Tutorial Protein Set 2
Matching
A)
B)
C)
D)
E)
F)
G)
H)
I)
J)
K)
L)
M)
uncharged
deprotonated
three
-amino group
two
C-terminus
lysine
racemic mixture
zero
protonated
isoleucine
tryptophan
phenylalanine
1. When a peptide bond is formed, an ______ reacts with a carboxylate group.
Ans: D
Section 4.1.B
Level of Difficulty: Easy
Learning objective: Amino Acid Structure
2. In the peptide Trp-Ser-Val, valine is at the ______.
Ans: F
Section 4.1.E
Level of Difficulty: Easy
Learning objective: Amino Acid Structure
3. At a pH above its pK, the phenolic group of tyrosine is ______.
Ans: B
Section 4.1.C
Level of Difficulty: Easy
Learning objective: Amino Acid Structure
4. At a pH below its pK, the
Ans: J
-amino group of lysine is ______.
Section 4.1.D
Level of Difficulty: Easy
Learning objective: Amino Acid Structure
5. At a pH below its pK
Ans: A or J
-carboxylate group of Asp is ______.
Section 4.1.D
Level of Difficulty: Easy
Learning objective: Amino Acid Structure
6. The net charge of the zwitterion form of Gly is ______.
Ans: I
Section 4.1.A
Level of Difficulty: Easy
Learning objective: Amino Acid Structure
7. Biological systems usually produce a single enantiomer, whereas chemical synthesis produces
a ______.
Ans: H
Section 4.2
Level of Difficulty: Easy
Learning objective: Amino Acid Structure
8. In the tripeptide Trp-Val-Phe, the N-terminal residue is ______.
Ans: L
Section 4.1.E
Level of Difficulty: Easy
Learning objective: Amino Acid Structure
9. In the tripeptide Lys-Pro-Ile, the C-terminal residue is _________.
Ans: K
Section 4.1.E
Level of Difficulty: Easy
Learning objective: Amino Acid Structure
10. In the tripeptide Lys-Pro-Ile, there are ______ charged groups at pH 7.
Ans: C
Section 4.1.C
Level of Difficulty: Easy
Learning objective: Amino Acid Structure
Multiple Choice
11. Which of the following amino acids has a charged polar side chain at pH 7?
A) Leu
B) Ala
C) Met
D) Trp
E) Glu
Ans: E
Section 4.1.C
Level of Difficulty: Easy
Learning objective: Amino Acid Structure
12. Which of the following amino acids has a sulfur atom in its side chain?
A) Asn
B) Ser
C) Phe
D) Met
E) Tyr
Ans: D
Section 4.1.C
Level of Difficulty: Easy
Learning objective: Amino Acid Structure
13. Which of the following amino acids has an uncharged polar side chain at pH 7?
A) Arg
B) Thr
C) Glu
D) Pro
E) Ile
Ans: B
Section 4.1.C
Level of Difficulty: Easy
Learning objective: Amino Acid Structure
14. At pH 7, arginine (pK
-amino 8.99, guanidino 12.48) would be
charged as follows:
-amino, +1 guanidino, +1 net charge
-amino, -1 guanidino, 0 net charge
-carboxylate, -amino, -1 guanidino, -1 net charge
D) -amino, +1 guanidino, +1 net charge
E) -amino, +1 guanidino, 0 net charge
Ans: D
Section 4.1.C
Level of Difficulty: Moderate
Learning objective: Amino Acid Structure
15. At pH 7, aspartic acid (pK
-carboxylate 3.9 ) would
be charged as follows:
A) 0 -carboxylate, +1 -amino, 0 -carboxylate, +1 net charge
B) -1 -carboxylate, +1 -amino, -1 -carboxylate, -1 net charge
C) 0 -carboxylate, -1 -amino, 0 -carboxylate, -1 net charge
D) +1 -carboxylate, -1 -amino, +1 -carboxylate, +1 net charge
E) +1 -carboxylate, +1 -amino, +1 -carboxylate, +3 net charge
Ans: B
Section 4.1.C
Level of Difficulty: Moderate
Learning objective: Amino Acid Structure
16. At pH 11, glutamic acid (pK
would be charged as follows:
A) +1 -carboxylate, 0 -amino, +1 -carboxylate, +2 net charge
B) -1 -carboxylate, +1 -amino, -1 -carboxylate, -1 net charge
C) 0 -carboxylate, 0 -amino, 0 -carboxylate, 0 net charge
D) +1 -carboxylate, -1 -amino, +1 -carboxylate, +1 net charge
E) -1 -carboxylate, 0 -amino, -1 -carboxylate, -2 net charge
Ans: E
Section 4.1.C
-carboxylate 4.07.
