Deck 24: Amino Acids and Proteins

Question 1

Which of these natural amino acids contains an indole ring?

A)Phenylalanine
B)Tyrosine
C)Tryptophan
D)4-Hydroxyproline
E)Asparigine

Answer 1

Tryptophan

Question 2

Which of these natural amino acids contains a phenolic group?

A)Phenylalanine
B)Tyrosine
C)Tryptophan
D)4-Hydroxyproline
E)Serine

Answer 2

Tyrosine

Question 3

Which of these natural amino acids,when present in a polypeptide,is not likely to exhibit significant hydrogen bonding through its side chain?

A)Leucine
B)Threonine
C)Tyrosine
D)Serine
E)All of these are likely to exhibit significant hydrogen bonding through the side chain.

Answer 3

Leucine

Question 4

Which of these amino acids has the R configuration at the stereogenic center but,nonetheless,is an L amino acid?

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

Question 5

Which of the following amino acids is theoretically capable of existing in diastereomeric forms?

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

Question 6

Which amino acid is achiral?

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

Question 7

Which of these natural amino acids contains two carboxylic acid groups?

A)Aspartic acid
B)Cysteine
C)Glutamic acid
D)Cystine and cysteine
E)Aspartic acidand glutamic acid

Question 8

Which of these natural amino acids contains an amide function?

A)Asparagine
B)Proline
C)Arginine
D)Histidine
E)None of these choices.

Question 9

Which of these natural amino acids,when present in a polypeptide,is likely to exhibit significant hydrogen bonding through its side chain?

A)Serine
B)Threonine
C)Tyrosine
D)Two of these choices.
E)All of these choices.

Question 10

Which of these amino acids is(are)R amino acid(s)?

A)II and IV
B)IV and V
C)I and III
D)V
E)All of these are R amino acids.

Question 11

Which of these natural amino acids contains a pyrrolidine ring?

A)Phenylalanine
B)Tyrosine
C)Tryptophan
D)4-Hydroxyproline
E)Serine

Question 12

Which of these natural amino acids contains an imidazole ring?

A)Histidine
B)Lysine
C)Tryptophan
D)4-Hydroxyproline
E)Two of these choices.

Question 13

Which of these natural amino acids contains an -OH group?

A)Serine
B)Threonine
C)Tyrosine
D)Two of these.
E)All of these choices.

Question 14

Which of these natural amino acids contains an amide function?

A)Asparagine
B)Glutamine
C)Methionine
D)Cysteine
E)Two of these

Question 15

Which of these amino acids cannot be described as an l-amino acid?

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

Question 16

Disulfide bonds in proteins:

A)result from an oxidation of thiols.
B)help to maintain the shape of proteins.
C)can be broken by reduction.
D)can link two cysteine amino acid residues.
E)All of these choices.

Question 17

Which of these amino acids contains a hydrophobic side chain?

A)Lysine
B)Serine
C)Methionine
D)Arginine
E)Cysteine

Question 18

Which of these amino acids is a D amino acid?

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

Question 19

Which of these natural amino acids contains a heterocyclic ring?

A)Asparagine
B)Proline
C)Arginine
D)Histidine
E)Proline and histidine

Question 20

Which amino acid is unlikely to be found in a natural protein?

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

Question 21

Which amino acid would have its isoelectric point near pH 10?

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

Question 22

What might be concluded upon determining that an unknown amino acid has its isoelectric point near pH 10?

A)It must have a hydrophobic side chain.
B)It must have a hydrophilic side chain.
C)Its side chain must contain more basic groups then acidic groups.
D)Its side chain must contain an acidic group.
E)None of these choices is a valid conclusion.

Question 23

The pH at which the concentration of the dipolar ion (zwitterion)form of an amino acid is at a maximum and the cationic and anionic forms are at equal concentrations is termed the

A)end point.
B)equivalence point.
C)neutral point.
D)isoelectric point.
E)dipolar point.

Question 24

What might be concluded upon determining that an unknown amino acid has its isoelectric point near pH 3?

