Question 1

What fragments will be obtained by a trypsin hydrolysis of the following octapeptide? Ala-Val-Trp-Lys-Phe-Gly-Arg-Met

Accepted Answer

A)   Ala-Val-Trp-Lys-Phe and Gly-Arg-Met
B)   Ala-Val-Trp-Lys-Phe -Gly and Arg-Met
C)   Ala-Val-Trp-Lys and Phe-Gly-Arg and Met
D)   Ala-Val-Trp-Lys and Phe and Gly-Arg and Met
E)   Ala-Val-Trp and Lys-Phe-Gly and Arg-MetF) C) and D)
G) A) and C)

Question 2

What is the name of the amide bond linking two amino acids?

Accepted Answer

A)   ionic
B)   hydrogen
C)   glycosidic
D)   nonpolar
E)   peptideF) C) and D)
G) C) and E)

Question 3

Which of the following will migrate toward the positive electrode in an electrophoresis experiment?

Accepted Answer

A)   I
B)   II
C)   III
D)   I and III
E)   none will migrateF) B) and D)
G) All of the above B

Question 4

Which molecule is an  α\alphaα -amino acid?

Accepted Answer

A)   
B)   
C)   
D)   
E)    F) All of the above
G) None of the above

Question 5

Which of the following molecules is  α\alphaα -aminopropanoic acid?

Accepted Answer

A)   
B)   
C)   
D)   
E)    F) B) and C)
G) A) and D)

Question 6

Based on the equilibria shown below, what is the net charge on structure IV?   A)  -2 B)  -1 C)  0 D)  +1 E)  +2" class="answers-bank-image d-inline" rel="preload" >

Accepted Answer

A)   -2
B)   -1
C)   0
D)   +1
E)   +2F) A) and B)
G) A) and C)

Question 7

At the isoelectric point, the structure of methionine (2-amino-4-methylthiobutanoic acid)  is:

Accepted Answer

A)   
B)   
C)   
D)   
E)   F) B) and E)
G) A) and D)

Question 8

The reaction of  with bromine water is likely to give:

Accepted Answer

A)   
B)   
C)   
D)   
E)   F) B) and C)
G) C) and D)

Question 9

Which reagent is used to determine the N-terminal amino acid of a peptide?

Accepted Answer

A)   Jones'
B)   Fehling's
C)   Ninhydrin
D)   Sanger's
E)   Tollens'F) C) and D)
G) B) and D)

Question 10

Which reagent is used specifically to cleave the C-terminal amino acid of a peptide?

Accepted Answer

A)   trypsin
B)   carboxypeptidase
C)   cyanogen bromide
D)   chymotrypsin
E)   HCl/H2OF) B) and D)
G) C) and D)

Question 11

A tetrapeptide contains the amino acids Phe, Ala, Gly, and Leu.Partial hydrolysis affords the dipeptides Phe-Ala, Ala-Gly, and Leu-Phe.The structure of the tetrapeptide is

Accepted Answer

A)   Ala-Gly-Leu-Phe.
B)   Leu-Phe-Ala-Gly.
C)   Gly-Ala-Phe-Leu.
D)   Leu-Phe-Gly-Ala.
E)   Phe-Leu-Gly-Ala.F) B) and C)
G) D) and E)

Question 12

If an amino acid has one carboxyl group and one amino group, and the pKa's are 2.4 and 9.8 respectively, what is its isoelectric point?

Accepted Answer

A)   3.7
B)   6.1
C)   7.0
D)   7.9
E)   12.2F) A) and B)
G) A) and C)

Question 13

What is the net charge of isoleucine at its isoelectric point?

Accepted Answer

A)   0
B)   +1
C)   +2
D)   -1
E)   -2F) B) and E)
G) A) and E)

Question 14

The mechanism by which Sanger's reagent reacts with an amine is

Accepted Answer

A)   nucleophilic aromatic substitution.
B)   electrophilic aromatic substitution.
C)   hydrolysis.
D)   nucleophilic acyl substitution.
E)   electrophilic addition.F) A) and E)
G) B) and C) A

Question 15

Which of the following  α\alphaα -amino acids contains an imidazole?

