,BIOD101/BIOD 101 Module 3 Exam | Essential Biology I with
Lab | Portage Learning | Q & A | 2026/2027 Edition (PDF)
1. Which of the following best describes the primary function of cellular respiration?
A) To convert light energy into chemical energy stored in glucose
B) To break down glucose and other organic molecules to produce ATP
C) To synthesize proteins from amino acids for cellular structures
D) To store genetic information for inheritance and protein synthesis
Correct Answer: To break down glucose and other organic molecules to produce ATP.
Rationale: Cellular respiration is the catabolic process by which cells break down glucose and other
organic molecules to harvest energy in the form of ATP. Photosynthesis performs the opposite function,
converting light energy into chemical energy.
2. What is the overall balanced chemical equation for aerobic cellular respiration?
A) C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP
B) 6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂
C) C₆H₁₂O₆ → 2C₃H₄O₃ + 2ATP + 2NADH
D) C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O
Correct Answer: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP.
Rationale: The overall equation for aerobic cellular respiration is glucose (C₆H₁₂O₆) plus oxygen (6O₂)
yielding carbon dioxide (6CO₂), water (6H₂O), and ATP. The equation in option B is for photosynthesis.
3. Where in the cell does glycolysis occur?
A) Mitochondrial matrix
B) Inner mitochondrial membrane
C) Cytoplasm
,D) Nucleus
Correct Answer: Cytoplasm.
Rationale: Glycolysis is the first step of cellular respiration and occurs in the cytoplasm of the cell. It
breaks down glucose into pyruvate, producing a small amount of ATP and NADH.
4. In which part of the mitochondrion does the citric acid cycle (Krebs cycle) take place?
A) Cytoplasm
B) Mitochondrial matrix
C) Inner mitochondrial membrane
D) Outer mitochondrial membrane
Correct Answer: Mitochondrial matrix.
Rationale: The citric acid cycle takes place in the mitochondrial matrix, the fluid-filled space inside the
inner mitochondrial membrane. It produces NADH, FADH₂, and ATP.
5. Where is the electron transport chain (ETC) located?
A) Cytoplasm
B) Mitochondrial matrix
C) Inner mitochondrial membrane
D) Outer mitochondrial membrane
Correct Answer: Inner mitochondrial membrane.
Rationale: The electron transport chain is embedded in the inner mitochondrial membrane. It uses
electrons from NADH and FADH₂ to create a proton gradient that drives ATP synthesis.
6. What is the primary purpose of the citric acid cycle (Krebs cycle)?
, A) To directly produce the majority of ATP during cellular respiration
B) To generate high-energy molecules (NADH and FADH₂) for use in the electron transport chain
C) To convert pyruvate into acetyl-CoA for entry into the cycle
D) To produce glucose from non-carbohydrate sources
Correct Answer: To generate high-energy molecules (NADH and FADH₂) for use in the electron transport
chain.
Rationale: The citric acid cycle generates high-energy molecules (NADH and FADH₂) that will be later
used to generate ATP in the electron transport chain.
7. What role does ATP synthase play in the electron transport chain?
A) It directly transfers electrons to oxygen.
B) It generates ATP through chemiosmosis.
C) It oxidizes NADH to NAD⁺.
D) It transports pyruvate into the mitochondria.
Correct Answer: It generates ATP through chemiosmosis.
Rationale: ATP synthase is responsible for generating ATP through chemiosmosis, using the proton
gradient established by the electron transport chain.
8. How does the electron transport chain generate ATP?
A) By substrate-level phosphorylation during glycolysis
B) By using the energy of electrons to pump protons and create a gradient that drives ATP synthase
C) By directly transferring phosphate to ADP
D) By breaking down glucose into pyruvate
Correct Answer: By using the energy of electrons to pump protons and create a gradient that drives ATP
synthase.
Lab | Portage Learning | Q & A | 2026/2027 Edition (PDF)
1. Which of the following best describes the primary function of cellular respiration?
A) To convert light energy into chemical energy stored in glucose
B) To break down glucose and other organic molecules to produce ATP
C) To synthesize proteins from amino acids for cellular structures
D) To store genetic information for inheritance and protein synthesis
Correct Answer: To break down glucose and other organic molecules to produce ATP.
Rationale: Cellular respiration is the catabolic process by which cells break down glucose and other
organic molecules to harvest energy in the form of ATP. Photosynthesis performs the opposite function,
converting light energy into chemical energy.
2. What is the overall balanced chemical equation for aerobic cellular respiration?
A) C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP
B) 6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂
C) C₆H₁₂O₆ → 2C₃H₄O₃ + 2ATP + 2NADH
D) C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O
Correct Answer: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP.
Rationale: The overall equation for aerobic cellular respiration is glucose (C₆H₁₂O₆) plus oxygen (6O₂)
yielding carbon dioxide (6CO₂), water (6H₂O), and ATP. The equation in option B is for photosynthesis.
3. Where in the cell does glycolysis occur?
A) Mitochondrial matrix
B) Inner mitochondrial membrane
C) Cytoplasm
,D) Nucleus
Correct Answer: Cytoplasm.
Rationale: Glycolysis is the first step of cellular respiration and occurs in the cytoplasm of the cell. It
breaks down glucose into pyruvate, producing a small amount of ATP and NADH.
4. In which part of the mitochondrion does the citric acid cycle (Krebs cycle) take place?
A) Cytoplasm
B) Mitochondrial matrix
C) Inner mitochondrial membrane
D) Outer mitochondrial membrane
Correct Answer: Mitochondrial matrix.
Rationale: The citric acid cycle takes place in the mitochondrial matrix, the fluid-filled space inside the
inner mitochondrial membrane. It produces NADH, FADH₂, and ATP.
5. Where is the electron transport chain (ETC) located?
A) Cytoplasm
B) Mitochondrial matrix
C) Inner mitochondrial membrane
D) Outer mitochondrial membrane
Correct Answer: Inner mitochondrial membrane.
Rationale: The electron transport chain is embedded in the inner mitochondrial membrane. It uses
electrons from NADH and FADH₂ to create a proton gradient that drives ATP synthesis.
6. What is the primary purpose of the citric acid cycle (Krebs cycle)?
, A) To directly produce the majority of ATP during cellular respiration
B) To generate high-energy molecules (NADH and FADH₂) for use in the electron transport chain
C) To convert pyruvate into acetyl-CoA for entry into the cycle
D) To produce glucose from non-carbohydrate sources
Correct Answer: To generate high-energy molecules (NADH and FADH₂) for use in the electron transport
chain.
Rationale: The citric acid cycle generates high-energy molecules (NADH and FADH₂) that will be later
used to generate ATP in the electron transport chain.
7. What role does ATP synthase play in the electron transport chain?
A) It directly transfers electrons to oxygen.
B) It generates ATP through chemiosmosis.
C) It oxidizes NADH to NAD⁺.
D) It transports pyruvate into the mitochondria.
Correct Answer: It generates ATP through chemiosmosis.
Rationale: ATP synthase is responsible for generating ATP through chemiosmosis, using the proton
gradient established by the electron transport chain.
8. How does the electron transport chain generate ATP?
A) By substrate-level phosphorylation during glycolysis
B) By using the energy of electrons to pump protons and create a gradient that drives ATP synthase
C) By directly transferring phosphate to ADP
D) By breaking down glucose into pyruvate
Correct Answer: By using the energy of electrons to pump protons and create a gradient that drives ATP
synthase.
