Deck 25: Amino Acids, Peptides, and Proteins

Question 1

How many different amino acids are found abundantly in proteins?

A) 10
B) 16
C) 20
D) 40
E) none of these

Answer 1

40

Question 2

Which of the following amino acids is achiral?

A) alanine
B) leucine
C) glycine
D) phenylalanine
E) none of these

Answer 2

glycine

Question 3

Amino acids are connected to each other by____________.

A) an ether linkage
B) a peptide linkage
C) an ester linkage
D) an amide linkage
E) both B & D

Answer 3

both B & D

Question 4

Which of the following statements is(are) true about $\alpha$ -amino acids?

A) the amino and carboxylic acid groups are separated by one carbon atom
B) the amino group is connected to a carbon atom that is $\alpha$ to the carboxylic acid group
C) the $\alpha$ carbon can be a chirality center
D) all of these

Question 5

Which of the following is a correct structure for L-valine?

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

Question 6

Proteins found in humans have all amino acids with ____configuration.

A) D
B) L
C) meso
D) A & B
E) none of these

Question 7

In $\alpha$ -amino acids the amino and carboxylic acid groups are separated by ____,

A) two carbon atoms
B) one carbon atom
C) peptide linkage
D) amide linkage
E) none of these

Question 8

Which of the following amino acids have an acidic side chain?

A) I & III
B) I, II & III
C) IV & V
D) II, IV & V
E) all of these

Question 9

Which of the following naturally occurring amino acids does not have the S configuration?

A) I
B) II
C) III
D) IV
E) none of these

Question 10

Which of the following is a correct structure for D-leucine?

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

Question 11

Which one of the following amino acid does not have an L-isomer?

A) valine
B) alanine
C) leucine
D) glycine
E) none of these

Question 12

When more than fifty amino acids are connected to each other, they form _________.

A) a tripeptide
B) a protein
C) a polypeptide
D) a tetrapeptide
E) none of these

Question 13

Draw the Fischer projection for L-aspartic acid and assign the configuration (R/S) at the chirality center.

Question 14

When four amino acids are connected to each other, they form ____________.

A) a tripeptide
B) a protein
C) a polypeptide
D) a tetrapeptide
E) none of these

Question 15

When thirty amino acids are connected to each other, they form ____________.

A) a tripeptide
B) a protein
C) a polypeptide
D) a tetrapeptide
E) none of these

Question 16

Which of the following amino acids have a basic side chain?

A) I & II
B) I, II & IV
C) III & V
D) I, II, III & IV
E) all of these

Question 17

The _______form of amino acid is a dipolar ion that carries both positive and negative charge.

A) cationic
B) anionic
C) zwitterionic
D) none of these

Question 18

Draw the Fischer projection for D-serine and assign the configuration (R/S) at the chirality center.

Question 19

Which of the following naturally occurring amino acids does not have the S configuration?

A) alanine
B) cysteine
C) tyrosine
D) isoleucine
E) none of these

Question 20

Draw the Fischer projection for L-cysteine and assign the configuration (R/S) at the chirality center.

Question 21

Which of the following is the predominant form of aspartic acid at pH 1?

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

Question 22

Which of the following is the predominant form of arginine at pH 2?

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

Question 23

Amino acids are considered amphoteric because _____________.

A) they only react with acids
B) they only react with bases
C) they react with both acids and bases
D) they do not react with acids or bases
E) none of these

Question 24

The pH at which the concentration of the zwitterionic form of an amino acid is at a maximum value is called the _______.

A) dipolar point
B) electric point
C) neutral point
D) isoelectric point
E) none of these

Question 25

Provide the structure of the predominant form of alanine at pH 2?

Question 26

Which of the following is used to detect the presence of amino acids using chromatography?

A) 2,4-DNP
B) methyl orange
C) phenolphthalein
D) ninhydrin
E) none of these

Question 27

Which of the following is the predominant form of asparagine at physiological pH?

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

Question 28

Which of the following amino acids have a pI around pH 3?

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

Question 29

Which of the following is the predominant form of serine at physiological pH?

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

Question 30

Which of the following is true about the amino acids with isoelectric point around
PH 10?

A) The side chain must be acidic.
B) The side chain must be basic.
C) The side chain must be polar.
D) The side chain must be non polar.
E) none of these

Question 31

Which of the following amino acids will migrate towards the anode at pH 7?
Glycine: pI=6.0
Lysine: pI=9.7

Question 32

Which of the following amino acids will migrate towards the anode at pH 6?
Phenylalanine: pI = 5.5
Leucine: pI = 6

Question 33

Which of the following amino acids will migrate towards the cathode at pH 7?
Glycine: pI=6.0
Lysine: pI=9.7

Question 34

Which of the following is the predominant form of lysine at pH 14?

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

Question 35

Separation of amino acids using electrophoresis is mainly based on ______.

A) differences in the pI values
B) concentration
C) differences in pH values
D) none of these

Question 36

Which of the following amino acids have a pI around pH 10?

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

Question 37

Which of the following is a zwitterionic form for alanine?

A) I
B) II
C) III
D) IV
E) both I & IV

Question 38

Which of the following amino acids will not migrate towards the cathode/anode at pH 6?
Phenylalanine: pI = 5.5
Leucine: pI = 6

Question 39

Provide the structure of the predominant form of valine at pH 10?

Question 40

Which of the following is true about the amino acids with isoelectric point around
PH 3?

A) The side chain must be acidic.
B) The side chain must be basic.
C) The side chain must be polar.
D) The side chain must be non polar.
E) none of these

Question 41

Provide the reagents necessary to prepare phenylalanine using a Strecker synthesis.

