Deck 4: Amino Acids

Question 1

Matching
The net charge of the zwitterion form of Gly is ______.

A)glutamate
B)uncharged
C)deprotonated
D)three
E)amino group
F)two
G)C-terminus
H)lysine
I)racemic mixture
J)cysteine
K)zero
L)protonated
M)isoleucine
N)tryptophan
O)phenylalanine
P)N-terminus

Answer 1

zero

Question 2

Matching
In the tripeptide Lys─Pro─Ile, the C-terminal residue is _________.

A)glutamate
B)uncharged
C)deprotonated
D)three
E)amino group
F)two
G)C-terminus
H)lysine
I)racemic mixture
J)cysteine
K)zero
L)protonated
M)isoleucine
N)tryptophan
O)phenylalanine
P)N-terminus

Answer 2

isoleucine

Question 3

Which of the following amino acids is the least abundant in proteins?

A)V
B)W
C)G
D)F
E)A

Answer 3

W

Question 4

Matching

-At a pH below its pK_a, the $\beta$ -carboxylate group of Asp is ______.

A)glutamate
B)uncharged
C)deprotonated
D)three
E)amino group
F)two
G)C-terminus
H)lysine
I)racemic mixture
J)cysteine
K)zero
L)protonated
M)isoleucine
N)tryptophan
O)phenylalanine
P)N-terminus

Question 5

Which amino acid does not have a primary $\alpha$ -amino group?

A)glutamine
B)arginine
C)lysine
D)proline
E)glutamate

Question 6

Matching
In the tripeptide Trp─Val─Phe, the N-terminal residue is ______.

A)glutamate
B)uncharged
C)deprotonated
D)three
E)amino group
F)two
G)C-terminus
H)lysine
I)racemic mixture
J)cysteine
K)zero
L)protonated
M)isoleucine
N)tryptophan
O)phenylalanine
P)N-terminus

Question 7

Matching
In the tripeptide Lys─Pro─Ile, there are ______ charged groups at pH 7.

A)glutamate
B)uncharged
C)deprotonated
D)three
E)amino group
F)two
G)C-terminus
H)lysine
I)racemic mixture
J)cysteine
K)zero
L)protonated
M)isoleucine
N)tryptophan
O)phenylalanine
P)N-terminus

Question 8

Matching
In the peptide Trp─Ser─Val, valine is at the ______.

A)glutamate
B)uncharged
C)deprotonated
D)three
E)amino group
F)two
G)C-terminus
H)lysine
I)racemic mixture
J)cysteine
K)zero
L)protonated
M)isoleucine
N)tryptophan
O)phenylalanine
P)N-terminus

Question 9

What percentage of the 20 amino acids is considered to be nutritionally essential to lab animals?

A)0%
B)25%
C)50%
D)75%
E)100%

Question 10

About half of the 20 amino acids are called essential because

A)they are essential for the synthesis of pyrimidines.
B)they are essential for the synthesis of purines.
C)they are essential for nitrogen metabolism.
D)our bodies need them for protein synthesis.
E)our bodies cannot synthesize them and therefore they need to be present in our diet.

Question 11

The formation of a dipeptide from two amino acids involves

A)side-chain complementarity.
B)loss of water.
C)oxidation of the $\alpha$ -carbon.
D)reduction of the $\alpha$ -carbon.
E)base catalysis.

Question 12

Matching

-At a pH below its pK_a, the $\varepsilon$ -amino group of lysine is ______.

A)glutamate
B)uncharged
C)deprotonated
D)three
E)amino group
F)two
G)C-terminus
H)lysine
I)racemic mixture
J)cysteine
K)zero
L)protonated
M)isoleucine
N)tryptophan
O)phenylalanine
P)N-terminus

Question 13

In the early 1930's William Rose fed laboratory rats a mixture of all 19 amino acids known to be present in proteins.He observed that his rats lost weight.This observation led to the discovery of ______ as the 20th amino acid found in proteins.

A)Gly
B)Ala
C)Tyr
D)Asn
E)Thr

Question 14

Matching
When a peptide bond is formed, an ______ reacts with a carboxylate group.

