WGU C785 Oa and pa Exam 2026
2026 | ACTUAL REAL EXAM
QUESTIONS AND ANSWERS WITH
A PRACTICE EXAM TEST BANK
AND STUDY GUIDE | VERIFIED
AND ACCURATE FOR
GUARANTEED PASS | GRADED A
Questions 1–10: Protein Structure & Amino Acids
Question 1
Which amino acid has a sulfur-containing side chain and forms disulfide bridges?
A) Methionine
B) Cysteine ✅
C) Serine
D) Threonine
Rationale: Cysteine contains a thiol (-SH) group that can oxidize to form disulfide
bonds (cystine), stabilizing protein tertiary and quaternary structure. Methionine
also contains sulfur but does not form disulfide bridges.
,Question 2
A mutation changes a polar amino acid to a nonpolar amino acid in the core of a
globular protein. What is the most likely consequence?
A) No effect
B) Protein misfolding or destabilization ✅
C) Increased solubility
D) Enhanced enzyme activity
Rationale: Hydrophobic interactions drive protein folding. Introducing a polar
amino acid into the hydrophobic core disrupts these interactions, often causing
misfolding or reduced stability. Changing polarity directionally alters core packing.
Question 3
Which level of protein structure is disrupted by denaturation but not by hydrolysis?
A) Primary structure
B) Secondary, tertiary, and quaternary structure ✅
C) Only secondary structure
D) Only quaternary structure
Rationale: Denaturation (heat, pH, urea) disrupts non-covalent interactions,
breaking secondary (hydrogen bonds), tertiary (hydrophobic, ionic, H-bonds), and
quaternary structure. Primary structure (peptide bonds) requires hydrolysis to
break.
Question 4
A patient with sickle cell disease has a mutation in the β-globin gene replacing
glutamate with valine at position 6. How does this affect hemoglobin function?
,A) Increased oxygen affinity
B) Polymerization under low oxygen → sickling ✅
C) Complete loss of heme binding
D) No functional change
Rationale: Glutamate (charged, hydrophilic) to valine (nonpolar, hydrophobic)
creates a sticky patch on deoxygenated hemoglobin, causing polymerization and
RBC sickling. Oxygen affinity decreases, not increases.
Question 5
Which test would directly confirm the diagnosis of sickle cell disease?
A) Complete blood count (CBC)
B) Hemoglobin electrophoresis ✅
C) Iron studies
D) Bone marrow biopsy
Rationale: Hemoglobin electrophoresis separates hemoglobins by charge. HbS
(sickle) migrates differently from HbA (normal). CBC shows anemia but is not
diagnostic.
Question 6
A patient with Alzheimer's disease has amyloid plaques. These plaques primarily
consist of:
A) Tau protein
B) β-amyloid peptide ✅
C) α-synuclein
D) Prion protein
, Rationale: Alzheimer's plaques are extracellular deposits of β-amyloid (Aβ),
derived from amyloid precursor protein (APP). Tau aggregates form
neurofibrillary tangles intracellularly.
Question 7
Which amino acid is most likely found in a transmembrane domain of a protein?
A) Lysine (charged)
B) Glutamic acid (charged)
C) Leucine (nonpolar) ✅
D) Serine (polar uncharged)
Rationale: Transmembrane domains cross the lipid bilayer hydrophobic core.
Nonpolar (hydrophobic) amino acids like leucine, valine, isoleucine, and
phenylalanine are favored. Charged/polar residues disrupt membrane integration.
Question 8
The peptide bond between amino acids has partial double-bond character. This
results in:
A) Free rotation around the bond
B) Rigidity and planarity ✅
C) Susceptibility to reducing agents
D) Ability to form disulfide bonds
Rationale: The C-N peptide bond has partial double bond character due to
resonance, making it rigid and planar (six atoms lie in a plane). Rotation occurs
around the N-Cα and Cα-C bonds, not the peptide bond itself.
