WGU C785 Final Exam 2024
With All The Correct Answers
Section 1: Amino Acids & Protein Structure
Question 1
Which of the following correctly identifies the four components of an amino acid?
A) Amino group, phosphate group, alpha carbon, and variable group
B) Amino group, carboxyl group, alpha carbon, and variable group
C) Carboxyl group, hydroxyl group, alpha carbon, and variable group
D) Amino group, carboxyl group, beta carbon, and variable group
Correct Answer: B
Rationale: The basic structure of an amino acid consists of an amino group (NH₂ or NH₃⁺), a
carboxyl group (COO⁻ or COOH), an alpha carbon (the central carbon), and a variable group (R
group) that determines the amino acid's unique properties.
Question 2
A student identifies an amino acid side chain ending in "CH₃." How should this amino acid be
classified?
A) Polar
B) Charged
C) Non-polar/hydrophobic
D) Hydrophilic
Correct Answer: C
Rationale: Non-polar/hydrophobic side chains end with "CH" (methyl, ethyl, etc.) or can be
remembered as "can't have" water. Polar side chains end with OH, SH, or NH. Charged side
chains have a positive or negative charge.
,Question 3 (SATA)
Which of the following amino acids are positively charged (basic) at physiological pH? Select all
that apply.
A) Aspartic acid
B) Lysine
C) Glutamic acid
D) Arginine
E) Histidine
Correct Answers: B, D, E
Rationale: The positively charged (basic) amino acids are lysine (Lys, K), arginine (Arg, R),
and histidine (His, H). Aspartic acid and glutamic acid are negatively charged (acidic).
Question 4
Which type of bond is formed between two cysteine amino acid side chains?
A) Hydrogen bond
B) Ionic bond
C) Disulfide bond
D) Hydrophobic interaction
Correct Answer: C
Rationale: Disulfide bonds are formed between the sulfhydryl (SH) groups of two cysteine
amino acids. These are covalent bonds and are the strongest type of bond involved in protein
structure.
Question 5
A protein is exposed to high temperatures. Which level of protein structure would be affected
first?
,A) Primary structure
B) Secondary structure
C) Tertiary structure
D) Quaternary structure
Correct Answer: B
Rationale: Secondary structure is formed by hydrogen bonds, which are susceptible to
temperature changes. Primary structure (peptide bonds) is more resistant to temperature
changes. Tertiary and quaternary structures are stabilized by various interactions including
hydrophobic, ionic, and disulfide bonds.
Question 6
Which environmental change would break hydrophobic bonds?
A) Temperature change
B) Salt or decreased pH
C) Reducing agents
D) Increased pH only
Correct Answer: A
Rationale: Hydrophobic bonds are broken by temperature changes. Ionic bonds are broken
by salt or decreased pH. Hydrogen bonds are broken by temperature, change in pH, or reducing
agents. Disulfide bonds are broken by reducing agents.
Question 7
A mutation changes a codon from GAA to GAG. Both codons code for glutamic acid. This is an
example of which type of mutation?
A) Missense mutation
B) Nonsense mutation
C) Silent mutation
D) Frameshift mutation
, Correct Answer: C
Rationale: A silent mutation changes the DNA sequence but does not change the amino
acid sequence because the genetic code is degenerate. GAA and GAG both code for glutamic
acid, so the protein remains unchanged.
Question 8
A patient presents with sickle cell disease. Which of the following best describes the molecular
basis of this condition?
A) Deletion of a single nucleotide leading to a frameshift
B) Substitution of valine for glutamic acid at the sixth position of the beta-globin chain
C) Substitution of glutamic acid for valine at the sixth position of the beta-globin chain
D) Insertion of an extra beta-globin gene
Correct Answer: B
Rationale: Sickle cell disease is caused by a single nucleotide mutation (GAG to GTG)
resulting in the substitution of valine (nonpolar) for glutamic acid (charged) at position 6 of the
beta-globin chain. This causes hemoglobin polymerization under low oxygen conditions.
Question 9
Which of the following interactions is most important for stabilizing the tertiary structure of a
globular protein?
A) Peptide bonds
B) Hydrogen bonds in the backbone
C) Hydrophobic interactions between nonpolar side chains
D) Phosphodiester bonds
Correct Answer: C
Rationale: Hydrophobic interactions between nonpolar amino acid side chains drive protein
folding, burying hydrophobic residues in the core away from water. This is a primary force in
tertiary structure formation.