A)glutamate
B)uncharged
C)deprotonated
D)three
E)amino group
F)two
G)C-terminus
H)lysine
I)racemic mixture
J)cysteine
K)zero
L)protonated
M)isoleucine
N)tryptophan
O)phenylalanine
P)N-terminus

Question 15

Matching
Glutathione is a tripeptide containing a central ______ residue.

A)glutamate
B)uncharged
C)deprotonated
D)three
E)amino group
F)two
G)C-terminus
H)lysine
I)racemic mixture
J)cysteine
K)zero
L)protonated
M)isoleucine
N)tryptophan
O)phenylalanine
P)N-terminus

Question 16

Matching
Biological systems usually produce a single enantiomer, whereas chemical synthesis produces a ______.

A)glutamate
B)uncharged
C)deprotonated
D)three
E)amino group
F)two
G)C-terminus
H)lysine
I)racemic mixture
J)cysteine
K)zero
L)protonated
M)isoleucine
N)tryptophan
O)phenylalanine
P)N-terminus

Question 17

Zwitterions are

A)amino acids.
B)ionic molecules that are racemic.
C)ions that bear both negatively and positively charged groups.
D)side chain carboxylate anions.
E)delocalized ions.

Question 18

Matching
GABA is a neurotransmitter derived from ______.

A)glutamate
B)uncharged
C)deprotonated
D)three
E)amino group
F)two
G)C-terminus
H)lysine
I)racemic mixture
J)cysteine
K)zero
L)protonated
M)isoleucine
N)tryptophan
O)phenylalanine
P)N-terminus

Question 19

Matching
At a pH above its pK_a, the phenol group of tyrosine is ______.

A)glutamate
B)uncharged
C)deprotonated
D)three
E)amino group
F)two
G)C-terminus
H)lysine
I)racemic mixture
J)cysteine
K)zero
L)protonated
M)isoleucine
N)tryptophan
O)phenylalanine
P)N-terminus

Question 20

Which of the following statements is true?

A)Amino acids can be derived from purines.
B)Purines and pyrimidines can be derived from amino acids.
C)Corn contains all 20 standard amino acids.
D)Amino acids can be derived from pyrimidines.
E)none of the above

Question 21

The pK₁, pK₂, and pK_R for the amino acid cysteine are 1.9, 10.7, and 8.4, respectively.At pH 5.0, cysteine would be charged predominantly as follows:

A)( $\alpha$ -carboxylate 0, $\alpha$ -amino 0, sulfhydryl 0, net charge 0)
B)( $\alpha$ -carboxylate +1, $\alpha$ -amino −1, sulfhydryl −1, net charge −1)
C)( $\alpha$ -carboxylate −1, $\alpha$ -amino +1, sulfhydryl +1, net charge +1)
D)( $\alpha$ -carboxylate −1, $\alpha$ -amino +1, sulfhydryl 0, net charge 0)
E)( $\alpha$ -carboxylate +1, $\alpha$ -amino −1, sulfhydryl 0, net charge 0)

Question 22

The disulfide bond between two cysteine molecules

A)is a peptide bond.
B)is an ionic interaction that is stable at physiological pH.
C)is a covalent bond formed by oxidation.
D)is a hydrogen bond between the two sulfhydryl groups.
E)is a dipole-dipole interaction.

Question 23

Which of the following amino acids has a charged polar side chain at pH 7.0?

A)Leu
B)Ala
C)Met
D)Trp
E)Glu

Question 24

While proteins are usually composed of linear chains of amino acids, branched chains of amino acids and internally cross-linked chains can be found in certain proteins.Polypeptide chains are most commonly linked to each other through

A)hydrogen bonds.
B)glycosidic bonds.
C)peptide bonds.
D)disulfide bonds.
E)ester linkages.

Question 25

Which of the following amino acids does not have an ionizable side chain?

A)Asp
B)Cys
C)Lys
D)His
E)Asn

Question 26

Which of the following amino acids has a sulfur atom in its side chain?

A)Asn
B)Ser
C)Phe
D)Met
E)Tyr

Question 27

Which of the following amino acids has an uncharged polar side chain at pH 7.0?

