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CHEM 210 Biochemistry
Module 7 Exam (2025/2026) –
Portage Learning Questions
and Verified Answers | 100%
Guarantee Pass
1. What is the primary purpose of glycolysis in cellular metabolism?
A. Synthesize glucose
B. Break down glucose to produce pyruvate and ATP
C. Generate amino acids
D. Produce fatty acids
Correct Answer: B (Break down glucose to produce pyruvate and ATP)
Rationale: Glycolysis is a cytoplasmic pathway that breaks down one glucose molecule
into two pyruvate molecules, producing 2 ATP and 2 NADH, providing energy and
intermediates for metabolism. Lehninger Principles of Biochemistry, 7th ed., Ch. 14.
2. Which enzyme catalyzes the rate-limiting step of glycolysis?
A. Hexokinase
B. Phosphofructokinase-1
C. Pyruvate kinase
D. Aldolase
Correct Answer: B (Phosphofructokinase-1)
Rationale: Phosphofructokinase-1 (PFK-1) catalyzes the conversion of fructose-6-
phosphate to fructose-1,6-bisphosphate, the committed step of glycolysis, regulated by
ATP and AMP levels. Lehninger Principles of Biochemistry, 7th ed., Ch. 14.
3. How many net ATP molecules are produced per glucose molecule in glycolysis?
A. 2
B. 4
C. 6
D. 8
Correct Answer: A (2)
Rationale: Glycolysis produces 4 ATP but consumes 2 ATP, resulting in a net gain of 2
ATP per glucose molecule, as measured in biochemical assays. Lehninger Principles of
Biochemistry, 7th ed., Ch. 14.
4. What is the primary role of the citric acid cycle in metabolism?
A. Synthesize glucose
B. Oxidize acetyl-CoA to produce NADH and FADH2
, 2
C. Break down fatty acids
D. Produce amino acids
Correct Answer: B (Oxidize acetyl-CoA to produce NADH and FADH2)
Rationale: The citric acid cycle (Krebs cycle) oxidizes acetyl-CoA to CO2, generating
NADH and FADH2 for the electron transport chain and 1 GTP per cycle, observed in
mitochondrial studies. Lehninger Principles of Biochemistry, 7th ed., Ch. 16.
5. Which molecule is the primary substrate entering the citric acid cycle?
A. Glucose
B. Pyruvate
C. Acetyl-CoA
D. Citrate
Correct Answer: C (Acetyl-CoA)
Rationale: Acetyl-CoA, derived from pyruvate or fatty acid oxidation, combines with
oxaloacetate to form citrate, initiating the citric acid cycle. Lehninger Principles of
Biochemistry, 7th ed., Ch. 16.
6. What is the final product of glycolysis under anaerobic conditions?
A. Pyruvate
B. Lactate
C. Acetyl-CoA
D. Ethanol
Correct Answer: B (Lactate)
Rationale: In anaerobic conditions, pyruvate is reduced to lactate by lactate
dehydrogenase to regenerate NAD+ for glycolysis, as seen in muscle tissue experiments.
Lehninger Principles of Biochemistry, 7th ed., Ch. 14.
7. Which enzyme is unique to gluconeogenesis and bypasses phosphofructokinase-1?
A. Pyruvate kinase
B. Fructose-1,6-bisphosphatase
C. Enolase
D. Phosphoglycerate kinase
Correct Answer: B (Fructose-1,6-bisphosphatase)
Rationale: Fructose-1,6-bisphosphatase converts fructose-1,6-bisphosphate to fructose-6-
phosphate, bypassing the irreversible PFK-1 step in glycolysis, critical for
gluconeogenesis. Lehninger Principles of Biochemistry, 7th ed., Ch. 15.
8. How many ATP molecules are produced per NADH in the electron transport chain?
A. 1.5
B. 2.5
C. 3.5
D. 4.5
Correct Answer: B (2.5)
Rationale: Each NADH donates electrons to the electron transport chain, yielding
approximately 2.5 ATP via oxidative phosphorylation, as determined by biochemical
measurements. Lehninger Principles of Biochemistry, 7th ed., Ch. 19.
