BIOD 102 Essential Biology II W/Lab Practice Exam Actual
Exam 2026/2027 | Complete Exam-Style Questions with
Detailed Rationales | Pass Guaranteed – A+ Graded
Section 1: Cellular Respiration & Fermentation (15 Questions)
Q1: During cellular respiration, glycolysis occurs in which cellular location?
A. The mitochondrial matrix
B. The inner mitochondrial membrane
C. The cytoplasm [CORRECT]
D. The intermembrane space
Correct Answer: C
Rationale: Correct because glycolysis is the metabolic pathway that breaks down
glucose into two pyruvate molecules and occurs exclusively in the cytoplasm of the cell.
Q2: What is the net ATP yield from one molecule of glucose during glycolysis?
A. 4 ATP
B. 2 ATP [CORRECT]
C. 32 ATP
D. 0 ATP
Correct Answer: B
Rationale: Correct because glycolysis produces 4 ATP through substrate-level
phosphorylation but consumes 2 ATP in the energy investment phase, resulting in a net
gain of 2 ATP.
Q3: In the absence of oxygen, mammalian muscle cells convert pyruvate to:
,A. Acetyl-CoA and CO₂
B. Ethanol and carbon dioxide
C. Lactate [CORRECT]
D. Citrate
Correct Answer: C
Rationale: Correct because under anaerobic conditions, mammalian muscle cells
regenerate NAD⁺ through lactic acid fermentation, reducing pyruvate to lactate without
releasing CO₂.
Q4: The Krebs cycle takes place in which compartment of the mitochondria?
A. The outer membrane
B. The intermembrane space
C. The mitochondrial matrix [CORRECT]
D. The cytoplasm
Correct Answer: C
Rationale: Correct because the Krebs cycle (citric acid cycle) enzymes are located in the
mitochondrial matrix, where acetyl-CoA is oxidized to produce NADH, FADH₂, and ATP.
Q5: Which molecule serves as the final electron acceptor in the electron transport chain
during aerobic respiration?
A. Carbon dioxide
B. Water
C. Oxygen [CORRECT]
D. NADH
Correct Answer: C
Rationale: Correct because oxygen has high electronegativity and accepts electrons at
the end of the electron transport chain, forming water with protons.
Q6: Most ATP generated during cellular respiration is produced by which process?
A. Substrate-level phosphorylation in glycolysis
B. Substrate-level phosphorylation in the Krebs cycle
C. Oxidative phosphorylation via chemiosmosis [CORRECT]
D. Decarboxylation of pyruvate
,Correct Answer: C
Rationale: Correct because oxidative phosphorylation uses the proton gradient
established by the electron transport chain to drive ATP synthase, producing
approximately 26–28 of the total 30–32 ATP.
Q7: Which of the following electron carriers produces fewer ATP molecules when
oxidized by the electron transport chain?
A. NADH
B. FADH₂ [CORRECT]
C. Both produce equal ATP
D. Neither produces ATP
Correct Answer: B
Rationale: Correct because FADH₂ donates electrons to Complex II, bypassing Complex
I and pumping fewer protons into the intermembrane space, resulting in approximately
1.5 ATP compared to NADH's 2.5 ATP.
Q8: During alcoholic fermentation in yeast, pyruvate is converted to:
A. Lactate and NAD⁺
B. Acetaldehyde and then ethanol [CORRECT]
C. Acetyl-CoA and CO₂
D. Oxaloacetate and NADH
Correct Answer: B
Rationale: Correct because yeast first decarboxylates pyruvate to acetaldehyde,
releasing CO₂, then reduces acetaldehyde to ethanol while oxidizing NADH to NAD⁺ to
sustain glycolysis.
Q9: A patient presents with muscle weakness and inability to perform sustained
exercise. Biopsy reveals defective mitochondrial ATP synthase. Which stage of cellular
respiration is primarily impaired?
A. Glycolysis
B. Krebs cycle
C. Oxidative phosphorylation [CORRECT]
, D. Pyruvate oxidation
Correct Answer: C
Rationale: Correct because ATP synthase is the enzyme complex responsible for
converting the proton motive force into ATP during oxidative phosphorylation, and its
defect directly compromises the majority of cellular ATP production.
Q10: In an experiment measuring oxygen consumption by isolated mitochondria, which
substrate would directly provide electrons to the electron transport chain without prior
processing through the Krebs cycle?
A. Glucose
B. Pyruvate
C. NADH [CORRECT]
D. Acetyl-CoA
Correct Answer: C
Rationale: Correct because NADH is an electron carrier that donates electrons directly
to Complex I of the electron transport chain, whereas other substrates must be
catabolized first to extract electrons.
Q11: What is the primary purpose of the fermentation pathways that occur in the
absence of oxygen?
A. To produce additional ATP beyond glycolysis
B. To regenerate NAD⁺ to allow glycolysis to continue [CORRECT]
C. To synthesize glucose for energy storage
D. To generate carbon skeletons for amino acid synthesis
Correct Answer: B
Rationale: Correct because fermentation oxidizes NADH to NAD⁺, which is essential to
maintain the NAD⁺ pool required for the glyceraldehyde-3-phosphate dehydrogenase
reaction in glycolysis.
