqueous solution water molecules are most ordered. a. alcohol b. aliphatic amino acid c. aromatic amino acid d. hydrocarbon chain e. carboxylic acid ANSWER: d 27. HCl is a strong acid that is easily and completely hydrolyzed in an aqueous solution. What is the concentration of hydroxyl ions in a 50 mM aqueous HCL solution? a. 2 × 10–7 M b. 5 × 10–6 M c. 2 × 10–12 M d. 2 × 10–13 M e. 5 × 10–4 M ANSWER: d 28. What is the net charge of a glycine molecule in human blood at pH 7.4, for an amino group of glycine pKa = 9.6 and for a carboxyl group pKa = 2.3? a. –2 b. –1 c. 0 d. +1 e. +2 ANSWER: c 29. Choose the correct name for the plot of pH changes in a weak acid solution under stepwise addition of a strong acid or base. a. van der Waals curve b. Michaelis–Menten curve c. Henderson–Hasselbalch curve d. compensatory respiratory alkalosis curve e. titration curve ANSWER: e 30. Tris buffers are commonly used in biochemistry because they buffer within the physiological range of pH due to a pKa of 8.1. What is the [A–]/[HA] ratio in a 0.1 M tris solution with pH 9.1? a. 1:100 b. 1:10 .. Powered by Cognero.

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Chapter 2 c. 10:1 d. 2:1 e. 1:2 ANSWER: c 31. What organ in the human body is crucial for blood pH regulation by compensatory respiratory alkalosis? a. heart b. kidneys c. liver d. lungs e. muscles ANSWER: d 32. Tris buffers are commonly used in biochemistry because they buffer within the physiological range of pH due to a pKa of 8.1. What is the concentration of the conjugate base in a 0.1 M tris solution with pH 5.1? a. 0.1 M b. 0.01 M c. 0.05 M d. 0.5 nM e. 0.1 mM ANSWER: e 33. What is the concentration of acetate in a 0.1 M acetic acid solution at pH near to pKa = 4.76? a. 0.5 M b. nearly 0.1 M c. 0.05 M d. 0.01 M e. almost 0 ANSWER: b 34. What is the [A–]/[HA] ratio when a weak acid is in a solution two pH units below its pKa? a. 1:100 b. 1:10 c. 10:1 d. 2:1 e. 1:2 ANSWER: a 35. What is the hydroxyl ion concentration in a urine sample that has a pH of 6? a. 10–6 M .. Powered by Cognero.

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Chapter 2 b. 10–8 M c. 106 M d. 10–14 M e. 6 M ANSWER: b 36. What is the H+ concentration in a urine sample that has a pH of 6? a. 10–6 M b. 10–8 M c. 106 M d. 10–14 M e. 8 M ANSWER: a 37. Typical van der Waals energies are about: a. 4–20 kJ/mol. b. 2–4 kJ/mol. c. 200–400 kJ/mol. d. 2–4 J/mol. e. 200–400 MJ/mol. ANSWER: b 38. Nonpolar molecules in water: a. dissolve independently. b. aggregate together. c. precipitate. d. dissociate to ions. e. form hydrogen bonds with water molecules. ANSWER: b 39. What is the [A–]/[HA] ratio when a weak acid is in a solution one pH unit above its pKa? a. 1:1 b. 1:10 c. 10:1 d. 2:1 e. 1:2 ANSWER: c 40. What are the primary chemical components present in a phosphate buffer at pH 7.4? .. Powered by Cognero.

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Chapter 2 a. H3PO4 and PO43– b. H2PO4– and PO43– c. HPO42– and PO43– d. H2PO4– and HPO42– e. H3PO4 and HPO42– ANSWER: d 41. What is the concentration of acetic acid in 250 ml of a 100 mM acetate buffer at pH 4.76? a. 250 mM b. 100 mM c. 50 mM d. 75 mM e. 25 mM ANSWER: c 42. Citric acid is an important intermediate in glucose metabolism and is synthesized in the mitochondrial matrix. The pKa values for each of the three carboxylic groups of the citric acid are 3.1, 4.8, and 6.4. What is the charge on a citrate molecule formed in the mitochondrial matrix where the pH is 7.8? a. +3 b. +2 c. –3 d. –2 e. +1 ANSWER: c 43. A student observes that when an unknown molecule is added to water, it forms micelles, which under the right conditions can form membranes. What can this student infer about this phenomenon? a. The unknown molecule is amphipathic. b. The micelle formation is driven by the resulting decrease in entropy of water. c. The unknown molecule forms many van der Waals interactions with water. d. The micelle formation is driven by the hydrophilic effect. e. The unknown molecule dissociates to ions in water. ANSWER: a 44. What is the term for the movement of particles due to the random fluctuations of energy content of the environment? a. dissociation b. Brownian motion c. hydrophobic interaction d. van der Waals interaction .. Powered by Cognero.

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Chapter 2 e. entropy ANSWER: b 45. What is the term for the electrostatic interactions between atoms with opposite electrical charges? a. salt bridges b. Brownian motion c. hydrophobic interactions d. hydrogen bonds e. van der Waals interactions ANSWER: a 46. Water weakens the electrostatic interaction of ions due to its: a. ionic bonds or salt bridges. b. Brownian motion. c. entropy. d. ion product of water. e. dielectric constant. ANSWER: e 47. What is the contact distance when two atoms no longer repulse each other yet have the strongest attraction? a. amphipathic b. Brownian c. hydrophobic d. hydrogen e. van der Waals ANSWER: e 48. Which type of amino acid is responsible for increasing entropy as a protein folds? a. nonpolar b. polar but uncharged c. charged positively d. charged negatively e. amphipathic ANSWER: a 49. The biochemical time scale is on the order of: a. 10−24 s to 10−18 s. b. 10−18 s to 10−12 s. c. 10−12 s to 10−6 s. d. 10−6 s to 10−3 s. e. 10−3 s to 10−1 s. .. Powered by Cognero.

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Chapter 2 ANSWER: c 50. Which of these molecules is polar? a. H2 b. O2 c. N2 d. C6H14 e. H2S ANSWER: e 51. Which type of interactions maintains the column of water in a tree trunk? a. covalent bonding b. ionic interactions c. hydrogen bonding d. van der Waals interactions e. salt bridges ANSWER: c 52. In which environment are electrostatic interactions the strongest? a. in a vacuum b. in water c. in ammonia d. in oil e. in acetic acid ANSWER: a 53. Which of these electric dipole orientations does NOT occur? a. the negative end of a dipole pointing toward a positively charged ion b. the negative end of one dipole pointing toward the positive end of another dipole c. two dipoles positioned so that both the positive and negative ends can interact d. the positive end of a dipole pointing toward a negatively charged ion e. the positive end of one dipole pointing toward the positive end of another dipole ANSWER: e 54. When sodium chloride dissolves in water: a. the sodium ions form noncovalent interactions with the hydrogen atoms of water molecules. b. the chloride ions form noncovalent interactions with the oxygen atoms of water molecules. c. the sodium ions form noncovalent interactions with each other. d. the sodium ions form noncovalent interactions with the chloride ions. e. the chloride ions form noncovalent interactions with the hydrogen atoms of water molecules. ANSWER: e .. Powered by Cognero.

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Chapter 2 55. Which type of interactions is principally responsible for the stability of a DNA double helix? a. covalent bonding b. ionic interactions c. hydrogen bonding d. van der Waals interactions e. salt bridges ANSWER: c 56. What would be the most likely consequence if complementary base pairs in DNA interacted through covalent bonding instead of through hydrogen bonding? a. The DNA double helix would be less stable. b. The DNA base sequences would be more vulnerable to harmful reactions. c. The DNA could undergo transcription, but not replication. d. The genes on the DNA could not be expressed. e. The DNA could undergo replication, but not transcription. ANSWER: d 57. What group in nucleotide bases is a hydrogen bond acceptor? a. N–H b. S–H c. P–O d. C=O e. C–H ANSWER: d 58. Which type of interactions allows geckos to walk up walls? a. covalent bonding b. ionic interactions c. hydrogen bonding d. van der Waals interactions e. salt bridges ANSWER: d 59. What motto can be used to describe van der Waals interactions? a. stability in distance b. stability in strength c. stability in numbers d. stability in charge e. stability in smallness ANSWER: c .. Powered by Cognero.

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Chapter 2 60. What is the Second Law of Thermodynamics? a. Energy cannot be created or destroyed. b. The total entropy of a system and its surroundings always increases in a spontaneous process. c. Energy can be created, but not destroyed. d. The total entropy of a system and its surroundings always decreases in a spontaneous process. e. Energy can be destroyed, but not created. ANSWER: b 61. A student adds an unknown solute to water and observes that the solute forms globules within the water. The unknown solute molecules most likely: a. form hydrogen bonds with water. b. dissociate into ions. c. form hydrogen bonds with one another. d. decrease the order of the water molecules. e. increase the order of the water molecules. ANSWER: d 62. What is the primary driver of protein folding? a. hydrogen bonding b. hydrophobic effect c. ionic interactions d. van der Waals interactions e. dipole-dipole interactions ANSWER: b 63. Which of these functional groups CANNOT form hydrogen bonds? a. hydrocarbon chains b. carboxylic acids c. amines d. thiols e. ketones ANSWER: a 64. Compensatory respiratory alkalosis: a. decreases blood pH by increasing the production of CO2. b. increases blood pH by increasing the release of CO2. c. increases blood pH by decreasing the production of CO2. d. decreases blood pH by decreasing the release of CO2. e. increases blood pH by increasing the production of CO2. ANSWER: b .. Powered by Cognero.

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Chapter 2 65. What is the pH of gastric (stomach) juice? a. 1 to 2 b. 3 to 4 c. 5 to 6 d. 7 to 8 e. 9 to 10 ANSWER: a 66. Which expression represents the pKa of an acid? a. b.

c. d.

e. ANSWER: e 67. Which expression is true when pH = pKa? a. b. c.

