Deck 24: Amino Acids, Peptides, and Proteins

Question 1

Which amino acid has a phenol in its side chain?

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

Answer 1

tyrosine

Question 2

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

Answer 2

none of the above

Question 3

How many standard amino acids are there?

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

Answer 3

20

Question 4

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

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

Question 5

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 6

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

Question 7

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

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

Question 8

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

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

Question 9

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

Question 10

Which of the standard amino acids is achiral?

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

Question 11

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

Question 12

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

Question 13

Provide the Fischer projection of L-aspartic acid.

Question 14

Peptide bonds are ________.

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

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

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

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

Question 17

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 18

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

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

Question 19

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 20

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 21

Which amino acid's side chain is positively charged at biological pH, pH = 7.4?

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

Question 22

Draw the form of L-tryptophan which is present at biological pH, pH = 7.4.

Question 23

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

Question 24

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 25

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

Question 26

Provide the structure of L-arginine at pH 2.0.

Question 27

Provide the structure of L-valine at pH 12.0.

Question 28

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

Question 29

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

Question 30

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 31

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 32

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

Question 33

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

Question 34

The pI of alanine is 6.0. Draw the structure for the predominant form of leucine that exists in:
a. an aqueous solution of pH = 4.0
b. an aqueous solution of pH = 6.0
c. an aqueous solution of pH = 8.0

Question 35

Which amino acid's side chain is negatively charged at biological pH, pH = 7.4?

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

Question 36

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

Question 37

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

Question 38

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 39

Draw the form of L-lysine which is present at biological pH, pH = 7.4.

Question 40

Provide the structure of the predominant form of lysine present in an aqueous solution at biological pH, pH = 7.4.

Question 41

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 42

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 43

Which of the following structures is the neutral form of L-serine?

A)
B)
C)
D) B and C

Question 44

Provide the structure of the predominant form of L-phenylalanine present in an aqueous solution at biological pH, pH = 7.4.

Question 45

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

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

Question 46

Describe how electrophoresis works.

Question 47

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 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

Draw the neutral form of L-phenylalanine in a line-wedge structure with the appropriate stereochemistry.

Question 50

Provide a reasonable synthesis of racemic alanine from ethanol.

Question 51

What would you start with when making phenyl alanine using the Strecker Synthesis?

Question 52

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

Question 53

Provide the structure of the predominant form of L-valine present in an aqueous solution at biological pH, pH = 7.4.

Question 54

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

Question 55

Provide the structure of the predominant form of L-methionine present in an aqueous solution at biological pH, pH = 7.4.

Question 56

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

Question 57

If the pI of amino acids with alkyl group side chains is 6.0, the pI of aspartic acid is ________.

A) larger than 6.0
B) equal to 6.0
C) smaller than 6.0
D) less than 0.0

Question 58

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

Even though we often write the structure of glycine as NH₂CHCOOH, why does this not accurately represent the structure of the amino acid?

Question 61

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 62

Suggest a method for resolving a racemic acid.

Question 63

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

Question 64

Show how 3-methylthiopropanal may be converted to methionine.

Question 65

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 66

What is the name of the amino acid produced when propanoic acid is subjected to the following sequence of reagents:

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

Question 67

Provide the necessary reagents to convert propionic acid to alanine.

Question 68

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 69

A student proposed to make aspartic acid from succinic acid using Br₂/PBr₃, then adding a large excess of NH₃. Why might this synthesis not work?

Question 70

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 71

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 72

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) L-glutamic acid
E) D-glutamic acid

Question 73

How would you make tryptophan using the Strecker Synthesis?

Question 74

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

Question 75

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

Question 76

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

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

Question 77

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

Question 78

Could L-proline be made using reductive amination? If so, show the starting material. If not, explain why.

Question 79

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 80

Draw the dipeptide Val-Tyr.