WGU C785 – Final Exam
Comprehensive Review
Guide with Practice
Questions Latest Edition
(2026)
Section 1: Protein Structure
Question 1:
Which level of protein structure is disrupted through the hydrolysis of
peptide bonds?
A. Quaternary
B. Tertiary
C. Primary
D. Secondary
Correct Answer: C. Primary
Detailed Explanation: The primary structure is the linear sequence of
amino acids held together by covalent peptide bonds. Peptide bonds are
formed by dehydration reactions and disrupted by hydrolysis (adding water
to cleave the bond). Secondary, tertiary, and quaternary structures depend
on non-covalent interactions (hydrogen bonds, hydrophobic interactions,
ionic bonds, van der Waals forces) and are not directly disrupted by peptide
bond hydrolysis.
,Question 2:
The alpha-helix structure in proteins is stabilized by which type of bond?
A. Disulfide bonds
B. Hydrogen bonds between backbone atoms
C. Ionic bonds between side chains
D. Hydrophobic interactions
Correct Answer: B. Hydrogen bonds between backbone atoms
Detailed Explanation: In an alpha-helix, hydrogen bonds form between
the carbonyl oxygen (C=O) of one amino acid residue and the amide
hydrogen (N-H) of the amino acid four residues down the chain. These
backbone-to-backbone hydrogen bonds create the characteristic spiral
shape. Disulfide bonds form between cysteine side chains and stabilize
tertiary structure, not secondary structure.
Question 3:
Which amino acid side chains can form ionic bonds in protein tertiary
structure?
A. Non-polar/hydrophobic amino acids
B. Polar but uncharged amino acids
C. Charged amino acids
D. All amino acids equally
Correct Answer: C. Charged amino acids
Detailed Explanation: Ionic bonds (salt bridges) form between oppositely
charged amino acid side chains. Positively charged amino acids include
lysine, arginine, and histidine. Negatively charged amino acids include
glutamate and aspartate. These interactions contribute significantly to
,tertiary structure stability, especially in proteins functioning in aqueous
environments.
Question 4:
Which event describes protein denaturation?
A. The protein breaks down into individual amino acids
B. The protein loses its secondary, tertiary, and quaternary structure but
retains primary structure
C. The protein synthesizes new peptide bonds
D. The protein changes its amino acid sequence
Correct Answer: B. The protein loses its secondary, tertiary, and
quaternary structure but retains primary structure
Detailed Explanation: Denaturation unfolds a protein from its functional
3D shape into a disordered state. Denaturing agents (heat, pH extremes,
organic solvents) disrupt non-covalent interactions stabilizing higher-order
structures but do NOT break covalent peptide bonds. The primary structure
remains intact. This differs from hydrolysis, which breaks peptide bonds and
destroys primary structure.
Question 5:
A mutation in the beta-hemoglobin gene replaces glutamate at position 6
with valine, leading to sickle cell anemia. If gene editing replaced valine
with a different amino acid, which replacement would provide the best
clinical outcome?
A. Leucine (non-polar)
B. Alanine (non-polar)
, C. Aspartate (negatively charged)
D. Glycine (non-polar)
Correct Answer: C. Aspartate (negatively charged)
Detailed Explanation: The healthy amino acid at position 6 of beta-
hemoglobin is glutamate, which carries a negative charge. This charge is
critical for maintaining hemoglobin structure and preventing aggregation.
The mutation to valine (non-polar, hydrophobic) causes hemoglobin
molecules to stick together, forming sickle-shaped cells. To restore normal
function, the replacement should be as similar to glutamate as possible—
aspartate is also negatively charged, making it the best choice.
Section 2: DNA Replication and Repair
Question 6:
Which enzyme is responsible for relieving supercoiling ahead of the
replication fork?
A. Helicase
B. DNA polymerase
C. Topoisomerase
D. Primase
Correct Answer: C. Topoisomerase
Detailed Explanation: As helicase unwinds DNA, it creates positive
supercoiling ahead of the replication fork. Topoisomerases relieve this
supercoiling to allow replication to proceed. Helicase unwinds the DNA,
DNA polymerase synthesizes new strands, and primase synthesizes RNA
primers.
