Deck 3: Amino Acids and Peptides

Question 1

Which of the following amino acids has a side chain that can make hydrogen bonds to other molecules?

A) Leu
B) Ser
C) Ala
D) Gly

Answer 1

B

Question 2

Asp and Glu both have amides as side chains.

Answer 2

False

Question 3

Which group consists only of amino acids with basic side chains?

A) leucine and lysine
B) arginine and leucine
C) lysine and arginine
D) arginine and isoleucine

Answer 3

C

Question 4

Which of the following has a hydrophilic side chain?

A) Asn
B) Leu
C) Ile
D) Gly

Question 5

The absolute configuration of amino acids are denoted by their relationship to the L- or D- forms of

A) glyceraldehyde
B) glucose
C) tartaric acid
D) alanine

Question 6

Chiral objects

A) are cyclic compounds in the chair form.
B) are not superimposable on their mirror images.
C) never occur in nature.
D) do not form crystals.

Question 7

The amino acids which occur in proteins

A) are all of the L- form.
B) are all of the D- form.
C) can be either the L- or D- form.
D) do not have L- and D- forms.

Question 8

Which amino acid is classified as polar?

A) L
B) H
C) P
D) I

Question 9

The side chain of Met is a poor hydrogen bond donor.

Question 10

Which group consists only of amino acids with polar side chains?

A) serine, threonine, and leucine
B) serine, threonine, and cysteine
C) serine, threonine, and valine
D) serine, threonine, and isoleucine

Question 11

Which amino acid has the one-letter symbol E?

A) lysine
B) phenylalanine
C) histidine
D) glutamic acid

Question 12

The amino and carboxyl groups of amino acids are bonded to which carbon?

A) Both are bonded to the α-carbon.
B) Both are bonded to the β-carbon.
C) The amino is bonded to the α-carbon, and the carboxyl is bonded to the β-carbon.
D) The amino is bonded to the β-carbon, and the carboxyl is bonded to the α-carbon.

Question 13

Which amino acid has the three-letter symbol asn?

A) aspartic acid
B) asparagine
C) alanine
D) arginine

Question 14

The side chain groups of amino acids are bonded to which carbon?

A) The α-carbon.
B) The β-carbon.
C) The carbonyl carbon.
D) Different amino acids have their side chains attached to different carbons.

Question 15

Which is a correct pair of abbreviations for an amino acid?

A) Gln / N
B) Tyr / T
C) Asn / N
D) Phe / P
E) Pro / Q

Question 16

Thr and Ser both have hydroxyls as side chains.

Question 17

Which of the following is an amino acid not found in proteins?

A) asparagine
B) ornithine
C) isoleucine
D) proline

Question 18

Which amino acid has a benzene-like ring?

A) Glutamic Acid
B) Histidine
C) Isoleucine
D) Serine
E) Tyrosine

Question 19

Which group consists only of amino acids with carboxylate side chains?

A) glutamate and cysteine
B) aspartate and glycine
C) glutamate and lysine
D) aspartate and glutamate

Question 20

Which of the following has no L or D configuration?

A) Glyceraldehyde
B) Proline
C) Glycine
D) All of these have an L or D configuration

Question 21

Which amino acid would likely be least water-soluble at pH 7.0

A) Histidine
B) Isoleucine
C) Isoleucine or Tyrosine, you cannot tell
D) Serine
E) Tyrosine

Question 22

Which of the following can be considered a unique characteristic of histidine?

A) Its side chain is attached to the alpha carbon
B) It has a basic side chain
C) It has a side chain that is chemically basic but has an acidic pKa
D) It is technically an "imino" acid

Question 23

Which amino acids would migrate furthest toward the anode (positive electrode) during electrophoresis?

A) Aspartic acid.
B) Arginine.
C) Tyrosine.
D) Histidine.
E) Glutamine.

Question 24

Which amino acid has a basic R group?

A) Glutamic Acid
B) Histidine
C) Isoleucine
D) Serine
E) Tyrosine

Question 25

Which is the correct one-letter designation for tryptophan?

A) E
B) T
C) W
D) Q
E) none of the choices

Question 26

Which amino acids contain sulfur?

A) cysteine and lysine
B) cysteine and methionine
C) arginine and methionine
D) cysteine and isoleucine

Question 27

The pK_a values of the alpha carboxyl groups of common amino acids are around

A) pH 2
B) pH 5
C) pH 7
D) pH 9

Question 28

Which amino acid takes on a negative charge when the R-group loses a proton?

