Chapter 5 Test - AP Biology

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Chapter 5 Test - AP Biology - Quiz

Questions and Answers
  • 1. 

    Which of the following is not one of the four major groups of macromolecules found in living organisms?

    • A.

      Glucose

    • B.

      Carbohydrates

    • C.

      Lipids

    • D.

      Proteins

    • E.

      Nucleic acids

    Correct Answer
    A. Glucose
    Explanation
    Glucose is not one of the four major groups of macromolecules found in living organisms. The four major groups of macromolecules are carbohydrates, lipids, proteins, and nucleic acids. Glucose is a type of carbohydrate and therefore belongs to one of the major groups.

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  • 2. 

    Polymers of polysaccharides, fats, and proteins are all synthesized from monomers by which process?

    • A.

      Connecting monosaccharides together (condensation reactions)

    • B.

      The addition of water to each monomer (hydrolysis)

    • C.

      The removal of water (dehydration reactions)

    • D.

      Ionic bonding of the monomers

    • E.

      The formation of disulfide bridges between monomers

    Correct Answer
    C. The removal of water (dehydration reactions)
    Explanation
    Polymers of polysaccharides, fats, and proteins are synthesized from monomers through the process of dehydration reactions. In this process, water molecules are removed, allowing the monomers to join together and form larger molecules. This occurs through the formation of covalent bonds between the monomers. Dehydration reactions are essential for the formation of complex macromolecules such as carbohydrates, lipids, and proteins, as they enable the monomers to link together and create the long chains characteristic of these polymers.

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  • 3. 

    Which of the following best summarizes the relationship between dehydration reactions and hydrolysis?

    • A.

      Dehydration reactions assemble polymers, and hydrolysis breaks down polymers.

    • B.

      Hydrolysis only occurs in the urinary system, and dehydration reactions only occur in the digestive tract.

    • C.

      Dehydration reactions can occur only after hydrolysis.

    • D.

      Hydrolysis creates monomers, and dehydration reactions break down polymers.

    • E.

      A and C are correct.

    Correct Answer
    A. Dehydration reactions assemble polymers, and hydrolysis breaks down polymers.
    Explanation
    Dehydration reactions involve the removal of water molecules to form bonds between monomers, resulting in the assembly of polymers. On the other hand, hydrolysis is a process that breaks down polymers into monomers by adding water molecules. Therefore, the correct answer is that dehydration reactions assemble polymers, and hydrolysis breaks down polymers.

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  • 4. 

    A molecule with the chemical formula C16H32O16 is probably a

    • A.

      Carbohydrate.

    • B.

      Lipid.

    • C.

      Protein.

    • D.

      Nucleic acid.

    • E.

      Hydrocarbon.

    Correct Answer
    A. Carbohydrate.
    Explanation
    A molecule with the chemical formula C16H32O16 is likely a carbohydrate because the ratio of carbon to hydrogen to oxygen atoms is consistent with the general formula for carbohydrates. Carbohydrates are organic compounds composed of carbon, hydrogen, and oxygen in a ratio of 1:2:1. The given formula matches this ratio, suggesting that the molecule is a carbohydrate.

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  • 5. 

    Consider a polysaccharide consisting of 576 glucose molecules. The total hydrolysis of the polysaccharide would result in the production of

    • A.

      575 glucose molecules.

    • B.

      575 water molecules.

    • C.

      576 glucose molecules.

    • D.

      A and B only

    • E.

      B and C only

    Correct Answer
    C. 576 glucose molecules.
    Explanation
    When a polysaccharide undergoes total hydrolysis, it is broken down into its individual glucose molecules. Since the polysaccharide consists of 576 glucose molecules, the total hydrolysis would result in the production of the same number of glucose molecules, which is 576. Therefore, the correct answer is 576 glucose molecules.

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  • 6. 

    Lactose, a sugar in milk, is composed of one glucose molecule joined by a glycosidic linkage to one galactose molecule. How is lactose classified?

    • A.

      As a pentose

    • B.

      As a hexose

    • C.

      As a monosaccharide

    • D.

      As a disaccharide

    • E.

      As a polysaccharide

    Correct Answer
    D. As a disaccharide
    Explanation
    Lactose is classified as a disaccharide because it is composed of two monosaccharide units, glucose and galactose, joined together by a glycosidic linkage. A pentose refers to a monosaccharide with five carbon atoms, while a hexose refers to a monosaccharide with six carbon atoms. Lactose is not a monosaccharide because it is composed of two sugar units, and it is not a polysaccharide because it is not made up of many sugar units. Therefore, the correct classification for lactose is as a disaccharide.

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  • 7. 

    Which of the following are polysaccharides?

    • A.

      Glycogen

    • B.

      Starch

    • C.

      Chitin

    • D.

      A and B only

    • E.

      A, B, and C

    Correct Answer
    E. A, B, and C
    Explanation
    Glycogen, starch, and chitin are all examples of polysaccharides. Polysaccharides are complex carbohydrates made up of multiple sugar molecules bonded together. Glycogen is the storage form of glucose in animals, starch is the storage form of glucose in plants, and chitin is a structural polysaccharide found in the exoskeleton of arthropods and cell walls of fungi. Therefore, the correct answer is A, B, and C.

