CHEM 210 Biochemistry Module 6 Exam
2026/2027 | Newly Released | Actual Exam |
Verified Q&A with Detailed Rationales | Portage
Learning | Guaranteed Pass - A+ Graded
Section 1: Energy Investment Phase
Q1: During the energy investment phase of glycolysis, how many ATP molecules are
consumed per glucose molecule?
A. 0
B. 1
C. 2
D. 4
Correct Answer: C
Rationale: The energy investment phase of glycolysis consumes 2 ATP molecules per
glucose molecule. Hexokinase uses 1 ATP to phosphorylate glucose to glucose-6-
phosphate, and phosphofructokinase-1 (PFK-1) uses a second ATP to phosphorylate
fructose-6-phosphate to fructose-1,6-bisphosphate. These 2 ATP are invested to
destabilize the molecule and facilitate subsequent cleavage and energy extraction.
Q2: Which enzyme catalyzes the first committed step of glycolysis?
A. Hexokinase
B. Phosphoglucose isomerase
C. Phosphofructokinase-1 (PFK-1)
D. Aldolase
,Correct Answer: C
Rationale: PFK-1 catalyzes the conversion of fructose-6-phosphate to fructose-1,6-
bisphosphate. This is considered the first committed step of glycolysis because it is the
first irreversible reaction unique to the glycolytic pathway. PFK-1 is also the major
regulatory enzyme of glycolysis, allosterically activated by AMP/fructose-2,6-
bisphosphate and inhibited by ATP/citrate.
Q3: Which glycolytic enzyme catalyzes an irreversible step and is inhibited by ATP?
A. Hexokinase
B. Phosphofructokinase-1
C. Pyruvate kinase
D. Glyceraldehyde-3-phosphate dehydrogenase
Correct Answer: B
Rationale: PFK-1 catalyzes an irreversible reaction (fructose-6-phosphate → fructose-
1,6-bisphosphate) and is a key regulatory enzyme. It is inhibited by high ATP (energy
abundance) and citrate, and activated by AMP and fructose-2,6-bisphosphate. This
ensures glycolysis is downregulated when cellular energy is sufficient.
Q4: Which step in glycolysis involves substrate-level phosphorylation?
A. Glucose → Glucose-6-phosphate
B. Fructose-6-phosphate → Fructose-1,6-bisphosphate
C. 1,3-Bisphosphoglycerate → 3-Phosphoglycerate
D. Phosphoenolpyruvate → Pyruvate
Correct Answer: D (and C)
Rationale: Substrate-level phosphorylation occurs in two glycolytic steps: (1) 1,3-
bisphosphoglycerate → 3-phosphoglycerate (catalyzed by phosphoglycerate kinase,
producing ATP), and (2) phosphoenolpyruvate (PEP) → pyruvate (catalyzed by
pyruvate kinase, producing ATP). These are the only two steps in glycolysis that directly
generate ATP without the electron transport chain.
,Q5: What is the net ATP yield from one molecule of glucose undergoing glycolysis
under aerobic conditions?
A. 1 ATP
B. 2 ATP
C. 4 ATP
D. 36 ATP
Correct Answer: B
Rationale: Glycolysis produces 4 ATP total via substrate-level phosphorylation (2 from
each of the two ATP-generating steps), but 2 ATP are consumed in the energy
investment phase, resulting in a net yield of 2 ATP per glucose. This does not include
ATP from the electron transport chain (which occurs in oxidative phosphorylation).
Q6: Which glycolytic enzyme is inhibited by high levels of glucose-6-phosphate?
A. Phosphofructokinase-1
B. Hexokinase
C. Pyruvate kinase
D. Aldolase
Correct Answer: B
Rationale: Hexokinase is inhibited by its product, glucose-6-phosphate, through
feedback inhibition. This prevents unnecessary glucose phosphorylation when glucose-
6-phosphate accumulates. In contrast, glucokinase (in the liver) is not inhibited by
glucose-6-phosphate and functions at higher glucose concentrations.
Q7: Which intermediate in glycolysis is cleaved into two triose phosphates?
A. Glucose-6-phosphate
B. Fructose-6-phosphate
, C. Fructose-1,6-bisphosphate
D. Dihydroxyacetone phosphate
Correct Answer: C
Rationale: Fructose-1,6-bisphosphate is cleaved by aldolase into two triose
phosphates: glyceraldehyde-3-phosphate (G3P) and dihydroxyacetone phosphate
(DHAP). DHAP is subsequently converted to G3P by triose phosphate isomerase,
allowing both molecules to continue through the payoff phase.
Q8: Which glycolysis reaction produces NADH?
A. Glucose → Glucose-6-phosphate
B. 1,3-Bisphosphoglycerate → 3-Phosphoglycerate
C. Glyceraldehyde-3-phosphate → 1,3-Bisphosphoglycerate
D. Phosphoenolpyruvate → Pyruvate
Correct Answer: C
Rationale: Glyceraldehyde-3-phosphate dehydrogenase catalyzes the oxidation of
G3P to 1,3-bisphosphoglycerate, reducing NAD⁺ to NADH. This step generates NADH,
which under aerobic conditions will enter the electron transport chain to produce
additional ATP.
Q9: Which enzyme is responsible for the conversion of glucose to glucose-6-phosphate
in the first step of glycolysis?
