WGU C785 Biochemistry Unit Exam Questions &
Answers Latest 2026/2027 with Complete Solution
Biochemistry Unit Studies | Key Domains: Amino Acids & Protein Structure, Enzyme Function &
Kinetics, Carbohydrate Metabolism (Glycolysis, Gluconeogenesis, PPP), Citric Acid Cycle & Oxidative
Phosphorylation, Lipid Metabolism, Nitrogen Metabolism & Nucleic Acids, DNA Replication &
Repair, and Genetic & Metabolic Regulation | Expert-Aligned Structure | Unit Exam Format
Introduction
This structured WGU C785 Biochemistry Unit Exam compilation for 2026/2027 provides a
comprehensive set of unit-specific exam questions with correct answers and rationales. It
emphasizes mastery of discrete biochemical modules, connecting molecular structures to metabolic
functions, interpreting experimental data, and understanding the regulatory mechanisms that
maintain cellular homeostasis.
Exam Structure:
• Comprehensive Unit Exam Set: (150+ QUESTIONS ACROSS ALL UNITS)
Answer Format
All correct answers must appear in bold and cyan blue, accompanied by concise rationales
explaining the structural property, enzymatic mechanism, metabolic pathway step, regulatory
signal, or consequence of a genetic mutation, and why alternative options are incorrect based on
fundamental biochemical principles.
1. Which amino acid is most likely to be found in the interior of a globular protein in an
aqueous environment?
A. Aspartic acid
B. Lysine
C. Phenylalanine
D. Arginine
C. Phenylalanine
,Phenylalanine is a nonpolar, hydrophobic amino acid that stabilizes the protein core by avoiding
water. Aspartic acid (A), lysine (B), and arginine (D) are charged and hydrophilic, favoring the protein
surface.
2. A protein loses its enzymatic activity when treated with urea but regains it upon urea
removal. Which level of protein structure was disrupted?
A. Primary
B. Secondary
C. Tertiary
D. Quaternary
C. Tertiary
Urea disrupts hydrogen bonding and hydrophobic interactions, denaturing tertiary structure (3D
folding) without breaking peptide bonds (primary structure). Since activity is restored, the primary
structure remains intact, allowing refolding.
3. An enzyme inhibitor increases the apparent Km but does not affect Vmax. This is
characteristic of:
A. Non-competitive inhibition
B. Uncompetitive inhibition
C. Competitive inhibition
D. Irreversible inhibition
C. Competitive inhibition
Competitive inhibitors bind the active site, increasing the apparent Km (more substrate needed to
outcompete inhibitor) but leaving Vmax unchanged. Non-competitive (A) decreases Vmax.
Uncompetitive (B) decreases both Km and Vmax.
4. Which cofactor is required for transamination reactions involving amino acids?
, A. NAD+
B. FAD
C. Pyridoxal phosphate (PLP)
D. Biotin
C. Pyridoxal phosphate (PLP)
PLP, derived from vitamin B6, is the essential cofactor for transaminases (aminotransferases),
facilitating the transfer of amino groups between amino acids and α-keto acids. NAD+ (A) and FAD (B)
are redox cofactors. Biotin (D) is used in carboxylation reactions.
5. In glycolysis, which enzyme catalyzes the first committed step?
A. Hexokinase
B. Phosphofructokinase-1 (PFK-1)
C. Aldolase
D. Pyruvate kinase
B. Phosphofructokinase-1 (PFK-1)
PFK-1 converts fructose-6-phosphate to fructose-1,6-bisphosphate, the first step unique to glycolysis
(not shared with other pathways like PPP or glycogen synthesis). Hexokinase (A) also phosphorylates
mannose and fructose. Aldolase (C) and pyruvate kinase (D) are downstream.
6. A deficiency in glucose-6-phosphate dehydrogenase (G6PD) primarily affects which
pathway?
A. Glycolysis
B. Citric acid cycle
, C. Pentose phosphate pathway (PPP)
D. Gluconeogenesis
C. Pentose phosphate pathway (PPP)
G6PD catalyzes the first step of the oxidative phase of the PPP, generating NADPH. Deficiency impairs
NADPH production, leading to oxidative stress and hemolysis. Glycolysis (A), citric acid cycle (B), and
gluconeogenesis (D) are not directly dependent on G6PD.
7. Which enzyme in the citric acid cycle is embedded in the inner mitochondrial membrane?
A. Citrate synthase
B. Isocitrate dehydrogenase
C. Succinate dehydrogenase
D. Malate dehydrogenase
C. Succinate dehydrogenase
Succinate dehydrogenase is Complex II of the electron transport chain and is the only citric acid cycle
enzyme embedded in the inner mitochondrial membrane. The others are soluble in the mitochondrial
matrix.
8. How many ATP molecules are produced directly (substrate-level phosphorylation) from
one turn of the citric acid cycle?