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e. ANSWER: a 68. Which scientist’s discovery laid the groundwork for the development of techniques for tracking individual atoms and molecules in biochemical reactions? a. Lawrence Joseph Henderson .. Powered by Cognero.

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Chapter 2 b. Charles-Augustin de Coulomb c. Marie Curie d. Robert Brown e. Karl Albert Hasselbalch ANSWER: c 69. What is the pH of a lactic acid solution (pKa = 3.86) when the concentration of lactic acid is 0.1 M and the concentration of lactate is 0.01 M? a. 1.86 b. 2.86 c. 3.86 d. 4.86 e. 5.86 ANSWER: b 70. Uncontrolled diabetes can lead to the accumulation of acidic compounds called ketone bodies in the blood. What happens to the H2CO3/HCO3⁻ buffer system in a person with this condition? a. HCO3⁻ is converted into H2CO3, which is then converted into CO2. b. H2CO3 is converted into HCO3⁻, which is then converted into CO2. c. CO2 is converted into H2CO3, which is then converted into HCO3⁻. d. CO2 is converted into HCO3⁻, which is then converted into H2CO3. e. HCO3⁻ is converted into CO2, which is then converted into H2CO3. ANSWER: a

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Chapter 3 1. What is NOT a function of amino acids? a. building blocks of proteins b. neurotransmitters c. precursors of nucleic acids d. building blocks of lipids e. precursors of hormones ANSWER: d 2. Recall the structural formula of an amino acid in the dipolar form. Choose the group that is coming out of the plane of the page toward the viewer. a. COO– b. NH3+ c. R d. C e. H ANSWER: c 3. Recall the structural formula of an amino acid in the dipolar form. Choose the group that is projected behind the page away from the viewer. a. COO– b. NH3+ c. R d. H e. C ANSWER: d 4. What are the CORRECT constituents of the α-amino acid? a. central carbon with hydrogen atom, amino group, carboxyl group, R group b. α hydrogen, amino group, carboxyl group, D group c. α carbon, amino group, carboxyl group, R group d. central carbon with hydrogen atom, amide group, carboxyl group, L group e. α carbon, amino group with hydrogen atom, carboxyl group, L group ANSWER: a 5. What makes α-amino acids chiral to the largest extent? a. D isomers are more dominant in α solution. b. The α-carbon atom is tetrahedral. c. α-amino acids are able to exist in both mirror-image forms. d. L isomers are more dominant in a solution. e. Four different groups of α-amino acids are connected to the tetrahedral α-carbon atom. .. Powered by Cognero.

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Chapter 3 ANSWER: e 6. What does NOT vary between amino acids? a. shape b. charge c. hydrophobicity d. L form in proteins e. hydrogen-bonding capacity ANSWER: d 7. Which amino acid contains a terminal carboxamide? a. glycine b. glutamine c. lysine d. glutamate e. phenylalanine ANSWER: b 8. Which statement about the role of functional groups of amino acids is FALSE? a. A narrow range of functional groups provides for the broad spectrum of protein function. b. Most of the properties of amino acids are conferred by functional groups. c. Functional groups are easier to identify in stereochemical renderings. d. A wide range of functional groups provides for the broad spectrum of protein function. e. Under physiological conditions, at least two functional groups of amino acids are charged. ANSWER: a 9. Which amino acid is more conformationally restricted and why? a. glycine because it is achiral b. proline because its side chain is bonded to both the nitrogen and the α-carbon atoms c. glycine because two hydrogen atoms are bonded to the α-atom d. proline because its side chain is aliphatic e. proline because its side chain is bonded to both the carboxyl carbon and the α-carbon atom ANSWER: b 10. Choose only the aromatic amino acids. a. Phe, Trp, Ser b. Trp, Tyr, Ile c. Tyr, Phe, His d. Phe, Tyr, Leu e. Trp, Phe, Val ANSWER: c .. Powered by Cognero.

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Chapter 3 11. Which amino acids have a branched side chain? a. Val, Leu, Met b. Ile, Leu, Ala c. Ala, Ile, Pro d. Leu, Gly, Val e. Ile, Leu, Val ANSWER: e 12. Which statement about serine, threonine, and tyrosine is FALSE? a. All of them have a hydroxyl group. b. All of them have nonpolar counterpart amino acids. c. They are all aliphatic. d. They are all polar. e. All of them form zwitterions at physiological pH. ANSWER: c 13. Interactions between these amino acids are parts of the driving force for protein folding. Choose all correct answers. a. Ile and Trp b. Ser and Tyr c. Trp and Met d. Phe and Gly e. Val and Thr ANSWER: a, c 14. The side chain of which amino acids can completely lose a proton at a slightly basic pH? a. methionine b. cysteine c. serine d. threonine e. tyrosine ANSWER: b 15. What would be the base-to-acid ratio of histidine at pH 3? a. 100 b. 1000 c. 0.003 d. 300 e. 0.001 ANSWER: e .. Powered by Cognero.

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Chapter 3 16. Which amino acid contains a guanidinium functional group? a. alanine b. lysine c. histidine d. arginine e. asparagine ANSWER: d 17. Which amino acid contains an imidazole ring? a. proline b. arginine c. asparagine d. tryptophan e. histidine ANSWER: e 18. Which amino acid contains a group uncharged or positively charged near a neutral pH? a. histidine b. proline c. cysteine d. serine e. aspartate ANSWER: a 19. What amino acid contains a thioether bond? a. serine b. threonine c. cysteine d. isoleucine e. methionine ANSWER: e 20. The tripeptide that should have the highest solubility in water is: a. HRK. b. QRH. c. KDG. d. WET. e. RKM. ANSWER: a .. Powered by Cognero.

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Chapter 3 21. Which functional group distinguishes asparagine from aspartic acid? a. hydroxyl b. carboxamine c. sulfhydryl d. carboxamide e. guanidinium ANSWER: d 22. Which amino acid can be used as a taste enhancer? a. glutamine b. asparagine c. glutamate d. aspartate e. glycine ANSWER: c 23. How many amino acids can human beings synthesize? a. 20 b. 11 c. 5 d. 18 e. 3 ANSWER: b 24. What is the reason for the edema in kwashiorkor? a. insufficient protein in the blood plasma b. distorted hydrophilicity of the protein c. distorted distribution of water within capillaries d. disrupted hydrophobic effect e. excessive protein in the blood plasma ANSWER: a 25. Which amino acids with ionizable groups have a typical pKa value higher than 10? Select all that apply. a. lysine b. cysteine c. tyrosine d. arginine e. histidine ANSWER: a, c, d 26. Which amino acid has a thiol group? .. Powered by Cognero.

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Chapter 3 a. histidine b. serine c. cysteine d. tyrosine e. asparagine ANSWER: c 27. Which ionizable group has the lowest affinity for protons? a. asparagine side chain group b. aspartic acid side chain group c. terminal α-amino group d. glutamic acid side chain group e. terminal α-carboxyl group ANSWER: e 28. What tripeptide is able to accept the largest number of protons at pH 7.4? a. RHN b. HKE c. DQE d. EHD e. DKE ANSWER: d 29. What amino acids can be involved in acid–base catalysis? a. glutamic acid and asparagine b. tyrosine and serine c. asparagine and arginine d. glutamic acid and cysteine e. threonine and lysine ANSWER: d 30. Which tripeptide is able to accept the least number of protons at pH 11? a. RHN b. HKE c. DQE d. EHD e. DKE ANSWER: a 31. Which amino acid can be part of a protein? a. L glycine .. Powered by Cognero.

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Chapter 3 b. D glycine c. L alanine d. D alanine e. L imidazole ANSWER: c 32. Which amino acid side chains are capable of ionization? Select all that apply. a. aspartate b. histidine c. serine d. alanine e. tyrosine ANSWER: a, b, e 33. The amino acids that contain sulfur are: a. cysteine and serine. b. cysteine and threonine. c. cysteine and methionine. d. threonine and methionine. e. serine and methionine. ANSWER: c 34. Which amino acid is often present in the active site of enzymes because of its ability to both donate and accept a proton at a physiological pH? a. arginine b. aspartic acid c. histidine d. glutamine e. lysine ANSWER: c 35. Which statement about the compactness of the protein interior is TRUE? a. A small number of sizes and shapes of hydrocarbon side chains enable their compact packing. b. A wide variety of aliphatic side chains complicate their packing with little empty space. c. Large and different polar side chains restrict protein folding. d. A wide variety of sizes and shapes of hydrocarbon side chains enable their packing with little empty space. e. A small variety of aromatic side chains are used to direct protein folding to a more compact form. ANSWER: d 36. What is the driving force for formation of the unique spatial structure of water-soluble proteins? .. Powered by Cognero.

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Chapter 3 a. the tendency of hydrophilic groups to cluster together b. the tendency of hydrophobic groups to repel each other c. the tendency of polar groups to interact with water molecules d. the tendency of hydrophobic groups to cluster together e. the tendency of hydrophilic groups to repel each other ANSWER: d 37. Which is a chiral type of amino acids found in proteins? a. L amino acids b. D amino acids c. zwitterions d. α-amino acids e. polar amino acids ANSWER: a 38. The amino acid with the smallest-size side chain allowing the greatest flexibility in a protein is _______. ANSWER: glycine 39. In what pH range is alanine present predominantly in its zwitterionic form? a. 0–2 b. 9–14 c. 8–10 d. 2–4 e. 2–9 ANSWER: e 40. What would be the overall charge of the peptide Asp-Gly-Arg-His at pH 1? a. –1 b. 0 c. 1 d. 2 e. 3 ANSWER: e 41. Which amino acids would be most soluble in a nonpolar solvent such as benzene? a. valine b. histidine c. glutamine d. glycine e. threonine ANSWER: a .. Powered by Cognero.

