CHAPTER 20: PROTEINS
MULTIPLE CHOICE
1. Proteins are polymers in which: Ans. = A
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. How do the standard amino acids differ from one another? Ans. = D
a. in whether or not the amino group is chiral
b. in whether or not the carboxyl group is chiral
c. in the number of chiral carbon atoms between the carboxyl group and the amino
group
d. in the identity of the R group (side chain)
3. Which of the following sets of elements is a possible composition for a standard amino
acid? Ans. = D
a. carbon, hydrogen, oxygen, and sulfur
b. carbon, hydrogen, nitrogen, and sulfur
c. carbon, hydrogen, and nitrogen
d. carbon, hydrogen, oxygen, nitrogen, and sulfur
4. Which of the following forms of the amino acid alanine (Ala) is the zwitterion form of this
amino acid? Ans. = B (zwitterion means net charge 0 or equal + and -)
a.
b.
c.
d.
Testbank
th
General, Organic, Biological Chemistry, 6 edition
1
5. In a solution that is highly acidic (low pH), which of the following forms of the amino acid
alanine (Ala) would predominate? Ans. = A (all amino acids forms cations at acidic pH)
a.
b.
c.
d.
6. Which of the following amino acids would be classified as a polar neutral amino acid? Ans.
= C (neutral means net charge 0 and polar means OH)
a.
b.
c.
d.
7. The joining together of two amino acids to form a dipeptide involves the reaction between:
Ans. = C
a. two amide groups
b. an amino group and an alpha-carbon
c. an amino group and a carboxyl group
d. an alpha-carbon and a hydroxyl group
Testbank
th
General, Organic, Biological Chemistry, 6 edition
2
8. How many peptide linkages are present in a tripeptide? Ans. = A
a. two
b. three
c. four
d. five
9. In the tetrapeptide Phe-Gln-Trp-His, the C-terminal amino acid is: Ans. = D (C-terminal end
is last amino acid whereas N-terminal end is first amino acid)
a. Phe
b. Gln
c. Trp
d. His
10. Which of the following biochemically important small peptides functions as an antioxidant?
Ans. = D
a. oxytocin
b. vasopressin
c. Met-enkephalin
d. glutathione
11. To which of the following levels of protein structure is the sequence of amino acids in a
protein directly related? Ans. = A
a. primary
b. secondary
c. tertiary
d. quaternary
12. Interactions between amino acid R groups is responsible for which of the following levels of
protein structure? Ans. = C
a. primary
b. secondary
c. tertiary
d. both secondary and tertiary
13. Quaternary structure is possible for a protein only when: Ans. = C
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 on itself.
14. The non-amino acid portion of a conjugated protein is called a: Ans. B
a. side chain
b. prosthetic group
c. hydrophobic group
d. hydrophilic group
Testbank
th
General, Organic, Biological Chemistry, 6 edition
3
15. The complete hydrolysis of a protein produces a mixture of: Ans. = D
a. polypeptides
b. free amino acids
c. polypeptides and free amino acids
d. dipeptides and free amino acids
16. Which of the following is an incorrect characterization for the protein hemoglobin? Ans. =
C (it contains heme which is not a protein)
a. multimeric protein
b. globular protein
c. simple protein
d. conjugated protein
17. Which of the following elements is present in some of the standard amino acids but not all
of them? Ans. = B
a. oxygen
b. sulfur
c. phosphorus
d. more than one correct response
e. no correct response
18. Which of the following statements concerning the tripeptide Val–Ala–Gly is correct? Ans.
=E
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.
19. Which of the following terms describes a protein secondary structure? Ans. = A
a. alpha helix
b. globular shape
c. fibrous shape
d. more than one correct response
e. no correct response
20. Parallel polypeptide chains in a beta-pleated sheet conformation are held together by: Ans. =
C
a. R-group interactions
b. covalent bonding
c. hydrogen bonding
d. more than one correct response
e. no correct response
Testbank
th
General, Organic, Biological Chemistry, 6 edition
4
21.Which of the following types of interactions contribute to protein tertiary structure? Ans. = D
(both A and B are correct)
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
22. R-group interaction between which of the following pairs of amino acids produces a
disulfide bond? Ans. = A
a. cysteine-cysteine
b. proline-proline
c. alanine-glycine
d. more than one correct response
e. no correct response
23. In which of the following pairs of proteins are both members of the pair fibrous proteins?
Ans. = A
a. alpha-keratin and collagen
b. collagen and hemoglobin
c. hemoglobin and myoglobin
d. more than one correct response
e. no correct response
24. Statements: Ans. = A
(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.
25. Statements: Ans. = A
(1) The major force responsible for protein secondary structure is hydrogen bonding.
(2) Amino acids found in proteins are 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.
Testbank
th
General, Organic, Biological Chemistry, 6 edition
5
26.Statements: Ans. = C (only statement 3 is correct)
(1) Partial hydrolysis of the tripeptide Ala-Gly-Cys produces three different dipeptides.
(2) The number of standard amino acids is 23.
(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.
27. Statements: Ans. = B (only statements 2 and 3 are correct)
(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.
NUMERIC RESPONSE
Use the following to answer the questions below:
Aspartic acid, an acidic amino acid, can have four different forms in solution. These four
forms are given in the response list. For each of the conditions or characterizations, select
from the response list the form of aspartic acid that will be dominant. Responses may be
used more than once or need not be used at all.
28. Zwitterion form: Ans. = C
29. Positively-charged form: Ans. = B
Testbank
th
General, Organic, Biological Chemistry, 6 edition
6
30. Form in a solution of pH 13: Ans. = A
31. Form in a solution of pH 1: Ans. = B
32. Form in which no net charge is present: Ans. = C
Use the following to answer the questions below:
For each of the amino acids, choose a correct classification from the response list.
Responses 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
Ans. = B
33.
34.
Ans. = C
35.
Ans. = B
36.
Ans. = A
37.
Ans. = D
Use the following to answer the questions below:
Determine the structural level (primary, secondary, etc.) associated with each of the protein
characteristics using the response list. Responses 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
Testbank
th
General, Organic, Biological Chemistry, 6 edition
7
38. Sequence of amino acids in a protein chain: Ans. = A
39. Three-dimensional shape resulting from R-group interactions: Ans. = C
40. Hydrogen bonding between amide hydrogen atoms and carbonyl oxygen atoms: Ans. = B
41. Alpha-helix configuration: Ans. = B
42. Beta pleated-sheet configuration: Ans. = B
Testbank
th
General, Organic, Biological Chemistry, 6 edition
8