WGU C785 Biochemistry Final Exam Actual Exam 2026/2027
– Complete Solution Set with Detailed Rationales | 100%
Verified | Pass Guaranteed – A+ Graded
Section A: Cellular Metabolism & Bioenergetics (10 Questions)
Q1: A patient presents with severe fatigue and muscle weakness. Laboratory analysis
reveals decreased ATP production in skeletal muscle cells. Which molecule serves as
the primary immediate energy currency that directly powers cellular work such as
muscle contraction and active transport?
A. NADH
B. FADH₂
C. ATP [CORRECT]
D. Creatine phosphate
Correct Answer: C
Rationale: ATP (adenosine triphosphate) is the universal immediate energy currency
that directly powers cellular work including muscle contraction, active transport, and
biosynthesis. NADH (A) and FADH₂ (B) are electron carriers that generate ATP indirectly
via oxidative phosphorylation. Creatine phosphate (D) serves as a rapid phosphate
reservoir to regenerate ATP but does not directly power cellular processes.
Q2: During cellular respiration, which coenzyme is reduced to carry high-energy
electrons from the TCA cycle to the electron transport chain?
,A. NAD⁺ → NADH [CORRECT]
B. NADP⁺ → NADPH
C. FAD → FADH (incorrect reduction state)
D. Coenzyme A → Acetyl-CoA
Correct Answer: A
Rationale: NAD⁺ is reduced to NADH during the TCA cycle (at isocitrate dehydrogenase,
α-ketoglutarate dehydrogenase, and malate dehydrogenase steps), carrying electrons to
Complex I of the ETC. NADPH (B) is primarily for reductive biosynthesis and antioxidant
defense, not ETC electron donation. FAD is reduced to FADH₂ (not FADH, C). Coenzyme
A (D) carries acyl groups, not electrons.
Q3: A biochemistry student is calculating the total ATP yield from one molecule of
glucose through complete aerobic respiration. Assuming the malate-aspartate shuttle
operates, what is the approximate total ATP yield?
A. 2 ATP
B. 18 ATP
C. 32 ATP [CORRECT]
D. 38 ATP
Correct Answer: C
Rationale: Complete oxidation of glucose yields approximately 32 ATP: glycolysis (2
ATP net + 2 NADH → 4-6 ATP), pyruvate dehydrogenase (2 NADH → 6 ATP), TCA cycle
(6 NADH → 15 ATP, 2 FADH₂ → 3 ATP, 2 GTP → 2 ATP). The malate-aspartate shuttle
,(vs. glycerol-3-phosphate shuttle) yields 2.5 ATP per cytosolic NADH. The outdated 38
ATP figure (D) uses old P/O ratios of 3 and 2.
Q4: In redox reactions, which statement accurately describes the relationship between
oxidation and reduction?
A. Oxidation involves gain of electrons; reduction involves loss of electrons
B. Oxidation involves loss of electrons; reduction involves gain of electrons [CORRECT]
C. Both oxidation and reduction involve gain of electrons
D. Neither process involves electron transfer
Correct Answer: B
Rationale: Oxidation is defined as loss of electrons (or hydrogen atoms), while reduction
is gain of electrons (or hydrogen atoms). This fundamental principle applies to all
metabolic redox reactions including glycolysis, the TCA cycle, and the ETC. Option A
reverses the definitions. Options C and D are biochemically incorrect.
Q5: A patient with beriberi (thiamine deficiency) experiences neurological symptoms
and lactic acidosis. Which enzyme complex requiring thiamine pyrophosphate (TPP) as
a cofactor is most directly affected?
A. Pyruvate carboxylase
B. Pyruvate dehydrogenase complex [CORRECT]
C. Lactate dehydrogenase
D. Phosphofructokinase-1
, Correct Answer: B
Rationale: The pyruvate dehydrogenase complex requires TPP (thiamine
pyrophosphate), lipoamide, FAD, NAD⁺, and CoA as cofactors. Thiamine deficiency
impairs PDH, causing pyruvate accumulation and shunting to lactate and alanine,
producing lactic acidosis and neurological deficits. Pyruvate carboxylase (A) requires
biotin. Lactate dehydrogenase (C) requires NADH. PFK-1 (D) is allosterically regulated
but does not require TPP.
Q6: During oxidative phosphorylation, what is the final electron acceptor at Complex IV
of the electron transport chain?
A. NAD⁺
B. Ubiquinone (Coenzyme Q)
C. Oxygen [CORRECT]
D. Cytochrome c
Correct Answer: C
Rationale: Molecular oxygen (O₂) is the terminal electron acceptor at Complex IV
(cytochrome c oxidase), where it combines with electrons and protons to form water.
Without oxygen, the ETC backs up and oxidative phosphorylation ceases. NAD⁺ (A)
accepts electrons in glycolysis/TCA. Ubiquinone (B) and cytochrome c (D) are
intermediate electron carriers, not terminal acceptors.
Q7: A patient is exposed to cyanide, which binds to the iron center of cytochrome c
oxidase. What is the immediate biochemical consequence?