A)Arg
B)Thr
C)Glu
D)Pro
E)Ile

Question 28

The pK₁, pK₂, and pK_R for the amino acid lysine are 2.2, 9.1, and 10.5, respectively.At pH 1.0, lysine would be charged predominantly as follows:

A)( $\alpha$ -carboxylate 0, $\alpha$ -amino −1, $\varepsilon$ -amino −1, net charge −2)
B)( $\alpha$ -carboxylate −1, $\alpha$ -amino +1, $\varepsilon$ -amino +1, net charge +1)
C)( $\alpha$ -carboxylate +1, $\alpha$ -amino +2, $\varepsilon$ -amino +2, net charge +5)
D)( $\alpha$ -carboxylate 0, $\alpha$ -amino +1, $\varepsilon$ -amino +1, net charge +2)
E)( $\alpha$ -carboxylate +2, $\alpha$ -amino +1, $\varepsilon$ -amino +1, net charge +4)

Question 29

The diagram below shows

A)an amino acid.
B)a dipeptide.
C)a tripeptide.
D)a tetrapeptide.
E)a polypeptide.

Question 30

The pK₁, pK₂, and pK_R for the amino acid histidine are 1.8, 9.3, and 6.0, respectively.At pH 4.0 would be charged predominantly as follows:

A)( $\alpha$ -carboxylate +1, $\alpha$ -amino 0, imidazole −1, net charge 0)
B)( $\alpha$ -carboxylate −1, $\alpha$ -amino +1, imidazole 0, net charge 0)
C)( $\alpha$ -carboxylate +1, $\alpha$ -amino +1, imidazole −1, net charge +1)
D)( $\alpha$ -carboxylate −1, $\alpha$ -amino +1, imidazole +1, net charge +1)
E)( $\alpha$ -carboxylate 0, $\alpha$ -amino +1, imidazole +1, net charge +2)

Question 31

the diagram shown below.
What is the name of the N-terminal amino acid in the peptide shown above?

A)cysteine
B)methionine
C)valine
D)alanine
E)tryptophan

Question 32

the diagram below
The ionization of amino acids depends on the pH and the pK_as of the ionizable groups.The pK₁ and pK₂ for the amino acid shown above are 2.1 and 8.8, respectively.At what pH is the amino acid ionized predominantly as shown?

A)pH 1.0
B)pH 2.1
C)pH 5.5
D)pH 8.8
E)pH 10.0

Question 33

the diagram below
What is the three-letter symbol for the amino acid shown above?

A)Ala
B)Asn
C)Gln
D)Asp
E)Glu

Question 34

The pK₁, pK₂, and pK_R for the amino acid arginine are 1.8, 9.0, and 12.5, respectively.At pH 7.0 arginine would be charged predominantly as follows:

A)( $\alpha$ -carboxylate 0, $\alpha$ -amino 0, guanidino +1, net charge +1)
B)( $\alpha$ -carboxylate +1, $\alpha$ -amino 0, guanidino -1, net charge 0)
C)( $\alpha$ -carboxylate +1, $\alpha$ -amino −1, guanidino −1, net charge −1)
D)( $\alpha$ -carboxylate −1, $\alpha$ -amino +1, guanidino +1, net charge +1)
E)( $\alpha$ -carboxylate −1, $\alpha$ -amino 0, guanidino +1, net charge 0)

Question 35

The pK₁, pK₂, and pK_R for the amino acid glutamate are 2.1, 9.5, and 4.1, respectively.At pH 11.0, glutamate would be charged predominantly as follows:

A)( $\alpha$ -carboxylate +1, $\alpha$ -amino 0, $\gamma$ -carboxylate +1, net charge +2)
B)( $\alpha$ -carboxylate −1, $\alpha$ -amino +1, $\gamma$ -carboxylate −1, net charge −1)
C)( $\alpha$ -carboxylate 0, $\alpha$ -amino 0, $\gamma$ -carboxylate 0, net charge 0)
D)( $\alpha$ -carboxylate +1, $\alpha$ -amino −1, $\gamma$ -carboxylate +1, net charge +1)
E)( $\alpha$ -carboxylate −1, $\alpha$ -amino 0, $\gamma$ -carboxylate −1, net charge −2)

Question 36

the diagram shown below.
How many amino acid residues are present in the peptide shown above?