A)It must have a hydrophobic side chain.
B)It must have a hydrophilic side chain.
C)Its side chain must contain a basic group.
D)Its side chain must contain more acidic groups then basic groups.
E)None of these choices is a valid conclusion.

Question 25

Logically,the following "unnatural" amino acid would be substituted for which natural amino acid in the synthesis of peptide analogs?

A)Methionine
B)Cysteine
C)Cystine
D)Tyrosine
E)It could be substituted for all of these amino acids.

Question 26

Which amino acid would not have its isoelectric point in the pH range 5-7?

A)Glycine
B)Proline
C)Cysteine
D)Glutamine
E)All of these amino acids have isoelectric point in the pH range 5-7

Question 27

Which amino acid would not have its isoelectric point in the pH range 5-7?

A)Leucine
B)Threonine
C)Methionine
D)Arginine
E)Cysteine

Question 28

Logically,the following "unnatural" amino acid would be substituted for which natural amino acid in the synthesis of peptide analogs?

A)Tyrosine
B)Proline
C)Tryptophan
D)Phenylalanine
E)Histidine

Question 29

Pipecolic acid logically would be substituted for which natural amino acid in the synthesis of peptide analogs?

A)Histidine
B)Proline
C)Tryptophan
D)Phenylalanine
E)Tyrosine

Question 30

What is the name of the aminoacids F; E; R,respectively:

A)Proline,aspartic acid,asparagine.
B)Proline,methionine,cysteine.
C)Phenylalanine,glutamic acid,arginine.
D)Proline,glutamic acid,glutamine.
E)Phenylalanine,asparagine,glutamine.

Question 31

Which of these amino acids is formed from a precursor amino acid only after the latter has been incorporated into a polypeptide chain?

A)Serine
B)Arginine
C)Isoleucine
D)Tryptophan
E)Hydroxyproline

Question 32

Which of these amino acids is described as an "essential" amino acid?

A)Threonine
B)Glycine
C)Tyrosine
D)Serine
E)All of these are "essential" amino acids.

Question 33

Logically,the following "unnatural" amino acid would be substituted for which natural amino acid in the synthesis of peptide analogs?

A)Leucine
B)Lysine
C)Arginine
D)Alanine
E)Valine

Question 34

What is the pI of the following amino acid?

A)2.1
B)5.9
C)3.2
D)6.5
E)7.0

Question 35

Logically,the following "unnatural" amino acid would be substituted for which natural amino acid in the synthesis of peptide analogs?

A)Aspartic acid
B)Glutamine
C)Lysine
D)Asparagine
E)Glutamic acid

Question 36

Which of the following sets of amino acids are essential amino acids:

A)Lysine,glutamic acid,asparagine.
B)Phenylalanine,threonine,lysine.
C)Threonine,tyrosine,tryptophan.
D)Proline,cysteine,hydroxyproline.
E)Arginine,histidine,lysine.

Question 37

Which amino acid would have its isoelectric point near pH 3?

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

Question 38

Which amino acid would have its isoelectric point near pH 10?

A)Glycine
B)Tryptophan
C)Serine
D)Proline
E)Lysine

Question 39

Which of these amino acids is described as an "essential" amino acid?

A)Methionine
B)Phenylalanine
C)Isoleucine
D)Tryptophan
E)All of these are "essential" amino acids.

Question 40

What is the pI of the following amino acid?

A)1.2
B)3.2
C)5.5
D)6.2
E)7.0

Question 41

What methods can be used for the identification of amino acids?

A)Amino acid analyzer using cation-exchange resin
B)Cation-exchange resin packed column in an HPLC instrument
C)Column chromatography on normal phase silica gel
D)Reaction with ninhydrin followed by IR spectroscopy
E)Two of these choices.

Question 42

Which is an isolable intermediate in the Strecker synthesis of an amino acid?

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

Question 43

What is the pI of the following amino acid?

A)12.0
B)3.6
C)4.8
D)6.0
E)7.2

Question 44

What is the product of the treatment of a racemic form of dl-phenylalanine with acetic anhydride followed by treatment with deacylase enzyme?