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  • 8. 

    Which of the following is true of both starch and cellulose?

    • A.

      They are both polymers of glucose.

    • B.

      They are geometric isomers of each other.

    • C.

      They can both be digested by humans.

    • D.

      They are both used for energy storage in plants.

    • E.

      They are both structural components of the plant cell wall.

    Correct Answer
    A. They are both polymers of glucose.
    Explanation
    Starch and cellulose are both polymers of glucose. This means that they are composed of repeating units of glucose molecules linked together. Starch is a storage polysaccharide found in plants, while cellulose is a structural polysaccharide that forms the cell wall of plants. Both starch and cellulose are made up of glucose monomers, but the arrangement of the glucose molecules differs between the two, resulting in different properties and functions.

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  • 9. 

    Which of the following is true of cellulose?

    • A.

      It is a polymer composed of sucrose monomers.

    • B.

      It is a storage polysaccharide for energy in plant cells.

    • C.

      It is a storage polysaccharide for energy in animal cells.

    • D.

      It is a major structural component of plant cell walls.

    • E.

      It is a major structural component of animal cell plasma membranes.

    Correct Answer
    D. It is a major structural component of plant cell walls.
    Explanation
    Cellulose is a major structural component of plant cell walls. Cellulose is a polysaccharide made up of glucose monomers, not sucrose monomers. It is not a storage polysaccharide for energy in either plant or animal cells. While it is true that lipids are a major component of animal cell plasma membranes, cellulose is not.

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  • 10. 

    Humans can digest starch but not cellulose because

    • A.

      The monomer of starch is glucose, while the monomer of cellulose is galactose.

    • B.

      Humans have enzymes that can hydrolyze the beta (β) glycosidic linkages of starch but not the alpha (α) glycosidic linkages of cellulose.

    • C.

      Humans have enzymes that can hydrolyze the alpha (α) glycosidic linkages of starch but not the beta (β) glycosidic linkages of cellulose.

    • D.

      Humans harbor starch-digesting bacteria in the digestive tract.

    • E.

      The monomer of starch is glucose, while the monomer of cellulose is maltose.

    Correct Answer
    C. Humans have enzymes that can hydrolyze the alpha (α) glycosidic linkages of starch but not the beta (β) glycosidic linkages of cellulose.
    Explanation
    The correct answer is that humans have enzymes that can hydrolyze the alpha (α) glycosidic linkages of starch but not the beta (β) glycosidic linkages of cellulose. This is because humans produce an enzyme called amylase, which can break down the alpha glycosidic linkages in starch, converting it into glucose. However, humans do not produce an enzyme that can break down the beta glycosidic linkages in cellulose, making it indigestible for us.

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  • 11. 

    Humans can digest starch but not cellulose because

    • A.

      ) the monomer of starch is glucose, while the monomer of cellulose is galactose.

    • B.

      Humans have enzymes that can hydrolyze the beta (β) glycosidic linkages of starch but not the alpha (α) glycosidic linkages of cellulose.

    • C.

      Humans have enzymes that can hydrolyze the alpha (α) glycosidic linkages of starch but not the beta (β) glycosidic linkages of cellulose.

    • D.

      Humans harbor starch-digesting bacteria in the digestive tract.

    • E.

      The monomer of starch is glucose, while the monomer of cellulose is maltose.

    Correct Answer
    C. Humans have enzymes that can hydrolyze the alpha (α) glycosidic linkages of starch but not the beta (β) glycosidic linkages of cellulose.
    Explanation
    The correct answer is that humans have enzymes that can hydrolyze the alpha (α) glycosidic linkages of starch but not the beta (β) glycosidic linkages of cellulose. This is because humans produce an enzyme called amylase, which can break down the alpha (α) glycosidic linkages in starch molecules, converting them into glucose for digestion. However, humans do not produce the enzyme cellulase, which is necessary to break down the beta (β) glycosidic linkages in cellulose molecules. Therefore, humans are unable to digest cellulose.

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  • 12. 

    A molecule with the formula C18H36O2 is probably a

    • A.

      Carbohydrate.

    • B.

      Lipid.

    • C.

      Protein.

    • D.

      Nucleic acid.

    • E.

      Hydrocarbon.

    Correct Answer
    B. Lipid.
    Explanation
    The molecule with the formula C18H36O2 is most likely a lipid because lipids are organic compounds that are composed of carbon, hydrogen, and oxygen atoms. Carbohydrates, proteins, and nucleic acids also contain carbon, hydrogen, and oxygen, but their formulas typically have different ratios of these elements. Hydrocarbons, on the other hand, consist only of carbon and hydrogen atoms, so they would not contain oxygen. Therefore, lipid is the most appropriate choice for this formula.

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  • 13. 

    Which of the following is (are) true for the class of large biological molecules known as lipids?

    • A.

      They are insoluble in water.

    • B.

      They are an important constituent of cell membranes.

    • C.

      They contain twice as much energy as an equivalent weight of polysaccharide.

    • D.

