BIOL 271 MODULE 2 EXAM 2026/2027 -
COMPREHENSIVE CELL BIOLOGY &
METABOLISM
1. In enzyme kinetics, what is the effect of a competitive inhibitor on Vmax and Km?
A. Vmax decreases, Km remains unchanged
B. Both Vmax and Km increase
C. Vmax remains unchanged, Km increases
D. Vmax increases, Km decreases
Answer: C
Conceptual Explanation: Competitive inhibitors bind to the active site, increasing the
substrate concentration needed to reach half-maximal velocity (Km increases), but they
can be outcompeted at high substrate concentrations, allowing the enzyme to reach its
original Vmax.
2. Which glycolytic enzyme catalyzes the highly regulated ‘committed step’ of the pathway?
A. Hexokinase
B. Phosphofructokinase-1 (PFK-1)
C. Pyruvate Kinase
,D. Glyceraldehyde-3-phosphate dehydrogenase
Answer: B
Conceptual Explanation: PFK-1 catalyzes the phosphorylation of fructose-6-phosphate to
fructose-1,6-bisphosphate, which is the primary rate-limiting and committed step in
glycolysis.
3. What is the role of Thermogenin (UCP1) in the mitochondria of brown adipose tissue?
A. It uncouples the proton gradient from ATP synthesis to generate heat
B. It catalyzes the conversion of NADH to FADH2
C. It increases ATP synthesis efficiency
D. It acts as a secondary messenger in the cAMP pathway
Answer: A
Conceptual Explanation: Thermogenin provides a pathway for protons to re-enter the
mitochondrial matrix without passing through ATP synthase, dissipating the
electrochemical gradient as heat.
4. Which complex in the Electron Transport Chain is inhibited by Cyanide?
A. Complex I
B. Complex IV
C. Complex III
D. Complex II
, Answer: B
Conceptual Explanation: Cyanide binds to the heme a3-cuB binuclear center of
Cytochrome c oxidase (Complex IV), preventing the final transfer of electrons to oxygen.
5. During the light-dependent reactions of photosynthesis, where is the highest concentration
of protons found?
A. Thylakoid lumen
B. Stroma
C. Intermembrane space
D. Cytosol
Answer: A
Conceptual Explanation: Protons are pumped into the thylakoid lumen during electron
transport and released there during the photolysis of water, creating a gradient for ATP
synthesis.
6. What is the primary function of the Pentose Phosphate Pathway?
A. Production of NADH for oxidative phosphorylation
B. Generation of NADPH and Ribose-5-phosphate
C. Synthesis of glucose from non-carbohydrate precursors
D. Degradation of glycogen into glucose-1-phosphate
Answer: B
COMPREHENSIVE CELL BIOLOGY &
METABOLISM
1. In enzyme kinetics, what is the effect of a competitive inhibitor on Vmax and Km?
A. Vmax decreases, Km remains unchanged
B. Both Vmax and Km increase
C. Vmax remains unchanged, Km increases
D. Vmax increases, Km decreases
Answer: C
Conceptual Explanation: Competitive inhibitors bind to the active site, increasing the
substrate concentration needed to reach half-maximal velocity (Km increases), but they
can be outcompeted at high substrate concentrations, allowing the enzyme to reach its
original Vmax.
2. Which glycolytic enzyme catalyzes the highly regulated ‘committed step’ of the pathway?
A. Hexokinase
B. Phosphofructokinase-1 (PFK-1)
C. Pyruvate Kinase
,D. Glyceraldehyde-3-phosphate dehydrogenase
Answer: B
Conceptual Explanation: PFK-1 catalyzes the phosphorylation of fructose-6-phosphate to
fructose-1,6-bisphosphate, which is the primary rate-limiting and committed step in
glycolysis.
3. What is the role of Thermogenin (UCP1) in the mitochondria of brown adipose tissue?
A. It uncouples the proton gradient from ATP synthesis to generate heat
B. It catalyzes the conversion of NADH to FADH2
C. It increases ATP synthesis efficiency
D. It acts as a secondary messenger in the cAMP pathway
Answer: A
Conceptual Explanation: Thermogenin provides a pathway for protons to re-enter the
mitochondrial matrix without passing through ATP synthase, dissipating the
electrochemical gradient as heat.
4. Which complex in the Electron Transport Chain is inhibited by Cyanide?
A. Complex I
B. Complex IV
C. Complex III
D. Complex II
, Answer: B
Conceptual Explanation: Cyanide binds to the heme a3-cuB binuclear center of
Cytochrome c oxidase (Complex IV), preventing the final transfer of electrons to oxygen.
5. During the light-dependent reactions of photosynthesis, where is the highest concentration
of protons found?
A. Thylakoid lumen
B. Stroma
C. Intermembrane space
D. Cytosol
Answer: A
Conceptual Explanation: Protons are pumped into the thylakoid lumen during electron
transport and released there during the photolysis of water, creating a gradient for ATP
synthesis.
6. What is the primary function of the Pentose Phosphate Pathway?
A. Production of NADH for oxidative phosphorylation
B. Generation of NADPH and Ribose-5-phosphate
C. Synthesis of glucose from non-carbohydrate precursors
D. Degradation of glycogen into glucose-1-phosphate
Answer: B