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

Question 37

The two peptides shown in the diagram below are linked through

A)a hydrogen bond.
B)a glycosidic bond.
C)a peptide bond.
D)a disulfide bond.
E)an ester linkage.

Question 38

The pK₁, pK₂, and pK_R for the amino acid aspartic acid are 2.0, 9.9, and 3.9, respectively.At pH 7.0, aspartic acid would be charged predominantly as follows:

A)( $\alpha$ -carboxylate 0, $\alpha$ -amino +1, $\beta$ -carboxylate 0, net charge +1)
B)( $\alpha$ -carboxylate −1, $\alpha$ -amino +1, $\beta$ -carboxylate −1, net charge −1)
C)( $\alpha$ -carboxylate 0, $\alpha$ -amino −1, $\beta$ -carboxylate 0, net charge −1)
D)( $\alpha$ -carboxylate +1, $\alpha$ -amino −1, $\beta$ -carboxylate +1, net charge +1)
E)( $\alpha$ -carboxylate +1, $\alpha$ -amino +1, $\beta$ -carboxylate +1, net charge +3)

Question 39

Which of the following tripeptides carries a net positive charge at pH 7.0?

A)Ala─Thr─Asn
B)Gln─Val─Ser
C)Arg─Glu─Met
D)Pro─Ile─Leu
E)Leu─Lys─Gly

Question 40

the diagram shown below.
What is the three-letter symbol for the C-terminal amino acid in the peptide shown above?

A)Gly
B)Asp
C)Tyr
D)Met
E)Phe

Question 41

The tripeptide glycylarginylglutamate contains four ionizable groups with pK_as of 2.1, 4.1 9.8, and 12.5.Calculate the pI for this molecule.

A)3.1
B)6.4
C)7.0
D)7.3
E)8.3

Question 42

All the standard amino acids except ____ are optically active.

A)Pro
B)Arg
C)Trp
D)Gly
E)Phe

Question 43

Ribosomes use L amino acids to synthesize proteins.These amino acids are called "L" because

A)they are chiral.
B)they turn polarized light to the left.
C)they have a configuration of groups around the C _$\alpha$ that can be related to the configuration of groups around the asymmetric carbon in L-glyceraldehyde.
D)they are all (S)-amino acids.
E)they are all (R)-amino acids.

Question 44

Ribosomes use L amino acids to synthesize proteins.These amino acids are called "L" because

A)they are chiral.
B)they turn polarized light to the left.
C)they are all (S)-amino acids.
D)they are all (R)-amino acids.
E)none of the above

Question 45

The isoelectronic point of an amino acid is the point where

A)the pK_a of the $\alpha$ -carboxylic acid is the same as the pK_a of the $\alpha$ -amino group.
B)the $\alpha$ -carboxylic acid is protonated and the $\alpha$ -amino group is unprotonated.
C)the solubility of the amino acid is maximized.
D)the $\alpha$ -carboxylic acid and the $\alpha$ -amino group are both half protonated.
E)the amino acid carries no net electrical charge.

Question 46

Which of the following tripeptides would be expected to be the most hydrophobic?

A)KYG
B)KYA
C)GYA
D)DYA
E)DYG

Question 47

Asx refers to

A)a negatively charged aspartic acid.
B)a positively charged asparagine.
C)a dipeptide containing both aspartic acid and asparagine.
D)either aspartic acid or asparagine.
E)an unnatural amino acid formed during acid hydrolysis of peptide bonds.

Question 48

The side-chains of amino acids have

A)a positive charge in every situation.
B)pK_as that assure the solubility of every protein.
C)constant pK_as no matter what aqueous environment they are found in.
D)different pK_as in peptides as compared to the free amino acids
E)polar functional groups.

Question 49

The peptide AYDG has an N-terminal _________ residue.

A)glycine
B)glutamic acid
C)glutamine
D)aspartic acid
E)alanine

Question 50

Which of the five amino acids shown below has 2 chiral centers?

A)
B)
C)
D)
E)

Question 51

Which one of the representations describes the oligopeptide shown below?

A)Tyr-Ala-Thr
B)Tyr-Gly-Cys
C)Tyr-Ala-Ser
D)Phe-Gly-Cys
E)Phe-Ala-Thr

Question 52

The __________ character of most standard amino acids causes solutions of amino acids to rotate the plane of polarized light.

