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Multiple Choice Questions
1) Which of the following is true regarding the -carbon of an amino acid?
A) there are always four different functional groups attached
B) the most commonly occurring form of amino acids are the D-amino acids
C) when assigning the R-S stereochemistry, the carboxylic acid is always the highest priority
functional group
D) for all amino acids except glycine, the -carbon is a stereocenter
E) none of the above
Answer: D
Difficulty: 1
Topic:
Amino Acids
2) At physiological pH, most amino acids are _______, meaning that they contain both a positive
and negative charge.
A) zwitterions
B) amphoteric
C) chiral
D) amphipathic
E) none of the above
Answer: A
Difficulty: 1
Topic:
Amino Acids
3) Which of the following pairs of amino acids contains both an aliphatic and an aromatic amino
acid?
A) Thr and Tyr
B) Val and Gln
C) Phe and Ile
D) Ser and Cys
E) none of the above
Answer: C
Difficulty: 1
Topic:
Amino Acids
4) At a pH of 5, all amino acids have at least ____ charged group(s) and at most, _____ charged
group(s).
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A) 0; 1
B) 1; 1
C) 1; 2
D) 2; 2
E) 2; 3
Answer: E
Difficulty: 1
Topic:
Amino Acids
5) Which of the following pairs of amino acids could form a hydrogen bond through their
R-groups?
A) serine and phenylalanine
B) aspartic acid and methionine
C) histidine and tyrosine
D) alanine and glutamine
E) leucine and cysteine
Answer: C
Difficulty:
2
Topic:
Amino Acids
6) Which of the following pairs of amino acids could form a charge-charge interaction through
their R-groups?
A) methionine and histidine
B) glutamine and lysine
C) serine and glutamic acid
D) aspartic acid and arginine
E) threonine and asparagine
Answer: D
Difficulty: 2
Topic:
Amino Acids
7) Of the following amino acids, which will have a pI closest to 3?
A) Cys
B) His
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C) Gly
D) Asp
E) Lys
Answer: D
Difficulty: 2
Topic:
Amino Acids
8) Which of the following undergoes an oxidation reaction to form a disulfide bond?
A) serine
B) cysteine
C) methionine
D) threonine
E) tyrosine
Answer: B
Difficulty: 1
Topic:
Amino Acids
9) Which of the following amino acids is derived from another amino acid by the addition of an
amine group?
A) lysine
B) asparagine
C) arginine
D) histidine
E) none of the above
Answer: B
Difficulty: 1
Topic: Amino Acids
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10) Which of the following amino acids is incorporated into proteins during ribosomal protein
synthesis?
A) sarcosine
B) ornithine
C) 4-hydroxyproline
D) phosphoserine
E) selenocysteine
Answer: E
Difficulty: 1
Topic: Amino Acids
11) Hydrolysis of a peptide bond produces:
A) an alcohol and an amine
B) an amine and a carboxylic acid
C) a carboxylic acid and an anhydride
D) an amide and a carboxylic acid
E) an alcohol and an amide
Answer: B
Difficulty:
1
Topic:
Peptides and the Peptide Bond
12) Which of the following bonds has partial double bond character?
A) 1
B) 2
C) 3
D) 4
E) 5
Answer: C
Difficulty: 1
Topic: Peptides and the Peptide Bond
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13) Given the following peptide, what pair of protease enzymes would be able to produce three
smaller peptides?
Gly-Ser-Ala-His-Phe-Pro-Asn-Ala-Val-Glu-Cys-Ala-Ser
A) chymotrypsin and thrombin
B) trypsin and chymotrypsin
C) thermolysin and chymotrypsin
D) trypsin and thermolysin
E) none of the above
Answer: C
Difficulty: 2
Topic: Peptides and the Peptide Bond
14) What is the sequence of the following peptide?
A) Ile-Ala-Glu
B) Val-Ala-Asp
C) Leu-Gly-Glu
D) Val-Ala-Asn
E) Val-Gly-Gln
Answer: B
Difficulty: 1
Topic: Peptides and the Peptide Bond
15) If a cis peptide bond is found in a protein, the most likely amino acid to contribute the amine
to the amide bond is ______.
