Biochemistry Chapter 4,5,& 6 Test Bank
Questions Exam2 Questions with Verified
Answers
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 -Answer- E
Which of the following amino acids has a sulfur atom in its side chain?
A) Asn
B) Ser
C) Phe
D) Met
E) Tyr -Answer- D
Which of the following amino acids does NOT have an ionizable side chain?
A) Asp
B) Cys
C) Lys
D) His
E) Asn -Answer- E
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 -Answer- B
What is the structure of Asn? -Answer-
The ionization of amino acids depends on the pH and the pKas of the ionizable
groups. The pK1 and pK2 for the amino acid (Asn shown in previous question) are
2.1 and 8.8, respectively. At what pH is the amino acid ionized predominantly as
shown? -Answer- pH 1.0
The pK1, pK2, and pKR 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: -
Answer- α-carboxylate-1, α-amino+1, guanidino+1, net charge +1
,The pK1, pK2, and pKR 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: -
Answer- α-carboxylate -1, α-amino +1, β-Carboxylate -1, Net charge -1
The pK 1 , pK 2 , 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: -Answer- α-
carboxylate −1, α-amino 0, γ-carboxylate −1, net charge −2
The pK 1 , pK 2 , 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: -Answer- α-carboxylate −1, α-amino
+1, imidazole +1, net charge +1
The pK 1 , pK 2 , 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: -Answer- α-carboxylate −1,
α-amino +1, sulfhydryl 0, net charge 0
The pK 1 , pK 2 , 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: -Answer- α-carboxylate 0, α-
amino +1, ε-amino +1, net charge +2
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 -
Answer- Disulfide Bonds
The disulfide bond betwee 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. -Answer- D) Is covalent bond formed by oxidation
The tripeptide glycylarginylglutamate contains four ionizable groups with pKas of 2.1,
4.1, 9.8, and 12.5. Calculate the pI for this molecule -Answer- 7.0
The tripeptide alanyllysylaspartate contains four ionizable groups with pKas 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 -Answer- E
, The isoelectronic point of an amino acid is the point where -Answer- the amino acid
carries no net electrical charge
The side-chains of amino acids have -Answer- Different pKas in peptides as
compared to the free amino acids
Axs refers to -Answer- either aspartic acid or asparganine
The peptide AYDG has an N-terminal ____ residue -Answer- Alanine
Which of the following tripeptides would be expected to be the most hydrophobic?
A) KYG
B) KYA
C) GYA
D) DYA
E) DYG -Answer- C
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 -Answer- A
Ribosomes use L amino acids to synthesize proteins. These amino acids are called
"L" because -Answer- They have a configuration of groups around the Cα that an be
related to the configuration of groups around the asymmetric carbon in L-
glyceraldehyde
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 -Answer- E
Which of the amino acids represented below has two chiral centers?
A) Ala
B) Leu
C) Ile
D) Pro
E) Asn -Answer- C
All the standard amino acids except ___ are optically active -Answer- Gly
The ___ Character of most standard amino acids causes solutions of amino acids to
rotate the plane of polarized light -Answer- Chiral
Questions Exam2 Questions with Verified
Answers
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 -Answer- E
Which of the following amino acids has a sulfur atom in its side chain?
A) Asn
B) Ser
C) Phe
D) Met
E) Tyr -Answer- D
Which of the following amino acids does NOT have an ionizable side chain?
A) Asp
B) Cys
C) Lys
D) His
E) Asn -Answer- E
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 -Answer- B
What is the structure of Asn? -Answer-
The ionization of amino acids depends on the pH and the pKas of the ionizable
groups. The pK1 and pK2 for the amino acid (Asn shown in previous question) are
2.1 and 8.8, respectively. At what pH is the amino acid ionized predominantly as
shown? -Answer- pH 1.0
The pK1, pK2, and pKR 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: -
Answer- α-carboxylate-1, α-amino+1, guanidino+1, net charge +1
,The pK1, pK2, and pKR 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: -
Answer- α-carboxylate -1, α-amino +1, β-Carboxylate -1, Net charge -1
The pK 1 , pK 2 , 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: -Answer- α-
carboxylate −1, α-amino 0, γ-carboxylate −1, net charge −2
The pK 1 , pK 2 , 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: -Answer- α-carboxylate −1, α-amino
+1, imidazole +1, net charge +1
The pK 1 , pK 2 , 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: -Answer- α-carboxylate −1,
α-amino +1, sulfhydryl 0, net charge 0
The pK 1 , pK 2 , 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: -Answer- α-carboxylate 0, α-
amino +1, ε-amino +1, net charge +2
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 -
Answer- Disulfide Bonds
The disulfide bond betwee 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. -Answer- D) Is covalent bond formed by oxidation
The tripeptide glycylarginylglutamate contains four ionizable groups with pKas of 2.1,
4.1, 9.8, and 12.5. Calculate the pI for this molecule -Answer- 7.0
The tripeptide alanyllysylaspartate contains four ionizable groups with pKas 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 -Answer- E
, The isoelectronic point of an amino acid is the point where -Answer- the amino acid
carries no net electrical charge
The side-chains of amino acids have -Answer- Different pKas in peptides as
compared to the free amino acids
Axs refers to -Answer- either aspartic acid or asparganine
The peptide AYDG has an N-terminal ____ residue -Answer- Alanine
Which of the following tripeptides would be expected to be the most hydrophobic?
A) KYG
B) KYA
C) GYA
D) DYA
E) DYG -Answer- C
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 -Answer- A
Ribosomes use L amino acids to synthesize proteins. These amino acids are called
"L" because -Answer- They have a configuration of groups around the Cα that an be
related to the configuration of groups around the asymmetric carbon in L-
glyceraldehyde
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 -Answer- E
Which of the amino acids represented below has two chiral centers?
A) Ala
B) Leu
C) Ile
D) Pro
E) Asn -Answer- C
All the standard amino acids except ___ are optically active -Answer- Gly
The ___ Character of most standard amino acids causes solutions of amino acids to
rotate the plane of polarized light -Answer- Chiral