      Only A and B are correct.

    • E.

      A, B, and C are correct.

    Correct Answer
    E. A, B, and C are correct.
    Explanation
    Lipids are large biological molecules that have certain characteristics. Firstly, they are insoluble in water, which means they do not dissolve in water. Secondly, they are an important constituent of cell membranes, playing a crucial role in maintaining the structure and function of cells. Lastly, lipids contain twice as much energy as an equivalent weight of polysaccharide, making them an efficient source of energy storage. Therefore, the correct answer is A, B, and C are correct.

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  • 14. 

    Triacylglycerol is a

    • A.

      Protein with tertiary structure.

    • B.

      Lipid made with three fatty acids and glycerol.

    • C.

      Lipid that makes up much of the plasma membrane.

    • D.

      Molecule formed from three alcohols by dehydration reactions.

    • E.

      Carbohydrate with three sugars joined together by glycosidic linkages.

    Correct Answer
    B. Lipid made with three fatty acids and glycerol.
    Explanation
    Triacylglycerol is a lipid made with three fatty acids and glycerol. This is because triacylglycerol, also known as triglyceride, is composed of a glycerol molecule bonded to three fatty acid molecules through ester linkages. This structure allows for the storage of energy in the form of fat, as well as insulation and protection of organs.

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  • 15. 

    Saturated fatty acids

    • A.

      Are the predominant fatty acid in corn oil.

    • B.

      Have double bonds between carbon atoms of the fatty acids.

    • C.

      Have a higher ratio of hydrogen to carbon than do unsaturated fatty acids.

    • D.

      Are usually liquid at room temperature.

    • E.

      Are usually produced by plants.

    Correct Answer
    C. Have a higher ratio of hydrogen to carbon than do unsaturated fatty acids.
    Explanation
    Saturated fatty acids have a higher ratio of hydrogen to carbon than unsaturated fatty acids because they do not have any double bonds between carbon atoms. This means that each carbon atom in a saturated fatty acid is bonded to the maximum number of hydrogen atoms possible. In contrast, unsaturated fatty acids have one or more double bonds between carbon atoms, which reduces the number of hydrogen atoms that can be bonded to each carbon atom. This difference in hydrogen to carbon ratio is what distinguishes saturated fatty acids from unsaturated fatty acids.

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  • 16. 

    The hydrogenation of vegetable oil would result in which of the following?

    • A.

      A decrease in the number of carbon-carbon double bonds in the oil (fat) molecules

    • B.

      An increase in the number of hydrogen atoms in the oil (fat) molecule

    • C.

      The oil (fat) being a solid at room temperature

    • D.

      A and C only

    • E.

      A, B, and C

    Correct Answer
    E. A, B, and C
    Explanation
    The hydrogenation of vegetable oil involves adding hydrogen atoms to the oil molecules, which results in a decrease in the number of carbon-carbon double bonds in the molecules. This process also increases the number of hydrogen atoms in the molecules. Additionally, hydrogenation can cause the oil to solidify at room temperature, turning it into a solid fat. Therefore, all options A, B, and C are correct.

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  • 17. 

    A polypeptide can best be described as a

    • A.

      Monomer of a protein polymer.

    • B.

      Polymer containing 20 amino acid molecules.

    • C.

      Polymer containing 19 peptide bonds.

    • D.

      Polymer containing 20 peptide bonds.

    • E.

      Polymer of amino acids.

    Correct Answer
    E. Polymer of amino acids.
    Explanation
    A polypeptide is a chain of amino acids linked together by peptide bonds. It is a polymer because it is made up of repeating units (amino acids) bonded together. Therefore, the correct answer is "polymer of amino acids."

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  • 18. 

    The 20 different amino acids found in polypeptides exhibit different chemical and physical properties because of different

    • A.

      Carboxyl groups attached to an alpha (α) carbon

    • B.

      Amino groups attached to an alpha (α) carbon

    • C.

      Side chains (R groups).

    • D.

      Alpha (α) carbons.

    • E.

      Asymmetric carbons.

    Correct Answer
    C. Side chains (R groups).
    Explanation
    The 20 different amino acids found in polypeptides exhibit different chemical and physical properties because of different side chains (R groups). The side chains, also known as R groups, vary in size, shape, charge, and chemical composition. These variations in the side chains determine the unique properties of each amino acid, such as its hydrophobicity, polarity, and ability to form hydrogen bonds or participate in chemical reactions. Therefore, the side chains play a crucial role in determining the overall structure and function of proteins.

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  • 19. 

    The bonding of two amino acid molecules to form a larger molecule requires which of the following?

    • A.

      Removal of a water molecule

    • B.

      Addition of a water molecule

    • C.

      Formation of an ionic bond

    • D.

      Formation of a hydrogen bond

    • E.

      Both A and C

    Correct Answer
    A. Removal of a water molecule
    Explanation
    When two amino acid molecules bond together to form a larger molecule, a process called dehydration synthesis or condensation reaction occurs. In this reaction, a water molecule is removed from the amino acids, resulting in the formation of a peptide bond between them. This process requires the removal of a water molecule, making the answer "removal of a water molecule" correct.