Q12: The conversion of pyruvate to acetyl-CoA before entering the Krebs cycle results in
the release of:
A. Oxygen and water
Exam 2026/2027 | Complete Exam-Style Questions with
Detailed Rationales | Pass Guaranteed – A+ Graded
Section 1: Cellular Respiration & Fermentation (15 Questions)
Q1: During cellular respiration, glycolysis occurs in which cellular location?
A. The mitochondrial matrix
B. The inner mitochondrial membrane
C. The cytoplasm [CORRECT]
D. The intermembrane space
Correct Answer: C
Rationale: Correct because glycolysis is the metabolic pathway that breaks down
glucose into two pyruvate molecules and occurs exclusively in the cytoplasm of the cell.
Q2: What is the net ATP yield from one molecule of glucose during glycolysis?
A. 4 ATP
B. 2 ATP [CORRECT]
C. 32 ATP
D. 0 ATP
Correct Answer: B
Rationale: Correct because glycolysis produces 4 ATP through substrate-level
phosphorylation but consumes 2 ATP in the energy investment phase, resulting in a net
gain of 2 ATP.
Q3: In the absence of oxygen, mammalian muscle cells convert pyruvate to:
,A. Acetyl-CoA and CO₂
B. Ethanol and carbon dioxide
C. Lactate [CORRECT]
D. Citrate
Correct Answer: C
Rationale: Correct because under anaerobic conditions, mammalian muscle cells
regenerate NAD⁺ through lactic acid fermentation, reducing pyruvate to lactate without
releasing CO₂.
Q4: The Krebs cycle takes place in which compartment of the mitochondria?
A. The outer membrane
B. The intermembrane space
C. The mitochondrial matrix [CORRECT]
D. The cytoplasm
Correct Answer: C
Rationale: Correct because the Krebs cycle (citric acid cycle) enzymes are located in the
mitochondrial matrix, where acetyl-CoA is oxidized to produce NADH, FADH₂, and ATP.
Q5: Which molecule serves as the final electron acceptor in the electron transport chain
during aerobic respiration?
A. Carbon dioxide
B. Water
C. Oxygen [CORRECT]
D. NADH
Correct Answer: C
Rationale: Correct because oxygen has high electronegativity and accepts electrons at
the end of the electron transport chain, forming water with protons.
Q6: Most ATP generated during cellular respiration is produced by which process?
A. Substrate-level phosphorylation in glycolysis
B. Substrate-level phosphorylation in the Krebs cycle
C. Oxidative phosphorylation via chemiosmosis [CORRECT]
D. Decarboxylation of pyruvate
,Correct Answer: C
Rationale: Correct because oxidative phosphorylation uses the proton gradient
established by the electron transport chain to drive ATP synthase, producing
approximately 26–28 of the total 30–32 ATP.
Q7: Which of the following electron carriers produces fewer ATP molecules when
oxidized by the electron transport chain?
A. NADH
B. FADH₂ [CORRECT]
C. Both produce equal ATP
D. Neither produces ATP
Correct Answer: B
Rationale: Correct because FADH₂ donates electrons to Complex II, bypassing Complex
I and pumping fewer protons into the intermembrane space, resulting in approximately
1.5 ATP compared to NADH's 2.5 ATP.
Q8: During alcoholic fermentation in yeast, pyruvate is converted to:
A. Lactate and NAD⁺
B. Acetaldehyde and then ethanol [CORRECT]
C. Acetyl-CoA and CO₂
D. Oxaloacetate and NADH
Correct Answer: B
Rationale: Correct because yeast first decarboxylates pyruvate to acetaldehyde,
releasing CO₂, then reduces acetaldehyde to ethanol while oxidizing NADH to NAD⁺ to
sustain glycolysis.
Q9: A patient presents with muscle weakness and inability to perform sustained
exercise. Biopsy reveals defective mitochondrial ATP synthase. Which stage of cellular
respiration is primarily impaired?
A. Glycolysis
B. Krebs cycle
C. Oxidative phosphorylation [CORRECT]
, D. Pyruvate oxidation
Correct Answer: C
Rationale: Correct because ATP synthase is the enzyme complex responsible for
converting the proton motive force into ATP during oxidative phosphorylation, and its
defect directly compromises the majority of cellular ATP production.
Q10: In an experiment measuring oxygen consumption by isolated mitochondria, which
substrate would directly provide electrons to the electron transport chain without prior
processing through the Krebs cycle?
A. Glucose
B. Pyruvate
C. NADH [CORRECT]
D. Acetyl-CoA
Correct Answer: C
Rationale: Correct because NADH is an electron carrier that donates electrons directly
to Complex I of the electron transport chain, whereas other substrates must be
catabolized first to extract electrons.
Q11: What is the primary purpose of the fermentation pathways that occur in the
absence of oxygen?
A. To produce additional ATP beyond glycolysis
B. To regenerate NAD⁺ to allow glycolysis to continue [CORRECT]
C. To synthesize glucose for energy storage
D. To generate carbon skeletons for amino acid synthesis
Correct Answer: B
Rationale: Correct because fermentation oxidizes NADH to NAD⁺, which is essential to
maintain the NAD⁺ pool required for the glyceraldehyde-3-phosphate dehydrogenase
reaction in glycolysis.
Q12: The conversion of pyruvate to acetyl-CoA before entering the Krebs cycle results in
the release of:
A. Oxygen and water