With All The Correct Answers
Section 1: Amino Acids & Protein Structure
Question 1
Which of the following correctly identifies the four components of an amino acid?
A) Amino group, phosphate group, alpha carbon, and variable group
B) Amino group, carboxyl group, alpha carbon, and variable group
C) Carboxyl group, hydroxyl group, alpha carbon, and variable group
D) Amino group, carboxyl group, beta carbon, and variable group
Correct Answer: B
Rationale: The basic structure of an amino acid consists of an amino group (NH₂ or NH₃⁺), a
carboxyl group (COO⁻ or COOH), an alpha carbon (the central carbon), and a variable group (R
group) that determines the amino acid's unique properties.
Question 2
A student identifies an amino acid side chain ending in "CH₃." How should this amino acid be
classified?
A) Polar
B) Charged
C) Non-polar/hydrophobic
D) Hydrophilic
Correct Answer: C
Rationale: Non-polar/hydrophobic side chains end with "CH" (methyl, ethyl, etc.) or can be
remembered as "can't have" water. Polar side chains end with OH, SH, or NH. Charged side
chains have a positive or negative charge.
,Question 3 (SATA)
Which of the following amino acids are positively charged (basic) at physiological pH? Select all
that apply.
A) Aspartic acid
B) Lysine
C) Glutamic acid
D) Arginine
E) Histidine
Correct Answers: B, D, E
Rationale: The positively charged (basic) amino acids are lysine (Lys, K), arginine (Arg, R),
and histidine (His, H). Aspartic acid and glutamic acid are negatively charged (acidic).
Question 4
Which type of bond is formed between two cysteine amino acid side chains?
A) Hydrogen bond
B) Ionic bond
C) Disulfide bond
D) Hydrophobic interaction
Correct Answer: C
Rationale: Disulfide bonds are formed between the sulfhydryl (SH) groups of two cysteine
amino acids. These are covalent bonds and are the strongest type of bond involved in protein
structure.
Question 5
A protein is exposed to high temperatures. Which level of protein structure would be affected
first?
,A) Primary structure
B) Secondary structure
C) Tertiary structure
D) Quaternary structure
Correct Answer: B
Rationale: Secondary structure is formed by hydrogen bonds, which are susceptible to
temperature changes. Primary structure (peptide bonds) is more resistant to temperature
changes. Tertiary and quaternary structures are stabilized by various interactions including
hydrophobic, ionic, and disulfide bonds.
Question 6
Which environmental change would break hydrophobic bonds?
A) Temperature change
B) Salt or decreased pH
C) Reducing agents
D) Increased pH only
Correct Answer: A
Rationale: Hydrophobic bonds are broken by temperature changes. Ionic bonds are broken
by salt or decreased pH. Hydrogen bonds are broken by temperature, change in pH, or reducing
agents. Disulfide bonds are broken by reducing agents.
Question 7
A mutation changes a codon from GAA to GAG. Both codons code for glutamic acid. This is an
example of which type of mutation?
A) Missense mutation
B) Nonsense mutation
C) Silent mutation
D) Frameshift mutation
, Correct Answer: C
Rationale: A silent mutation changes the DNA sequence but does not change the amino
acid sequence because the genetic code is degenerate. GAA and GAG both code for glutamic
acid, so the protein remains unchanged.
Question 8
A patient presents with sickle cell disease. Which of the following best describes the molecular
basis of this condition?
A) Deletion of a single nucleotide leading to a frameshift
B) Substitution of valine for glutamic acid at the sixth position of the beta-globin chain
C) Substitution of glutamic acid for valine at the sixth position of the beta-globin chain
D) Insertion of an extra beta-globin gene
Correct Answer: B
Rationale: Sickle cell disease is caused by a single nucleotide mutation (GAG to GTG)
resulting in the substitution of valine (nonpolar) for glutamic acid (charged) at position 6 of the
beta-globin chain. This causes hemoglobin polymerization under low oxygen conditions.
Question 9
Which of the following interactions is most important for stabilizing the tertiary structure of a
globular protein?
A) Peptide bonds
B) Hydrogen bonds in the backbone
C) Hydrophobic interactions between nonpolar side chains
D) Phosphodiester bonds
Correct Answer: C
Rationale: Hydrophobic interactions between nonpolar amino acid side chains drive protein
folding, burying hydrophobic residues in the core away from water. This is a primary force in
tertiary structure formation.