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Chapter 3 42. Below is a list of five tripeptides identified by their single letter codes. Which tripeptide contains an amino acid capable of forming covalent disulfide bonds? a. FNC b. RGK c. VIL d. MDE e. SYT ANSWER: a 43. In which part of a globular protein are Trp and Phe located and why? a. exterior due to the hydrophilic effect b. interior due to the hydrophobic effect c. exterior forming polar H bonds with water d. interior forming ionic bonds with other amino acids e. exterior forming ionic polar bonds with water ANSWER: b 44. Amino acids can contain all of the following functional groups EXCEPT: a. indole. b. thioester. c. phenyl. d. sulfhydryl. e. amine. ANSWER: b 45. Which amino acids contain reactive aliphatic hydroxyl groups? Select all that apply. a. serine b. threonine c. methionine d. cysteine e. alanine ANSWER: a, b 46. Which amino acids are positively charged at a neutral pH? a. lysine and arginine b. histidine and arginine c. cysteine and arginine d. lysine and proline e. glutamine and histidine ANSWER: a .. Powered by Cognero.

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Chapter 3 47. What would be the interactions between side chains of aspartate and arginine at a neutral pH? a. hydrophobic b. ionic c. hydrogen bonding d. steric e. covalent ANSWER: b 48. Below is a list of five tripeptides identified by their single letter codes. Which tripeptide has the most polar side chains? a. FNC b. RGK c. VIL d. MDE e. SYT ANSWER: e 49. Below is a list of five tripeptides identified by their single letter codes. Which tripeptide is negatively charged at a physiological pH? a. FNC b. RGK c. VIL d. MDE e. SYT ANSWER: d 50. Which of these amino acids is considered a polar amino acid with a neutral R group? a. valine b. lysine c. serine d. arginine e. aspartic acid ANSWER: c 51. Which amino acid has a side chain that can form a disulfide bond? a. alanine b. serine c. cysteine d. glutamine e. leucine .. Powered by Cognero.

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Chapter 3 ANSWER: c 52. Which of these amino acids has a negatively charged side chain at neutral pH? a. glycine b. histidine c. methionine d. aspartic acid e. arginine ANSWER: d 53. Which amino acid has a ring structure that makes it more conformationally restricted than other amino acids? a. proline b. tryptophan c. phenylalanine d. tyrosine e. isoleucine ANSWER: a 54. What is the significance of the inflection points in the regions of an amino acid titration curve where pH changes are minimized? a. They indicate the pH values at which nearly all molecules of the amino acid are electrically neutral (uncharged). b. They represent the pKa values of the ionizable groups in the amino acid. c. They reflect regions in which the ionizable groups in the amino acid have minimal buffering capacity. d. They correspond to the pH values at which the ionizable groups in the amino acid are fully ionized. ANSWER: b 55. Which form of amino acids was selected during evolution to be a constituent of proteins? a. D isomer b. L isomer c. zwitterion d. neutral e. charged ANSWER: b 56. Which amino acid is most likely to be found in the active site of an enzyme whose reaction mechanism requires the transfer of a proton from one molecule to another? a. serine b. threonine c. histidine .. Powered by Cognero.

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Chapter 3 d. glutamine e. alanine ANSWER: c 57. Which statement best describes the isoelectric point (pI) of an amino acid with an ionizable side chain? a. It is the pH at which the side chain is fully ionized. b. It is the pH at which the amino acid carries no net charge. c. It is the arithmetic mean of all the pKa values of the amino acid. d. It is the pH at which the amino acid is most soluble in water. ANSWER: b 58. Which amino acid has a side chain that contains a thioether group? a. valine b. methionine c. cysteine d. leucine e. isoleucine ANSWER: b 59. How many different proteogenic amino acids can a species use to construct proteins? a. 10 b. 15 c. 20 d. 25 e. 30 ANSWER: c 60. What is the significance of a pKa value in the context of amino acids? a. It indicates the concentration of the amino acid in solution. b. It represents the pH at which an amino acid is at its isoelectric point. c. It is the pH at which an amino acid changes from a polar to a nonpolar molecule. d. It is the pH at which a functional group in an amino acid can gain or lose a proton. e. It determines the overall charge of the protein at physiological pH. ANSWER: d 61. How many inflection points does the titration curve of glycine have? a. 0 b. 1 c. 2 d. 3 e. 4 .. Powered by Cognero.

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Chapter 3 ANSWER: d 62. The isoelectric point (pI) of glutamic acid can be calculated by averaging the pKa values of: a. the α-carboxyl group and the R group. b. the α-amino group and the R group. c. the two ionizable groups with positive charges. d. all ionizable groups present. e. the α-amino group and the α-carboxyl group. ANSWER: a 63. Selenocysteine is unique among amino acids because it: a. contains a sulfur atom instead of selenium. b. is the only amino acid that is not chiral. c. is considered the 21st proteogenic amino acid. d. can only be found in human proteins. e. is not found in any organisms. ANSWER: c 64. Kwashiorkor is a condition that highlights the importance of which type of nutrient in the diet? a. fats b. carbohydrates c. vitamins d. proteins e. minerals ANSWER: d 65. What is the primary reason that only L isomers of amino acids are used in protein construction? a. L isomers are more stable than D isomers. b. L isomers are easier to synthesize biologically. c. L isomers were likely selected during evolution by chance. d. D isomers are not found in nature. ANSWER: c 66. Which amino acid is unique in being achiral? a. alanine b. valine c. glycine d. leucine ANSWER: c 67. What is the significance of the one-letter code for amino acids developed by Margaret Oakley Dayhoff? .. Powered by Cognero.

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Chapter 3 a. It facilitated the early comparison of protein sequences by computers. b. It represents the three-dimensional structure of amino acids. c. It is used to identify amino acids that are essential in the diet. d. It classified amino acids based on their polarity and charge at neutral pH. ANSWER: a 68. Which amino acid has a side chain that can form covalent bonds that are particularly important in stabilizing some proteins? a. serine b. threonine c. cysteine d. methionine ANSWER: c 69. Histidine's side chain has a pKa near 6.0, making it functionally significant in enzymes because: a. it can significantly acidify the active site environment. b. it can easily bind and release protons at physiological pH. c. it can contribute to the hydrophobic effect that drives the formation of the unique three-dimensional architecture of the enzyme. d. it can form covalent bonds that stabilize the enzyme’s structure. ANSWER: b 70. What is the primary role of disulfide bonds in the structure of proteins? a. They increase the solubility of proteins in water. b. They help in the transport of proteins across cell membranes. c. They maintain the stability of a protein's tertiary structure. d. They act as catalysts for biochemical reactions within the protein. ANSWER: c

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Chapter 4 1. What will be the weight of a protein consisting of 250 amino acid residues? a. 27,500 g mol–1 b. 22,000 g mol–1 c. 5500 g mol–1 d. 25,000 g mol–1 e. 250 kDa ANSWER: a 2. What groups of amino acids are linked in the primary sequence? a. β-amino group and α-carboxyl group b. α-amino group and β-carboxyl group c. α-amino group and α-carboxyl group d. α-nitro group and α-carboxyl group e. β-nitro group and β-carboxyl group ANSWER: c 3. What does polarity mean? a. ends of a polypeptide chain have different charges of the carboxyl group b. ends of a polypeptide chain always have different amino acid residues c. ends of an amino acid residue can link only the same amino acid residue d. a polypeptide chain has the amino-terminal residue and the carboxyl-terminal residue e. a polypeptide chain has the amino-terminal residue with a different charge ANSWER: d 4. Which statements about the polypeptide Gly-Tyr-Gly-Phe-Met-Ser are CORRECT? Select all that apply. a. Glycine is the C-terminal residue. b. Serine is the N-terminal residue. c. Serine is the C-terminal residue. d. Methionine is the N-terminal residue. e. Glycine is the N-terminal residue. ANSWER: c, e 5. What is the regularly repeating part of a polypeptide called? a. the distinctive side chain b. a variable part c. a peptide d. the backbone e. an oligopeptide ANSWER: d .. Powered by Cognero.

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Chapter 4 6. What is the distance between the nitrogen and carbon atoms in a peptide bond? a. 1.45 Å b. 1.27 Å c. 1.51 Å d. 5.4 Å e. 1.32 Å ANSWER: e 7. Why are peptide bonds of proteins found mainly in the trans configuration in nature? a. In the cis configuration, side chains of amino acids are most distant from each other but steric clashes between the groups are necessary. b. In the trans configuration, side chains of amino acids are most distant from each other and steric clashes between the groups are excluded. c. In the trans configuration, side chains of amino acids are least distant from each other and steric clashes between the groups are excluded. d. In the trans configuration, the two adjacent rigid peptide units may rotate about amino acid bonds. e. The trans configuration contributes to the rotation of radicals in a clockwise direction. ANSWER: b 8. What is the difference between a peptide and a protein? a. the number of amino acid residues b. the configuration of peptide bonds c. the structure of amino acid residues d. the charge of functional groups e. torsion angles ANSWER: a 9. What structures of polypeptide chains were proposed by Linus Pauling and Robert Corey? a. primary structures b. turns and loops c. secondary structures d. the alpha helix and the beta pleated sheet e. cis and trans configurations ANSWER: d 10. In the formation of the alpha helix, the carbonyl group is connected by: a. a hydrogen bond not with a neighboring NH group, but with a NH group located at a distance of four amino acid residues from it. b. a hydrogen bond with a neighboring NH group. c. a disulfide bond not with a neighboring NH group, but with a NH group located at a distance of four amino acid residues from it. .. Powered by Cognero.

