Deck 24: Amino Acids, Peptides, and Proteins

Question 1

Which of the following amino acids does not have an aromatic substructure within its side chain?

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

Answer 1

proline

Question 2

Provide the single letter code for the following peptide
Arg-Phe-Tyr-Cys-Asp-Trp-Gln-Ala-Glu-Glu-His-Lys

Answer 2

RFYCDWQAEEHK

Question 3

Nearly all naturally occurring amino acids:

A) are racemic mixtures.
B) are achiral.
C) have the (R) configuration at the α-carbon.
D) have the (S) configuration at the α-carbon.
E) have basic side chains.

Answer 3

have the (S) configuration at the α-carbon.

Question 4

Proteins which provide all the essential amino acids in about the right proportions are called:

A) globular proteins.
B) enzymes.
C) complete proteins.
D) glycoproteins.
E) nucleoproteins.

Question 5

If the side chain of asparagine is hydrolyzed, what amino acid is formed?

Question 6

Provide the Fischer projection of L-aspartic acid.

Question 7

Which of the following amino acids has its α-carbon as part of a 5-membered ring?

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

Question 8

Which of the following amino acids has a nonpolar side chain?

A) serine
B) aspartic acid
C) asparagine
D) threonine
E) leucine

Question 9

Peptide bonds are:

A) ester linkages.
B) imido linkages.
C) ether linkages.
D) amide linkages.
E) disulfide linkages.

Question 10

Which amino acid has an amide group in its side chain?

A) tyrosine
B) tryptophan
C) isoleucine
D) asparagine
E) histidine

Question 11

What is the one letter symbol of the amino acid below?

A) G
B) Q
C) W
D) T
E) F

Question 12

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 13

Which of the following amino acids has a side chain which contains a nonbasic nitrogen?

A) proline
B) glutamine
C) histidine
D) tyrosine
E) lysine

Question 14

Which amino acid has a phenol in its side chain?

A) tyrosine
B) tryptophan
C) isoleucine
D) asparagine
E) histidine

Question 15

Which amino acid has an indole ring in its side chain?

A) tyrosine
B) tryptophan
C) isoleucine
D) asparagine
E) histidine

Question 16

What is the one letter symbol of the amino acid below?

A) G
B) Q
C) W
D) R
E) M

Question 17

Which of the following amino acids does not contain an aromatic R-group?

A) tyrosine
B) phenylalanine
C) tryptophan
D) histidine
E) none of the above

Question 18

Which of the standard amino acids is achiral?

A) lysine
B) proline
C) valine
D) alanine
E) glycine

Question 19

Which amino acid has an imidazole ring in its side chain?

A) tyrosine
B) tryptophan
C) isoleucine
D) asparagine
E) histidine

Question 20

How many standard amino acids are there?

A) 4
B) 12
C) 20
D) 30
E) 64

Question 21

Which amino acid's side chain is negatively charged at biological pH?

A) arginine
B) tyrosine
C) aspartic acid
D) serine
E) glutamine

Question 22

Provide the structure of the predominant form of lysine present in an aqueous solution at biological pH.

Question 23

Which of the following amino acids are classified as essential amino acids?
(More than one answer is possible.)

A) isoleucine
B) proline
C) tryptophan
D) histidine

Question 24

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

Question 25

Provide the structure of L-arginine at pH 2.0.

Question 26

Draw the Fischer projection of L-glutamic acid at a pH of 2.

Question 27

Which of the following reagents can be used to convert disulfide bridges into cysteic acid residues?

A) HCO₃H
B) Zn, HCl
C) PhNCS
D) PhCH₂OCOCl
E) CH₃I

Question 28

Provide the structure of L-aspartic acid at pH 12.0.

Question 29

Draw the Fischer projection of L-valine at a pH of 12.

Question 30

Draw the Fischer projection of L-valine at a pH of 2.

Question 31

Provide the structure of the predominant form of alanine present in an aqueous solution at a pH of 2.0.

Question 32

Amino acids have:

A) high melting points and low solubility in water.
B) large dipole moments and are more acidic than most carboxylic acids.
C) high melting points and large dipole moments.
D) low solubility in water and small dipole moments.
E) small dipole moments and are hydrophobic.

Question 33

Which amino acid's side chain is positively charged at biological pH?

A) arginine
B) tyrosine
C) aspartic acid
D) serine
E) glutamine

Question 34

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

Question 35

Addition of alanine to distilled water will produce:

A) a slightly basic solution.
B) denaturation.
C) a neutral solution.
D) a slightly acidic solution.
E) hydrolysis.

Question 36

Draw the Fischer projection of L-glutamic acid at a pH of 12.

Question 37

Provide the structure of the predominant form of glutamine present in an aqueous solution at a pH of 12.0.

Question 38

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

Question 39

Most naturally occurring amino acids are L-amino acids. Does this mean they are levorotatory? Explain.

Question 40

Provide the structure of L-valine at pH 12.0.

