BIO 171 COMPREHENSIVE PRACTICE
EXAM QUESTIONS AND ANSWERS
1. Which of the following best describes the effect of a non-competitive inhibitor on enzyme
kinetics?
A. It increases the Km without affecting the Vmax.
B. It decreases both the Vmax and the Km.
C. It decreases the Vmax without changing the Km.
D. It increases both the Vmax and the Km.
Answer: C
Conceptual Explanation: Non-competitive inhibitors bind to an allosteric site, reducing
the enzyme’s turnover number (Vmax) but not affecting the affinity of the enzyme for the
substrate (Km).
2. In the process of oxidative phosphorylation, what is the direct source of energy that drives
ATP synthesis via ATP synthase?
A. The oxidation of NADH and FADH2.
B. The flow of electrons through the electron transport chain.
C. The H+ concentration gradient across the inner mitochondrial membrane.
,D. The hydrolysis of high-energy phosphate bonds.
Answer: C
Conceptual Explanation: ATP synthase uses the electrochemical gradient (proton-motive
force) created by the pumping of H+ ions into the intermembrane space to synthesize ATP.
3. If a cell with a solute potential of -0.7 MPa and a pressure potential of 0.2 MPa is placed in
a solution with a water potential of -0.9 MPa, what will happen?
A. Water will move into the cell because the cell’s water potential is lower.
B. Water will move out of the cell because the solution’s water potential is lower.
C. There will be no net movement of water.
D. The cell will burst due to high turgor pressure.
Answer: B
Conceptual Explanation: The cell’s water potential is -0.7 + 0.2 = -0.5 MPa. Since water
moves from higher potential (-0.5) to lower potential (-0.9), it moves out of the cell.
4. Which statement correctly distinguishes between C4 and CAM plants?
A. C4 plants fix carbon at night, while CAM plants fix carbon during the day.
B. C4 plants are adapted to cold climates, while CAM plants are adapted to tropical
wetlands.
C. CAM plants do not use Rubisco, whereas C4 plants do.
, D. C4 plants separate carbon fixation and the Calvin cycle spatially, while CAM plants
separate them temporally.
Answer: D
Conceptual Explanation: C4 plants use bundle-sheath cells (spatial), while CAM plants
open stomata at night to store CO2 as organic acids (temporal).
5. In a population in Hardy-Weinberg equilibrium, the frequency of a recessive allele (q) is
0.3. What is the frequency of the heterozygous genotype?
A. 0.09
B. 0.42
C. 0.21
D. 0.49
Answer: B
Conceptual Explanation: If q = 0.3, then p = 0.7. The frequency of heterozygotes is 2pq =
2(0.7)(0.3) = 0.42.
6. During DNA replication, which enzyme is responsible for relieving the torsional strain
(supercoiling) ahead of the replication fork?
A. Helicase
B. DNA Polymerase III
C. Topoisomerase
EXAM QUESTIONS AND ANSWERS
1. Which of the following best describes the effect of a non-competitive inhibitor on enzyme
kinetics?
A. It increases the Km without affecting the Vmax.
B. It decreases both the Vmax and the Km.
C. It decreases the Vmax without changing the Km.
D. It increases both the Vmax and the Km.
Answer: C
Conceptual Explanation: Non-competitive inhibitors bind to an allosteric site, reducing
the enzyme’s turnover number (Vmax) but not affecting the affinity of the enzyme for the
substrate (Km).
2. In the process of oxidative phosphorylation, what is the direct source of energy that drives
ATP synthesis via ATP synthase?
A. The oxidation of NADH and FADH2.
B. The flow of electrons through the electron transport chain.
C. The H+ concentration gradient across the inner mitochondrial membrane.
,D. The hydrolysis of high-energy phosphate bonds.
Answer: C
Conceptual Explanation: ATP synthase uses the electrochemical gradient (proton-motive
force) created by the pumping of H+ ions into the intermembrane space to synthesize ATP.
3. If a cell with a solute potential of -0.7 MPa and a pressure potential of 0.2 MPa is placed in
a solution with a water potential of -0.9 MPa, what will happen?
A. Water will move into the cell because the cell’s water potential is lower.
B. Water will move out of the cell because the solution’s water potential is lower.
C. There will be no net movement of water.
D. The cell will burst due to high turgor pressure.
Answer: B
Conceptual Explanation: The cell’s water potential is -0.7 + 0.2 = -0.5 MPa. Since water
moves from higher potential (-0.5) to lower potential (-0.9), it moves out of the cell.
4. Which statement correctly distinguishes between C4 and CAM plants?
A. C4 plants fix carbon at night, while CAM plants fix carbon during the day.
B. C4 plants are adapted to cold climates, while CAM plants are adapted to tropical
wetlands.
C. CAM plants do not use Rubisco, whereas C4 plants do.
, D. C4 plants separate carbon fixation and the Calvin cycle spatially, while CAM plants
separate them temporally.
Answer: D
Conceptual Explanation: C4 plants use bundle-sheath cells (spatial), while CAM plants
open stomata at night to store CO2 as organic acids (temporal).
5. In a population in Hardy-Weinberg equilibrium, the frequency of a recessive allele (q) is
0.3. What is the frequency of the heterozygous genotype?
A. 0.09
B. 0.42
C. 0.21
D. 0.49
Answer: B
Conceptual Explanation: If q = 0.3, then p = 0.7. The frequency of heterozygotes is 2pq =
2(0.7)(0.3) = 0.42.
6. During DNA replication, which enzyme is responsible for relieving the torsional strain
(supercoiling) ahead of the replication fork?
A. Helicase
B. DNA Polymerase III
C. Topoisomerase