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Chapter 4 d. a peptide bond with a neighboring NO group. e. a hydrogen bond with a single amino acid on an adjacent strand. ANSWER: a 11. What helices are energetically more favorable? a. right-handed b. counterclockwise c. left-handed d. twisted ribbons e. disulfide-bonded ANSWER: a 12. Aspartate can't form the α-helix because it: a. has a ring structure. b. has closely located radicals that have a tendency to steric clashes. c. has hydrogen-bond acceptors that compete for the main chain groups. d. is a too short amino acid to form the α-helix. e. does not have NH groups. ANSWER: c 13. What is the distance between adjacent amino acids along the α helix and along the β strand (respectively)? a. 3.5 Å and 1.5 Å b. 5.4 Å and 45 Å c. 5.4 Å and 3.6 Å d. 1.5 Å and 36 Å e. 1.5 Å and 3.5 Å ANSWER: e 14. Name the secondary structure shown in the figure

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Chapter 4

a. α helix b. reverse turns c. β sheet d. parallel β sheet e. mixed β sheet ANSWER: e 15. Collagen has: a. pyrrolidine rings, which stabilize helices and glycine residues at every third position (because only glycine residues can fit inside of the super-helical cable). b. pyrrolidine rings, which can push off and destabilize the helix and glycine residues at every second position (because only glycine residues can fit inside of the super-helical cable). c. rings of proline and glutamine residues at every second position. d. rings of glycine, which can stabilize helices and proline residues at every third position (because only proline residues can fit inside of the super-helical cable). e. rings of proline and glycine residues at every second position. ANSWER: a 16. What tertiary structure does myoglobin have? a. eight β sheets and α helices, turns and loops b. eight α helices, turns and loops between helices, and heme group c. eight β sheets, turns and loops between helices, and heme group d. seven β sheets, turns and loops between helices e. seven α helices, turns and loops between helices ANSWER: b 17. Where are the majority of nonpolar residues located in myoglobin? a. The outside of myoglobin. .. Powered by Cognero.

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Chapter 4 b. The interior of myoglobin. c. Myoglobin consists of only nonpolar residues. d. The outside and the interior of myoglobin. e. The outside of the super helix. ANSWER: b 18. How can you protect side chains of the main chain from interaction with water? a. pair all of the NO and CO groups by peptide bonding b. convert all nonpolar residues to polar ones c. form α helices and β sheets d. form quaternary structure e. form superhelices ANSWER: c 19. What is a helix-turn-helix motif? a. supersecondary structure in which an α helix is separated from another α helix by a turn b. supersecondary structure in which a β sheet is separated from a helix by a turn c. secondary structure in which two right-handed α helices are intertwined d. secondary structure in which two left-handed α helices are intertwined e. secondary structure in which an α helix is separated from a β sheet by a loop ANSWER: a 20. What types of interactions are in the quaternary structure? Select all that apply. a. disulfide bonds b. ionic bonds c. hydrogen bonds d. peptide bonds e. van der Waals forces ANSWER: b, c, e 21. A denatured protein is a protein: a. with high enzymatic activity. b. with destroyed noncovalent bonds. c. in which the disulfides are fully converted into sulfhydryls. d. that was treated with β-mercaptoethanol. e. that has been transformed into a random coiled peptide incapable of normal activities. ANSWER: e 22. What led to the conclusion that information about catalytic activity is contained in the primary sequence? a. Anfinsen's experiment, which showed that denatured protein can spontaneously restore its structure after exposure to denaturing agents .. Powered by Cognero.

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Chapter 4 b. Sanger's experiment, which showed that a protein has a precisely defined amino acid sequence c. Sanger's experiment, which showed that denatured protein can spontaneously restore its structure after exposure to denaturing agents d. Ramachandran's experiment about the φ and ψ angles e. Anfinsen's experiment, which showed that a protein has a precisely defined amino acid sequence ANSWER: a 23. What is the difference between calculated and actual folding time called? a. Dawkins' paradox b. folding funnel c. Ramachandran plot d. Levinthal's paradox e. Anfinsen's paradox ANSWER: d 24. What proteins have multiple conformations? a. ribonuclease and α-keratin b. collagen and prions c. synuclein and lymphotactin d. myoglobin and lymphotactin e. synuclein and collagen ANSWER: c 25. Proteins that are exceptions to the paradigm that a given protein amino acid sequence will fold into a particular three-dimensional structure are those that: a. perform different functions in different conditions and with a different partner. b. are only hydrophobic. c. are only hydrophilic. d. perform different functions with the same partners. e. have a different structure. ANSWER: a 26. Prions are: a. proteins that are normally present in the brain. b. agents that are similar in size to viruses but consist only of protein. c. agents causing viral brain diseases. d. uncommon for brain proteins with a complex structure. e. proteins contributing to the correct folding of proteins. ANSWER: a 27. In a Ramachandran plot: .. Powered by Cognero.

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Chapter 4 a. the values of 0 to +180 for the angle of the N–αC bond and of 0 to –180 for the angle of the αC–C bond are strongly disfavored. b. the φ angle is positive if the amino group is rotated to the left from the α carbon. c. only a small part of conformations is sterically excluded because two atoms cannot be in the same place at the same time. d. clockwise rotations of the torsion angles correspond to the negative values. e. the ψ angle corresponds to the bond between the amino group and α carbon. ANSWER: a 28. Which amino acids of the portion of the polypeptide AIGHTSM will be hydrogen-bonded to each other in the α helix? a. A-T, I-S, G-M b. A-H, I-T, G-S c. A-G, I-H, G-T d. A-I, G-H, T-S e. A-M, I-S, G-T ANSWER: a 29. Choose the CORRECT statement concerning the folding funnel. a. As the percentage of protein residues in native conformation increases, the total energy of the protein decreases, which increases the entropy of the protein. b. The energy of the protein grows as more hydrophobic interactions occur upon protein folding. c. In the nucleation-condensation model, both local and long-range interactions take place to lead to the formation of the native state. d. The molten globule model assumes that local interactions facilitate long-range hydrophobic interactions upon protein folding. e. The molten globule state has a lower energy than the partially correct intermediate. ANSWER: c 30. In the study of a new protein, you have observed the existence of several distinct stable conformations of the protein depending on presence or absence of other proteins in the solution. One form is 100% α helical, another contains about 75% α helices, and for the third one half of the protein had no distinctive secondary elements. Explain the results of your study. a. Most if not all of the forms are intermediates of the native protein. b. The protein should belong to the IDP class and is most likely involved in some signaling pathway. c. An intrinsically disordered form of the protein should have been present in the absence of any other protein, while in the presence of some other protein the folding should have proceeded as implied by the model of molten globule. d. The protein doesn't adhere to the paradigm of the folding funnel, and the existence of several forms strongly implies that the protein belongs to the metamorphic proteins. e. The protein doesn't adhere to the paradigm of the folding funnel, and the intrinsically disordered structure implies that this protein is metamorphic. .. Powered by Cognero.

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Chapter 4 ANSWER: b 31. Choose the CORRECT statement concerning prions. a. The prion precursor contains mostly extended structural elements rather than tightly coiled ones. b. A large number of β strands prevents extensive contacts between different proteins. c. The difference in the free energy between PrP and PrPSC is small. d. Prions usually consist of two subunits of the normal PrP protein. e. The decrease in the content of α-helical structural elements is unique for prions and always leads to pathological conditions. ANSWER: c 32. Choose the CORRECT statement about the secondary structure of protein. a. Adjacent strands in the parallel β sheet can be formed from the amino acids that are neighbors in the protein sequence. b. Loops and turns are required only to connect β strands while α helices are taking the whole length of the protein. c. Neighboring amino acids can form any possible secondary structure. d. Adjacent strands in the antiparallel β sheet can be formed from the amino acids that are neighbors in the protein sequence. e. One β strand is stable enough to exist in the protein structure. ANSWER: d 33. How many hydrogen bonds should be present within the antiparallel β sheet that curls into a closed barrellike structure if overall it has 8 β strands each 5 amino acids long? Do not consider the bonds that should be present in turns between the strands. a. 10 b. 30 c. 36 d. 44 e. 80 ANSWER: c 34. Compact globular units, called _______, are polypeptide chains folded into two or more compact regions. ANSWER: domains 35. The secondary structure that is stabilized by CO and NH hydrogen bonding within the peptide chain is called a(n): a. turn. b. loop. c. α helix. d. β sheet. e. β strand. .. Powered by Cognero.

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Chapter 4 ANSWER: c 36. Every third residue in the protein collagen is: a. leucine. b. glycine. c. proline. d. tyrosine. e. titin. ANSWER: b 37. Select all that apply. Human hemoglobin: a. is the oxygen-carrying protein in mitochondria. b. exists as an α2β2 tetramer. c. consists of α helices and β sheets. d. contains heme groups. e. has a tertiary structure. ANSWER: b, d 38. The amino acid residue that would MOST likely be buried in the interior of a water-soluble globular protein is: a. aspartate. b. serine. c. phenylalanine. d. lysine. e. glutamine. ANSWER: c 39. The folding of a protein into its native shape can best be described as a(n): a. random event. b. random event catalyzed by ribosome proteins to maintain a low energy structure. c. series of controlled folds with a few random-shaped structures. d. series of repeatable random events where the lowest energy structure is maintained. e. event where the highest possible energy state is stabilized with discrete folding intermediates. ANSWER: d 40. What structures did Pauling and Corey predict in 1951? Select all that apply. a. α helix b. β sheet c. turns between β sheets d. loops between α helices e. β strand .. Powered by Cognero.

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Chapter 4 ANSWER: a, b 41. Peptides differ from proteins in: a. the direction of β strands. b. the number of amino acid residues. c. the three-dimensional structure. d. the primary structure. e. polarity. ANSWER: b 42. Lymphotactin is an example of: a. metamorphic proteins. b. peptides. c. protein hormones. d. fatty-acid-binding proteins. e. fibrous proteins. ANSWER: a 43. Two amino acids undergo oxidation to form a dimer called: a. proline. b. glycine. c. cystine. d. tyrosine. e. leucine. ANSWER: c 44. What determines a protein's function? a. its structure b. its gene sequence c. N-terminal amino acids d. time of its formation e. C-terminal amino acids ANSWER: a 45. Why is the peptide bond planar? a. Bulky side chains prevent free rotation around the bond. b. It exhibits partial double-bond character, preventing rotation. c. Hydrogen bonding between the NH and C=O groups limits movement. d. The bond can have either cis conformation or trans conformation. e. It has different peptide bonds. ANSWER: b .. Powered by Cognero.