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  • 20. 

    Polysaccharides, lipids, and proteins are similar in that they

    • A.

      Are synthesized from monomers by the process of hydrolysis.

    • B.

      Are synthesized from monomers by dehydration reactions.

    • C.

      Are synthesized as a result of peptide bond formation between monomers.

    • D.

      Are decomposed into their subunits by dehydration reactions.

    • E.

      All contain nitrogen in their monomer building blocks.

    Correct Answer
    B. Are synthesized from monomers by dehydration reactions.
    Explanation
    Polysaccharides, lipids, and proteins are similar in that they are synthesized from monomers by dehydration reactions. Dehydration reactions involve the removal of a water molecule to form a covalent bond between monomers, resulting in the synthesis of larger molecules. This process is commonly observed in the formation of macromolecules such as polysaccharides (formed from monosaccharides), lipids (formed from fatty acids and glycerol), and proteins (formed from amino acids). Therefore, the correct answer is that these biomolecules are synthesized from monomers by dehydration reactions.

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  • 21. 

    Dehydration reactions are used in forming which of the following compounds?

    • A.

      Triacylglycerides

    • B.

      Polysaccharides

    • C.

      Proteins

    • D.

      A and C only

    • E.

      A, B, and C

    Correct Answer
    E. A, B, and C
    Explanation
    Dehydration reactions are used in forming triacylglycerides, polysaccharides, and proteins. In these reactions, water molecules are removed to form bonds between the monomers, resulting in the formation of larger compounds. Triacylglycerides are formed by removing water molecules between fatty acids and glycerol, polysaccharides are formed by removing water molecules between sugar monomers, and proteins are formed by removing water molecules between amino acids. Therefore, all three compounds can be formed through dehydration reactions.

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  • 22. 

    Upon chemical analysis, a particular protein was found to contain 556 amino acids. How many peptide bonds are present in this protein?

    • A.

      139

    • B.

      554

    • C.

      555

    • D.

      556

    • E.

      558

    Correct Answer
    C. 555
    Explanation
    The number of peptide bonds in a protein is equal to the number of amino acids minus one. Since the protein in question contains 556 amino acids, there would be 555 peptide bonds present.

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  • 23. 

    Which bonds are created during the formation of the primary structure of a protein?

    • A.

      Peptide bonds

    • B.

      Hydrogen bonds

    • C.

      Disulfide bonds

    • D.

      Phosphodiester bonds

    • E.

      A, B, and C

    Correct Answer
    A. Peptide bonds
    Explanation
    Peptide bonds are created during the formation of the primary structure of a protein. These bonds form between the amino acids in a protein chain, linking them together to create a linear sequence. Hydrogen bonds, disulfide bonds, and phosphodiester bonds are not involved in the formation of the primary structure of a protein.

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  • 24. 

    What maintains the secondary structure of a protein?

    • A.

      Peptide bonds

    • B.

      Hydrogen bonds

    • C.

      Disulfide bonds

    • D.

      Ionic bonds

    • E.

      Phosphodiester bonds

    Correct Answer
    B. Hydrogen bonds
    Explanation
    Hydrogen bonds maintain the secondary structure of a protein. Secondary structure refers to the local folding patterns within a protein, including alpha helices and beta sheets. These structures are stabilized by hydrogen bonds formed between the backbone atoms of the protein. Hydrogen bonds occur when a hydrogen atom is bonded to an electronegative atom, such as oxygen or nitrogen, and is attracted to another electronegative atom nearby. These bonds provide stability and contribute to the overall shape and function of the protein.

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  • 25. 

    Which type of interaction stabilizes the alpha (α) helix and the beta (β) pleated sheet structures of proteins?

    • A.

      Hydrophobic interactions

    • B.

      Nonpolar covalent bonds

    • C.

      Ionic bonds

    • D.

      Hydrogen bonds

    • E.

      Peptide bonds

    Correct Answer
    D. Hydrogen bonds
    Explanation
    Hydrogen bonds stabilize the alpha helix and beta pleated sheet structures of proteins. These bonds occur between the hydrogen atom of one amino acid and the electronegative atom (usually oxygen or nitrogen) of another amino acid in the protein chain. The hydrogen bond forms a weak attraction between these atoms, helping to maintain the secondary structure of the protein. The alpha helix is stabilized by hydrogen bonds between the carbonyl oxygen of one amino acid and the amide hydrogen of another amino acid, while the beta pleated sheet is stabilized by hydrogen bonds between adjacent strands.

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  • 26. 

    The α helix and the β pleated sheet are both common polypeptide forms found in which level of protein structure?

    • A.

      Primary

    • B.

      Secondary

    • C.

      Tertiary

    • D.

      Quaternary

    • E.

      All of the above

    Correct Answer
    B. Secondary
    Explanation
    The α helix and the β pleated sheet are both common polypeptide forms found in the secondary level of protein structure. The secondary structure refers to the local folding patterns of the polypeptide chain, specifically the hydrogen bonding between the amino acids. The α helix is a coiled structure held together by hydrogen bonds, while the β pleated sheet consists of strands that are connected by hydrogen bonds. The primary structure refers to the linear sequence of amino acids, while the tertiary structure refers to the overall 3D folding of the polypeptide chain. The quaternary structure refers to the arrangement of multiple polypeptide chains in a protein complex.