A) Glutamic Acid
B) Histidine
C) Glutamine
D) Tyrosine
E) Glutamic Acid and Tyrosine

Question 29

Given the R-groups in the peptide, ALA-GLN-ARG-SER-HIS, it would likely be:

A) Very water soluble
B) Somewhat water soluble
C) Not very water soluble
D) Not soluble at all
E) You cannot tell from the sequence

Question 30

Which of the following is true about uncommon amino acids?

A) They are found in all proteins
B) When they are found in proteins, they are first created by modification of the parent amino acid and then incorporated into the protein
C) They are formed in the protein by post-translational modification of the parent amino acid
D) They are always based on modification of tyrosine
E) none of the choices

Question 31

The pK_a values of the amino groups of common amino acids

A) occur at very low pH values
B) occur in a range from pH 9 to pH 11
C) all occur at pH 8
D) all occur above pH 12

Question 32

Which amino acid has a polar, non-ionic R-group

A) Glutamic Acid
B) Histidine
C) Isoleucine
D) Serine
E) Tyrosine

Question 33

Which of the following is not considered an uncommon amino acid?

A) thyroxine
B) Hydroxylysine
C) Hydroxyproline
D) Tryptophan

Question 34

Which amino acid takes on a positive charge when the R-group gains a proton?

A) Glutamic Acid
B) Histidine
C) Glutamine
D) Tyrosine
E) Glycine

Question 35

Which amino acid would have the greatest negative charge at pH = 7.0?

A) Glutamic Acid
B) Histidine
C) Isoleucine
D) Serine
E) Tyrosine

Question 36

Which amino acid has the least polar R-group H?

A) Glutamic Acid
B) Histidine
C) Isoleucine
D) Serine
E) Tyrosine

Question 37

What is the charge on the tetrapeptide lys-lys-his-glu at pH 7?

A) 0
B) +1
C) +2
D) −1

Question 38

Which of the following is NOT a correct combination of an amino acid, its three-letter designation, and its one-letter designation?

A) Lysine, lys, L
B) Glycine, gly, G
C) Histidine, his, H
D) Tryptophan, Trp, W
E) Arginine, arg, R

Question 39

Which statement is true about the classification of amino acids?

A) Alanine and valine are basic amino acids.
B) Lysine and arginine are acidic amino acids.
C) Glutamic acid and asparagine are hydrophobic amino acids.
D) Tryptophan and phenylalanine are aromatic amino acids.
E) Methionine and cysteine are hydroxyl-containing amino acids.

Question 40

The pK_a values of the side chains of the common amino acids

A) are always at low pH
B) are always at high pH
C) depend on the chemical nature of the side chain
D) are not known

Question 41

Refer to Exhibit 3A. Calculate the pI of ASN:

A) 2.5
B) 5.0
C) 5.5
D) 6.0
E) 10.7

Question 42

Which of the following correctly lists the isoelectric pH's of asp, asn, and arg from lowest to highest?

A) D N R
B) D R N
C) R N D
D) R D N
E) N R D
F) N D R

Question 43

Refer to Exhibit 3A. The pI of the peptide ALA-GLN-ARG-SER-HIS would be:

A) Strongly acid
B) Weakly acid (4-6)
C) About neutral (6-8)
D) Weakly basic (8-10)
E) Strongly basic

Question 44

Refer to Exhibit 3A. Which one has the R-group with the highest pK?

A) Alanine
B) Arginine
C) Histidine
D) Cysteine
E) Aspartic Acid

Question 45

What is the predominant form of the amino acid abbreviated val at pH 7?

A) positive
B) neutral
C) negative

Question 46

Exhibit 3B A titration curve.

Refer to Exhibit 3B. Which point most likely represents the pK for the carboxyl group?

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

Question 47

Refer to Exhibit 3A. Which one has a pI of 5.0?

A) Alanine
B) Arginine
C) Histidine
D) Cysteine
E) Glutamic acid

Question 48

The net charge on the amino acid cys in a solution at pH 7 is closest to

A) −2
B) −1.
C) 0.
D) +1.

Question 49

Refer to Exhibit 3A. The pI of an amino acid is the pH at which it has a zero net charge. What is the increasing order of isoelectric points (low pH to high) for these three amino acids?

A) ALA, HIS, ASP
B) ASP, ALA, HIS
C) HIS, ALA, ASP
D) ALA, ASL, HIS
E) ASP, HIS, ALA

Question 50

Refer to Exhibit 3A. At pH 7, what percent of histidine has a neutral charge?

A) 9%
B) 50%
C) 91%
D) 100%

Question 51

Which of the following amino acids has a net charge of +1 at pH 4 and a net charge of 0 at pH 8?

A) glu
B) arg
C) his
D) tyr

Question 52

The net charge on the peptide abbreviated CAKE in a solution at pH 7 is closest to

A) −2
B) −1.
C) 0.
D) +1.