A. Phosphofructokinase-1
B. Glucokinase
C. Hexokinase
D. Pyruvate kinase
Correct Answer: C (and B in liver)
Rationale: The first step of glycolysis is catalyzed by hexokinase (in most tissues)
or glucokinase (in the liver and pancreas). Hexokinase has a high affinity for glucose
2026/2027 | Newly Released | Actual Exam |
Verified Q&A with Detailed Rationales | Portage
Learning | Guaranteed Pass - A+ Graded
Section 1: Energy Investment Phase
Q1: During the energy investment phase of glycolysis, how many ATP molecules are
consumed per glucose molecule?
A. 0
B. 1
C. 2
D. 4
Correct Answer: C
Rationale: The energy investment phase of glycolysis consumes 2 ATP molecules per
glucose molecule. Hexokinase uses 1 ATP to phosphorylate glucose to glucose-6-
phosphate, and phosphofructokinase-1 (PFK-1) uses a second ATP to phosphorylate
fructose-6-phosphate to fructose-1,6-bisphosphate. These 2 ATP are invested to
destabilize the molecule and facilitate subsequent cleavage and energy extraction.
Q2: Which enzyme catalyzes the first committed step of glycolysis?
A. Hexokinase
B. Phosphoglucose isomerase
C. Phosphofructokinase-1 (PFK-1)
D. Aldolase
,Correct Answer: C
Rationale: PFK-1 catalyzes the conversion of fructose-6-phosphate to fructose-1,6-
bisphosphate. This is considered the first committed step of glycolysis because it is the
first irreversible reaction unique to the glycolytic pathway. PFK-1 is also the major
regulatory enzyme of glycolysis, allosterically activated by AMP/fructose-2,6-
bisphosphate and inhibited by ATP/citrate.
Q3: Which glycolytic enzyme catalyzes an irreversible step and is inhibited by ATP?
A. Hexokinase
B. Phosphofructokinase-1
C. Pyruvate kinase
D. Glyceraldehyde-3-phosphate dehydrogenase
Correct Answer: B
Rationale: PFK-1 catalyzes an irreversible reaction (fructose-6-phosphate → fructose-
1,6-bisphosphate) and is a key regulatory enzyme. It is inhibited by high ATP (energy
abundance) and citrate, and activated by AMP and fructose-2,6-bisphosphate. This
ensures glycolysis is downregulated when cellular energy is sufficient.
Q4: Which step in glycolysis involves substrate-level phosphorylation?
A. Glucose → Glucose-6-phosphate
B. Fructose-6-phosphate → Fructose-1,6-bisphosphate
C. 1,3-Bisphosphoglycerate → 3-Phosphoglycerate
D. Phosphoenolpyruvate → Pyruvate
Correct Answer: D (and C)
Rationale: Substrate-level phosphorylation occurs in two glycolytic steps: (1) 1,3-
bisphosphoglycerate → 3-phosphoglycerate (catalyzed by phosphoglycerate kinase,
producing ATP), and (2) phosphoenolpyruvate (PEP) → pyruvate (catalyzed by
pyruvate kinase, producing ATP). These are the only two steps in glycolysis that directly
generate ATP without the electron transport chain.
,Q5: What is the net ATP yield from one molecule of glucose undergoing glycolysis
under aerobic conditions?
A. 1 ATP
B. 2 ATP
C. 4 ATP
D. 36 ATP
Correct Answer: B
Rationale: Glycolysis produces 4 ATP total via substrate-level phosphorylation (2 from
each of the two ATP-generating steps), but 2 ATP are consumed in the energy
investment phase, resulting in a net yield of 2 ATP per glucose. This does not include
ATP from the electron transport chain (which occurs in oxidative phosphorylation).
Q6: Which glycolytic enzyme is inhibited by high levels of glucose-6-phosphate?
A. Phosphofructokinase-1
B. Hexokinase
C. Pyruvate kinase
D. Aldolase
Correct Answer: B
Rationale: Hexokinase is inhibited by its product, glucose-6-phosphate, through
feedback inhibition. This prevents unnecessary glucose phosphorylation when glucose-
6-phosphate accumulates. In contrast, glucokinase (in the liver) is not inhibited by
glucose-6-phosphate and functions at higher glucose concentrations.
Q7: Which intermediate in glycolysis is cleaved into two triose phosphates?
A. Glucose-6-phosphate
B. Fructose-6-phosphate
, C. Fructose-1,6-bisphosphate
D. Dihydroxyacetone phosphate
Correct Answer: C
Rationale: Fructose-1,6-bisphosphate is cleaved by aldolase into two triose
phosphates: glyceraldehyde-3-phosphate (G3P) and dihydroxyacetone phosphate
(DHAP). DHAP is subsequently converted to G3P by triose phosphate isomerase,
allowing both molecules to continue through the payoff phase.
Q8: Which glycolysis reaction produces NADH?
A. Glucose → Glucose-6-phosphate
B. 1,3-Bisphosphoglycerate → 3-Phosphoglycerate
C. Glyceraldehyde-3-phosphate → 1,3-Bisphosphoglycerate
D. Phosphoenolpyruvate → Pyruvate
Correct Answer: C
Rationale: Glyceraldehyde-3-phosphate dehydrogenase catalyzes the oxidation of
G3P to 1,3-bisphosphoglycerate, reducing NAD⁺ to NADH. This step generates NADH,
which under aerobic conditions will enter the electron transport chain to produce
additional ATP.
Q9: Which enzyme is responsible for the conversion of glucose to glucose-6-phosphate
in the first step of glycolysis?
A. Phosphofructokinase-1
B. Glucokinase
C. Hexokinase
D. Pyruvate kinase
Correct Answer: C (and B in liver)
Rationale: The first step of glycolysis is catalyzed by hexokinase (in most tissues)
or glucokinase (in the liver and pancreas). Hexokinase has a high affinity for glucose
