Deck 22: Amino Acids, Peptides, and Proteins

Question 1

Name the following compound.

A)cysteine
B)threonine
C)methionine
D)serine
E)asparagine

Answer 1

methionine

Question 2

Draw glutamate.

Answer 2

Question 3

Which of the following molecules is the skeletal structure of an amino acid?

A)
B)
C)
D)
E)

Answer 3

Question 4

Which of the following amino acids is not an aromatic compound?

A)phenylalanine
B)threonine
C)histidine
D)tryptophan
E)tyrosine

Question 5

Which of the following amino acids has an aliphatic R group?

A)serine
B)cysteine
C)asparagine
D)tyrosine
E)leucine

Question 6

Provide the Fischer projection of L-aspartic acid.

Question 7

What is the net charge of arginine in a solution of pH 1.0?

Question 8

Draw the form of L-tryptophan which is present at biological pH.

Question 9

Which of the following amino acids has a sulfur in the R group?

A)serine
B)cysteine
C)asparagine
D)tyrosine
E)leucine

Question 10

Which of the following is an L-amino acid?

A)I
B)II
C)III
D)IV
E)V

Question 11

Name the following compound.

A)tyrosine
B)lysine
C)arginine
D)histidine
E)phenylalanine

Question 12

Draw and name the amino acids which may be described as heterocyclic.

Question 13

Name the following compound.

A)alanine
B)leucine
C)valine
D)glycine
E)isoleucine

Question 14

Which of the following amino acids has an aromatic R group?

A)serine
B)cysteine
C)asparagine
D)tyrosine
E)leucine

Question 15

In nature, which is the most commonly found isomer, L-amino acids or D-amino acids?

Question 16

Draw the form of L-lysine which is present at biological pH.

Question 17

Which of the following terms best describes the side chain of valine?

A)acidic
B)basic
C)charged, polar
D)uncharged, polar
E)nonpolar

Question 18

Which of the following amino acids has a heterocyclic R group?

A)glycine
B)threonine
C)proline
D)aspartic acid
E)arginine

Question 19

The α-carbon of all the amino acids is a chirality center except for ________.

A)glycine
B)threonine
C)proline
D)aspartic acid
E)arginine

Question 20

Explain what essential amino acids are and list all of them.

Question 21

Which of the following amino acids has the highest isoelectric point?

A)arginine
B)aspartic acid
C)glycine
D)proline
E)phenylalanine

Question 22

Which of the following amino acids has a side chain with an ionizable proton and can exist in four different forms, depending on the pH of the solution?

A)I
B)II
C)III
D)IV
E)V

Question 23

What is the pI of glycine? The structure and pKa values are shown below.

A)7)26
B)5)97
C)3)63
D)7)50
E)11.94

Question 24

Which of the following best describes the side chain of arginine at a pH of 11?

A)hydrophobic
B)nonpolar
C)charged and polar
D)uncharged but polar
E)aprotic

Question 25

Draw the predominant form of histidine at pH=0.

Question 26

What is thin-layer chromatography?

A)a technique that separates amino acids on the basis of their polarity
B)a technique that separates amino acids on the basis of their solubility in water
C)a technique that separates amino acids on the basis of their pI values
D)a technique that separates amino acids on the basis of pKa of α-COOH values
E)a technique that separates amino acids on the basis of pKa of α-⁺NH₃ values

Question 27

Which of the following amino acids has its isoelectric point at the lowest pH?

A)glutamic acid
B)lysine
C)valine
D)glycine
E)methionine

Question 28

Draw the predominant form of proline at pH=12.

Question 29

What is the pI of arginine? The structure and pKa values are shown below.

A)10.76
B)7)90
C)5)61
D)7)33
E)9)67

Question 30

Which of the following amino acids will be retained longest in the column when separated by cation-exchange chromatography?

A)I
B)II
C)III
D)IV
E)V

Question 31

Give the pH at which histidine exists in the following form.

A)0
B)4
C)8
D)12
E)14

Question 32

Define what is meant by isoelectric point (pI)and give an example.

Question 33

Which of the following is a zwitterion?

A)
B)
C)
D)
E)

Question 34

Draw the predominant form of aspartate at physiological pH.

Question 35

Calculate the isoelectric point for the following compound.

A)3)22
B)5)34
C)5)93
D)6)91
E)9)67

Question 36

Which of the following amino acids will be closest to the origin when separated by thin-layer chromatography?

A)I
B)II
C)III
D)IV
E)V

Question 37

Which of the following best represents the structure of an amino acid in basic solution (pH = 11)?

A)
B)
C)
D)
E)

Question 38

What is electrophoresis?

A)a technique that separates amino acids on the basis of their polarity
B)a technique that separates amino acids on the basis of their solubility in water
C)a technique that separates amino acids on the basis of their pI values
D)a technique that separates amino acids on the basis of pKa of α-COOH values
E)a technique that separates amino acids on the basis of pKa of α-⁺NH₃ values

Question 39

Draw the form in which glutamate exists at pH = 0.

Question 40

Draw structures for the forms of glycine present in basic, neutral, and acidic solutions.

Question 41

You are given a mixture that contains glutamic acid (pI = 3.2), arginine (pI = 10.8), and valine (pI = 6.0), and you subject the mixture to electrophoresis.
a) Which amino acids migrate toward the cathode when the electrophoresis is carried out at a pH of 7.1?
b) Which amino acids migrate toward the anode when the electrophoresis is carried out at a pH of 7.1?
c) Which amino acid migrates farthest toward the anode at a pH of 7.1?
d) Since amino acids themselves are colorless, how is the separation of amino acids after electrophoresis detected?

