BIOL 101 Exam 2 V3 | BIOL 101 Principles of Biology | Actual Q&A
with Rationale (BIOL101 Exam 2) | Liberty University
1. What is the primary function of the electron transport chain during aerobic cellular
respiration?
A. To break down glucose into pyruvate
B. To produce carbon dioxide as a waste product
C. To establish a proton gradient across the inner mitochondrial membrane
D. To synthesize glucose from carbon dioxide and water
Correct Answer: C
Explanation: The electron transport chain functions by transferring electrons through a
series of proteins, which releases energy used to pump protons into the intermembrane
space. This creates an electrochemical gradient, often referred to as the proton-motive
force. Ultimately, this gradient drives ATP synthesis via chemiosmosis through the enzyme
ATP synthase.
2. In the process of photosynthesis, where do the light-dependent reactions specifically take
place?
A. Cytosol
B. Stroma
C. Thylakoid membranes
D. Mitochondrial matrix
Correct Answer: C
Explanation: The light-dependent reactions occur within the thylakoid membranes of the
chloroplast where chlorophyll pigments are located. These pigments absorb light energy to
excite electrons, leading to the production of ATP and NADPH. The oxygen released during
photosynthesis is also a byproduct of water splitting that occurs in this specific location.
3. Which phase of the cell cycle is characterized by the replication of DNA?
A. G1 phase
B. G2 phase
C. S phase
D. M phase
Correct Answer: C
,Explanation: The S phase, or synthesis phase, is the specific period during interphase
when the cell duplicates its genomic DNA. This ensures that each daughter cell receives a
complete set of genetic instructions following cell division. Without this critical replication
step, the resulting cells would lack the necessary genetic material to function properly.
4. What is the role of oxygen in cellular respiration?
A. It serves as the final electron acceptor in the electron transport chain
B. It catalyzes the conversion of glucose to pyruvate
C. It acts as the primary source of electrons
D. It is used to fix carbon dioxide in the Calvin cycle
Correct Answer: A
Explanation: Oxygen is highly electronegative and serves as the final electron acceptor at
the end of the electron transport chain. By accepting electrons and picking up protons, it
forms water as a byproduct. If oxygen is not present, the electron transport chain stops,
leading to a halt in aerobic ATP production.
5. During mitosis, at which stage do sister chromatids separate and move toward opposite
poles?
A. Anaphase
B. Metaphase
C. Prophase
D. Telophase
Correct Answer: A
Explanation: Anaphase begins when the cohesin proteins holding sister chromatids
together are cleaved, allowing them to separate. The kinetochore microtubules then
shorten, pulling the individual chromosomes toward opposite ends of the cell. This process
ensures that each new nucleus will have an identical set of chromosomes.
6. Which molecule is the primary product of the Calvin cycle that can be used to form
glucose?
A. Glyceraldehyde-3-phosphate (G3P)
B. NADPH
C. ATP
D. RuBP
Correct Answer: A
, Explanation: The Calvin cycle fixes carbon dioxide into an organic form through a series of
enzymatic reactions. The actual sugar product produced is glyceraldehyde-3-phosphate
(G3P), not glucose directly. Two molecules of G3P are typically required to synthesize one
molecule of glucose in subsequent metabolic pathways.
7. What is the net yield of ATP molecules produced per glucose molecule during glycolysis
alone?
A. 36 ATP
B. 4 ATP
C. 32 ATP
D. 2 ATP
Correct Answer: D
Explanation: Glycolysis requires an initial investment of 2 ATP molecules to
phosphorylate glucose. Although 4 ATP molecules are produced through substrate-level
phosphorylation, the net gain for the cell is only 2 ATP. This process occurs in the cytosol
and does not require oxygen to proceed.
8. In DNA replication, which enzyme is responsible for unwinding the double helix?
A. Helicase
B. DNA polymerase
C. Ligase
D. Primase
Correct Answer: A
Explanation: Helicase is the enzyme that breaks the hydrogen bonds between the
nitrogenous bases of the two DNA strands. This action creates the replication fork,
providing the single-stranded templates necessary for replication. As helicase unwinds the
DNA, other proteins stabilize the strands to prevent them from re-annealing.
9. Which of the following best describes a result of meiosis?
A. Four non-identical haploid cells
B. Two identical diploid cells
C. Two non-identical haploid cells
D. Four identical diploid cells
Correct Answer: A
Explanation: Meiosis consists of two rounds of division that reduce the chromosome
number by half. This results in four daughter cells, each containing only one set of
with Rationale (BIOL101 Exam 2) | Liberty University
1. What is the primary function of the electron transport chain during aerobic cellular
respiration?