A)chiral
B)zwitterionic
C)polar
D)hydrophobic
E)none of the above

Question 53

the diagram below.

-What is the name of this molecule?

A)GABA
B)thyroxine
C)( $\gamma$ -carboxyglutamate)
D)glutathione
E)epinephrine

Question 54

Typically, modified amino acids, those with side chain modifications that are present in proteins

A)are synthesized due to genetic mutations.
B)are assembled by specialized bacterial enzymes.
C)are formed by modification of standard side chain residues after the protein is synthesized.
D)are toxic.
E)are racemic.

Question 55

The tripeptide alanyllysylaspartate contains four ionizable groups with pK_as of 2.0, 3.9, 9.9, and 10.5.Calculate the pI for this molecule.

A)3.0
B)6.0
C)6.2
D)10.2
E)none of the above

Question 56

An amide bond between a side-chain carboxylate and an $\alpha$ -amino group is also called a(n)

A)disulfide bond.
B)anhydride bond.
C)ester bond.
D)isopeptide bond.
E)glycosidic bond.

Question 57

Which of the amino acids represented below has two chiral centers?

A)Ala
B)Leu
C)Ile
D)Pro
E)Asn

Question 58

the diagram below.
Residues 1 and 2 in the peptide shown above are connected through a

A)hydrogen bond.
B)an isopeptide bond.
C)an ester linkage.
D)disulfide bond.
E)a glycosidic bond.

Question 59

What is the three-letter abbreviation for the peptide valylarginylisoleucine?

A)Val─Arg─Ile
B)Val─Agn─Leu
C)Vln─Arg─Ile
D)Val─Agn─Isl
E)Vln─Arg─Leu

Question 60

All amino acids derived from proteins have the same stereochemical conformation as.

A)L-glyceraldehyde.
B)(R)-alanine.
C)D-glucose.
D)(S)-cysteine.
E)glycine.

Question 61

In general, amino acids are chiral molecules that act as building blocks for proteins.In addition, amino acids and amino acid derivative can act as extracellular messenger molecules such as hormones or neurotransmitters.
a.How many different amino acids can be incorporated into proteins during translation?
b.Do ribosomes use L or D amino acids for protein synthesis?
c.Name one amino acid or amino acid derivative that can act as hormone or neurotransmitter.
d.Draw the predominant structure of valine at pH 10 (pK_as are 2.3 and 9.7).

Question 62

The picture below shows the structure of serotonin. a.From which amino acid is serotonin derived?
b.What are the structural differences between serotonin and this amino acid?
c.What is the function of serotonin?
d.Which illness can be caused by reduced levels of serotonin in the brain?

Question 63

The figure below shows the predominant structure of an oligopeptide at pH 7.0. a.How many amino acids are present in this peptide?
b.Circle one peptide bond in this peptide.
c.Draw a square around one alpha carbon in this peptide
d.The pK_as of the ionizable groups in this peptide are 2.0, 4.0, and 9.0.What is the ionic charge of this molecule at pH 1.0
e.What is the name of the N-terminal amino acid in this peptide?

Question 64

the diagram below.
What is the three-letter symbol of the N-terminal amino acid in the structure shown above?

A)Asp
B)Asn
C)Gln
D)Glu
E)Lys

Question 65

The picture below shows the structure of $\gamma$ -amino-butyric acid (GABA).
a.From which amino acid is GABA derived (give the name of the amino acid closest in structure to GABA).
b.What is the structural difference between GABA and this amino acid.
c.What is the function of GABA.

Question 66

Tryptophan is an amino acid (pK_as are 2.5, and 9.4).
a.How many different amino acids can be incorporated into proteins during translation?
b.Give the three- and one-letter abbreviation for tryptophan.
c.Draw the predominant structure of tryptophan at pH 7.0.
d.Calculate the pI of Tryptophan.

Question 67

Glutamine is an amino acid (pK_as are 2.2, and 9.1).Draw the predominant structure of glutamine at pH 1.0.

Question 68

Glutamic acid is an amino acid (pK_as are 2.1, 4.1 and 9.5).Calculate the isoelectric point of glutamic acid.