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  • 27. 

    The tertiary structure of a protein is the

    • A.

      Bonding together of several polypeptide chains by weak bonds.

    • B.

      Order in which amino acids are joined in a polypeptide chain.

    • C.

      Unique three-dimensional shape of the fully folded polypeptide.

    • D.

      Organization of a polypeptide chain into an α helix or β pleated sheet.

    • E.

      Overall protein structure resulting from the aggregation of two or more polypeptide subunits.

    Correct Answer
    C. Unique three-dimensional shape of the fully folded polypeptide.
    Explanation
    The tertiary structure of a protein refers to the unique three-dimensional shape that a fully folded polypeptide adopts. This structure is determined by the interactions between the amino acid residues in the polypeptide chain, such as hydrogen bonding, disulfide bridges, hydrophobic interactions, and electrostatic interactions. These interactions stabilize the protein's three-dimensional shape and are crucial for its proper function. The bonding together of several polypeptide chains by weak bonds refers to the quaternary structure of a protein, which is not the same as the tertiary structure.

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  • 28. 

    A strong covalent bond between amino acids that functions in maintaining a polypeptide's specific three-dimensional shape is a (an)

    • A.

      Ionic bond.

    • B.

      Hydrophobic interaction.

    • C.

      Van der Waals interaction.

    • D.

      Disulfide bond.

    • E.

      Hydrogen bond.

    Correct Answer
    D. Disulfide bond.
    Explanation
    A disulfide bond is a strong covalent bond between two sulfur atoms in different amino acids, forming a bridge that helps maintain a polypeptide's specific three-dimensional shape. This bond is formed through the oxidation of sulfhydryl groups (-SH) on the amino acid side chains, creating a stable linkage. Ionic bonds involve the attraction between positively and negatively charged ions, hydrogen bonds involve the attraction between a hydrogen atom and an electronegative atom, van der Waals interactions involve weak attractions between molecules, and hydrophobic interactions involve the exclusion of nonpolar substances by water. None of these options describe the specific type of bond that maintains a polypeptide's shape.

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  • 29. 

    At which level of protein structure are interactions between the side chains (R groups) most important?

    • A.

      Primary

    • B.

      Secondary

    • C.

      Tertiary

    • D.

      Quaternary

    • E.

      All of the above

    Correct Answer
    C. Tertiary
    Explanation
    In the tertiary level of protein structure, interactions between the side chains (R groups) are most important. This is because the tertiary structure involves the folding and bending of the polypeptide chain, bringing different R groups into close proximity. These interactions, such as hydrogen bonding, disulfide bonds, hydrophobic interactions, and electrostatic attractions, play a crucial role in stabilizing the overall 3D structure of the protein. The specific arrangement and interactions of the R groups determine the protein's shape, stability, and function.

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  • 30. 

    The R group or side chain of the amino acid serine is –CH2-OH. The R group or side chain of the amino acid alanine is –CH3. Where would you expect to find these amino acids in a globular protein in aqueous solution?

    • A.

      Serine would be in the interior, and alanine would be on the exterior of the globular protein.

    • B.

      Alanine would be in the interior, and serine would be on the exterior of the globular protein.

    • C.

      Both serine and alanine would be in the interior of the globular protein.

    • D.

      Both serine and alanine would be on the exterior of the globular protein.

    • E.

      Both serine and alanine would be in the interior and on the exterior of the globular protein.

    Correct Answer
    B. Alanine would be in the interior, and serine would be on the exterior of the globular protein.
    Explanation
    In a globular protein in aqueous solution, the amino acid alanine, with its nonpolar side chain (-CH3), would be found in the interior of the protein. This is because the nonpolar side chain would prefer to be shielded from the surrounding water molecules. On the other hand, serine, with its polar side chain (-CH2-OH), would be found on the exterior of the protein. The polar side chain can form hydrogen bonds with water molecules, making it more favorable to be exposed to the aqueous environment.

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  • 31. 

    The globular protein transthyretin results from the aggregation of four polypeptide subunits.  Each of the subunits is a polypeptide chain with an α helix region.  Which structure(s) must the transthyretin protein have?

    • A.

      Primary structure

    • B.

      Primary and secondary structure

    • C.

      Primary, secondary, and tertiary structure

    • D.

      Primary, secondary, tertiary, and quaternary structure

    • E.

      Primary, secondary, tertiary, quaternary, and alpha structure

    Correct Answer
    D. Primary, secondary, tertiary, and quaternary structure
    Explanation
    The globular protein transthyretin is composed of four polypeptide subunits, each of which has an α helix region. The primary structure refers to the sequence of amino acids in a protein, which is necessary for the formation of the polypeptide chains. The secondary structure refers to the local folding patterns of the polypeptide chain, such as α helices. The tertiary structure refers to the overall three-dimensional shape of the protein, which is crucial for its function. The quaternary structure refers to the arrangement of multiple polypeptide subunits in a protein complex. Therefore, transthyretin must have primary, secondary, tertiary, and quaternary structures to form its functional globular shape with four subunits.