Question 42

What is the major organic product of the following reaction?

A)
B)
C)
D)
E)

Question 43

Describe how electrophoresis works.

Question 44

Provide the major organic product(s)of the reaction below.

Question 45

What is the name of the amino acid produced when propanoic acid is subjected to the following sequence of reagents:? 1. PBr₃, Br₂;
2) H₂O;
3) NH₃, Δ?

A)alanine
B)aspartic acid
C)glutamic acid
D)valine
E)asparagine

Question 46

What is an amino acid analyzer?

Question 47

Give the product for the following reaction.

A)alanine
B)leucine
C)valine
D)isoleucine
E)glycine

Question 48

Explain what is meant by kinetic resolution and give an example.

Question 49

Provide the major organic product(s)of the reaction below.

Question 50

Give the product for the following reaction.

A)alanine
B)leucine
C)valine
D)isoleucine
E)glycine

Question 51

Rate the following amino acids in decreasing order of migration towards the cathode (negative electrode)when separated by electrophoresis in a solution of pH= 7.3.
I. lysine: pI= 9.87
II. alanine: pI= 6.02
III. aspartate: pI= 5.95

Question 52

Give the product for the following reaction.

Question 53

Give the product for the following reaction.

A)alanine
B)leucine
C)valine
D)isoleucine
E)glycine

Question 54

Give the product for the following reaction.

A)alanine
B)leucine
C)valine
D)isoleucine
E)glycine

Question 55

Which of the following is an acceptable name for the peptide sequence shown below? Glu-Glu-His-Val-Cys

A)1,2-diglutamylhistidylvalylcysteine
B)glutamylglutamylhistidylvalylcysteine
C)1-glutamyl-2-glutamylhistidylvalylcysteine
D)diglutamylhistidylvalylcysteine
E)biglutamylhistidylvalylcysteine

Question 56

What is the product obtained from the mild oxidation of the thiol shown below? mild
2 R-SH

A)R-S-R
B)R-OH
C)R-S-S-R
D)R-OO-R
E)R-S-OH

Question 57

What amino acid can be obtained by the reductive amination of γ-ketoglutaric acid, HO₂CCH₂CH₂COCO₂H?

A)glycine
B)serine
C)lysine
D)aspartic acid
E)glutamic acid

Question 58

Provide the major organic product(s)of the reaction below.

Question 59

Which labeled bond in the following molecule is known as the peptide bond?

A)1
B)2
C)3
D)4
E)5

Question 60

Rank the following amino acids in order of time of elution from a cation-exchange resin and a buffer pH of 4.0: aspartic acid, phenylalanine, arginine, and alanine.

Question 61

Explain the importance of the Merrifield method in peptide synthesis.

Question 62

Draw the dipeptide Val-Tyr at pH 7.0.

Question 63

Provide the structure of the tripeptide val-gly-ser at pH 2.

Question 64

In peptide synthesis, give the use of trifluoroacetic acid.

A)activates the carboxyl group of an amino acid
B)protects the carboxyl group of an amino acid
C)protects the amino group of an amino acid
D)activates the amino group of an amino acid
E)removes the protecting group on the N-terminal amino acid

Question 65

Which of the following structures can polypeptides have?

A)primary structure
B)secondary structure
C)tertiary structure
D)quaternary structure
E)all of the above

Question 66

Provide the structure of the tripeptide val-gly-ser at biological pH.

Question 67

Give the product for the following reaction.

A)
B)
C)
D)
E)

Question 68

Which type of protein, globular or fibrous, tends to function primarily as structural parts of an organism?

Question 69

In peptide synthesis, give the use of di-tert-butyl dicarbonate.

A)activates the carboxyl group of an amino acid
B)protects the carboxyl group of an amino acid
C)protects the amino group of an amino acid
D)activates the amino group of an amino acid
E)removes the protecting group on the N-terminal amino acid

Question 70

Provide the structure of the tripeptide glu-ser-ala at pH 2.

Question 71

Provide the structure of Thr-Gln-Met at pH 7.0.

Question 72

Draw the structure of the tetrapeptide Ser-Leu-Phe-Pro at pH 7.0.

Question 73

Provide the structure of Ala-Ser-Gly at biological pH.

Question 74

In conventional peptide synthesis, the nitrogen of a given amino acid must be deactivated or blocked while the carboxyl group is activated. Which of the following reagents is used to protect the amino group of an amino acid?

A)di-tert-butyl dicarbonate
B)dicyclohexylcarbodiimide
C)ninhydrin
D)trifluoroacetic acid
E)phenylisothiocyanate

Question 75

When a disulfide linkage is formed, the compound containing this new linkage has been ________.

A)hydrolyzed
B)dehydrated
C)electrolyzed
D)oxidized
E)reduced

Question 76

Provide the structure of the tripeptide glu-ser-ala at pH 12.

Question 77

In peptide synthesis, give the use of dicyclohexylcarbodiimide.

A)activates the carboxyl group of an amino acid
B)protects the carboxyl group of an amino acid
C)protects the amino group of an amino acid
D)activates the amino group of an amino acid
E)removes the protecting group on the N-terminal amino acid

Question 78

Provide the structure of the tripeptide val-gly-ser at pH 12.

Question 79

Explain the chemistry behind giving a "permanent" to a head of hair.

Question 80

Give a detailed, stepwise mechanism for the formation of the activated acyl derivative from the reaction of an amino acid with N,N'-dicyclohexylcarbodiimide.