9. Which molecule inhibits the citric acid cycle when ATP levels are high?
A. Citrate
B. Glucose
C. Pyruvate
CHEM 210 Biochemistry
Module 7 Exam (2025/2026) –
Portage Learning Questions
and Verified Answers | 100%
Guarantee Pass
1. What is the primary purpose of glycolysis in cellular metabolism?
A. Synthesize glucose
B. Break down glucose to produce pyruvate and ATP
C. Generate amino acids
D. Produce fatty acids
Correct Answer: B (Break down glucose to produce pyruvate and ATP)
Rationale: Glycolysis is a cytoplasmic pathway that breaks down one glucose molecule
into two pyruvate molecules, producing 2 ATP and 2 NADH, providing energy and
intermediates for metabolism. Lehninger Principles of Biochemistry, 7th ed., Ch. 14.
2. Which enzyme catalyzes the rate-limiting step of glycolysis?
A. Hexokinase
B. Phosphofructokinase-1
C. Pyruvate kinase
D. Aldolase
Correct Answer: B (Phosphofructokinase-1)
Rationale: Phosphofructokinase-1 (PFK-1) catalyzes the conversion of fructose-6-
phosphate to fructose-1,6-bisphosphate, the committed step of glycolysis, regulated by
ATP and AMP levels. Lehninger Principles of Biochemistry, 7th ed., Ch. 14.
3. How many net ATP molecules are produced per glucose molecule in glycolysis?
A. 2
B. 4
C. 6
D. 8
Correct Answer: A (2)
Rationale: Glycolysis produces 4 ATP but consumes 2 ATP, resulting in a net gain of 2
ATP per glucose molecule, as measured in biochemical assays. Lehninger Principles of
Biochemistry, 7th ed., Ch. 14.
4. What is the primary role of the citric acid cycle in metabolism?
A. Synthesize glucose
B. Oxidize acetyl-CoA to produce NADH and FADH2
, 2
C. Break down fatty acids
D. Produce amino acids
Correct Answer: B (Oxidize acetyl-CoA to produce NADH and FADH2)
Rationale: The citric acid cycle (Krebs cycle) oxidizes acetyl-CoA to CO2, generating
NADH and FADH2 for the electron transport chain and 1 GTP per cycle, observed in
mitochondrial studies. Lehninger Principles of Biochemistry, 7th ed., Ch. 16.
5. Which molecule is the primary substrate entering the citric acid cycle?
A. Glucose
B. Pyruvate
C. Acetyl-CoA
D. Citrate
Correct Answer: C (Acetyl-CoA)
Rationale: Acetyl-CoA, derived from pyruvate or fatty acid oxidation, combines with
oxaloacetate to form citrate, initiating the citric acid cycle. Lehninger Principles of
Biochemistry, 7th ed., Ch. 16.
6. What is the final product of glycolysis under anaerobic conditions?
A. Pyruvate
B. Lactate
C. Acetyl-CoA
D. Ethanol
Correct Answer: B (Lactate)
Rationale: In anaerobic conditions, pyruvate is reduced to lactate by lactate
dehydrogenase to regenerate NAD+ for glycolysis, as seen in muscle tissue experiments.
Lehninger Principles of Biochemistry, 7th ed., Ch. 14.
7. Which enzyme is unique to gluconeogenesis and bypasses phosphofructokinase-1?
A. Pyruvate kinase
B. Fructose-1,6-bisphosphatase
C. Enolase
D. Phosphoglycerate kinase
Correct Answer: B (Fructose-1,6-bisphosphatase)
Rationale: Fructose-1,6-bisphosphatase converts fructose-1,6-bisphosphate to fructose-6-
phosphate, bypassing the irreversible PFK-1 step in glycolysis, critical for
gluconeogenesis. Lehninger Principles of Biochemistry, 7th ed., Ch. 15.
8. How many ATP molecules are produced per NADH in the electron transport chain?
A. 1.5
B. 2.5
C. 3.5
D. 4.5
Correct Answer: B (2.5)
Rationale: Each NADH donates electrons to the electron transport chain, yielding
approximately 2.5 ATP via oxidative phosphorylation, as determined by biochemical
measurements. Lehninger Principles of Biochemistry, 7th ed., Ch. 19.
9. Which molecule inhibits the citric acid cycle when ATP levels are high?
A. Citrate
B. Glucose
C. Pyruvate
