CHAPTER 20
Proteins
Test Bank
TYPE I MULTIPLE-CHOICE QUESTIONS
In each of the following multiple-choice questions, place the letter of the correct response in the blank at the left. There is only one correct response for each question.
20.1 a Proteins are polymers in which
a) unbranched chains of amino acids are present.
b) branched chains of amino acids are present.
c) both unbranched and branched chains of amino acids are present.
d) alternating amino acid and glucose monomer units are present.
20.2 d [Algorithmic]Which of the following statements concerning proteins is incorrect?
a) Next to water, proteins are the most abundant molecules in the human body.
b) All proteins contain the elements C, H, O, and N.
c) More than one amino acid chain may be present in a protein.
d) Adjacent amino acids in a protein chain cannot be identical.
20.3 c [Algorithmic]Which of the following statements concerning standard amino acids is incorrect?
a) There are twenty of them.
b) They are all alpha-amino acids.
c) All of them possess at least one chiral center.
d) All of them except one are “left-handed” (L-isomer).
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Test Bank Chapter 20: Proteins 233
20.4 d [Algorithmic]How do the standard amino acids differ from one another?
a) in the location of the amino group
b) in the location of the carboxyl group
c) in the number of carbon atoms between the amino group and the carboxyl group
d) in the identity of the R group (side chain)
20.5 d Which of the following sets of elements is a possible composition for a standard amino acid?
a) carbon, hydrogen, oxygen, and sulfur
b) carbon, hydrogen, nitrogen, and sulfur
c) carbon, hydrogen, and nitrogen
d) carbon, hydrogen, oxygen, nitrogen and sulfur
20.6 b Which of the following forms of the amino acid alanine (Ala) is the zwitterion form of this amino acid?
20.7 a In a solution that is highly acidic (low pH), which of the following forms of the amino acid alanine (Ala) would predominate?
20.8 c Which of the following amino acids would be classified as a polar neutral amino acid?
20.9 c [Algorithmic]The joining together of two amino acids to form a dipeptide involves the reaction between
a) two amino groups.
b) two carboxyl groups.
c) an amino group and a carboxyl group.
d) a carboxyl group and a hydroxyl group.
20.10 a Which of the following would be a correct representation of a portion of a protein “backbone”?
20.11 a [Algorithmic]How many peptide linkages are present in a tripeptide?
a) two
b) three
c) four
d) five
20.12 d [Algorithmic]In the tetrapeptide Ala–Cys–Val–Leu, the C-terminal amino acid is
a) Ala.
b) Cys.
c) Val.
d) Leu.
20.13 b [Algorithmic]How many different tripeptides can be formed from two molecules of valine (Val) and one molecule of serine (Ser)?
a) two
b) three
c) four
d) six
20.14 d Which of the following biochemically important small peptides functions as an antioxidant?
a) oxytocin
b) vasopressin
c) Met-enkephalin
d) glutathione
20.15 a To which of the following levels of protein structure is the sequence of amino acids in a protein directly related?
a) primary
b) secondary
c) tertiary
d) quaternary
20.16 c Interactions between amino acid R groups is responsible for which of the following levels of protein structure?
a) primary
b) secondary
c) tertiary
d) both secondary and tertiary
20.17 c Quaternary structure is possible for a protein only when
a) the amino acid cysteine is present.
b) all amino acids have nonpolar R groups.
c) two or more protein chains are present.
d) a protein chain bends back upon itself.
20.18 b The non-amino acid portion of a conjugated protein is called a
a) side chain.
b) prosthetic group.
c) hydrophobic group.
d) hydrophilic group.
20.19 b The complete hydrolysis of a protein produces a mixture of
a) polypeptides.
b) free amino acids.
c) polypeptides and free amino acids.
d) dipeptides and free amino acids.
20.20 c Which of the following is an incorrect characterization for the protein hemoglobin?
a) multimeric protein
b) globular protein
c) simple protein
d) conjugated protein
TYPE II MULTIPLE-CHOICE QUESTIONS
In each of the following multiple-choice questions, place the letter of the correct response in the blank at the left. There may be more than one correct response for a question (choice d) or no correct response for a question (choice e).
