,BIOD 101 Module 3 | Essential Biology I | Portage Learning |
Questions & Verified Answers | 2026 Edition
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. This energy is then used to power various
cellular activities. 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. This equation represents the catabolic
breakdown of glucose to release energy. The equation shown in option B is for photosynthesis, which is
the reverse process.
3. What are the three distinct processes of cellular respiration, and where does each occur?
A) Glycolysis (cytoplasm), Citric Acid Cycle (mitochondrial matrix), Electron Transport Chain (inner
mitochondrial membrane)
,B) Glycolysis (mitochondria), Citric Acid Cycle (cytoplasm), Electron Transport Chain (mitochondrial
matrix)
C) Glycolysis (cytoplasm), Citric Acid Cycle (inner mitochondrial membrane), Electron Transport Chain
(mitochondrial matrix)
D) Glycolysis (mitochondrial matrix), Citric Acid Cycle (cytoplasm), Electron Transport Chain (inner
mitochondrial membrane)
Correct Answer: Glycolysis (cytoplasm), Citric Acid Cycle (mitochondrial matrix), Electron Transport
Chain (inner mitochondrial membrane)
Rationale: Cellular respiration consists of three main stages: glycolysis occurs in the cytoplasm, the citric
acid cycle (Krebs cycle) takes place in the mitochondrial matrix, and the electron transport chain is
located in the inner mitochondrial membrane. Each stage occurs in a specific cellular compartment that
facilitates its function.
4. What happens during the energy investment phase of glycolysis?
A) Two ATP molecules are produced, and two NADH molecules are generated
B) Two ATP molecules are used to split glucose into two molecules of glyceraldehyde 3-phosphate
C) Glucose is converted directly into pyruvate without any ATP involvement
D) Four ATP molecules are produced, resulting in a net gain of two ATP
Correct Answer: Two ATP molecules are used to split glucose into two molecules of glyceraldehyde 3-
phosphate
Rationale: The energy investment phase of glycolysis uses two ATP molecules to phosphorylate and split
one glucose molecule into two molecules of glyceraldehyde 3-phosphate (G3P). This phase prepares the
molecule for the energy payoff phase where ATP is generated.
5. What is produced during the energy payoff phase of glycolysis?
A) Two ATP molecules are consumed, and two NADH molecules are produced
B) Four ATP molecules and two NADH molecules are produced
C) Two pyruvate molecules and two ATP molecules are produced
, D) Glucose is regenerated from pyruvate
Correct Answer: Four ATP molecules and two NADH molecules are produced
Rationale: The energy payoff phase of glycolysis produces four ATP molecules (via substrate-level
phosphorylation) and two NADH molecules. When combined with the two ATP consumed in the
investment phase, the net yield is two ATP and two NADH per glucose molecule.
6. What is the net ATP yield from glycolysis per glucose molecule?
A) 4 ATP
B) 3 ATP
C) 2 ATP
D) 1 ATP
Correct Answer: 2 ATP
Rationale: Glycolysis produces a gross total of four ATP molecules, but two ATP molecules are consumed
during the energy investment phase. The net yield is therefore two ATP molecules per glucose molecule,
along with two NADH molecules that will enter the electron transport chain.
7. Which enzyme catalyzes the conversion of glucose to glucose-6-phosphate during glycolysis?
A) Phosphofructokinase
B) Hexokinase
C) Phosphoglucoisomerase
D) Pyruvate kinase
Correct Answer: Hexokinase
Rationale: Hexokinase facilitates the transfer of an inorganic phosphate from ATP to glucose, forming
glucose-6-phosphate (G6P). This is the first committed step of glycolysis and traps glucose inside the cell
by making it more chemically reactive.
Questions & Verified Answers | 2026 Edition
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. This energy is then used to power various
cellular activities. 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. This equation represents the catabolic
breakdown of glucose to release energy. The equation shown in option B is for photosynthesis, which is
the reverse process.
3. What are the three distinct processes of cellular respiration, and where does each occur?
A) Glycolysis (cytoplasm), Citric Acid Cycle (mitochondrial matrix), Electron Transport Chain (inner
mitochondrial membrane)
,B) Glycolysis (mitochondria), Citric Acid Cycle (cytoplasm), Electron Transport Chain (mitochondrial
matrix)
C) Glycolysis (cytoplasm), Citric Acid Cycle (inner mitochondrial membrane), Electron Transport Chain
(mitochondrial matrix)
D) Glycolysis (mitochondrial matrix), Citric Acid Cycle (cytoplasm), Electron Transport Chain (inner
mitochondrial membrane)
Correct Answer: Glycolysis (cytoplasm), Citric Acid Cycle (mitochondrial matrix), Electron Transport
Chain (inner mitochondrial membrane)
Rationale: Cellular respiration consists of three main stages: glycolysis occurs in the cytoplasm, the citric
acid cycle (Krebs cycle) takes place in the mitochondrial matrix, and the electron transport chain is
located in the inner mitochondrial membrane. Each stage occurs in a specific cellular compartment that
facilitates its function.
4. What happens during the energy investment phase of glycolysis?
A) Two ATP molecules are produced, and two NADH molecules are generated
B) Two ATP molecules are used to split glucose into two molecules of glyceraldehyde 3-phosphate
C) Glucose is converted directly into pyruvate without any ATP involvement
D) Four ATP molecules are produced, resulting in a net gain of two ATP
Correct Answer: Two ATP molecules are used to split glucose into two molecules of glyceraldehyde 3-
phosphate
Rationale: The energy investment phase of glycolysis uses two ATP molecules to phosphorylate and split
one glucose molecule into two molecules of glyceraldehyde 3-phosphate (G3P). This phase prepares the
molecule for the energy payoff phase where ATP is generated.
5. What is produced during the energy payoff phase of glycolysis?
A) Two ATP molecules are consumed, and two NADH molecules are produced
B) Four ATP molecules and two NADH molecules are produced
C) Two pyruvate molecules and two ATP molecules are produced
, D) Glucose is regenerated from pyruvate
Correct Answer: Four ATP molecules and two NADH molecules are produced
Rationale: The energy payoff phase of glycolysis produces four ATP molecules (via substrate-level
phosphorylation) and two NADH molecules. When combined with the two ATP consumed in the
investment phase, the net yield is two ATP and two NADH per glucose molecule.
6. What is the net ATP yield from glycolysis per glucose molecule?
A) 4 ATP
B) 3 ATP
C) 2 ATP
D) 1 ATP
Correct Answer: 2 ATP
Rationale: Glycolysis produces a gross total of four ATP molecules, but two ATP molecules are consumed
during the energy investment phase. The net yield is therefore two ATP molecules per glucose molecule,
along with two NADH molecules that will enter the electron transport chain.
7. Which enzyme catalyzes the conversion of glucose to glucose-6-phosphate during glycolysis?
A) Phosphofructokinase
B) Hexokinase
C) Phosphoglucoisomerase
D) Pyruvate kinase
Correct Answer: Hexokinase
Rationale: Hexokinase facilitates the transfer of an inorganic phosphate from ATP to glucose, forming
glucose-6-phosphate (G6P). This is the first committed step of glycolysis and traps glucose inside the cell
by making it more chemically reactive.