A. 1
B. 2
C. 3
D. 4
Answers Latest 2026/2027 with Complete Solution
Biochemistry Unit Studies | Key Domains: Amino Acids & Protein Structure, Enzyme Function &
Kinetics, Carbohydrate Metabolism (Glycolysis, Gluconeogenesis, PPP), Citric Acid Cycle & Oxidative
Phosphorylation, Lipid Metabolism, Nitrogen Metabolism & Nucleic Acids, DNA Replication &
Repair, and Genetic & Metabolic Regulation | Expert-Aligned Structure | Unit Exam Format
Introduction
This structured WGU C785 Biochemistry Unit Exam compilation for 2026/2027 provides a
comprehensive set of unit-specific exam questions with correct answers and rationales. It
emphasizes mastery of discrete biochemical modules, connecting molecular structures to metabolic
functions, interpreting experimental data, and understanding the regulatory mechanisms that
maintain cellular homeostasis.
Exam Structure:
• Comprehensive Unit Exam Set: (150+ QUESTIONS ACROSS ALL UNITS)
Answer Format
All correct answers must appear in bold and cyan blue, accompanied by concise rationales
explaining the structural property, enzymatic mechanism, metabolic pathway step, regulatory
signal, or consequence of a genetic mutation, and why alternative options are incorrect based on
fundamental biochemical principles.
1. Which amino acid is most likely to be found in the interior of a globular protein in an
aqueous environment?
A. Aspartic acid
B. Lysine
C. Phenylalanine
D. Arginine
C. Phenylalanine
,Phenylalanine is a nonpolar, hydrophobic amino acid that stabilizes the protein core by avoiding
water. Aspartic acid (A), lysine (B), and arginine (D) are charged and hydrophilic, favoring the protein
surface.
2. A protein loses its enzymatic activity when treated with urea but regains it upon urea
removal. Which level of protein structure was disrupted?
A. Primary
B. Secondary
C. Tertiary
D. Quaternary
C. Tertiary
Urea disrupts hydrogen bonding and hydrophobic interactions, denaturing tertiary structure (3D
folding) without breaking peptide bonds (primary structure). Since activity is restored, the primary
structure remains intact, allowing refolding.
3. An enzyme inhibitor increases the apparent Km but does not affect Vmax. This is
characteristic of:
A. Non-competitive inhibition
B. Uncompetitive inhibition
C. Competitive inhibition
D. Irreversible inhibition
C. Competitive inhibition
Competitive inhibitors bind the active site, increasing the apparent Km (more substrate needed to
outcompete inhibitor) but leaving Vmax unchanged. Non-competitive (A) decreases Vmax.
Uncompetitive (B) decreases both Km and Vmax.
4. Which cofactor is required for transamination reactions involving amino acids?
, A. NAD+
B. FAD
C. Pyridoxal phosphate (PLP)
D. Biotin
C. Pyridoxal phosphate (PLP)
PLP, derived from vitamin B6, is the essential cofactor for transaminases (aminotransferases),
facilitating the transfer of amino groups between amino acids and α-keto acids. NAD+ (A) and FAD (B)
are redox cofactors. Biotin (D) is used in carboxylation reactions.
5. In glycolysis, which enzyme catalyzes the first committed step?
A. Hexokinase
B. Phosphofructokinase-1 (PFK-1)
C. Aldolase
D. Pyruvate kinase
B. Phosphofructokinase-1 (PFK-1)
PFK-1 converts fructose-6-phosphate to fructose-1,6-bisphosphate, the first step unique to glycolysis
(not shared with other pathways like PPP or glycogen synthesis). Hexokinase (A) also phosphorylates
mannose and fructose. Aldolase (C) and pyruvate kinase (D) are downstream.
6. A deficiency in glucose-6-phosphate dehydrogenase (G6PD) primarily affects which
pathway?
A. Glycolysis
B. Citric acid cycle
, C. Pentose phosphate pathway (PPP)
D. Gluconeogenesis
C. Pentose phosphate pathway (PPP)
G6PD catalyzes the first step of the oxidative phase of the PPP, generating NADPH. Deficiency impairs
NADPH production, leading to oxidative stress and hemolysis. Glycolysis (A), citric acid cycle (B), and
gluconeogenesis (D) are not directly dependent on G6PD.
7. Which enzyme in the citric acid cycle is embedded in the inner mitochondrial membrane?
A. Citrate synthase
B. Isocitrate dehydrogenase
C. Succinate dehydrogenase
D. Malate dehydrogenase
C. Succinate dehydrogenase
Succinate dehydrogenase is Complex II of the electron transport chain and is the only citric acid cycle
enzyme embedded in the inner mitochondrial membrane. The others are soluble in the mitochondrial
matrix.
8. How many ATP molecules are produced directly (substrate-level phosphorylation) from
one turn of the citric acid cycle?
A. 1
B. 2
C. 3
D. 4