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Chapter 4 46. Where are β turns and loops often found? a. in a hydrophobic pocket b. on the interior cleft c. at the protein interface with a ligand d. on the surface of proteins e. between β sheets ANSWER: d 47. Your study group is trying to identify differences in the four levels of protein structure. The secondary structure but not the tertiary structure is stabilized by: a. ionic attractions between oppositely charged side chains. b. H-bonding between polar side chains. c. hydrophobic interactions between nonpolar side chains. d. H-bonding between the oxygen of the backbone carbonyl and the hydrogen of the backbone amine. e. van der Waals forces. ANSWER: d 48. A clinician friend comes to you and tells you she has a patient that she thinks has some sort of defect in the collagen structure. She wants to know what kinds of structural differences there might be. Which of the following is FALSE for defects leading to scurvy or brittle bone disease? a. Proline residues are not hydroxylated. b. Glycine is replaced by other amino acids. c. Prolyl hydroxylase activity is deficient. d. Accumulation of defective collagen causes cell death. e. There is violation of the quaternary structure. ANSWER: e 49. Which of the following structures is lost when a peptide bond is formed between two amino acids? a. amino group b. water c. carboxyl group d. carbonyl group e. amino-terminal residue ANSWER: b 50. Which of the following proteins contains examples of the α-helical character? Select all that apply. a. keratin b. ferritin c. myosin d. tropomyosin .. Powered by Cognero.

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Chapter 4 e. CD4 ANSWER: a, b, c, d 51. The three dimensional structure of proteins depends on its ____. a. primary structure b. secondary structure c. tertiary structure d. quaternary structure e. polypeptide structure ANSWER: a 52. Which statement about peptide bonds is TRUE? a. Peptide bonds join amino acids by linking the α-carboxyl group of one amino acid residue to the side chain of another amino acid residue. b. Peptide bonds join amino acids by linking the α-carboxyl group of one amino acid residue to the αcarboxyl group of another amino acid residue. c. Peptide bonds formed between amino acids result in the loss of a water molecule. d. The equilibrium of peptide bonds between amino acids lies on the side of synthesis rather than hydrolysis under most conditions. e. Peptide bonds are quite stable kinetically because their rate of hydrolysis is extremely fast. ANSWER: c 53. Which of the following amino acid residues is the carboxyl-terminal residue in the polypeptide Met-SerTyr-Phe-Val-Leu? a. methionine b. serine c. tyrosine d. phenylalanine e. leucine ANSWER: e 54. The regularly repeating part of a polypeptide is called the ____. a. side chain b. alpha chain c. amino chain d. main chain e. beta chain ANSWER: d 55. A protein with a molecular weight of 76,000 g mol-1 has a mass of ____. a. 76,000 kilodaltons .. Powered by Cognero.

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Chapter 4 b. 760,000 kilodaltons c. 76 kilodaltons d. 76 daltons e. 760,000 daltons ANSWER: c 56. The constrained conformation of peptide backbones are a result of what? a. the planar nature of peptide bonds b. the uncharged nature of peptide bonds c. the partial double-bond character of peptide bonds d. the trans configuration of peptide bonds e. the cis configuration of peptide bonds ANSWER: c 57. A Ramachandran plot shows that the majority of possible ϕ and ψ combinations are prevented due to ____. a. steric collisions between atoms b. a preference for the cis configuration of the peptide bond c. the length of bond between the nitrogen and the α-carbon atoms d. the planar nature of peptide bonds ANSWER: a 58. Hydrogen-bonding between the repeating functional groups of the polypeptide backbone is responsible for which level of protein structure? a. primary structure b. secondary structure c. tertiary structure d. quaternary structure ANSWER: b 59. The α helix of a protein contains five total turns. How many total amino acid residues compose this α helix? a. 45 b. 100 c. 6 d. 18 e. 5 ANSWER: d 60. Which of the following statements about α helices is TRUE? a. In schematic representations of proteins, α helices are depicted as globular balls. b. The pitch of the α helix is the sum of the length of all the turns of the helix. c. Each residue in an α helix is related to the next one by a rise of 2.5 Å along the helix axis. .. Powered by Cognero.

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Chapter 4 d. Right-handed α helices are energetically more favorable because there are fewer steric clashes between the side chains and the backbone. e. The CO group of residue i in an α helix forms a hydrogen bond with the NH group of residue i + 3. ANSWER: d 61. Which of the following statements about α helices, β sheets, and β strands is FALSE? a. The structural confirmation of a β strand is almost fully extended rather than tightly coiled as in the α helix. b. The α helix is the most common secondary structure found in proteins, followed by the β sheet. c. The distance between adjacent amino acids along a β strand is approximately 3.5 Å, in contrast with a distance of 1.5 Å along an α helix. d. The side chains of the amino acids composing α helices extend outward in a helical array, and the side chains of adjacent amino acids in β sheets point in opposite directions. e. None of the above. ANSWER: e 62. In a parallel β sheet, hydrogen bonds connect each amino acid with ___ amino acid(s) on the adjacent strand. a. one b. two c. three d. four e. five ANSWER: b 63. Which level of protein structure is primarily the result of the interactions between the side chains of the peptide chain? a. primary structure b. secondary structure c. tertiary structure d. quaternary structure ANSWER: c 64. β-mercaptoethanol is a chemical that disrupts disulfide bridges. Which level of protein structure would be MOST affected by exposure of a protein to β-mercaptoethanol? a. primary structure b. secondary structure c. tertiary structure d. quaternary structure ANSWER: c 65. Which is NOT a molecular interaction found in the quaternary structure of proteins? .. Powered by Cognero.

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Chapter 4 a. Van der Waals forces b. hydrogen bonding c. disulfide bonds d. ionic bonds e. hydrophobic interactions ANSWER: c 66. Where are nonpolar residues normally located in a protein that functions in an aqueous environment, such as in the interior of a cell? a. interior of the protein, shielded from water b. exterior of the protein, exposed to water c. exterior of the protein, interacting with other nonpolar residues d. interior of the protein, interacting with other polar residues e. none of the above ANSWER: a 67. Polypeptide subunits interact to form which level of protein structure? a. primary structure b. secondary structure c. tertiary structure d. quaternary structure ANSWER: d 68. What term describes a protein converting into a randomly coiled peptide devoid of normal functional activity? a. mutation b. denaturation c. deamination d. prion e. metamorphic ANSWER: b 69. The folding of proteins inside living cells is aided by the presence of what? a. prions b. ribosomes c. chaperones d. helper T cells e. none of the above ANSWER: c 70. What statement(s) is TRUE of the diseases Alzheimer disease, Parkinson disease, Huntington disease, and .. Powered by Cognero.

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Chapter 4 transmissible spongiform encephalopathies? a. These diseases are associated with improperly folded proteins. b. These diseases result in the formation of protein aggregates called amyloid fibrils. c. A common feature of these diseases is the conversion of normally soluble proteins into insoluble fibrils rich in β sheets. d. all of the above ANSWER: d

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Chapter 5 1. The prosthetic group of myoglobin that causes its ability to bind oxygen is: a. heme. b. porphyrin. c. protoporphyrin. d. pyrrole. e. oxymyoglobin. ANSWER: a 2. What is the term for hemoglobin in the R state? a. αβ dimer b. oxyhemoglobin c. deoxyhemoglobin d. desoxyhemoglobin e. cytoglobin ANSWER: b 3. What is the term for hemoglobin in the T state? a. αβ dimer b. oxyhemoglobin c. deoxyhemoglobin d. desoxyhemoglobin e. cytoglobin ANSWER: c 4. What is the quaternary structure of adult human hemoglobin A? a. monomer b. dimer of the α subunit and β subunit c. trimer of the α, β, and γ subunits d. tetramer of the two α subunits and two β subunits e. tetramer of the four α subunits ANSWER: d 5. How does oxygen-binding affinity of hemoglobin change after the binding of 2,3-BPG? a. increases greatly b. increases slightly c. decreases d. is strongly inhibited e. does not change ANSWER: c 6. Unlike adult forms of hemoglobin, fetal hemoglobin contains: .. Powered by Cognero.

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Chapter 5 a. two γ chains instead of α chains. b. one γ chain instead of an α chain. c. two ε chains instead of β chains. d. one ε chain instead of an α chain. e. two γ chains instead of β chains. ANSWER: e 7. Why does fetal hemoglobin bind oxygen more tightly than adult hemoglobin? a. Fetal hemoglobin has a single mutation in the β subunit; therefore, it is called the γ chain. b. The substitution of a serine residue for histidine 143 in the γ chain of the 2,3-BPG-binding site causes reduced affinity for 2,3-bisphosphogycerate. c. The substitution of a histidine residue for serine 143 in the γ chain of the 2,3-BPG-binding site causes increased affinity for 2,3-bisphosphogycerate. d. One of the substitutions in the fetal α chain is alanine for proline, which facilitates a van der Waals interaction and depresses the formation of the R state. e. One of the changes in the fetal α chain is a substitution of proline for alanine, which disrupts a van der Waals contact and facilitates the formation of the R state. ANSWER: b 8. With how many positively charged amino acids does 2,3-BPG interact in each chain of deoxyhemoglobin? a. 1 b. 2 c. 3 d. 4 e. 6 ANSWER: c 9. Where is the 2,3-BPG-binding site in deoxyhemoglobin? a. in the central cavity b. near the heme pocket c. in the hydrophobic core d. on the α1β1–α2β2 interface e. in the groove on the surface ANSWER: a 10. The effect of pH on oxygen binding of hemoglobin is called: a. pH effect. b. metabolic acidosis effect. c. Born effect. d. Herrick effect. e. Bohr effect. .. Powered by Cognero.