20.21 d Which of the following statements concerning protein structure is correct?
a) Amino acids are connected to each other through peptide bonds.
b) At least one unit of each of the 20 standard amino acids musts be present.
c) More than one chain of amino acids may be present.
d) more than one correct response
e) no correct response
20.22 b Which of the following elements is present in some of the standard amino acids but not all of them?
a) oxygen
b) sulfur
c) phosphorus
d) more than one correct response
e) no correct response
20.23 d Glycine, the simplest amino acid, is different from all of the other standard amino acids in that it
a) does not have a chiral center.
b) has a side chain that does not contain carbon.
c) occurs naturally as a D-isomer rather than as a L-isomer.
d) more than one correct response
e) no correct response
20.24 b In a solution of high pH, all of the acidic and basic sites in an amino acid are
a) protonated.
b) deprotonated.
c) negatively charged.
d) more than one correct response
e) no correct response
20.25 d Which of the following types of standard amino acids exist as zwitterions in the solid state?
a) polar neutral amino acids
b) polar acidic amino acids
c) nonpolar amino acids
d) more than one correct response
e) no correct response
20.26 e Which of the following statements concerning the tripeptide Val–Ala–Gly is correct?
a) The C-terminal amino acid residue is Val.
b) The N-terminal amino acid residue is Gly.
c) Three peptide linkages are present.
d) more than one correct response
e) no correct response
20.27 a Which of the following tripeptides is a possible product from the partial hydrolysis of Ala–Val–Gly–Gly–Ala–Val?
a) Gly–Gly–Ala
b) Ala–Val–Ala
c) Ala–Val–Val
d) more than one correct response
e) no correct response
20.28 a Six isomeric tetrapeptides can be made from which of the following combinations of amino acids?
a) Ala, Ala, Val, and Val
b) Val, Val, Val, and Ala
c) Ala, Ala, Val, and Gly
d) more than one correct response
e) no correct response
20.29 a Which of the following terms describes a protein secondary structure?
a) alpha helix
b) globular shape
c) fibrous shape
d) more than one correct response
e) no correct response
20.30 c Parallel polypeptide chains in a beta-pleated sheet conformation are held together by
a) R-group interactions.
b) covalent bonding.
c) hydrogen bonding.
d) more than one correct response
e) no correct response
20.31 d Which of the following types of interactions contribute to protein tertiary structure?
a) hydrophobic interactions between nonpolar R groups
b) hydrogen bonds between polar neutral R groups
c) hydrogen bonds between C=O and N–H groups
d) more than one correct response
e) no correct response
20.32 a R-group interaction between which of the following pairs of amino acids produces a disulfide bond?
a) cysteine-cysteine
b) proline-proline
c) alanine-glycine
d) more than one correct response
e) no correct response
20.33 e Which of the following levels of protein structure is not disrupted when protein hydrolysis occurs?
a) primary structure
b) secondary structure
c) tertiary structure
d) more than one correct response
e) no correct response
20.34 a In which of the following pairs of proteins are both members of the pair fibrous proteins?
a) alpha-keratin and collagen
b) collagen and hemoglobin
c) hemoglobin and myoglobin
d) more than one correct response
e) no correct response
20.35 d Which of the following statements concerning proteins is correct?
a) Some, but not all, multimeric proteins are also conjugated proteins.
b) All monomeric proteins are also simple proteins.
c) Some, but not all, globular proteins are also multimeric proteins.
d) more than one correct response
e) no correct response
MULTIPLE-CHOICE FORMAT TRUE-FALSE QUESTIONS
In each of the following multiple-choice questions, characterize EACH of the three given statements as being TRUE or FALSE and then indicate the collective true-false status of the statements using the choices a) All three statements are true.
b) Two of the three statements are true.
c) Only one of the statements is true.
d) None of the statements is true.
20.36 b - TTF Statements:
(1) In pure form, amino acids are white crystalline solids with limited solubility in water.
(2) In an alpha-helix structure, all of the amino acid side chains lie outside the helix.
(3) Protein denaturation affects all four levels of protein structure.
a) All three statements are true.
b) Two of the three statements are true.
c) Only one of the statements is true.
d) None of the statements is true.
