Deck 3: Amino Acids and Peptides

Question 1

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 1

lysine and arginine

Question 2

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 2

Ser

Question 3

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

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

Answer 3

ornithine

Question 4

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 5

Which amino acid has the three-letter symbol asn?

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

Question 6

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 7

Which amino acid has the one-letter symbol E?

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

Question 8

Thr and Ser both have hydroxyls as side chains.

Question 9

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 10

Which of the following has a hydrophilic side chain?

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

Question 11

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 12

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 13

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

Question 14

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 15

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 16

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 17

Asp and Glu both have amides as side chains.

Question 18

Which amino acid is classified as polar?

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

Question 19

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 20

Which amino acid has a benzene-like ring?

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

Question 21

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 22

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 23

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 24

Which amino acid has a basic R group?

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

Question 25

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 26

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 27

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 28

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 29

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

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

Question 30

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 31

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 32

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 33

Which amino acids contain sulfur?

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

Question 34

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 35

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

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

Question 36

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 37

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 38

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

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

Question 39

Which is the correct one-letter designation for tryptophan?

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

Question 40

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

A) 0
B) +1
C) +2
D) − 1

Question 41

Exhibit 3A (for this chapter) 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

Exhibit 3A (for this chapter) Refer to Exhibit 3A. Which one has a pI of 5.0?

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

Question 44

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 45

Exhibit 3A (for this chapter) 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 46

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 47

Exhibit 3A (for this chapter) Refer to Exhibit 3A. At pH 7, what percent of histidine has a neutral charge?

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

Question 48

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

A) positive
B) neutral
C) negative

Question 49

The isoelectric pH of glycine is closest to

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

Question 50

Exhibit 3A (for this chapter) 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 51

Exhibit 3A (for this chapter)
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 52

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

A) positive
B) neutral
C) negative

Question 53

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 54

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

A) positive
B) neutral
C) negative

Question 55

Exhibit 3A (for this chapter) 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

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 57

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 58

Exhibit 3A (for this chapter) 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 59

Exhibit 3A (for this chapter) 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 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

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 62

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 63

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 64

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 65

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 66

Which of the following types of amino acids has uncharged side chains at neutral pH?

A) Nonpolar amino acids
B) Acidic amino acids
C) Polar-neutral amino acids
D) Basic amino acids

Question 67

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 68

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 69

The method for separating molecules on the basis of the ratio of their charge to size is called _____.

A) electrolysis
B) electrophoresis
C) electroplating
D) electroporation

Question 70

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

Question 71

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 72

Explain how thyroxine differs from its parent amino acid, tyrosine.

Question 73

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 74

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 75

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 76

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 77

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 78

​ Which of the following statements is true of resonance structures?

A) Resonance structures differ from one another only in the positioning of electrons.
B) Resonance structures differ from one another only in the number of electrons.
C) Two resonance structures will always have the same number of single bonds and double bonds.
D) Two resonance structures will always have single bonds and double bonds in the same position.

Question 79

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 80

What do amino acids such as alanine, leucine, isoleucine, tryptophan, and valine have in common?

A) They all are polar-neutral amino acids.
B) They all are nonpolar amino acids.
C) They all are acidic amino acids.
D) They all are basic amino acids.