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Chapter 5 ANSWER: e 11. During the acidification inside erythrocytes, the specific way to stabilize the T state of hemoglobin is the formation of the salt bridge between: a. β1 His 146 and β2 Asp 94. b. β1 Asp 94 and N-terminal His of the β1 chain. c. α2 Lys 40 and β1 Asp 94. d. protonated β1 Asp 94 and C-terminal His of the β1 chain. e. β1 Asp 94 and protonated C-terminal His of the β1 chain. ANSWER: e 12. Hemoglobin: a. doesn't help to transport hydrogen ions. b. doesn't help to transport carbon dioxide from actively metabolizing tissues to lungs. c. isn't the main transporter of oxygen. d. isn't the main transporter of carbon dioxide. e. doesn't bind oxygen in lungs where the partial pressure of oxygen is high. ANSWER: d 13. In the human organism, myoglobin: a. helps to transport hydrogen ions in the body. b. helps to transport carbon dioxide from actively metabolizing tissues to lungs. c. facilitates the diffusion of oxygen to cellular sites that require oxygen d. is the main storage of carbon dioxide in muscles. e. binds oxygen in lungs where the partial pressure of oxygen is high and releases it in muscles in times of need. ANSWER: c 14. Unlike hemoglobin A, hemoglobin S: a. tends to form large fibrous aggregates when it is deoxygenated. b. tends to form large fibrous aggregates when it is oxygenated. c. has much lower oxygen-binding affinity. d. has much higher oxygen-binding affinity. e. has modified regulation due to mutation. ANSWER: a 15. What is the reason hemoglobin S aggregates? Choose the MOST accurate statement. a. The exposed hydrophobic valine makes a better van der Waals contact surface between Hb tetramers. b. The exposed hydrophobic valine on the β chain interacts with a complementary hydrophobic patch on the β chain of another hemoglobin molecule. .. Powered by Cognero.

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Chapter 5 c. The exposed hydrophobic valine on the β chain interacts with a hydrophobic patch on the α chain of another hemoglobin molecule. d. The hydrophobic valine, instead of glutamate, disturbs folding of the β chain; therefore, more hydrophobic side chains become exposed. e. The valine side chain produces a hydrophobic patch in oxygenated hemoglobin. ANSWER: b 16. Which form of hemoglobin aggregates in a newborn that is heterozygous for the sickle-cell hemoglobin allele? a. oxygenated HbA b. deoxygenated HbS c. oxygenated HbF d. deoxygenated HbA e. oxygenated HbS ANSWER: b 17. What is the evidence that myoglobin binds oxygen in a noncooperative manner? a. sigmoidal shape of the oxygen-binding curve b. hyperbolic shape of the oxygen-binding curve c. saturation level of the oxygen-binding curve d. the speed of oxygen binding at high pO2 e. the speed of oxygen binding at moderate pO2 ANSWER: b 18. What is the evidence that hemoglobin binds oxygen in a cooperative manner? a. saturation level of the oxygen-binding curve b. hyperbolic shape of the oxygen-binding curve c. sigmoidal shape of the oxygen-binding curve d. the speed of oxygen binding at high pO2 e. the speed of oxygen binding at moderate pO2 ANSWER: c 19. Choose the WRONG statement describing the coordination of the iron ion in hemoglobin. a. The Fe2+ ion is coordinated to the four nitrogen atoms in the center of the protoporphyrin of the heme. b. The fifth coordination site is occupied by the "proximal histidine" of the globin chain. c. The oxygen is bound to the sixth coordination site of the iron. d. The bonding between iron and oxygen leads to the rearrangement of electrons of the iron ion such that the number of electrons is decreased and the iron ion becomes effectively smaller. e. Histidine that occupies the fifth coordination site is capable of inhibiting oxidation of the iron to the .. Powered by Cognero.

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Chapter 5 ferric state. ANSWER: e 20. How many heme groups does a normal adult hemoglobin tetramer contain? a. 1 b. 2 c. 3 d. 4 e. 5 ANSWER: d 21. What is the maximal number of oxygen molecules that can be bound to one tetramer of normal adult hemoglobin A? a. 5 b. 4 c. 3 d. 2 e. 1 ANSWER: b 22. Carbon dioxide reacts with the amino terminal groups of hemoglobin to form carbamate groups, which carry a _______ charge. ANSWER: negative 23. Normal adult hemoglobin A: a. isn't a tetramer. b. isn't composed of two α subunits and two β subunits. c. doesn't have a structure very similar to myoglobin. d. can't be best described as a pair of nonidentical αβ dimers. e. is not able to bind an oxygen molecule by each subunit. ANSWER: d 24. What is the Bohr effect? a. the ability of hemoglobin to retain oxygen when in competition with myoglobin b. the regulation of hemoglobin oxygen binding by hydrogen ions and carbon dioxide c. the alteration of hemoglobin conformation during low oxygen stress d. the ability of hemoglobin to bind oxygen when the iron ion moves out of the porphyrin plane e. the regulation of hemoglobin oxygen-binding affinity by pH level ANSWER: b 25. Choose a FALSE statement about how oxygen binding to hemoglobin results in the T-to-R-state transition. .. Powered by Cognero.

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Chapter 5 a. When oxygen binds to hemoglobin, the iron ion moves out of the porphyrin plane. b. The movement of the iron ion causes changes in the quaternary structure that correspond to T-to-Rstate transition. c. The histidine residue bound in the fifth coordination site moves with the iron. d. Because proximal histidine is part of an α helix, the α helix moves as well. e. The carboxyl terminal of the α helix lies between the two αβ dimers. ANSWER: a 26. What is the partial pressure of oxygen in the alveoli of the human lungs? a. 10 torr b. 20 torr c. 100 torr d. 156 torr e. 760 torr ANSWER: c 27. Which statements concerning the following equilibrium is FALSE? CO2 + H2O H2CO3 a. An increase in the pressure of CO2 in actively metabolizing tissues will result in a decrease of pH inside red blood cells. b. This reaction is catalyzed by carbonic anhydrase in red blood cells. c. H2CO3 dissociates to H+ and a bicarbonate ion, HCO3–. d. The majority of CO2 is transported to the lungs in the form of HCO3–. e. The oxygen-binding affinity of hemoglobin increases as pH decreases ANSWER: e 28. How many oxygen-binding sites in hemoglobin are occupied when blood travels through capillaries? a. about 98% b. about 66% c. about 7% d. about 32% e. about 50% ANSWER: d 29. In the allosteric regulation of oxygen binding to Hb, _____ does NOT participate. a. carbon dioxide b. carbon monoxide c. hydrogen ion d. carbonic acid e. 2,3-bisphosphoglycerate .. Powered by Cognero.

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Chapter 5 ANSWER: b 30. What is the oxidation state of the heme iron in myoglobin and hemoglobin under normal conditions? a. Fe2+ b. Fe3+ c. ferric ion d. oxidized e. Fe0 ANSWER: a 31. What prevents oxidation of the heme iron to the ferric form? a. protoporphyrin b. proximal histidine c. distal histidine d. β 82 lysine e. 2,3-bisphosphoglycerate ANSWER: c 32. What is the magnitude of rotation of one αβ dimer with respect to the other one upon oxygenation of hemoglobin? a. 3 degrees b. 30 degrees c. 90 degrees d. 5 degrees e. 15 degrees ANSWER: e 33. What would be the expected result of substitution of aspartate 94 of the β chain with a serine residue? a. 2,3-BPG would bind tighter because of the loss of a negative charge. b. Oxygen-binding affinity would increase because of a disruption of a van der Waals contact, thus facilitating the formation of the R state. c. The formation of the salt bridge with C-terminal histidine in the β chain would be disrupted; therefore, hemoglobin sensitivity to acidification is expected to be reduced. d. 2,3-BPG would bind less tightly because of the loss of a negative charge. e. This substitution would have no effect on the allosteric properties of hemoglobin. ANSWER: c 34. If any of the histidine residues substitute with an arginine residue in the 2,3-BPG binding site of hemoglobin, 2,3-BPG would likely be bound: a. tighter because of the loss of a positive charge. b. tighter because of the gain of a positive charge. .. Powered by Cognero.

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Chapter 5 c. less tightly because of the loss of a positive charge. d. less tightly because of the gain of a positive charge. e. in the same way. ANSWER: e 35. Carbon dioxide forms carbamate groups in hemoglobin by reacting with: a. aspartate residues. b. cysteine residues. c. N-terminal amino groups. d. tyrosine residues. e. heme. ANSWER: c 36. Sickle-cell anemia is caused by: a. a decreased production of α chains of hemoglobin. b. a substitution of a Glu residue for a Phe residue at the β6 position. c. the loss of the heme group because the proximal His is oxidized. d. a substitution of a Val residue for a Glu residue at the β6 position. e. a substitution of a Glu residue for His at the C-terminal of the α chain. ANSWER: d 37. If a Lys residue is substituted with a Ser residue in the 2,3-bisphosphoglycerate (2,3-BPG) binding site of hemoglobin, 2,3-BPG would bind: a. 2 tighter because of the loss of a positive charge. b. tighter because of the gain of a positive charge. c. less tightly because of the loss of a positive charge. d. less tightly because of the gain of a positive charge. e. in the same way. ANSWER: c 38. fMRI measures the changes in the: a. fifth coordination site upon binding of iron, revealing the amount of carbon monoxide bound in carbon monoxide poisoning. b. fifth coordination site upon binding of iron, revealing sensory brain activity. c. magnetic properties of γ-chain hemoglobin and is a noninvasive way of measuring fetal hemoglobin levels during pregnancy. d. magnetic properties of hemoglobin, revealing the relative amounts of deoxy- and oxyhemoglobin in the circulation of a specific organ. e. pO2 levels in the circulatory system in any organism. ANSWER: d .. Powered by Cognero.