20.37 a - TTT Statements:
(1) Some tertiary-structure interactions involve covalent bonding.
(2) Nonpolar amino acids contain one amino group, one carboxyl group, and a nonpolar side chain.
(3) The two amino acids present in a dipeptide are linked via an amide linkage.
a) All three statements are true.
b) Two of the three statements are true.
c) Only one of the statements is true.
d) None of the statements is true.
20.38 a - TTT Statements:
(1) The major force responsible for protein secondary structure is hydrogen bonding.
(2) Amino acids found in proteins are almost always L-isomers.
(3) Conjugated proteins always contain one or more prosthetic groups.
a) All three statements are true.
b) Two of the three statements are true.
c) Only one of the statements is true.
d) None of the statements is true.
20.39 c - FFT Statements:
(1) Partial hydrolysis of the tripeptide Ala-Gly-Cys produces three different dipeptides.
(2) The number of standard amino acids is twenty-three.
(3) Enkephalins are peptides that bind at receptor sites in the brain to reduce pain.
a) All three statements are true.
b) Two of the three statements are true.
c) Only one of the statements is true.
d) None of the statements is true.
20.40 b - FTT Statements:
(1) In a peptide, the number of amino acids and the number of peptide bonds are always equal.
(2) HDL and LDL are examples of lipoproteins.
(3) Tertiary structure interactions in proteins always involve amino acid R groups.
a) All three statements are true.
b) Two of the three statements are true.
c) Only one of the statements is true.
d) None of the statements is true.
20.41 d - FFF Statements:
(1) In the tripeptide Gly-Ala-Ser, the amino acid at the N-terminal end is Ser.
(2) More than one polypeptide chain may be present in a conjugated protein but not in a simple protein.
(3) In solution at physiological pH, the side chain of a polar basic amino acid bears a negative charge.
a) All three statements are true.
b) Two of the three statements are true.
c) Only one of the statements is true.
d) None of the statements is true.
20.42 c - TFF Statements:
(1) Collagen, the most abundant protein in humans, is both a fibrous protein and a glycoprotein.
(2) Quaternary structure, the highest level of protein organization, is found in all proteins in which 80 or more amino acids are present.
(3) A protein chain lacks directionality because its two ends always involve the same amino acid.
a) All three statements are true.
b) Two of the three statements are true.
c) Only one of the statements is true.
d) None of the statements is true.
20.43 b - TFT Statements:
(1) For a tripeptide in which the three amino acids are different, six isomeric forms are possible.
(2) The “backbone” of a protein is an alternating sequence of C and N atoms.
(3) Both alpha-helix and beta-pleated sheet configurations can be present in the same protein.
a) All three statements are true.
b) Two of the three statements are true.
c) Only one of the statements is true.
d) None of the statements is true.
20.44 b - TFT Statements:
(1) For neutral amino acids, three different forms can exist, with the form found dependent of solution pH.
(2) Hydrophobic interactions are the strongest of the tertiary-structure interactions.
(3) Protein digestion is an enzyme-catalyzed hydrolysis reaction.
a) All three statements are true.
b) Two of the three statements are true.
c) Only one of the statements is true.
d) None of the statements is true.
20.45 b - TFT Statements:
(1) The antirejection drug cyclosporine is structurally a small cyclic peptide.
(2) The chemical basis for a hair permanent is reversible denaturation in which peptide linkages are broken and reformed.
(3) Among the standard amino acids, there are more nonessential ones than essential ones.
a) All three statements are true.
b) Two of the three statements are true.
c) Only one of the statements is true.
d) None of the statements is true.
MATCHING QUESTIONS
Aspartic acid, an acidic amino acid, can have four different forms in solution. These four forms are given in the response list on the right. For each of the conditions or characterizations on the left, select from the response list the form of aspartic acid that will be dominant. Responses on the right may be used more than once or need not be used at all.
20.46 c Zwitterion form20.47 b Positively-charged form
20.48 a Form in a solution of pH 13
20.49 b Form in a solution of pH 1
20.50 c Form in which no net charge is present /
For each of the amino acids on the left, choose a correct classification from the response list on the right. Responses on the right may be used more than once or need not be used at all.