A)S-Phenylalanine
B)R-Phenylalanine
C)d-Phenylalanine
D)Both are hydrolyzed
E)The mixture is not affected by this enzyme.

Question 45

The purple color of the anion formed in the ninhydrin test for α-amino acids is due to:

A)the attraction of the anion to a metal in a pi-complex.
B)intermolecular hydrogen bonding.
C)molecular vibrations.
D)the highly conjugated nature of the anion.
E)the color of the ninhydrin.

Question 46

What is the pK_a of the carboxylic acids present in the following compounds in the given order:

A)10.1; 2.32; 4.45
B)2.32; 2.32; 5.00
C)4.45; 3.22; 4.75
D)2.32; 4.50; 4.75
E)3.47; 2.32; 4.45

Question 47

Which of the following would provide a synthesis of leucine?

A)(CH₃)₂C=CHCH₂OH,HBr/peroxides; then CrO₃/H₂SO₄/H₂O; then excess NH₃
B)Potassium phthalimide,BrCH(CO₂C₂H₅)₂; then (CH₃)₂CHCHClCO₂C₂H₅,NaOEt; then KOH/H₂O; then HCl,heat
C)Potassium phthalimide,BrCH(CO₂C₂H₅)₂; then (CH₃)₂CHCH₂Br,NaOEt; then KOH/H₂O; then HCl,heat
D)(CH₃)₂CHCOOH,PCl₅; then NH₃
E)Two of these choices.

Question 48

Which of the following would provide a synthesis of phenylalanine?

A)Phenylacetaldehyde,NH₃,HCN; then H₃O⁺ and heat
B)Potassium phthalimide,BrCH(CO₂C₂H₅)₂; C₆H₅CH₂Br,NaOEt; then NaOH; then HCl,heat
C)Potassium phthalimide,(C₆H₅)CH₂CH₂Br; then KOH/H₂O; then HCl,heat
D)C₆H₅CH₂COOH,SOCl₂; then NH₃
E)Two of these choices.

Question 49

What would be the predominant form of lysine in water at pH 14?

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

Question 50

What is the pI of phenylalanine (pK_a1 = 1.8; pK_a2= 9.1)?

A)2.3
B)1.8
C)5.5
D)9.1
E)10.9

Question 51

A heptapeptide Ala₂,Glu,Phe,Pro,Tyr,Val gives labeled alanine when heated with DNFB followed by hydrolysis.On partial hydrolysis the unlabeled heptapeptide gives the following: Ala·Glu,Pro·Tyr,Ala·Val,Tyr·Ala,Val·Phe·Pro.
What is the amino acid sequence of the heptapeptide?

A)Ala·Phe·Pro·Tyr·Ala·Glu·Val
B)Ala·Val·Phe·Pro·Tyr·Ala·Glu
C)Ala·Val·Phe·Pro·Tyr·Glu·Ala
D)Ala·Val·Phe·Tyr·Pro·Ala·Glu
E)Val·Ala·Phe·Tyr·Pro·Ala·Glu

Question 52

Which one of these amino acids does not give the usual purple color with ninhydrin?

A)Histidine
B)Proline
C)Tryptophan
D)Leucine
E)Aspartic acid

Question 53

The predominant form of aspartic acid in water at pH 1 would be:

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

Question 54

Which of the following would provide a synthesis of valine?

A)Potassium phthalimide,(CH₃)₂CHCHClCO₂C₂H₅; then KOH/H₂O; then HCl
B)(CH₃)₂C=CHCH₂OH,HBr/peroxides; then CrO₃/H₂SO₄/H₂O; then excess NH₃
C)Potassium phthalimide,(CH₃)₂CHCH₂Br; then KOH/H₂O; then CO₂,H₃O⁺
D)CH₃CH₂COOH,(C₆H₅)₃CNa; then NH₃
E)Two of these choices.

Question 55

For the accompanying fully-protonated amino acid,what is the arrangement of pK_a values in order of increasing magnitude?

