BIO 1124 Exam 3 New 2025 Version Oklahoma
University with 80 Questions, 100% Correct
Answers and Rationales
Question 1
What is the primary function of the rough endoplasmic reticulum?
A) Lipid synthesis
B) Protein synthesis and transport
C) ATP production
D) Detoxification
Correct Answer: B) Protein synthesis and transport
Rationale: The rough ER is studded with ribosomes, which synthesize proteins that are then
transported through the ER for modification or secretion. Lipid synthesis occurs in the smooth
ER, ATP in mitochondria, and detoxification in the liver’s smooth ER.
Question 2
Which molecule is the final electron acceptor in the electron transport chain?
A) Glucose
B) Oxygen
C) NADH
D) Carbon dioxide
Correct Answer: B) Oxygen
Rationale: Oxygen accepts electrons at the end of the electron transport chain, combining with
protons to form water. NADH donates electrons, while glucose and carbon dioxide are not
involved in this step.
Question 3
What is the main purpose of the Krebs cycle?
A) Produce oxygen
B) Generate ATP directly
C) Oxidize pyruvate and produce electron carriers
D) Synthesize glucose
Correct Answer: C) Oxidize pyruvate and produce electron carriers
Rationale: The Krebs cycle oxidizes acetyl-CoA (from pyruvate) to produce NADH and
FADH2, which carry electrons to the ETC. It generates minimal ATP directly and doesn’t
produce oxygen or glucose.
Question 4
Which structure in plant cells is responsible for maintaining turgor pressure?
A) Cell wall
B) Chloroplast
C) Nucleus
D) Mitochondrion
, Correct Answer: A) Cell wall
Rationale: The cell wall provides rigidity and works with the vacuole to maintain turgor pressure
against water influx. Chloroplasts perform photosynthesis, and the nucleus and mitochondria
have other roles.
Question 5
What type of transport requires energy to move substances against their concentration gradient?
A) Diffusion
B) Facilitated diffusion
C) Active transport
D) Osmosis
Correct Answer: C) Active transport
Rationale: Active transport uses energy (e.g., ATP) to move substances against their gradient.
Diffusion, facilitated diffusion, and osmosis are passive and don’t require energy.
Question 6
Which phase of the cell cycle involves DNA replication?
A) G1 phase
B) S phase
C) G2 phase
D) M phase
Correct Answer: B) S phase
Rationale: The S (synthesis) phase is when DNA replication occurs, doubling the genetic
material before mitosis. G1 and G2 are growth phases, and M is mitosis.
Question 7
What gas is fixed into organic molecules during the Calvin cycle?
A) Oxygen
B) Nitrogen
C) Carbon dioxide
D) Hydrogen
Correct Answer: C) Carbon dioxide
Rationale: The Calvin cycle uses CO2, ATP, and NADPH to produce glucose. Oxygen is a
byproduct of the light reactions, and nitrogen and hydrogen aren’t fixed in this process.
Question 8
Which enzyme unwinds DNA during replication?
A) DNA polymerase
B) Helicase
C) Ligase
D) Primase
Correct Answer: B) Helicase
Rationale: Helicase unwinds and separates the DNA double helix. DNA polymerase synthesizes
new strands, ligase joins fragments, and primase adds RNA primers.
Question 9
University with 80 Questions, 100% Correct
Answers and Rationales
Question 1
What is the primary function of the rough endoplasmic reticulum?
A) Lipid synthesis
B) Protein synthesis and transport
C) ATP production
D) Detoxification
Correct Answer: B) Protein synthesis and transport
Rationale: The rough ER is studded with ribosomes, which synthesize proteins that are then
transported through the ER for modification or secretion. Lipid synthesis occurs in the smooth
ER, ATP in mitochondria, and detoxification in the liver’s smooth ER.
Question 2
Which molecule is the final electron acceptor in the electron transport chain?
A) Glucose
B) Oxygen
C) NADH
D) Carbon dioxide
Correct Answer: B) Oxygen
Rationale: Oxygen accepts electrons at the end of the electron transport chain, combining with
protons to form water. NADH donates electrons, while glucose and carbon dioxide are not
involved in this step.
Question 3
What is the main purpose of the Krebs cycle?
A) Produce oxygen
B) Generate ATP directly
C) Oxidize pyruvate and produce electron carriers
D) Synthesize glucose
Correct Answer: C) Oxidize pyruvate and produce electron carriers
Rationale: The Krebs cycle oxidizes acetyl-CoA (from pyruvate) to produce NADH and
FADH2, which carry electrons to the ETC. It generates minimal ATP directly and doesn’t
produce oxygen or glucose.
Question 4
Which structure in plant cells is responsible for maintaining turgor pressure?
A) Cell wall
B) Chloroplast
C) Nucleus
D) Mitochondrion
, Correct Answer: A) Cell wall
Rationale: The cell wall provides rigidity and works with the vacuole to maintain turgor pressure
against water influx. Chloroplasts perform photosynthesis, and the nucleus and mitochondria
have other roles.
Question 5
What type of transport requires energy to move substances against their concentration gradient?
A) Diffusion
B) Facilitated diffusion
C) Active transport
D) Osmosis
Correct Answer: C) Active transport
Rationale: Active transport uses energy (e.g., ATP) to move substances against their gradient.
Diffusion, facilitated diffusion, and osmosis are passive and don’t require energy.
Question 6
Which phase of the cell cycle involves DNA replication?
A) G1 phase
B) S phase
C) G2 phase
D) M phase
Correct Answer: B) S phase
Rationale: The S (synthesis) phase is when DNA replication occurs, doubling the genetic
material before mitosis. G1 and G2 are growth phases, and M is mitosis.
Question 7
What gas is fixed into organic molecules during the Calvin cycle?
A) Oxygen
B) Nitrogen
C) Carbon dioxide
D) Hydrogen
Correct Answer: C) Carbon dioxide
Rationale: The Calvin cycle uses CO2, ATP, and NADPH to produce glucose. Oxygen is a
byproduct of the light reactions, and nitrogen and hydrogen aren’t fixed in this process.
Question 8
Which enzyme unwinds DNA during replication?
A) DNA polymerase
B) Helicase
C) Ligase
D) Primase
Correct Answer: B) Helicase
Rationale: Helicase unwinds and separates the DNA double helix. DNA polymerase synthesizes
new strands, ligase joins fragments, and primase adds RNA primers.
Question 9