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Chapter 5 39. What is the organic portion of the heme group in hemoglobin? a. carbonic acid b. histidine c. pyrrole ring d. carbamate e. protoporphyrin ANSWER: e 40. What is the chemical form in which most of the carbon dioxide is transported in the blood? a. carbonic acid b. carbonate ion c. bicarbonate ion d. carbamate e. carbon monoxide ANSWER: c 41. What is the molecule whose function is to facilitate diffusion of oxygen in muscle cells? a. hemoglobin b. myoglobin c. protoporphyrin d. carbamate e. histidine ANSWER: b 42. What factor influences the binding of oxygen to myoglobin? a. the concentration of bicarbonate ions, HCO3– b. the partial pressure of oxygen, pO2 c. the concentration of hemoglobin present in the tissue d. the concentration of 2,3-bisphosphogycerate e. the concentration of the cooperative effect ANSWER: b 43. The iron atom in heme is bound to the fifth coordination site of which molecule? a. protoporphyrin b. oxygen c. carbonic acid d. carbamate e. histidine ANSWER: e .. Powered by Cognero.

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Chapter 5 44. What statement concerning the differences between hemoglobin and myoglobin is TRUE? a. Both hemoglobin and myoglobin are tetrameric proteins. b. Hemoglobin exhibits a hyperbolic O2 saturation curve, while myoglobin exhibits a sigmoid-shaped curve. c. Hemoglobin exhibits cooperative binding of O2, while myoglobin does not. d. Hemoglobin exhibits a higher degree of O2 saturation at all physiologically relevant partial pressures of O2 than myoglobin does. e. Both hemoglobin and myoglobin help to transport carbon dioxide from actively metabolizing tissues to lungs. ANSWER: c 45. Which of the statements concerning myoglobin is FALSE? a. The globin chain contains an extensive α-helix structure. b. The heme group is bound to the globin chain by two disulfide bonds between cysteine residues. c. The iron of the heme group is in the Fe2+ oxidation state. d. The diameter of the iron ion decreases upon binding of oxygen. e. The function of myoglobin is oxygen storage in muscle. ANSWER: b 46. Fetal hemoglobin: a. is composed of two α and two γ subunits. b. binds 2,3-BPG more tightly than normal adult hemoglobin. c. binds oxygen with less affinity than HbA at all pO2. d. does not exist in the T state. e. does not exist in the R state. ANSWER: a 47. What statement about oxygen transport by hemoglobin is TRUE? a. Oxygen binds to the proximal histidine residue of the globin chain. b. Bonding of carbon dioxide to hemoglobin molecules increases the binding of oxygen. c. Hemoglobin binds more oxygen as the pH is lowered. d. Hemoglobin binds more oxygen at higher 2,3-BPG concentrations. e. The binding of each O2 molecule to hemoglobin increases its affinity for the next O2. ANSWER: e 48. Molecular recognition is referred to as: a. the ability of specific molecules to bind to one another in the face of many alternatives. b. the chemical nature of molecules to recognize similar-sized molecules. c. the evolutionary nature of molecules to adapt to recognizing other molecules. d. the self-recognition abilities of all biochemical molecules. .. Powered by Cognero.

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Chapter 5 ANSWER: a 49. In receptor, R, and ligand, L, binding interactions, L1/2 represents: a. The time it takes for half of all receptors to be paired with a ligand b. The concentration of L at which half of the receptor amount is bound to L and half is free c. The concentration of R at which half of the ligand amount is bound to R and half is free d. The half-life of L ANSWER: b 50. Estrogen receptors have the strongest affinity for the ligand estradiol. However, estrogen receptors also bind bisphenol A, a precursor found in plastics, and tamoxifen, a cancer drug. Bisphenol A and tamoxifen can both be labelled as which of the following? a. disruptive ligands b. off-target ligands c. competitor ligands d. unnatural ligands ANSWER: c 51. For the estrogen receptor, bisphenol A and tamoxifen both have Kd values of 200nM, compared to a Kd of 1nM with estradiol. What does this say about the molecular affinities of the estrogen receptor for bisphenol A and tamoxifen compared to estradiol? a. The bisphenol A and tamoxifen ligands bind with significantly lower affinity compared to estradiol. b. The bisphenol A and tamoxifen ligands bind with significantly higher affinity compared to estradiol. c. The dissociation rates of the bisphenol A and tamoxifen ligands is lower than the dissociation rate of the estradiol ligand. d. The association rates of the bisphenol A and tamoxifen ligands is higher than the association rate of the estradiol ligand. ANSWER: a 52. Which of the following is the most commonly used metric to measure and communicate binding affinity by biochemists? a. association constants b. equilibrium constants c. dissociation constants d. affinity constants ANSWER: c 53. Which protein-ligand interaction is one of the strongest known to biochemists and is leveraged as an affinity tag in numerous laboratory methods? a. avidin-streptavidin b. immunoglobulin-RNAseH c. horseradish peroxidase-BCIP .. Powered by Cognero.

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Chapter 5 d. alkaline phosphatase-NBT e. avidin-biotin ANSWER: e 54. Why is molecular recognition especially important to the immune system? a. Cells of the immune system have no ability to distinguish between foreign molecules and molecules from normal cells and thus require molecular recognition. b. Cells of the immune system must identify and respond to signs of invading pathogens such as bacteria and viruses in the presence of vast numbers of highly similar molecules from normal cells. c. The immune system needs to recognize molecular entities in order to transmit electrical signals. d. The immune system needs to recognize molecular entities in order to provide cells and tissues with oxygen. e. The immune system needs to recognize molecular entities in order to metabolise sugars for energy. ANSWER: b 55. The adaptive immune response uses: a. soluble proteins called immunoglobulins that recognize foreign particles and mark them for destruction b. enzymatic barriers such as lysozyme to defend against foreign pathogens c. physical barriers such as skin to limit exposure to foreign invaders d. T-cell-mediated responses against bacteria and viruses ANSWER: a 56. Vaccines prevent serious infection without causing disease by priming the: a. innate immune system b. cell-mediated immune system c. humoral immune system d. natural immune system e. adaptive immune system ANSWER: e 57. A major function of hemoglobin, a component of red blood cells, is to: a. bind and carry CO2 from the lungs to cells and tissues b. bind and carry CO2 back to the lungs c. bind and carry O2 back to the lungs d. transport O2 from the heart to the lungs e. transport O2 from the lungs to the heart ANSWER: b 58. The bound prosthetic group that allows both hemoglobin and myoglobin to bind oxygen is called___. a. myosin .. Powered by Cognero.

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Chapter 5 b. heme c. actin d. histidine ANSWER: b 59. A mutation occurs in the distal histidine of heme. Which of the following would be the most deleterious effect on hemoglobin and myoglobin due to this mutation? a. the pickup of dangerous ligands like carbon monoxide in place of oxygen b. the reduction of the heme iron to the ferric ion c. smaller ligands will be given access to the heme iron d. movement of the iron ion into the plane of the porphyrin ANSWER: a 60. Functional magnetic resonance imaging (fMRI), a powerful method for examining brain function, reveals active parts of the brain by: a. highlighting regions of increased blood flow richer in oxyhemoglobin b. highlighting regions of decreased blood flow richer in oxyhemoglobin c. highlighting regions of increased blood flow richer in deoxyhemoglobin d. highlighting regions of decreased blood flow richer in deoxyhemoglobin ANSWER: a 61. Allosteric proteins are characterized by their more complicated properties compared to other proteins, usually arising from their: a. irregular splice sites b. requirement for chaperone assistance when folding c. multisubunit quaternary structures d. hydrophobic alpha helices ANSWER: c 62. The sigmoidal oxygen-binding curve of hemoglobin in red blood cells demonstrates a binding behavior referred to as: a. complimentary b. cooperative c. symbiotic d. direct ANSWER: b 63. What is the physiological significance of the cooperative binding of oxygen by hemoglobin? a. cooperative binding leads to efficient oxygen transport b. red blood cells export oxygen and import carbon dioxide at greater rates c. hemoglobin reaches equilibrium with myoglobin more efficiently .. Powered by Cognero.

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Chapter 5 d. cooperative binding limits the pickup of dangerous molecules besides oxygen such as carbon monoxide ANSWER: a 64. Why is hemoglobin a more efficient oxygen transporter than myoglobin? a. Myoglobin does not bind oxygen tight enough to be an efficient oxygen transporter. b. Hemoglobin binds oxygen more tightly than myoglobin, making it a better carrier of oxygen. c. Myoglobin binds oxygen too tightly to be an efficient oxygen transporter. d. Myoglobin has a higher affinity for dangerous molecules such as carbon monoxide compared to hemoglobin. ANSWER: c 65. The deoxygenated state of hemoglobin is referred to as: a. the A state b. the R state c. the T state d. the low state ANSWER: c 66. The oxygenated state of hemoglobin is referred to as: a. the A state b. the R state c. the T state d. the high state ANSWER: b 67. Why does fetal hemoglobin bind oxygen more tightly than adult hemoglobin? a. Fetal hemoglobin has a single mutation in the β subunit; therefore, it is called the γ chain. b. The substitution of a serine residue for histidine 143 in the γ chain of the 2,3-BPG-binding site causes reduced affinity of 2,3-bisphosphogycerate for fetal hemoglobin. c. The substitution of a histidine residue for serine 143 in the γ chain of the 2,3-BPG-binding site causes increased affinity of 2,3-bisphosphogycerate for fetal hemoglobin. d. One of the substitutions in the fetal α chain is alanine for proline, which facilitates a van der Waals interaction and depresses the formation of the R state. e. One of the changes in the fetal α chain is a substitution of proline for alanine, which disrupts a van der Waals contact and facilitates the formation of the R state. ANSWER: b

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Chapter 6 1. Sedimentation of a particle isn't affected by: a. mass. b. shape. c. the density of the solution. d. charge. e. size. ANSWER: d 2. Genome rather than proteome: a. is a fixed characteristic of the cell. b. provides a list of gene products that are present in an organism. c. varies with the cell type and developmental stage. d. is influenced by the presence of hormones or inhibitors, or other environmental conditions. e. is the level of functional information, which encompasses the types, functions, and interactions of proteins that yield a functional unit. ANSWER: a 3. The technique that obtains the isolation of the protein of interest from the thousands of other proteins in the cell is called: a. salting out. b. purification. c. precipitation. d. dialysis. e. exclusion. ANSWER: b 4. What technique significantly increases the resolving power of protein purification? a. salting out b. gel electrophoresis c. ion-exchange chromatography d. high-performance liquid chromatography e. affinity chromatography ANSWER: d 5. What properties rise upon protein purification? a. enzyme activity b. amount of total protein c. specific activity d. bands on the gel electrophoresis e. total activity ANSWER: c .. Powered by Cognero.