2026 | ACTUAL REAL EXAM
QUESTIONS AND ANSWERS WITH
A PRACTICE EXAM TEST BANK
AND STUDY GUIDE | VERIFIED
AND ACCURATE FOR
GUARANTEED PASS | GRADED A
Questions 1–10: Protein Structure & Amino Acids
Question 1
Which amino acid has a sulfur-containing side chain and forms disulfide bridges?
A) Methionine
B) Cysteine ✅
C) Serine
D) Threonine
Rationale: Cysteine contains a thiol (-SH) group that can oxidize to form disulfide
bonds (cystine), stabilizing protein tertiary and quaternary structure. Methionine
also contains sulfur but does not form disulfide bridges.
,Question 2
A mutation changes a polar amino acid to a nonpolar amino acid in the core of a
globular protein. What is the most likely consequence?
A) No effect
B) Protein misfolding or destabilization ✅
C) Increased solubility
D) Enhanced enzyme activity
Rationale: Hydrophobic interactions drive protein folding. Introducing a polar
amino acid into the hydrophobic core disrupts these interactions, often causing
misfolding or reduced stability. Changing polarity directionally alters core packing.
Question 3
Which level of protein structure is disrupted by denaturation but not by hydrolysis?
A) Primary structure
B) Secondary, tertiary, and quaternary structure ✅
C) Only secondary structure
D) Only quaternary structure
Rationale: Denaturation (heat, pH, urea) disrupts non-covalent interactions,
breaking secondary (hydrogen bonds), tertiary (hydrophobic, ionic, H-bonds), and
quaternary structure. Primary structure (peptide bonds) requires hydrolysis to
break.
Question 4
A patient with sickle cell disease has a mutation in the β-globin gene replacing
glutamate with valine at position 6. How does this affect hemoglobin function?
,A) Increased oxygen affinity
B) Polymerization under low oxygen → sickling ✅
C) Complete loss of heme binding
D) No functional change
Rationale: Glutamate (charged, hydrophilic) to valine (nonpolar, hydrophobic)
creates a sticky patch on deoxygenated hemoglobin, causing polymerization and
RBC sickling. Oxygen affinity decreases, not increases.
Question 5
Which test would directly confirm the diagnosis of sickle cell disease?
A) Complete blood count (CBC)
B) Hemoglobin electrophoresis ✅
C) Iron studies
D) Bone marrow biopsy
Rationale: Hemoglobin electrophoresis separates hemoglobins by charge. HbS
(sickle) migrates differently from HbA (normal). CBC shows anemia but is not
diagnostic.
Question 6
A patient with Alzheimer's disease has amyloid plaques. These plaques primarily
consist of:
A) Tau protein
B) β-amyloid peptide ✅
C) α-synuclein
D) Prion protein
, Rationale: Alzheimer's plaques are extracellular deposits of β-amyloid (Aβ),
derived from amyloid precursor protein (APP). Tau aggregates form
neurofibrillary tangles intracellularly.
Question 7
Which amino acid is most likely found in a transmembrane domain of a protein?
A) Lysine (charged)
B) Glutamic acid (charged)
C) Leucine (nonpolar) ✅
D) Serine (polar uncharged)
Rationale: Transmembrane domains cross the lipid bilayer hydrophobic core.
Nonpolar (hydrophobic) amino acids like leucine, valine, isoleucine, and
phenylalanine are favored. Charged/polar residues disrupt membrane integration.
Question 8
The peptide bond between amino acids has partial double-bond character. This
results in:
A) Free rotation around the bond
B) Rigidity and planarity ✅
C) Susceptibility to reducing agents
D) Ability to form disulfide bonds
Rationale: The C-N peptide bond has partial double bond character due to
resonance, making it rigid and planar (six atoms lie in a plane). Rotation occurs
around the N-Cα and Cα-C bonds, not the peptide bond itself.
