CHEM 121. Chapter 20 Name: __________________________ Date: _____________
1. 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.
2. Which of the followings 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) no protein can have two of the same amino acids in it
3. 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) none of the standard amino acids are chiral
D) ansvard
4. How do the standard amino acids differ from one another?
A) in the location of the amino group
B) the number of carboxyl groups
C) the number of chiral carbon atoms between the carboxyl group and the amino group
D) in the identity of the R group (side chain)
5. 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
Page 1
6. Which of the following forms of the amino acid alanine (Ala) is the zwitterion form of
this amino acid?
A)
B)
C)
D)
Page 2
7. In a solution that is highly acidic (low pH), which of the following forms of the amino
acid alanine (Ala) would predominate?
A)
B)
C)
D)
Page 3
8. Which of the following amino acids would be classified as a polar neutral amino acid?
A)
B)
C)
D)
9. The joining together of two amino acids to form a dipeptide involves the reaction
between
A) two amide groups
B) two carboxyl groups
C) an amino group and a carboxyl group
D) an amino group and a hydroxyl group
Page 4
10. Which of the following would be a correct representation of a portion of a protein
“backbone”?
A)
B)
C)
D)
11. How many peptide linkages are present in a hexapeptide?
A) four
B) five
C) six
D) seven
12. In the tetrapeptide Gly-Gln-Tyr-Lys, the C-terminal amino acid is
A) Gly
B) Gln
C) Tyr
D) Lys
13. How many different tripeptides can be formed from two molecules of isoleucine (Ile)
and one molecule of arginine (Arg)?
A) two
B) three
C) four
D) five
Page 5
14. Which of the following biochemically important small peptides functions as an
antioxidant?
A) oxytocin
B) vasopressin
C) Met-enkephalin
D) glutathione
15. 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
16. 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
17. 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.
18. The non-amino acid portion of a conjugated protein is called a
A) side chain.
B) prosthetic group.
C) hydrophobic group.
D) hydrophilic group.
19. 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.
Page 6
20. Which of the following is an incorrect characterization for the protein hemoglobin?
A) multimeric protein
B) globular protein
C) simple protein
D) conjugated protein
21. 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
22. 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
23. 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
24. 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
Page 7
25. 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
26. 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
27. 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
28. 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
29. 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
Page 8
30. 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
31. 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
32. 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
33. 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
34. 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
Page 9
35. 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
Use the following to answer questions 36-45:
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.
36. 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.
37. 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.
Page 10
38. 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.
39. 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.
40. 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.
41. 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.
Page 11
42. 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.
43. 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.
44. 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.
45. 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.
Page 12
Use the following to answer questions 46-50:
Aspartic acid, an acidic amino acid, can have four different forms in solutionThese four forms
are given in the response listFor each of the conditions or characterizations, select from the
response list the form of aspartic acid that will be dominantResponses may be used more than
once or need not be used at all.
a) H2N
CH
COO
_
CH2
+
b) H3N
COO
CH
COOH
CH2
+
c) H3N
COOH
CH
COO
CH2
COOH
d) H3N
CH
COO
CH2
COO
46. Zwitterion form
47. Positively-charged form
48. Form in a solution of pH 13
49. Form in a solution of pH 1
50. Form in which no net charge is present
Page 13
Use the following to answer questions 51-55:
For each of the amino acids, choose a correct classification from the response listResponses may
be used more than once or need not be used at all.
a) nonpolar amino acid
b) polar neutral amino acid
c) polar acidic amino acid
d) polar basic amino acid
COO
51. H3N CH CH2 OH
COO
52. H3N CH CH2 COO
COO
O
53. H3N CH (CH2)2 C NH2
COO
54. H3N CH CH3
COO
55. H3N CH (CH2)4 NH3
Use the following to answer questions 56-60:
Use the response list to answer the following questions concerning the pentapeptide
Gly–Ala–Gly–Gly–Ala
Responses may be used more than once or need not be used at all.
a) zero
b) two
c) three
d) four
Page 14
56. Number of peptide linkages present
57. Number of different amino acids produced by complete hydrolysis
58. Number of possible different dipeptides produced by partial hydrolysis
59. Number of possible different tripeptides produced by partial hydrolysis
60. Number of possible different tripeptides produced by denaturation
Use the following to answer questions 61-65:
Determine the structural level (primary, secondary, etc.) associated with each of the protein
characteristics using the response listResponses may be used more than once or need not be used
at all.
a) primary structure
b) secondary structure
c) tertiary structure
d)quaternary structure
61. Sequence of amino acids in a protein chain
62. Three-dimensional shape resulting from R-group interactions
63. Hydrogen bonding between amide hydrogen atoms and carbonyl oxygen atoms
64. Alpha-helix configuration
65. Beta pleated-sheet configuration
Page 15
Use the following to answer questions 66-70:
Identify the standard amino acid with each of the characteristics using the response listResponses
may be used more than once or need not be used at all.
a) proline
b) cysteine
c) glycine
d) alanine
66. Only standard amino acid whose side chain does not contain carbon
67. Only standard amino acid with a cyclic side chain
68. Only standard amino acid that is achiral
69. Only standard amino acid that participates in disulfide bonds
70. Only standard amino acid with a methyl group attached to its alpha carbon atom
Page 16
Answer Key
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
41.
42.
43.
44.
A
D
C
D
D
B
A
C
C
A
A
D
B
D
A
C
C
B
B
C
D
D
D
B
D
E
A
A
A
C
D
A
E
A
D
B
A
A
C
B
D
C
B
B
Page 17
45.
46.
47.
48.
49.
50.
51.
52.
53.
54.
55.
56.
57.
58.
59.
60.
61.
62.
63.
64.
65.
66.
67.
68.
69.
70.
B
c
b
a
b
c
b
c
b
a
d
d
b
c
c
a
a
c
b
b
b
c
a
c
b
d
Page 18