BIOD 102 / BIOD102 Essential Biology II W/Lab Actual
Exam 2025/2026 with Detailed Rationales | Complete
Exam-Style Questions | Pass Guaranteed – A+ Graded
SECTION 1: CELLULAR RESPIRATION & METABOLISM (Questions 1–12)
Q1: Which cellular compartment is the exclusive site of glycolysis in eukaryotic cells?
A. Mitochondrial matrix
B. Inner mitochondrial membrane
C. Cytoplasm [CORRECT]
D. Peroxisome
Correct Answer: C
Rationale: Correct because glycolysis is the metabolic pathway that breaks down
glucose into two pyruvate molecules and occurs entirely in the cytoplasm, yielding a
net gain of 2 ATP and 2 NADH per glucose.
Q2: During aerobic cellular respiration, which molecule serves as the terminal
electron acceptor at the end of the electron transport chain?
A. NAD+
B. FAD
C. Oxygen [CORRECT]
D. Carbon dioxide
Correct Answer: C
Rationale: Correct because oxygen accepts electrons and protons at Complex IV of
the electron transport chain, forming water as the final product and enabling
continuous electron flow for proton pumping.
Q3: What is the net ATP yield from substrate-level phosphorylation during glycolysis
per molecule of glucose?
A. 4 ATP
B. 2 ATP [CORRECT]
C. 32 ATP
D. 36 ATP
Correct Answer: B
,Rationale: Correct because glycolysis generates 4 ATP through substrate-level
phosphorylation but consumes 2 ATP during the energy investment phase, resulting
in a net production of 2 ATP per glucose molecule.
Q4: Which of the following molecules is NOT a direct product of the Krebs cycle
(citric acid cycle)?
A. NADH
B. FADH2
C. GTP
D. Pyruvate [CORRECT]
Correct Answer: D
Rationale: Correct because pyruvate is converted to acetyl-CoA by the pyruvate
dehydrogenase complex before entering the Krebs cycle; the cycle itself produces
NADH, FADH2, GTP, and CO2, but not pyruvate.
Q5: Under anaerobic conditions, human muscle cells convert pyruvate to which end
product to regenerate NAD+?
A. Acetyl-CoA
B. Ethanol and carbon dioxide
C. Lactate [CORRECT]
D. Oxaloacetate
Correct Answer: C
Rationale: Correct because human muscle cells perform lactic acid fermentation, in
which pyruvate is reduced by NADH to form lactate, regenerating NAD+ to sustain
glycolytic ATP production in the absence of oxygen.
Q6: A 12-year-old patient presents with exercise intolerance, muscle weakness, and
severe lactic acidosis after mild physical activity. Muscle biopsy reveals structurally
normal mitochondria, but biochemical assay shows a defective pyruvate
dehydrogenase complex. Which metabolic consequence best explains the lactic
acidosis?
A. Pyruvate cannot enter glycolysis and accumulates in muscle fibers
B. Pyruvate cannot be converted to acetyl-CoA and is shunted to lactate [CORRECT]
C. Pyruvate is converted to ethanol instead of lactate in human cells
D. Acetyl-CoA accumulates and directly inhibits lactate dehydrogenase
Correct Answer: B
, Rationale: Correct because the pyruvate dehydrogenase complex catalyzes the
conversion of pyruvate to acetyl-CoA for Krebs cycle entry; when defective, pyruvate
is diverted to lactate via lactate dehydrogenase, causing lactic acidosis.
Q7: Which coenzymes carry high-energy electrons from glycolysis and the Krebs
cycle to the electron transport chain?
A. ATP synthase and cytochrome c
B. NADH and FADH2 [CORRECT]
C. Coenzyme A and biotin
D. Acetyl-CoA and pyruvate
Correct Answer: B
Rationale: Correct because NADH donates electrons to Complex I and FADH2
donates electrons to Complex II of the electron transport chain, providing the energy
required to pump protons and establish the proton-motive force.
Q8: In eukaryotic cells, where are the protein complexes of the electron transport
chain and ATP synthase physically located?
A. Cytoplasm
B. Mitochondrial matrix
C. Inner mitochondrial membrane [CORRECT]
D. Outer mitochondrial membrane
Correct Answer: C
Rationale: Correct because the electron transport chain complexes and ATP
synthase are embedded in the inner mitochondrial membrane, where they create the
electrochemical proton gradient that drives oxidative phosphorylation.
Q9: What is the primary function of the proton gradient generated across the inner
mitochondrial membrane during electron transport?
A. To directly phosphorylate glucose to glucose-6-phosphate
B. To drive ATP synthesis through chemiosmosis and ATP synthase [CORRECT]
C. To convert NADH to NAD+ for reuse in glycolysis
D. To produce carbon dioxide as a waste product
Correct Answer: B
Rationale: Correct because the proton-motive force drives protons back into the
mitochondrial matrix through ATP synthase, causing conformational changes that
catalyze the phosphorylation of ADP to ATP.