Question 53

The isoelectric pH of glycine is closest to

A) pH 4
B) pH 6
C) pH 8
D) pH 10

Question 54

Refer to Exhibit 3A. Which of these amino acids could act as a good buffer at pH = 4.5

A) Alanine
B) Arginine
C) Asparagine
D) Cysteine
E) Aspartic Acid

Question 55

Refer to Exhibit 3A. What is the order of the pIs in increasing order (from acid to base)?

A) Alanine, Arginine, Asparagine, Cysteine, and Aspartic Acid
B) Aspartic Acid, Alanine, Asparagine, Cysteine, and Arginine
C) Aspartic Acid, Cysteine, Asparagine, Alanine, and Arginine
D) Arginine, Alanine, Asparagine, Cysteine, and Aspartic Acid
E) Aspartic Acid, Cysteine, Arginine, Alanine, and Asparagine,

Question 56

What is the predominant form of the amino acid abbreviated R at pH 7?

A) positive
B) neutral
C) negative

Question 57

Refer to Exhibit 3A. Calculate the pI of CYS?

A) 1.7
B) 5.0
C) 8.3
D) 9.6
E) 10.8

Question 58

At its isolectric pH, glycine will have

A) both of its ionizable functional groups dissociated.
B) neither of its ionizable functional groups dissociated.
C) only its carboxyl group dissociated.
D) only its amino group dissociated.

Question 59

What is the predominant form of the amino acid abbreviated E at pH 7?

A) positive
B) neutral
C) negative

Question 60

Exhibit 3B A titration curve.

Refer to Exhibit 3B. Which points on the graph represent pK's?

A) 1 and 7
B) 2, 4 and 6
C) 3 and 5
D) 2, 3, 4, 5 and 6
E) The pKs cannot be determined without more information.

Question 61

Exhibit 3B A titration curve.

Refer to Exhibit 3B. At which point would the amino acid have its maximum negative charge?

A) 1
B) 2
C) 4
D) 6
E) 7

Question 62

Exhibit 3B A titration curve.

Refer to Exhibit 3B. The amino acid depicted by the titration curve is

A) aspartic acid
B) histidine
C) lysine
D) tyrosine
E) lysine or tyrosine

Question 63

Exhibit 3B A titration curve.

Refer to Exhibit 3B. The point labeled #1 represents:

A) The fully protonated form
B) The pH with maximum negative charge
C) The end point of titration with base (OH−)
D) The pI of the amino acid
E) None of these

Question 64

The peptide bond

A) is formed by elimination of water between two amino groups in an amindo acid
B) limits the possible orientations of the peptide backbone in a protein
C) has acidic and basic characteristics
D) all of these

Question 65

The order in which amino acids are linked in peptides is given

A) from the C-terminal to the N-terminal end
B) from the N-terminal to the C-terminal end
C) in alphabetical order
D) in order of increasing molecular weights of the amino acid residues

Question 66

How many different tripeptides can be assembled using one molecule each of the amino acids glycine, glutamic acid, and lysine?

A) 3
B) 6
C) 9
D) 27

Question 67

Which is the C-terminal amino acid in the peptide ALA-GLN-ARG-SER-HIS?

A) ALA
B) GLN
C) ARG
D) SER
E) HIS

Question 68

How many possible tetrapeptides can be made using all four of the amino acids D, W, F, and R?

A) 4
B) 6
C) 12
D) 24
E) none of the choices

Question 69

Which of the following is true about oxytocin?

A) it is a peptide hormone
B) during pregnancy the number of receptors for oxytocin increases
C) it is involved in stimulating the flow of milk during nursing
D) all of the choices

Question 70

The peptide bond

A) is planar
B) can be written as a resonance hybrid
C) is the basis of protein structure.
D) all of the above

Question 71

Oxytocin and vasopressin

A) differ from each other by a single amino acid
B) do not contain sulfur
C) are peptide hormones
D) are tripeptides

Question 72

Which of the following correctly describes peptide bonds?

A) They are special type of amide bond.
B) They are a very stable bonds.
C) They are formed when water is split out from an amino group and a carboxylic acid.
D) They are a bond which displays resonance.
E) All of these

Question 73

Which of the following is the most similar between oxytocin and vasopressin?

A) their biological function
B) their amino acid sequences
C) their isoelectric point
D) their overall structure

Question 74

This amino acid displays a free amino group in the peptide ALA-GLN-ARG-SER-HIS:

A) ALA
B) GLN
C) SER
D) HIS

Question 75

Which groups of a pair of amino acids must react to form a peptide bond?

A) the two carboxyls
B) the two aminos
C) the two R-groups
D) the carboxyl of one and the amino of the other