A. To break down glucose into pyruvate
B. To produce carbon dioxide as a waste product
C. To establish a proton gradient across the inner mitochondrial membrane
D. To synthesize glucose from carbon dioxide and water
Correct Answer: C
Explanation: The electron transport chain functions by transferring electrons through a
series of proteins, which releases energy used to pump protons into the intermembrane
space. This creates an electrochemical gradient, often referred to as the proton-motive
force. Ultimately, this gradient drives ATP synthesis via chemiosmosis through the enzyme
ATP synthase.
2. In the process of photosynthesis, where do the light-dependent reactions specifically take
place?
A. Cytosol
B. Stroma
C. Thylakoid membranes
D. Mitochondrial matrix
Correct Answer: C
Explanation: The light-dependent reactions occur within the thylakoid membranes of the
chloroplast where chlorophyll pigments are located. These pigments absorb light energy to
excite electrons, leading to the production of ATP and NADPH. The oxygen released during
photosynthesis is also a byproduct of water splitting that occurs in this specific location.
3. Which phase of the cell cycle is characterized by the replication of DNA?
A. G1 phase
B. G2 phase
C. S phase
D. M phase
Correct Answer: C
,Explanation: The S phase, or synthesis phase, is the specific period during interphase
when the cell duplicates its genomic DNA. This ensures that each daughter cell receives a
complete set of genetic instructions following cell division. Without this critical replication
step, the resulting cells would lack the necessary genetic material to function properly.
4. What is the role of oxygen in cellular respiration?
A. It serves as the final electron acceptor in the electron transport chain
B. It catalyzes the conversion of glucose to pyruvate
C. It acts as the primary source of electrons
D. It is used to fix carbon dioxide in the Calvin cycle
Correct Answer: A
Explanation: Oxygen is highly electronegative and serves as the final electron acceptor at
the end of the electron transport chain. By accepting electrons and picking up protons, it
forms water as a byproduct. If oxygen is not present, the electron transport chain stops,
leading to a halt in aerobic ATP production.
5. During mitosis, at which stage do sister chromatids separate and move toward opposite
poles?
A. Anaphase
B. Metaphase
C. Prophase
D. Telophase
Correct Answer: A
Explanation: Anaphase begins when the cohesin proteins holding sister chromatids
together are cleaved, allowing them to separate. The kinetochore microtubules then
shorten, pulling the individual chromosomes toward opposite ends of the cell. This process
ensures that each new nucleus will have an identical set of chromosomes.
6. Which molecule is the primary product of the Calvin cycle that can be used to form
glucose?
A. Glyceraldehyde-3-phosphate (G3P)
B. NADPH
C. ATP
D. RuBP
Correct Answer: A
, Explanation: The Calvin cycle fixes carbon dioxide into an organic form through a series of
enzymatic reactions. The actual sugar product produced is glyceraldehyde-3-phosphate
(G3P), not glucose directly. Two molecules of G3P are typically required to synthesize one
molecule of glucose in subsequent metabolic pathways.
7. What is the net yield of ATP molecules produced per glucose molecule during glycolysis
alone?
A. 36 ATP
B. 4 ATP
C. 32 ATP
D. 2 ATP
Correct Answer: D
Explanation: Glycolysis requires an initial investment of 2 ATP molecules to
phosphorylate glucose. Although 4 ATP molecules are produced through substrate-level
phosphorylation, the net gain for the cell is only 2 ATP. This process occurs in the cytosol
and does not require oxygen to proceed.
8. In DNA replication, which enzyme is responsible for unwinding the double helix?
A. Helicase
B. DNA polymerase
C. Ligase
D. Primase
Correct Answer: A
Explanation: Helicase is the enzyme that breaks the hydrogen bonds between the
nitrogenous bases of the two DNA strands. This action creates the replication fork,
providing the single-stranded templates necessary for replication. As helicase unwinds the
DNA, other proteins stabilize the strands to prevent them from re-annealing.
9. Which of the following best describes a result of meiosis?
A. Four non-identical haploid cells
B. Two identical diploid cells
C. Two non-identical haploid cells
D. Four identical diploid cells
Correct Answer: A
Explanation: Meiosis consists of two rounds of division that reduce the chromosome
number by half. This results in four daughter cells, each containing only one set of