Question 41

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

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

Question 42

Provide a synthesis of racemic valine from 3-methylbutanoic acid.

Question 43

The isoelectric point is important in:

A) the enzymatic resolution of amino acids.
B) electrophoresis.
C) determination of the C-terminal amino acid.
D) determination of the N-terminal amino acid.
E) the ninhydrin test.

Question 44

Provide the structure of the predominant form of L-valine present in an aqueous solution at biological pH.

Question 45

Describe how electrophoresis works.

Question 46

In an electrophoresis carried out at pH 9.0, does phenylalanine migrate toward the cathode, migrate toward the anode, or not migrate at all? Explain briefly.

Question 47

What is the net charge of arginine in a solution of pH 10.0?

Question 48

Given the following pKa values, what is the major ionization state of histidine at pH 11? (α-COOH = 2.0, α-NH₃⁺ = 9.0 and R-group imine = 6.5)

A)

B)

C)

D)

E)

Question 49

Provide the structure of the predominant form of L-methionine present in an aqueous solution at biological pH.

Question 50

Provide the structure of the predominant form of L-phenylalanine present in an aqueous solution at biological pH.

Question 51

What is the isoelectric point of lysine within in +/- 1 pH unit?

A) 3
B) 6
C) 9
D) 12

Question 52

Provide the structure of the predominant form of L-alanine present in an aqueous solution at pH 2.

Question 53

Provide the structure of the predominant form of L-leucine present in an aqueous solution at pH 2.

Question 54

A solution of glycine has a pH equal to the pKa1 of glycine. What forms of glycine are present and in what ratio?

Question 55

Which of the following amino acids has an isoelectric pH of 3.2?

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

Question 56

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

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

Question 57

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

A) glycine
B) aspartic acid
C) valine
D) arginine
E) methionine

Question 58

Provide a reasonable synthesis of PhCH₂CH(NH₃⁺)CO₂H from BrCH(CO₂CH₂CH₃)₂.

Question 59

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

A) arginine
B) aspartic acid
C) valine
D) glycine
E) methionine

Question 60

Provide a reasonable synthesis of racemic alanine from ethanol.

Question 61

What is the major end product of the following reaction series?

A) Ala
B) Gly
C) Leu
D) Ile
E) Val

Question 62

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 63

A polypeptide was treated with a certain enzyme to yield the following amino acid sequences. What enzyme was used to induce the observed fragmentations?
Val-Pro-Phe Leu-Ser-Lys-Glu-Trp $~~~~~~~~$$~~~~~~~~$ Arg-Ile-Ser-Ser-Leu-Tyr

Question 64

Show the step-wise synthesis of glutamic acid starting with α-ketoglutarate and ammonia.

Question 65

Disulfide linkages can form between:

A) two cysteine residues.
B) two methionine residues.
C) a cysteine residue and a methionine residue.
D) two threonine residues.
E) a methionine residue and a threonine residue.

Question 66

Which of the following reagents are commonly used to acylate the amino group of an amino acid?

A) both acetic anhydride and benzyl chloroformate
B) both benzyl chloroformate and α-bromoacetic acid
C) both α-bromoacetic acid and tosyl chloride
D) both tosyl chloride and acetic anhydride
E) both benzyl chloroformate and tosyl chloride

Question 67

How can an α-ketoacid be converted to an α-aminoacid?

Question 68

Provide the necessary reagents to convert propionic acid to alanine.

Question 69

Provide the structure of the major organic product which results when L-phenylalanine is treated with a large excess of PhCH₂OH and gaseous HCl.

Question 70

Which of the following indicators is commonly used to visualize bands of amino acids?

A) ninhydrin
B) bromocresol green
C) potassium permanganate
D) vanillin dip

Question 71

Suggest a method for resolving a racemic acid.

Question 72

Which of the following will result in removal of a benzyl ester protecting group?

A) acid hydrolysis only
B) decarbonylation only
C) catalytic hydrogenation only
D) both acid hydrolysis and decarbonylation
E) both catalytic hydrogenation and acid hydrolysis

Question 73

Show how 3-methylthiopropanal may be converted to methionine.

Question 74

Amides are:

A) the most reactive acid derivative.
B) the most acidic acid derivative.
C) the most stable acid derivative.
D) the least stable acid derivative.
E) both A and D

Question 75

Provide the major organic product in the reaction of L-methionine with benzyl chloroformate.

Question 76

The nonprotein part of a conjugated protein is called a ________ group.

Question 77

In biosynthesis, which amino acid serves as the source of the amino group for other amino acids?

A) D-phenylalanine
B) L-phenylalanine
C) racemic phenylalanine
D) SL-glutamic acid
E) D-glutamic acid

Question 78

Draw the dipeptide Val-Tyr.

Question 79

Provide a synthesis of isoleucine from N-phthalimidomalonic ester.

Question 80

Provide a detailed, stepwise mechanism for the Strecker synthesis of racemic alanine from acetaldehyde.