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  • 32. 

    What would be an unexpected consequence of changing one amino acid in a protein consisting of 325 amino acids?

    • A.

      The primary structure of the protein would be changed.

    • B.

      The tertiary structure of the protein might be changed.

    • C.

      The biological activity or function of the protein might be altered.

    • D.

      Only A and C are correct.

    • E.

      A, B, and C are correct.

    Correct Answer
    E. A, B, and C are correct.
    Explanation
    Changing one amino acid in a protein can have multiple consequences. Firstly, it can alter the primary structure of the protein, as the sequence of amino acids would be different. Additionally, this change can also affect the tertiary structure of the protein, as the altered amino acid may disrupt the folding pattern. Lastly, the biological activity or function of the protein may be altered, as even a single amino acid change can affect the protein's ability to interact with other molecules or carry out its specific function. Therefore, all options A, B, and C are correct.

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  • 33. 

    Altering which of the following levels of structural organization could change the function of a protein?

    • A.

      Primary

    • B.

      Secondary

    • C.

      Tertiary

    • D.

      Quaternary

    • E.

      All of the above

    Correct Answer
    E. All of the above
    Explanation
    Changing any of the levels of structural organization (primary, secondary, tertiary, quaternary) can alter the function of a protein. The primary structure refers to the sequence of amino acids in the protein, and any change in this sequence can result in a different protein with different functions. The secondary structure refers to the folding of the protein into alpha helices or beta sheets, and altering this folding pattern can affect the protein's function. The tertiary structure refers to the overall 3D shape of the protein, and changing this shape can impact its function. The quaternary structure refers to the arrangement of multiple protein subunits, and modifying this arrangement can also change the protein's function. Therefore, altering any of these levels of structural organization can influence the function of a protein.

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  • 34. 

    All of the following molecules are proteins except

    • A.

      Hemoglobin.

    • B.

      Transthyretin.

    • C.

      Collagen.

    • D.

      Lysozyme.

    • E.

      Glycogen.

    Correct Answer
    E. Glycogen.
    Explanation
    Hemoglobin, transthyretin, collagen, and lysozyme are all examples of proteins. Hemoglobin is a protein found in red blood cells that is responsible for carrying oxygen. Transthyretin is a protein that transports thyroid hormones and vitamin A in the blood. Collagen is a protein that provides structural support to tissues such as skin, tendons, and bones. Lysozyme is an enzyme that helps to break down bacterial cell walls. On the other hand, glycogen is a polysaccharide, not a protein. It is a storage form of glucose in animals and is found primarily in the liver and muscles.

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  • 35. 

    What is the term used for a change in a protein's three-dimensional shape or conformation due to disruption of hydrogen bonds, disulfide bridges, or ionic bonds?

    • A.

      Hydrolysis

    • B.

      Stabilization

    • C.

      Destabilization

    • D.

      Renaturation

    • E.

      Denaturation

    Correct Answer
    E. Denaturation
    Explanation
    Denaturation is the correct answer because it refers to the change in a protein's three-dimensional shape or conformation due to disruption of hydrogen bonds, disulfide bridges, or ionic bonds. This disruption can be caused by factors such as heat, pH changes, or exposure to certain chemicals. Denaturation often leads to loss of protein function and can be irreversible in some cases.

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  • 36. 

    What is the term used for a protein molecule that assists in the proper folding of other proteins?

    • A.

      Tertiary protein

    • B.

      Chaperonin

    • C.

      Enzyme protein

    • D.

      Renaturing protein

    • E.

      Denaturing protein

    Correct Answer
    B. Chaperonin
    Explanation
    A chaperonin is a type of protein molecule that aids in the correct folding of other proteins. It acts as a protective container, providing a favorable environment for the folding process to occur. Chaperonins help prevent misfolding and aggregation of proteins, ensuring their proper structure and function.

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  • 37. 

    Of the following functions, the major purpose of RNA is to

    • A.

      Transmit genetic information to offspring.

    • B.

      Function in the synthesis of protein.

    • C.

      Make a copy of itself, thus ensuring genetic continuity.

    • D.

      Act as a pattern or blueprint to form DNA.

    • E.

      Form the genes of higher organisms.

    Correct Answer
    B. Function in the synthesis of protein.
    Explanation
    RNA functions in the synthesis of proteins. RNA molecules are responsible for carrying the genetic information from DNA to the ribosomes, where proteins are synthesized. This process is known as protein synthesis or translation. RNA molecules act as templates for the assembly of amino acids into proteins, following the instructions encoded in the DNA. Therefore, the major purpose of RNA is to function in the synthesis of proteins.

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  • 38. 

    Which of the following best describes the flow of information in eukaryotic cells?

    • A.

      DNA → RNA → proteins

    • B.

      RNA → proteins → DNA

    • C.

      Proteins → DNA → RNA

    • D.

      RNA → DNA → proteins

    • E.