A)I < II < III
B)II < I < III
C)III < I < II
D)III < II < I
E)II < III < I

Question 56

A pentapeptide has the molecular formula: Asp,Glu,His,Phe,Val.Partial hydrolysis of the pentapeptide gives: Val·Asp,Glu·His,Phe·Val,and Asp·Glu.What is the amino acid sequence of the pentapeptide?

A)Phe·Val·Asp·Glu·His
B)His·Glu·Asp·Val·Phe
C)Asp·Glu·His·Phe·Val
D)Phe·Val·Glu·His·Asp
E)Glu·His·Phe·Val·Asp

Question 57

Which of the following would provide a synthesis of alanine?

A)CH₂=CHCH₂OH,HBr; then CrO₃/H₂SO₄/H₂O; then excess NH₃
B)Potassium phthalimide,ClCH₂CO₂C₂H₅; then KOH/H₂O; then HCl
C)Potassium phthalimide,C₆H₅CH₂Br; then KOH/H₂O; then CO₂,H₃O⁺
D)CH₃CH₂COOH,(C₆H₅)₃CNa; then NH₃
E)Two of these choices.

Question 58

Why is this sequence,CH₂=CHCH₂OH + HBr,then CrO₃/H₂SO₄/H₂O,finally excess NH₃,not a good method for the preparation of l-alanine?

A)NH₃ is not sufficiently nucleophilic to perform the final step.
B)HBr does not add to substituted alkenes.
C)1° alcohols are not oxidized by CrO₃ in acidic solution.
D)Initial HBr addition produces a racemic intermediate which leads to racemic product.
E)Steric hindrance precludes nucleophilic substitution at a 2° carbon atom.

Question 59

What product(s)would you expect from the following reaction?

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

Question 60

What is the pI of the following amino acid?

A)1.5
B)6.3
C)5.6
D)9.8
E)7.2

Question 61

Which one is the correct reaction sequence for the attachment of valine on the N-terminus of a growing peptide?

A)Amino group deprotection,addition of Val and base,heating.
B)Amino group cleavage on Val,activation of carboxylic acid functionality on growing peptide chain,reaction between the two.
C)Amino group protection on the growing peptide chain,activation of the carboxylic acid functionality on Val,reaction with growing peptide.
D)Amino group deprotection on growing peptide,activation of the carboxylic acid functionality on Val,reaction with growing peptide.
E)Mix Val and growing peptide,add base and incubate the two for a period of time.

Question 62

The Edman degradation uses this reagent to identify the N-terminal amino acid of a peptide or protein.

A)C₆H₅NHNH₂
B)C₆H₅NH₂
C)C₆H₅N=C=S
D)C₆H₅N=C=O
E)Aminopeptidase

Question 63

What is lysozyme?

A)It is a hydrolytic DNA.
B)It is an enzyme that breaches the cell wall of gram-positive bacteria.
C)It is a protein that causes DNA hydrolysis.
D)It is an enzymatic protein contained in the nucleous.
E)It is a protein that can bind and hydrolyze esters.

Question 64

Which of the following statements are correct:
(I)Lysozyme produces hydrolysis of specific acetal linkages in peptidoglycan polymers.
(II)Lysozyme binds the cell wall substrate in a cleft within its tertiary structure.
(III)Evidence suggests sequential S_N2 reactions and a covalent enzyme-substrate intermediate.
(IV)One product of the hydrolytic reaction shows inversion of configuration.
(V)The entire lysozyme molecule acts as a leaving group in the cleavage reaction.

A)I,II
B)III,IV
C)I,II,III,IV
D)I,II,V
E)All are correct.

Question 65

When the pentapeptide below is heated first with 2,4-dinitrofluorobenzene (and base)and then subjected to acidic hydrolysis,which amino acid will bear the dinitrophenyl group? Leu·Val·Gly·Phe·Ile

A)Leucine
B)Valine
C)Glycine
D)Phenylalanine
E)Isoleucine

Question 66

Which of these are methods to determine the sequence of amino acids in a peptide?