Level of Difficulty: Moderate
Learning objective: Amino Acid Structure
17. At pH 4, histidine (pK
-amino 9.33, 6.04 imidazole) would be
charged as follows:
-amino, -1 imidazole, 0 net charge
B) -amino, 0 imidazole, 0 net charge
-amino, -1 imidazole, +1 net charge
D) -amino, +1 imidazole, +1 net charge
-amino, +1 imidazole, +2 net charge
Ans: D
Section 4.1.C
Level of Difficulty: Moderate
Learning objective: Amino Acid Structure
18. At pH 5, cysteine (pK
-amino 10.7, sulfhydryl 8.37 ) would be
charged as follows:
-amino, 0 sulfhydryl, 0 net charge
-carboxylate, -amino, -1 sulfhydryl, -1 net charge
C) -amino, +1 sulfhydryl, +1 net charge
D) -amino, 0 sulfhydryl, 0 net charge
E) +1 -carboxylate, -1 -amino, 0 sulfhydryl, 0 net charge
Ans: D
Section 4.1.C
Level of Difficulty: Moderate
Learning objective: Amino Acid Structure
19. At pH 1, lysine (pK
charged as follows:
-carboxylate, B) C) +1 -carboxylate, +2
D) 0 -carboxylate, +1
E) +2 -carboxylate, +1
-
-
-amino, -amino, -2 net charge
-amino, +1 net charge
-amino, +2 -amino, +5 net charge
-amino, +1 -amino, +2 net charge
-amino, +1 -amino, +4 net charge
Ans: D
Section 4.1.C
Level of Difficulty: Moderate
Learning objective: Amino Acid Structure
-amino 10.54 ) would be
20. The disulfide bond between two cysteine molecules:
A) is a peptide bond.
B) is an ionic bond that is stable at physiological pH.
C) is a covalent bond formed by oxidation.
D) is a hydrogen bond between the two sulfhydryl groups.
E) is a weak ion-induced dipole attraction.
Ans: C
Section 4.1.C
Level of Difficulty: Easy
Learning objective: Amino Acid Structure
21. What proportion of the 20 amino acids are considered to be nutritionally essential to lab
animals?
A) 0%
B) 25%
C) 50%
D) 75%
E) 100%
Ans: C
Section 4.1
Level of Easy:
Learning objective: Amino Acid Structure
22. Which of the following statements is/are true?
A) amino acids can be derived from purines and pyrimidines
B) purines and pyrimidines can be derived from amino acids
C) no protein contains every standard amino acid
D) A and C
E) B and C
Ans: B
Section 4.1
Level of Difficulty: Easy
Learning objective: Amino Acid Structure
23. The isoelectronic point of an amino acid is the point where:
A) The pK of the carboxylic acid is the same as the amino group
B) Sodium ions are attracted to the amino groups
C) the solubility of the amino acid is maximized
D) the amino acid racemizes
E) the amino acid carries no net electrical charge
Ans: E
Section 4.1.D
Level of Difficulty: Moderate
Learning objective: Amino Acid Structure
24. Amino acid side-chain residues have:
A) a positive charge in every situation
B) pKs that assure the solubility of every protein
C) constant pKs no matter what aqueous environment they are found in
D) different pKs in peptides as compared to the free amino acids
E) polar functional groups
Ans: D
Section 4.1.D
Level of Difficulty: Moderate
Learning objective: Amino Acid Structure
25. Asx refers to
A) a negatively charged aspartic acid
B) a positively charged asparagine
C) a dipeptide containing both aspartic acid and asparagine
D) either aspartic acid or asparagine
E) an unnatural amino acid formed on protein hydrolysis
Ans: D
Section 4.1.E
Level of Difficulty: Easy
Learning objective: Amino Acid Structure
26. The formation of a dipeptide from two amino acids requires:
A) side-chain complementarity
B) loss of water
-carbon
-carbon
E) base catalysis
Ans: B
Section 4.1.B
Level of Difficulty: Easy
Learning objective: Amino Acid Structure
27. The peptide AYDG has an N-terminal _________ residue.
A) glycine
B) glutamic acid
C) glutamine
D) aspartic acid
E) alanine
Ans: E
Section 4.1.E
Level of Difficulty: Easy
Learning objective: Amino Acid Structure
28. Which of the following tripeptides would be expected to be the most hydrophobic:
A) KYG
B) KYA
C) GYA
D) DYA
E) DYG
Ans: C
Section 4.1.E
Level of Difficulty: Moderate
Learning objective: Amino Acid Structure
29. What is the abbreviation for the peptide valylarginylisoleucine?
A) Val-Arg-Ile
B) Val-Agn-Leu
C) Vln-Arg-Ile
D) Val-Agn-Isl
E) Vln-Arg-Leu
Ans: A
Section 4.1.E
Level of Difficulty: Easy
Learning objective: Amino Acid Structure
30. The least abundant amino acid in proteins is:
A) V
B) W
C) G
D) F
E) A
Ans: B
Section 4.1
Level of Difficulty: Moderate
Learning objective: Amino Acid Structure
31. Zwitterions are:
A) amino acids
B) ionic molecules that are racemic
C) molecules that bear both negatively and positively charged groups
D) side chain carboxylate anions
E) delocalized ions
Ans: C
Section 4.1.A
Level of Difficulty: Easy
Learning objective: Amino Acid Structure
32. All the standard amino acids except ____ are optically active.
A) Pro
B) Arg
C) Trp
D) Gly
E) Phe
Ans: D
Section 4.2
Level of Difficulty: Easy
Learning objective: Amino Acid Structure
33. The __________ character of most standard amino acids causes solutions of amino acids to
rotate plane polarized light.
A) chiral
B) zwitterionic
C) polar
D) all of the above
E) none of the above
Ans: A
Section 4.2
Level of Difficulty: easy
Learning objective: Amino Acid Structure
34. All amino acids derived from proteins have the same conformation as:
A) L-glyceraldehyde
B) dextro-glyceraldehyde
C) D-glucose
D) cis-lysine
E) glycine
Ans: A
Section 4.2
Level of Difficulty: Easy
Learning objective: Amino Acid Structure
35. Typically, ‘unnatural’ amino acids with side chain modifications
A) are synthesized due to genetic mutations
B) are assembled by specialized bacterial enzymes
C) are formed by modification of standard side chain residues after the protein synthesis
D) are toxic
E) are racemic
Ans: C
Section 4.3.A
Level of Difficulty: Moderate
Learning objective: Amino Acid Structure
36. An amide bond between a sideA) disulfide bond
B) amino amide bond
C) nor-peptide bond
D) isopeptide bond
E) hormone bond
-amino group is also called a(n):
Ans: D
Section 4.3
Level of Difficulty: Moderate
Learning objective: Amino Acid Structure
Short Answer
39. Why can amino acid-binding proteins distinguish the enantiomeric forms of the free amino
acids?
Ans: Proteins consist of L-amino acids, so their binding sites are also chiral and can therefore
recognize a particular enantiomer of an amino acid.
Level of Difficulty: Moderate
Learning objective: Amino Acid Structure
38. Why do bacterial cell walls containing peptides with D-amino acids often escape digestion
by the proteases that other organisms use to kill bacteria?
Ans: The proteases only recognize L-amino acids.
Level of Difficulty: Moderate
Learning objective: Amino Acid Structure
Fill in the Blank
39. Histamine is formed from histidine by a ________ reaction.
Ans: decarboxylation
Section 4.3.A
Level of Difficulty: Moderate
Learning objective: Amino Acid Structure
40. _________ is a neurotransmitter formed from tyrosine by hydroxylation and
decarboxylation reactions.
Ans: Dopamine
Section 4.3.B
Level of Difficulty: Moderate
Learning objective: Amino Acid Structure
41. Proline differs from the other 19 amino acids in proteins in that it has a _________ amino
group.
Ans: secondary
Section 4.1.C
Level of Difficulty: Moderate
Learning objective: Amino Acid Structure