      DNA → proteins → RNA

    Correct Answer
    A. DNA → RNA → proteins
    Explanation
    In eukaryotic cells, the flow of information starts with DNA, which contains the genetic instructions. These instructions are then transcribed into RNA molecules through a process called transcription. The RNA molecules are then translated into proteins through a process called translation. Therefore, the correct answer is DNA → RNA → proteins.

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  • 39. 

    Which of the following descriptions best fits the class of molecules known as nucleotides?

    • A.

      A nitrogenous base and a phosphate group

    • B.

      A nitrogenous base and a pentose sugar

    • C.

      A nitrogenous base, a phosphate group, and a pentose sugar

    • D.

      A phosphate group and an adenine or uracil

    • E.

      A pentose sugar and a purine or pyrimidine

    Correct Answer
    C. A nitrogenous base, a phosphate group, and a pentose sugar
    Explanation
    Nucleotides are the building blocks of nucleic acids, such as DNA and RNA. They consist of three components: a nitrogenous base, a phosphate group, and a pentose sugar. The nitrogenous base can be adenine, guanine, cytosine, thymine (in DNA), or uracil (in RNA). The phosphate group provides a negative charge and links nucleotides together through phosphodiester bonds. The pentose sugar, either ribose or deoxyribose, forms the backbone of the nucleotide. Therefore, the description that best fits nucleotides is "a nitrogenous base, a phosphate group, and a pentose sugar."

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  • 40. 

    Which of the following are nitrogenous bases of the pyrimidine type?

    • A.

      Guanine and adenine

    • B.

      Cytosine and uracil

    • C.

      Thymine and guanine

    • D.

      Ribose and deoxyribose

    • E.

      Adenine and thymine

    Correct Answer
    B. Cytosine and uracil
    Explanation
    Cytosine and uracil are nitrogenous bases of the pyrimidine type. Pyrimidines are one of the two types of nitrogenous bases found in DNA and RNA. The other type is purines. Guanine and adenine are purines, not pyrimidines. Thymine is a pyrimidine, but it is not listed as an option with cytosine and uracil. Ribose and deoxyribose are sugars, not nitrogenous bases. Therefore, the correct answer is cytosine and uracil.

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  • 41. 

    Which of the following are nitrogenous bases of the purine type?

    • A.

      Cytosine and guanine

    • B.

      Guanine and adenine

    • C.

      Adenine and thymine

    • D.

      Thymine and uracil

    • E.

      Uracil and cytosine

    Correct Answer
    B. Guanine and adenine
    Explanation
    Guanine and adenine are nitrogenous bases of the purine type. Purines are one of the two types of nitrogenous bases found in DNA and RNA, the other being pyrimidines. Guanine and adenine have a double-ring structure, which is characteristic of purines. Cytosine, thymine, and uracil are pyrimidines, which have a single-ring structure. Therefore, guanine and adenine are the correct answer as they are the nitrogenous bases of the purine type.

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  • 42. 

    All of the following nitrogenous bases are found in DNA except

    • A.

      Thymine.

    • B.

      Adenine.

    • C.

      Uracil.

    • D.

      Guanine.

    • E.

      Cytosine.

    Correct Answer
    C. Uracil.
    Explanation
    Uracil is not found in DNA, but it is found in RNA. DNA contains the nitrogenous bases adenine, thymine, guanine, and cytosine. Thymine pairs with adenine, while guanine pairs with cytosine in DNA. Uracil replaces thymine in RNA and pairs with adenine. Therefore, uracil is the correct answer as it is not found in DNA.

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  • 43. 

    A double-stranded DNA molecule contains a total of 120 purines and 120 pyrimidines. This DNA molecule could be comprised of

    • A.

      120 adenine and 120 uracil molecules.

    • B.

      120 thymine and 120 adenine molecules.

    • C.

      120 cytosine and 120 thymine molecules.

    • D.

      240 adenine and 240 cytosine molecules.

    • E.

      240 guanine and 240 thymine molecules.

    Correct Answer
    B. 120 thymine and 120 adenine molecules.
    Explanation
    The correct answer is 120 thymine and 120 adenine molecules. This is because purines (adenine and guanine) always pair with pyrimidines (thymine and cytosine) in DNA. Adenine pairs with thymine through two hydrogen bonds, while guanine pairs with cytosine through three hydrogen bonds. Therefore, if there are 120 purines (adenine and guanine) in the DNA molecule, there must also be 120 pyrimidines (thymine and cytosine). Since the question specifies that there are a total of 120 purines and 120 pyrimidines, the only possible combination is 120 thymine and 120 adenine molecules.

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  • 44. 

    The difference between the sugar in DNA and the sugar in RNA is that the sugar in DNA

    • A.

      Is a six-carbon sugar and the sugar in RNA is a five-carbon sugar.

    • B.

      Can form a double-stranded molecule.

    • C.

      Has a six-membered ring of carbon and nitrogen atoms.

    • D.

      Can attach to a phosphate.

    • E.

      Contains one less oxygen atom.