A)Ladder sequencing; partial hydrolysis and sequence comparison.
B)Partial hydrolysis; tandem mass spectrometry and IR.
C)Partial hydrogenolysis and mass spectrometry.
D)Edman's degradation and NMR.
E)DNFB in acid,Edman's degradation and labeling.

Question 67

What statements are true about enzymes?
(I)They are biological catalysts,non-specific,that increase the reaction rate by 1000 times.
(II)They are catalysts that increase reaction rates by a factor or 1 million or more.
(III)Enzymes are remarkably specific,leading Fischer to formulate a lock-and-key hypothesis.
(IV)Enzymes undergo an induced fit upon binding the substrate.
(V)Enzyme and substrate form a complex

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

Question 68

It is known that enzymes vary considerably in their geometric specificity because:

A)All enzymes bind only one compound as substrate.
B)All enzymes can bind any type of substrate.
C)Only a few enzymes can bind only one compound as substrate.
D)Some enzymes bind only one compound as substrate but others recognize a range of compounds with similar chemical groups.
E)The enzymes will recognize only one type of geometrical shape in the substrate.

Question 69

The secondary structure of proteins is derived from:

A)peptide linkages.
B)disulfide linkages.
C)hydrogen bond formation.
D)hydrophobic interactions.
E)acid-base interactions.

Question 70

This reagent is used to "protect" the amino group of an amino acid which is to be joined to a second amino acid by a peptide bond.

A)
B)
C)
D)
E)

Question 71

What is the induced fit in an enzyme?

A)It is the formation of hydrogen bonding between the enzyme and substrate.
B)It is a change of secondary structure of the enzyme before binding the substrate.
C)It is a conformational change produced upon binding of the substrate.
D)It is a change in quaternary structure of the enzyme to produce the catalysis.
E)It is the change in the substrate after the catalytic reaction took place.

Question 72

The occurrence of this amino acid in a polypeptide chain disrupts an α-helix:

A)Proline
B)Alanine
C)Methionine
D)Histidine
E)Tyrosine

Question 73

Which amino acid of a polypeptide would become labeled when the polypeptide is treated with 2,4-dinitrofluorobenzene in base,even though the amino acid is not a terminal amino acid?

A)Lysine
B)Glycine
C)Alanine
D)Phenylalanine
E)Leucine

Question 74

What product would be obtained upon treating alanine with the following reagent?

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

Question 75

Which attractive force is responsible for maintaining the tertiary structure of a protein?

A)Disulfide linkages
B)Hydrogen bonds
C)van der Waals forces
D)Hydrophobic interactions
E)All of these choices.

Question 76

The primary structure of a protein refers to its:

A)sequence of amino acid residues.
B)disulfide bonds.
C)helical structure.
D)hydrogen bonding.
E)All of these choices.

Question 77

Enzymes catalyze stereospecific reactions.Stereospecific reactions are those that:

A)Lead to different stereoisomers from different stereoisomeric substrates.
B)Lead to the same stereoisomer despite starting with different stereoisomeric substrates.
C)Both stereoisomers,cis or trans can produce identical products.
D)Transform different substrates.
E)Transform one conformer into another conformer by rotation of the bonds.

Question 78

A prosthetic group is a

A)peptide chain linked to a protein
B)nonprotein group part of a conjugated protein
C)protein
D)smaller protein part of a bigger one
E)protein unit forming part of a protein

Question 79

Why is dicyclohexylcarbodiimide (DCC)used in peptide synthesis?

A)DCC "protects" the amino group of the intended N-terminal amino acid.
B)DCC activates the carboxyl group of one amino acid so that this amino acid reacts more readily with a second amino acid.
C)DCC cleaves the blocking groups from the final peptide.
D)DCC is the resin used in the automated synthesis of peptides.
E)DCC removes the peptide from the resin at the conclusion of the synthesis.

Question 80

How many different tripeptides can exist,each containing one residue of glycine,one of l-threonine,and one of l-arginine?

A)2
B)3
C)6
D)8
E)9