Exam 2025/2026 with Detailed Rationales | Complete
Exam-Style Questions | Pass Guaranteed – A+ Graded
SECTION 1: CELLULAR RESPIRATION & METABOLISM (Questions 1–12)
Q1: Which cellular compartment is the exclusive site of glycolysis in eukaryotic cells?
A. Mitochondrial matrix
B. Inner mitochondrial membrane
C. Cytoplasm [CORRECT]
D. Peroxisome
Correct Answer: C
Rationale: Correct because glycolysis is the metabolic pathway that breaks down
glucose into two pyruvate molecules and occurs entirely in the cytoplasm, yielding a
net gain of 2 ATP and 2 NADH per glucose.
Q2: During aerobic cellular respiration, which molecule serves as the terminal
electron acceptor at the end of the electron transport chain?
A. NAD+
B. FAD
C. Oxygen [CORRECT]
D. Carbon dioxide
Correct Answer: C
Rationale: Correct because oxygen accepts electrons and protons at Complex IV of
the electron transport chain, forming water as the final product and enabling
continuous electron flow for proton pumping.
Q3: What is the net ATP yield from substrate-level phosphorylation during glycolysis
per molecule of glucose?
A. 4 ATP
B. 2 ATP [CORRECT]
C. 32 ATP
D. 36 ATP
Correct Answer: B
,Rationale: Correct because glycolysis generates 4 ATP through substrate-level
phosphorylation but consumes 2 ATP during the energy investment phase, resulting
in a net production of 2 ATP per glucose molecule.
Q4: Which of the following molecules is NOT a direct product of the Krebs cycle
(citric acid cycle)?
A. NADH
B. FADH2
C. GTP
D. Pyruvate [CORRECT]
Correct Answer: D
Rationale: Correct because pyruvate is converted to acetyl-CoA by the pyruvate
dehydrogenase complex before entering the Krebs cycle; the cycle itself produces
NADH, FADH2, GTP, and CO2, but not pyruvate.
Q5: Under anaerobic conditions, human muscle cells convert pyruvate to which end
product to regenerate NAD+?
A. Acetyl-CoA
B. Ethanol and carbon dioxide
C. Lactate [CORRECT]
D. Oxaloacetate
Correct Answer: C
Rationale: Correct because human muscle cells perform lactic acid fermentation, in
which pyruvate is reduced by NADH to form lactate, regenerating NAD+ to sustain
glycolytic ATP production in the absence of oxygen.
Q6: A 12-year-old patient presents with exercise intolerance, muscle weakness, and
severe lactic acidosis after mild physical activity. Muscle biopsy reveals structurally
normal mitochondria, but biochemical assay shows a defective pyruvate
dehydrogenase complex. Which metabolic consequence best explains the lactic
acidosis?
A. Pyruvate cannot enter glycolysis and accumulates in muscle fibers
B. Pyruvate cannot be converted to acetyl-CoA and is shunted to lactate [CORRECT]
C. Pyruvate is converted to ethanol instead of lactate in human cells
D. Acetyl-CoA accumulates and directly inhibits lactate dehydrogenase
Correct Answer: B
, Rationale: Correct because the pyruvate dehydrogenase complex catalyzes the
conversion of pyruvate to acetyl-CoA for Krebs cycle entry; when defective, pyruvate
is diverted to lactate via lactate dehydrogenase, causing lactic acidosis.
Q7: Which coenzymes carry high-energy electrons from glycolysis and the Krebs
cycle to the electron transport chain?
A. ATP synthase and cytochrome c
B. NADH and FADH2 [CORRECT]
C. Coenzyme A and biotin
D. Acetyl-CoA and pyruvate
Correct Answer: B
Rationale: Correct because NADH donates electrons to Complex I and FADH2
donates electrons to Complex II of the electron transport chain, providing the energy
required to pump protons and establish the proton-motive force.
Q8: In eukaryotic cells, where are the protein complexes of the electron transport
chain and ATP synthase physically located?
A. Cytoplasm
B. Mitochondrial matrix
C. Inner mitochondrial membrane [CORRECT]
D. Outer mitochondrial membrane
Correct Answer: C
Rationale: Correct because the electron transport chain complexes and ATP
synthase are embedded in the inner mitochondrial membrane, where they create the
electrochemical proton gradient that drives oxidative phosphorylation.
Q9: What is the primary function of the proton gradient generated across the inner
mitochondrial membrane during electron transport?
A. To directly phosphorylate glucose to glucose-6-phosphate
B. To drive ATP synthesis through chemiosmosis and ATP synthase [CORRECT]
C. To convert NADH to NAD+ for reuse in glycolysis
D. To produce carbon dioxide as a waste product
Correct Answer: B
Rationale: Correct because the proton-motive force drives protons back into the
mitochondrial matrix through ATP synthase, causing conformational changes that
catalyze the phosphorylation of ADP to ATP.