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Chapter 6 6. Choose the CORRECT definition of the given terms. a. The total amount of protein is the measure of enzyme activity. b. Enzyme activity is the ratio of total activity to the amount of protein in the enzyme assay. c. An assay is not always based on some unique biochemical properties of the protein of interest. d. The purification level is obtained by dividing specific activity of the initial extract by the total volume of the fraction. e. The total activity is obtained by measuring specific activity of the fraction used in the assay and multiplying it by the fraction's total volume. ANSWER: b 7. A mixture of all components of the cell that do NOT contain intact cells is called: a. a pellet. b. supernatant. c. dialysate. d. centrifugate. e. homogenate. ANSWER: e 8. If you want to get several fractions of decreasing density, each still containing hundreds of different proteins, in a step-by-step fashion what technique would you use? a. gradient centrifugation b. differential centrifugation c. western blotting d. gel electrophoresis e. one of the chromatography methods ANSWER: b 9. Select all that apply. An intermediate product of protein purification is: a. crude supernatant extract. b. crude pellet extract. c. homogenate. d. supernatant extract. e. dialysate. ANSWER: b, d 10. What technique is used to remove salt from a solution? a. gel electrophoresis b. salting out c. dialysis d. centrifugation .. Powered by Cognero.

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Chapter 6 e. fractioning ANSWER: c 11. Proteins with different sedimentation coefficients can be separated by: a. gradient centrifugation. b. differential centrifugation. c. two-dimensional electrophoresis. d. affinity chromatography. e. ELISA. ANSWER: b 12. The protein in a solution with a high concentration of (NH4)2SO4 doesn't bind to a column. What technique should you use to solve this problem? a. SDS-PAGE b. ELISA c. centrifugation d. dialysis e. HPLC ANSWER: d 13. In which order will proteins A (55 kDa), B (60 Da), and C (50,000 Da) emerge from the column upon molecular exclusion chromatography? a. A → B → C b. A → C → B c. B → A → C d. B → C → A e. C → A → B ANSWER: b 14. How can a protein that is positively charged at pH 7 be eluted in ion-exchange chromatography? a. displacement of the protein by another ligand b. increasing volume of the buffer c. increasing pH of the buffer d. increasing concentration of salt in the buffer e. decreasing concentration of salt in the buffer ANSWER: d 15. What technique is used to separate proteins by their net charge? a. molecular exclusion chromatography b. ion-exchange chromatography c. two-dimensional electrophoresis .. Powered by Cognero.

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Chapter 6 d. ELISA e. immunoprecipitation ANSWER: b 16. What amino acids should be prevailing in a protein at pH 7 for binding of that protein to beads containing negatively charged carboxylate groups? a. serine b. phenylalanine c. histidine d. glycine e. cysteine ANSWER: c 17. Molecular exclusion chromatography is a technique of protein separation according to: a. size. b. isoelectric point. c. binding affinity. d. charge. e. definition of individual proteins. ANSWER: a 18. What is affinity chromatography based on? a. separation of proteins by size b. moving a molecule with a net charge in an electric field c. affinity of proteins for specific chemical groups or specific molecules d. separation of proteins by their net charge e. high affinity of the antibody for the proteins ANSWER: c 19. What is ion-exchange chromatography based on? a. separation of proteins by size b. moving a molecule with a net charge in an electric field c. affinity of proteins for specific chemical groups or specific molecules d. separation of proteins by their net charge e. high affinity of the antibody for the proteins ANSWER: d 20. The largest number of individual proteins from a mixture is separated by: a. affinity chromatography. b. molecular exclusion chromatography. c. ion-exchange chromatography. .. Powered by Cognero.

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Chapter 6 d. gel filtration. e. high-performance liquid chromatography. ANSWER: e 21. What technique is used to separate proteins by their charge and then by their size? a. molecular exclusion chromatography b. ion-exchange chromatography c. two-dimensional electrophoresis d. ELISA e. immunoprecipitation ANSWER: c 22. Choose the FALSE statement about protein electrophoresis. a. The gel serves as a molecular sieve that enhances separation. b. The distance and speed that a protein moves depend on its shape. c. Small proteins move rapidly through the gel. d. The proteins in the gel can be visualized by staining them with silver. e. It is performed in a thin, horizontal slab of polyacrylamide. ANSWER: e 23. Separation of proteins only by their molecular weight can be achieved by putting them in an environment where they are surrounded by negative charges. What provides these negative charges? a. the flow from the cathode to the anode b. electricity c. adjusted pH d. SDS e. β-mercaptoethanol ANSWER: d 24. Protein purification can be monitored by measuring: a. specific activity and performing SDS-PAGE. b. total activity and performing SDS-PAGE. c. total protein and performing HPLC. d. specific activity and performing two-dimensional electrophoresis. e. total activity and performing HPLC. ANSWER: a 25. For enzymes, the assay is a measure of: a. total protein. b. total enzyme. c. enzyme activity. .. Powered by Cognero.

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Chapter 6 d. specific activity. e. total activity. ANSWER: c 26. Differential centrifugation rather than gradient centrifugation: a. is referred to as ultracentrifugation. b. doesn't depend on the shape of the particle. c. requires the formation of a density gradient in a centrifuge tube. d. can use radioactivity marks to determine the receptor from the fraction. e. applies the harvesting of the separated bands of protein, collecting them drop by drop. ANSWER: b 27. Choose the CORRECT statement. a. The binding between Ig and antigen is a step in the immune response. b. An epitope is composed of heavy and light chains. c. Antigens are synthesized by an animal in response to the presence of foreign substances. d. The Fc domain of the Ig is formed by two heavy chains and two flexible linkers. e. Nucleic acids can't be effective antigens. ANSWER: a 28. What reagent helps to visualize amino acids in amino acid composition analysis? a. phenyl isothiocyanate b. clostripain c. β-mercaptoethanol d. hydroxylamine e. fluorescamine ANSWER: e 29. Polyclonal antibodies rather than monoclonal antibodies: a. can be obtained by fusing of antibody-producing cells and myeloma cells. b. are generated from a large number of cells of a single kind. c. are used in purification of receptors or other proteins by immunoprecipitation. d. such as Trastuzumab are used to treat some forms of breast cancer. e. have an advantage for the detection of a protein with low abundance. ANSWER: e 30. Select all that apply. Enzyme-linked immunosorbent assay: a. uses an enzyme, noncovalently linked to a specific antibody, that reacts with a colorless substrate to produce a colored product. b. is used in tests for HIV infection. c. comes in several forms, including indirect and sandwich. .. Powered by Cognero.

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Chapter 6 d. can detect less than 10–9 g of a protein. e. can be performed only with polyclonal antibodies. ANSWER: a, c, e 31. Which statements describe sandwich ELISA? Select all that apply. a. The antibody to a particular antigen is adsorbed to the bottom of a well. b. The production of color indicates the amount of an antibody to a specific antigen. c. This technique is used in tests for HIV infection. d. The detection antibody with an enzyme linked to it binds to a specific antibody. e. It is a quantitative method that permits the measurement of small quantities of an antigen. ANSWER: a, e 32. What technique allows the detection of very small quantities of a particular protein in a cell or in body fluid and makes it possible to find a protein in a complex mixture, which is useful in monitoring protein purification and in the cloning of genes? a. sandwich ELISA b. indirect ELISA c. gradient centrifugation d. immunoblotting e. MALDI-TOF ANSWER: d 33. What technique helps to determine amino acid sequence by removing one amino acid at a time from the amino end of a peptide? a. Edman degradation b. specific cleavage c. peptides overlapping d. electrospray ionization e. MALDI-TOF ANSWER: a 34. What reagent cleaves the carboxyl side of lysine and arginine residues in proteins? a. hydroxylamine b. staphylococcal protease c. clostripain d. trypsin e. carboxypeptidase A ANSWER: d 35. Which statement about mass spectrometry is FALSE? a. In electrospray ionization, the protein or peptide under study is co-precipitated with an organic .. Powered by Cognero.

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Chapter 6 compound that absorbs laser light of an appropriate wavelength. b. In the time of flight analysis, tiny amounts of biomolecules as small as a few picomoles (pmol) or femtomoles (fmol) can be analyzed. c. In tandem mass spectrometry, peptides can be fragmented by bombardment with argon to generate a family of product ions in which one or more amino acids are removed from one end of the initial peptide analyte. d. MALDI-TOF is one of the most accurate means of determining protein mass. e. In MALDI-TOF, peptide masses are matched in a database against proteins that have been "electronically cleaved" by a computer simulating the same fragmentation technique used for the experimental sample. ANSWER: a 36. What is the most common protease used in sample preparation for a MALDI-TOF assay? a. pepsin b. papain c. trypsin d. thrombin e. carboxypeptidase A ANSWER: c 37. When enzymes are purified, the assay is often based on: a. light absorbance. b. catalytic activity. c. pH. d. temperature changes. e. mRNA levels. ANSWER: b 38. Two-dimensional electrophoresis is a combination of what two techniques? a. isoelectric focusing and affinity chromatography b. ion-exchange chromatography and SDS-PAGE c. affinity chromatography and SDS-PAGE d. isoelectric focusing and SDS-PAGE e. isoelectric focusing and ion-exchange chromatography ANSWER: d 39. What technique can be used to determine the size of a target protein? a. Edman degradation b. affinity chromatography c. western blot d. ELISA .. Powered by Cognero.

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