Comprehensive Review
Guide with Practice
Questions Latest Edition
(2026)
Section 1: Protein Structure
Question 1:
Which level of protein structure is disrupted through the hydrolysis of
peptide bonds?
A. Quaternary
B. Tertiary
C. Primary
D. Secondary
Correct Answer: C. Primary
Detailed Explanation: The primary structure is the linear sequence of
amino acids held together by covalent peptide bonds. Peptide bonds are
formed by dehydration reactions and disrupted by hydrolysis (adding water
to cleave the bond). Secondary, tertiary, and quaternary structures depend
on non-covalent interactions (hydrogen bonds, hydrophobic interactions,
ionic bonds, van der Waals forces) and are not directly disrupted by peptide
bond hydrolysis.
,Question 2:
The alpha-helix structure in proteins is stabilized by which type of bond?
A. Disulfide bonds
B. Hydrogen bonds between backbone atoms
C. Ionic bonds between side chains
D. Hydrophobic interactions
Correct Answer: B. Hydrogen bonds between backbone atoms
Detailed Explanation: In an alpha-helix, hydrogen bonds form between
the carbonyl oxygen (C=O) of one amino acid residue and the amide
hydrogen (N-H) of the amino acid four residues down the chain. These
backbone-to-backbone hydrogen bonds create the characteristic spiral
shape. Disulfide bonds form between cysteine side chains and stabilize
tertiary structure, not secondary structure.
Question 3:
Which amino acid side chains can form ionic bonds in protein tertiary
structure?
A. Non-polar/hydrophobic amino acids
B. Polar but uncharged amino acids
C. Charged amino acids
D. All amino acids equally
Correct Answer: C. Charged amino acids
Detailed Explanation: Ionic bonds (salt bridges) form between oppositely
charged amino acid side chains. Positively charged amino acids include
lysine, arginine, and histidine. Negatively charged amino acids include
glutamate and aspartate. These interactions contribute significantly to
,tertiary structure stability, especially in proteins functioning in aqueous
environments.
Question 4:
Which event describes protein denaturation?
A. The protein breaks down into individual amino acids
B. The protein loses its secondary, tertiary, and quaternary structure but
retains primary structure
C. The protein synthesizes new peptide bonds
D. The protein changes its amino acid sequence
Correct Answer: B. The protein loses its secondary, tertiary, and
quaternary structure but retains primary structure
Detailed Explanation: Denaturation unfolds a protein from its functional
3D shape into a disordered state. Denaturing agents (heat, pH extremes,
organic solvents) disrupt non-covalent interactions stabilizing higher-order
structures but do NOT break covalent peptide bonds. The primary structure
remains intact. This differs from hydrolysis, which breaks peptide bonds and
destroys primary structure.
Question 5:
A mutation in the beta-hemoglobin gene replaces glutamate at position 6
with valine, leading to sickle cell anemia. If gene editing replaced valine
with a different amino acid, which replacement would provide the best
clinical outcome?
A. Leucine (non-polar)
B. Alanine (non-polar)
, C. Aspartate (negatively charged)
D. Glycine (non-polar)
Correct Answer: C. Aspartate (negatively charged)
Detailed Explanation: The healthy amino acid at position 6 of beta-
hemoglobin is glutamate, which carries a negative charge. This charge is
critical for maintaining hemoglobin structure and preventing aggregation.
The mutation to valine (non-polar, hydrophobic) causes hemoglobin
molecules to stick together, forming sickle-shaped cells. To restore normal
function, the replacement should be as similar to glutamate as possible—
aspartate is also negatively charged, making it the best choice.
Section 2: DNA Replication and Repair
Question 6:
Which enzyme is responsible for relieving supercoiling ahead of the
replication fork?
A. Helicase
B. DNA polymerase
C. Topoisomerase
D. Primase
Correct Answer: C. Topoisomerase
Detailed Explanation: As helicase unwinds DNA, it creates positive
supercoiling ahead of the replication fork. Topoisomerases relieve this
supercoiling to allow replication to proceed. Helicase unwinds the DNA,
DNA polymerase synthesizes new strands, and primase synthesizes RNA
primers.