Accepted Answer

A)   arginine
B)   asparagine
C)   aspartic acid
D)   histidine
E)   tyrosine F) B) and D)
G) C) and E) D

Question 16

Which of the following reagents is used to protect the N-terminal amino acid in a solid phase peptide synthesis?

Accepted Answer

A)   
B)   
C)   
D)   
E)   F) B) and C)
G) A) and B)

Question 17

In the dipeptide shown the following segment of the molecule is likely to lie in a single plane:

Accepted Answer

A)   
B)   
C)   
D)   
E)   F) A) and D)
G) A) and C)

Question 18

The dipeptides  are

Accepted Answer

A)   constitutional isomers.
B)   stereoisomers.
C)   diastereoisomers.
D)   enantiomers.
E)   identical.F) B) and D)
G) A) and B)

Question 19

Dicyclohexylcarbodiimide (DCC)  is used

Accepted Answer

A)   to determine the N-terminal amino acid of a peptide.
B)   to sequence amino acids in a peptide.
C)   to detect amino acids derived from hydrolysis of a peptide.
D)   to couple amino acids during solid-phase peptide synthesis.
E)   to hydrolyze peptides on the carboxyl side of aromatic amino acid residues.F) A) and E)
G) C) and D)

Question 20

In the octapeptide, Phe-Ile-Ser-Asp-Gly-His-Gly-Tyr, which is the C-terminal amino acid?

Accepted Answer

A)   Ser
B)   Phe
C)   Tyr
D)   His
E)   GlyF) B) and D)
G) B) and C)

Exam 17: Amino Acids, Peptides, and Proteins

What fragments will be obtained by a trypsin hydrolysis of the following octapeptide? Ala-Val-Trp-Lys-Phe-Gly-Arg-Met

Correct AnswerverifiedShow Answer

What is the name of the amide bond linking two amino acids?

Correct AnswerverifiedShow Answer

Which of the following will migrate toward the positive electrode in an electrophoresis experiment?

Correct AnswerverifiedB

Which molecule is an α\alphaα -amino acid?

Correct AnswerverifiedShow Answer

Which of the following molecules is α\alphaα -aminopropanoic acid?

Correct AnswerverifiedShow Answer

Based on the equilibria shown below, what is the net charge on structure IV?

Correct AnswerverifiedShow Answer

At the isoelectric point, the structure of methionine (2-amino-4-methylthiobutanoic acid) is:

Correct AnswerverifiedShow Answer

The reaction of with bromine water is likely to give:

Correct AnswerverifiedShow Answer

Which reagent is used to determine the N-terminal amino acid of a peptide?

Correct AnswerverifiedShow Answer

Which reagent is used specifically to cleave the C-terminal amino acid of a peptide?

Correct AnswerverifiedShow Answer

A tetrapeptide contains the amino acids Phe, Ala, Gly, and Leu.Partial hydrolysis affords the dipeptides Phe-Ala, Ala-Gly, and Leu-Phe.The structure of the tetrapeptide is

Correct AnswerverifiedShow Answer

If an amino acid has one carboxyl group and one amino group, and the pKa's are 2.4 and 9.8 respectively, what is its isoelectric point?

Correct AnswerverifiedShow Answer

What is the net charge of isoleucine at its isoelectric point?

Correct AnswerverifiedShow Answer

The mechanism by which Sanger's reagent reacts with an amine is

Correct AnswerverifiedA

Which of the following α\alphaα -amino acids contains an imidazole?

Correct AnswerverifiedD

Which of the following reagents is used to protect the N-terminal amino acid in a solid phase peptide synthesis?

Correct AnswerverifiedShow Answer

In the dipeptide shown the following segment of the molecule is likely to lie in a single plane:

Correct AnswerverifiedShow Answer

The dipeptides are

Correct AnswerverifiedShow Answer

Dicyclohexylcarbodiimide (DCC) is used

Correct AnswerverifiedShow Answer

In the octapeptide, Phe-Ile-Ser-Asp-Gly-His-Gly-Tyr, which is the C-terminal amino acid?

Correct AnswerverifiedShow Answer

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B

Which molecule is an $\alpha$ -amino acid?

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Which of the following molecules is $\alpha$ -aminopropanoic acid?

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A

Which of the following $\alpha$ -amino acids contains an imidazole?

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D

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