Protein Chapter Quiz (Lab) Answer Key for Review

Question 1

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.

Answer 1

A. (They are constructed from one or more unbranched chains of amino acids; that is, they are polymers)

Question 2

2. Which of the following statements concerning proteins is
   incorrect?

a. The amino acids in a protein can be polar, nonpolar,
or neutral in nature.
b. All proteins contain the elements C, H, O, and N.
c. All proteins are made of amino acids.
d. The amino acids in a protein are linked by ionic
bonds.

Answer 2

D. (each are linked to its neighbor through a covalent peptide bond)

Question 3

3. Which of the following statements concerning standard
   amino acids is incorrect?

a. There are four main categories of amino acids.
b. They are all alpha-amino acids.
c. None of the standard amino acids are chiral.
d. Each of them has an amino group and a carboxyl
group

Answer 3

C. (The amino acids are all chiral, with the exception of glycine, whose side chain is H)

Question 4

4. How do the standard amino acids differ from one another?

a. in whether or not the amino group is chiral two
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)

Answer 4

D. (R-group is the only unique feature in each amino acid)

Question 5

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

Answer 5

D.

Question 6

9. The joining together of two amino acids to form a dipeptide
   involves the reaction between

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

Answer 6

C.

Question 7

11. How many peptide linkages are present in a tripeptide?

a. two
b. three
c. four
d. five

Answer 7

A.

Question 8

12. In the tetrapeptide Phe-Gln-Trp-His, the C-terminal amino
    acid is

a. Phe
b. Gln
c. Trp
d. His

Answer 8

D.

Question 9

13. How many different tripeptides can be formed from two
    molecules of leucine (Leu) and one molecule of glutamic
    acid (Glu)?

a. two
b. three
c. four
d. five

Answer 9

B.

Question 10

14. 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

Answer 10

A. (linear sequence of the amino acids connected by the peptide bonds)

Question 11

15. 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

Answer 11

C.

Question 12

16. 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 on itself.

Answer 12

C. (To be considered to have quaternary structure, a protein must have two or more peptide chains forming subunits)

Question 13

17. The non-amino acid portion of a conjugated protein is called
    a(n)

a. side chain
b. prosthetic group
c. R group
d. secondary structure

Answer 13

B.

Question 14

18. 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

Answer 14

B.

Question 15

19. Which of the following is an incorrect characterization for the
    protein hemoglobin?

a. multimeric protein
b. globular protein
c. simple protein
d. conjugated protein

Answer 15

C. (Hemoglobin is a complex protein which has a quaternary structure and contains iron. There are four subunits in the hemoglobin molecule - two alpha subunits and two beta subunits.)

Question 16

20. 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.

Answer 16

D. (Within a protein, multiple amino acids are linked together by peptide bonds, thereby forming a long chain. Proteins are built from a set of only twenty amino acids, each of which has a unique side chain. The side chains of amino acids have different chemistries.)

Question 17

21. 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.

Answer 17

B.

Question 18

22. 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

Answer 18

D.

Question 19

23. 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

Answer 19

B. (both the carboxyl and amine groups are deprotonated; the amino acid carries a net negative charge, and is dibasic)

Question 20

24. 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

Answer 20

D.

Question 21

25. 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. The peptide linkages are present.
d. more than one correct response
e. no correct response

Answer 21

E.

Question 22

26. 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

Answer 22

A.

Question 23

27. A total of 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

Answer 23

A.

Question 24

28. 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

Answer 24

A.

Question 25

29. Parallel polypeptide chains in a beta-pleated sheet
    conformation are held together by

a. R-group interasctions
b. covalent bonding
c. hydrogen bonding
d. More than one correct response.
e. No correct response.

Answer 25

C.

Question 26

30. 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.

Answer 26

D.

Question 27

31. 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

Answer 27

A.

Question 28

32. 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

Answer 28

E.

Question 29

33. 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

Answer 29

A.