A) phenylalanine
B) leucine
C) proline
D) glycine
E) arginine
Answer: C
Difficulty: 1
Topic: Peptides and the Peptide Bond
16) Given the following peptide, what would be the overall charge at pH 5?
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Met-Glu-Ser-Arg-His-Phe-Pro-Asn-Ala-Glu-Cys-Ala-Ser
A) +2
B) +1
C) 0
D) -1
E) -2
Answer: C
Difficulty: 2
Topic: Peptides and the Peptide Bond
17) The prevalence of the trans orientation in peptide bonds results in the R-groups of adjacent
amino acids being oriented approximately ______ degrees with respect to each other.
A) 30
B) 60
C) 90
D) 120
E) 180
Answer: E
Difficulty: 1
Topic: Peptides and the Peptide Bond
18) The conversion of ________ represents a conservative change while the conversion of
________ represents a nonconservative change.
A) Asp to Arg;
B) Tyr to Phe;
C) Gln to Asn;
D) Ile to Leu;
E) Cys to His;
Ile to Ser
Lys to Arg
Ser to Thr
Asn to Ala
Lys to Glu
Answer: D
Difficulty: 2
Topic:
Proteins: Polypeptides of Defined Sequence
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19) The peptide hormone insulin is composed of two peptide held together primarily by what
mechanism?
A) disulfide bonds between cysteine residues
B) charge-charge interactions between acidic and basic amino acids
C) extensive hydrogen bonding due to the relatively high serine and glutamine content
D) hydrophobic interactions
E) an amide bond formed from the R-groups of a glutamic acid residue and a lysine residue
Answer: A
Difficulty: 1
Topic: Proteins: Polypeptides of Defined Sequence
20) Which of the following events occurs after the formation of disulfide bonds during the
conversion of preproinsulin to mature insulin?
A) folding of proinsulin into a stable conformation
B) transport of the molecule through the membranes
C) cleavage of the peptide sequence that joins the A and B chains
D) cleavage of the leader sequence
E) posttranslational modification of specific proline residues
Answer: C
Difficulty: 1
Topic:
From Gene to Protein
21) Which of the following pairs of amino acids represents a conservation of the type of amino
acid when considering the sequence of a protein from different species?
A) Asp and Asn
B) Lys and His
C) Leu and Val
D) Gly and Ile
E) Phe and Trp
Answer: C
Difficulty: 2
Topic:
Protein Sequence Homology
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22) In the sequence of cytochrome c, the presence of cysteine at position 17 in hundreds of
different species indicates that this particular amino acid is _________.
A) conserved
B) mutated
C) homologous
D) variable
E) none of the above
Answer: A
Difficulty: 1
Topic:
Protein Sequence Homology
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Short Answer Questions
1) What is the pI for the following peptide: Ala-Glu-Val-Asp-Lys-Leu
Answer: Use R-groups of Glu and Asp:
Difficulty: 1
Topic:
(4.2 + 3.9)/2 = 4.05 (4.1 using correct SF)
Amino Acids
2) Draw each of the structures of aspartic acid that predominate at pH 1, 3, 7, and 11.
Answer:
1
Difficulty: 2
3
7
Topic:
Amino Acids
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11
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3) A peptide was treated with protease enzymes and cyanogen bromide followed by complete
hydrolysis of the resulting products. Based upon the following data, determine the sequence
of the original peptide.
Chymotrypsin gave two peptides containing the following amino acids:
Leu, Pro
Asp, Gln, Arg, Met, Tyr, Val
Cyanogen bromide gave two peptides containing the following amino acids:
Asp, Met
Gln, Leu, Arg, Tyr, Pro, Val
Trypsin gave two peptides containing the following amino acids:
Gln, Leu, Tyr, Pro
Asp, Arg, Met, Val
Answer:
Chymotrypsin treatment shows the C-term 3 amino acids to be Tyr-Pro-Leu
Cyanogen bromide treatment shows that the N-term is Asp-Met
Trypsin places Arg giving the overall peptide as Asp-Met-Val-Arg-Gln-Tyr-Pro-Leu
Difficulty:
3
Topic:
Peptides and the Peptide Bond
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