    Correct Answer
    E. Contains one less oxygen atom.
    Explanation
    The correct answer is that the sugar in DNA contains one less oxygen atom. This is because the sugar in DNA, called deoxyribose, has a hydrogen atom in place of the oxygen atom found in the sugar in RNA, called ribose. This difference in the sugar structure is one of the key distinctions between DNA and RNA molecules.

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  • 45. 

    Which of the following statements best summarizes the structural differences between DNA and RNA?

    • A.

      RNA is a protein, whereas DNA is a nucleic acid.

    • B.

      DNA is a protein, whereas RNA is a nucleic acid.

    • C.

      DNA nucleotides contain a different sugar than RNA nucleotides.

    • D.

      RNA is a double helix, but DNA is single-stranded.

    • E.

      A and D are correct.

    Correct Answer
    C. DNA nucleotides contain a different sugar than RNA nucleotides.
    Explanation
    The correct answer is that DNA nucleotides contain a different sugar than RNA nucleotides. DNA and RNA are both nucleic acids, not proteins. While DNA is double-stranded and RNA is typically single-stranded, this is not a statement that summarizes the structural differences between DNA and RNA. The main structural difference between DNA and RNA lies in the sugar component of their nucleotides, with DNA containing deoxyribose sugar and RNA containing ribose sugar.

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  • 46. 

    In the double helix structure of nucleic acids, cytosine hydrogen bonds to

    • A.

      Deoxyribose.

    • B.

      Ribose.

    • C.

      Adenine.

    • D.

      Thymine.

    • E.

      Guanine.

    Correct Answer
    E. Guanine.
    Explanation
    In the double helix structure of nucleic acids, cytosine hydrogen bonds to guanine. This is a key feature of DNA and RNA molecules, where complementary base pairing occurs. Cytosine and guanine form three hydrogen bonds with each other, creating a stable and specific pairing. This base pairing is essential for the accurate replication and transmission of genetic information.

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  • 47. 

    The two strands making up the DNA double helix molecule

    • A.

      Cannot be separated.

    • B.

      Contain ribose and deoxyribose in opposite strands.

    • C.

      Are held together by hydrogen bonds.

    • D.

      Are attached through a phosphate to hold the strands together.

    • E.

      Contain uracil but not thymine.

    Correct Answer
    C. Are held together by hydrogen bonds.
    Explanation
    The DNA double helix molecule is composed of two strands that are held together by hydrogen bonds. These bonds form between complementary nitrogenous bases on each strand, specifically adenine (A) with thymine (T), and cytosine (C) with guanine (G). The hydrogen bonds provide stability and strength to the DNA molecule, allowing it to maintain its structure. Without these bonds, the strands would easily separate, making DNA replication and transcription impossible.

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  • 48. 

    If one strand of a DNA molecule has the sequence of bases 5'ATTGCA3', the other complementary strand would have the sequence

    • A.

      5'TAACGT3'.

    • B.

      3'TAACGT5'.

    • C.

      5'UAACGU3'.

    • D.

      3'UAACGU5'.

    • E.

      5'UGCAAU3'.

    Correct Answer
    B. 3'TAACGT5'.
    Explanation
    The complementary strand of DNA is formed by pairing the nucleotides in a specific way. Adenine (A) always pairs with thymine (T), and guanine (G) always pairs with cytosine (C). Therefore, the complementary strand for the given sequence 5'ATTGCA3' would be 3'TAACGT5'. Each base in the original sequence is paired with its complementary base in the complementary strand.

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  • 49. 

    The structural feature that allows DNA to replicate is the

    • A.

      Sugar-phosphate backbone.

    • B.

      Complementary pairing of the nitrogenous bases.

    • C.

      Disulfide bonding (bridging) of the two helixes.

    • D.

      Twisting of the molecule to form an α helix.

    • E.

      Three-component structure of the nucleotides.

    Correct Answer
    B. Complementary pairing of the nitrogenous bases.
    Explanation
    The correct answer is the complementary pairing of the nitrogenous bases. This is because DNA replication occurs through the process of complementary base pairing, where adenine (A) pairs with thymine (T) and cytosine (C) pairs with guanine (G). This allows for the accurate replication of the DNA molecule, as each strand serves as a template for the synthesis of a new complementary strand. The sugar-phosphate backbone provides stability to the DNA molecule, but it is the specific pairing of the nitrogenous bases that allows for replication.

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  • 50. 

    A new organism is discovered in the forests of Costa Rica. Scientists there determine that the polypeptide sequence of hemoglobin from the new organism has 72 amino acid differences from humans, 65 differences from a gibbon, 49 differences from a rat, and 5 differences from a frog.  These data suggest that the new organism

    • A.

      Is more closely related to humans than to frogs.

    • B.

      Is more closely related to frogs than to humans.

    • C.

      May have evolved from gibbons but not rats.

    • D.

      Is more closely related to humans than to rats.

    • E.

      May have evolved from rats but not from humans and gibbons.

    Correct Answer
    B. Is more closely related to frogs than to humans.
    Explanation
    The given information states that the new organism has the fewest amino acid differences with frogs compared to humans, gibbons, and rats. This suggests that the new organism is more closely related to frogs than to humans.

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  • Mar 22, 2023
    Quiz Edited by
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