Question 42

How will you prepare phenylalanine using a Hell-Volhard-Zelinski reaction?

Question 43

Which amino acid is produced from the following reaction sequence?

A) alanine
B) valine
C) leucine
D) isoleucine
E) none of these

Question 44

Which amino acid is produced from the following reaction?

A) methionine
B) serine
C) cysteine
D) lysine
E) none of these

Question 45

Provide the reagents necessary to synthesize the following amino acid via the amidomalonate synthesis.

Question 46

How will you prepare glycine staring with ethanol and using a Hell-Volhard-Zelinski reaction?

Question 47

Which amino acid is produced from the following reaction sequence?

A) alanine
B) valine
C) leucine
D) isoleucine
E) none of these

Question 48

Which amino acid is produced from the following reaction?

A) methionine
B) serine
C) cysteine
D) lysine
E) none of these

Question 49

Which amino acid is produced from the following reaction sequence?

A) alanine
B) valine
C) leucine
D) isoleucine
E) none of these

Question 50

Provide the structure of the predominant form of the following amino acids at pH 7 and predict the migration towards anode or cathode during electrophoresis.

Question 51

Which amino acid is produced from the following reaction sequence?

A) alanine
B) valine
C) leucine
D) isoleucine
E) none of these

Question 52

Provide the structure of the amino acid produced from the following reaction sequence.

Question 53

Which of the following aldehydes would produce isoleucine using a Strecker synthesis?

A) 3-methylbutanal
B) 2-methylbutanal
C) 2-methylpropanal
D) propanal
E) none of these

Question 54

Provide the structure of the amino acid produced from the following reaction sequence.

Question 55

Provide the reagents necessary to synthesize the following amino acid via the amidomalonate synthesis.

Question 56

Which of the following amino acids will move the farthest when subjected to electrophoresis at pH 7?

A) I
B) II
C) III
D) II & III
E) none of these

Question 57

Which amino acid is produced from the following reaction sequence?

A) alanine
B) valine
C) leucine
D) isoleucine
E) none of these

Question 58

Which of the following aldehydes would produce glycine using a Strecker synthesis?

A) methanal
B) ethanal
C) propanal
D) none of these

Question 59

Which amino acid is produced from the following reaction sequence?

A) alanine
B) valine
C) leucine
D) isoleucine
E) none of these

Question 60

Provide the structure of the predominant form of the following amino acids at pH 6 and predict the migration towards anode or cathode during electrophoresis.

Question 61

Which of the following alkenes is used to prepare isoleucine using an asymmetric catalytic hydrogenation?

A) I
B) II
C) III
D) IV
E) none of these

Question 62

Provide the structure of the amino acid produced from the following reaction sequence.

Question 63

What is the correct sequence of amino acids for the following tripeptide?

A) Ser-Met-Ile
B) Ser-Cys-Ile
C) Thr-Met-Leu
D) Thr-Cys-Leu
E) none of these

Question 64

Which of the following peptides results after a single Edman degradation of the tetrapeptide Gly-Phe-Tyr-Ser?

A) Gly-Phe-Tyr
B) Tyr-Ser
C) Phe-Tyr-Ser
D) Gly-Phe
E) none of these

Question 65

Which of the following is a correct bond-line structure for the tripeptide Ser-Lys-Cys?

A) I
B) II
C) III
D) IV
E) none of these

Question 66

Which of the following reagent(s) is(are) used to remove the N-terminus amino acid residue using Edman degradation?

A) I
B) II
C) III
D) IV
E) none of these

Question 67

Draw a bond-line structure for the tetrapetide Ile-Ser-Leu-Gly.

Question 68

What is the correct sequence of amino acids for the following tripeptide?

A) Leu-Phe-Ala
B) Val-Phe-Ala
C) Ile-Tyr-Leu
D) Leu-Tyr-Val
E) none of these

Question 69

Which of the following results after three steps of Edman degradation of the heptapeptide Lys-His-Gly-Phe-Tyr-Ser-Ala?

A) Lys-His-Gly
B) Phe-Tyr-Ser-Ala
C) Tyr-Ser-Ala
D) Lys-His-Gly-Phe
E) none of these

Question 70

Provide the structure of the amino acid produced from the following reaction.

Question 71

Disulfide bridges are formed by:

A) oxidation of thiol groups
B) joining cysteine residues within a peptide
C) joining cysteine residues between two strands of a peptide
D) all of these

Question 72

Chymotrypsin, a digestive enzyme, catalyzes the hydrolysis of the peptide bond at the carboxyl end of which of the following amino acids?

A) phenylalanine
B) tyrosine
C) tryptophan
D) histidine
E) A, B & C

Question 73

What is the three letter abbreviation for the amino acid sequence of the following peptide?

Question 74

Which of the following is a correct bond-line structure for the tripeptide Val-Asp-Ala?

A) I
B) II
C) III
D) IV
E) none of these

Question 75

Edman degradation removes the amino acid residue from the _______ of the peptide.

A) C-terminus
B) N-terminus
C) middle
D) none of these

Question 76

Draw a bond-line structure for the tetrapetide Ala-Ser-Cys-Phe.

Question 77

Provide the reagents necessary to prepare cysteine using a Strecker synthesis.

Question 78

Trypsin, a digestive enzyme, catalyzes the hydrolysis of the peptide bond at the carboxyl end of which of the following amino acids?

A) arginine
B) lysine
C) histidine
D) tryptophan
E) A & B

Question 79

The s-trans conformation of a peptide bond is more stable than the s-cis conformation because:

A) there is a restricted rotation around the peptide bond
B) rotation is allowed around the peptide bond
C) it has reduced steric hindrance
D) none of these

Question 80

Provide the structure of the amino acid produced from the following reaction.