– Complete Solution Set with Detailed Rationales | 100%
Verified | Pass Guaranteed – A+ Graded
Section A: Cellular Metabolism & Bioenergetics (10 Questions)
Q1: A patient presents with severe fatigue and muscle weakness. Laboratory analysis
reveals decreased ATP production in skeletal muscle cells. Which molecule serves as
the primary immediate energy currency that directly powers cellular work such as
muscle contraction and active transport?
A. NADH
B. FADH₂
C. ATP [CORRECT]
D. Creatine phosphate
Correct Answer: C
Rationale: ATP (adenosine triphosphate) is the universal immediate energy currency
that directly powers cellular work including muscle contraction, active transport, and
biosynthesis. NADH (A) and FADH₂ (B) are electron carriers that generate ATP indirectly
via oxidative phosphorylation. Creatine phosphate (D) serves as a rapid phosphate
reservoir to regenerate ATP but does not directly power cellular processes.
Q2: During cellular respiration, which coenzyme is reduced to carry high-energy
electrons from the TCA cycle to the electron transport chain?
,A. NAD⁺ → NADH [CORRECT]
B. NADP⁺ → NADPH
C. FAD → FADH (incorrect reduction state)
D. Coenzyme A → Acetyl-CoA
Correct Answer: A
Rationale: NAD⁺ is reduced to NADH during the TCA cycle (at isocitrate dehydrogenase,
α-ketoglutarate dehydrogenase, and malate dehydrogenase steps), carrying electrons to
Complex I of the ETC. NADPH (B) is primarily for reductive biosynthesis and antioxidant
defense, not ETC electron donation. FAD is reduced to FADH₂ (not FADH, C). Coenzyme
A (D) carries acyl groups, not electrons.
Q3: A biochemistry student is calculating the total ATP yield from one molecule of
glucose through complete aerobic respiration. Assuming the malate-aspartate shuttle
operates, what is the approximate total ATP yield?
A. 2 ATP
B. 18 ATP
C. 32 ATP [CORRECT]
D. 38 ATP
Correct Answer: C
Rationale: Complete oxidation of glucose yields approximately 32 ATP: glycolysis (2
ATP net + 2 NADH → 4-6 ATP), pyruvate dehydrogenase (2 NADH → 6 ATP), TCA cycle
(6 NADH → 15 ATP, 2 FADH₂ → 3 ATP, 2 GTP → 2 ATP). The malate-aspartate shuttle
,(vs. glycerol-3-phosphate shuttle) yields 2.5 ATP per cytosolic NADH. The outdated 38
ATP figure (D) uses old P/O ratios of 3 and 2.
Q4: In redox reactions, which statement accurately describes the relationship between
oxidation and reduction?
A. Oxidation involves gain of electrons; reduction involves loss of electrons
B. Oxidation involves loss of electrons; reduction involves gain of electrons [CORRECT]
C. Both oxidation and reduction involve gain of electrons
D. Neither process involves electron transfer
Correct Answer: B
Rationale: Oxidation is defined as loss of electrons (or hydrogen atoms), while reduction
is gain of electrons (or hydrogen atoms). This fundamental principle applies to all
metabolic redox reactions including glycolysis, the TCA cycle, and the ETC. Option A
reverses the definitions. Options C and D are biochemically incorrect.
Q5: A patient with beriberi (thiamine deficiency) experiences neurological symptoms
and lactic acidosis. Which enzyme complex requiring thiamine pyrophosphate (TPP) as
a cofactor is most directly affected?
A. Pyruvate carboxylase
B. Pyruvate dehydrogenase complex [CORRECT]
C. Lactate dehydrogenase
D. Phosphofructokinase-1
, Correct Answer: B
Rationale: The pyruvate dehydrogenase complex requires TPP (thiamine
pyrophosphate), lipoamide, FAD, NAD⁺, and CoA as cofactors. Thiamine deficiency
impairs PDH, causing pyruvate accumulation and shunting to lactate and alanine,
producing lactic acidosis and neurological deficits. Pyruvate carboxylase (A) requires
biotin. Lactate dehydrogenase (C) requires NADH. PFK-1 (D) is allosterically regulated
but does not require TPP.
Q6: During oxidative phosphorylation, what is the final electron acceptor at Complex IV
of the electron transport chain?
A. NAD⁺
B. Ubiquinone (Coenzyme Q)
C. Oxygen [CORRECT]
D. Cytochrome c
Correct Answer: C
Rationale: Molecular oxygen (O₂) is the terminal electron acceptor at Complex IV
(cytochrome c oxidase), where it combines with electrons and protons to form water.
Without oxygen, the ETC backs up and oxidative phosphorylation ceases. NAD⁺ (A)
accepts electrons in glycolysis/TCA. Ubiquinone (B) and cytochrome c (D) are
intermediate electron carriers, not terminal acceptors.
Q7: A patient is exposed to cyanide, which binds to the iron center of cytochrome c
oxidase. What is the immediate biochemical consequence?
