BIOL 101 Exam 2 V1 | BIOL 101 Principles of Biology | Actual Q&A
with Rationale (BIOL101 Exam 2) | Liberty University
1. Where does glycolysis occur within a eukaryotic cell?
A. Cytosol
B. Mitochondrial matrix
C. Inner mitochondrial membrane
D. Chloroplast stroma
Correct Answer: A
Explanation: Glycolysis is the initial stage of cellular respiration and takes place in the
cytosol of the cell. This process involves the metabolic breakdown of glucose into two
molecules of pyruvate. It is considered an ancient metabolic pathway because it does not
require oxygen to function.
2. What is the net gain of ATP molecules produced during the process of glycolysis?
A. 2 ATP
B. 36 ATP
C. 4 ATP
D. 32 ATP
Correct Answer: A
Explanation: Although glycolysis produces a total of four ATP molecules, two are
consumed during the initial energy investment phase. This results in a net yield of two ATP
molecules available for the cell’s immediate use. This net gain represents a small fraction of
the total energy stored in a glucose molecule.
3. In aerobic respiration, what is the role of oxygen?
A. To serve as a source of carbon
B. To provide energy for the proton pump
C. To catalyze the conversion of glucose
D. To act as the final electron acceptor
Correct Answer: D
Explanation: Oxygen is highly electronegative and functions as the final electron acceptor
at the end of the electron transport chain. It combines with low-energy electrons and
,hydrogen ions to form water as a byproduct. Without oxygen, the entire transport chain
stops, preventing the regeneration of NAD+ and FAD.
4. Which molecule enters the Krebs cycle (Citric Acid Cycle) to begin the process?
A. Glucose
B. Pyruvate
C. Acetyl CoA
D. Oxaloacetate
Correct Answer: C
Explanation: Before entering the Krebs cycle, pyruvate is oxidized into a two-carbon
fragment called an acetyl group. This group is then attached to Coenzyme A, forming Acetyl
CoA. This molecule delivers the acetyl group to the four-carbon oxaloacetate to begin the
cycle.
5. Where is the majority of ATP synthesized during cellular respiration?
A. Glycolysis
B. Krebs Cycle
C. Fermentation
D. Electron Transport Chain and Chemiosmosis
Correct Answer: D
Explanation: The electron transport chain creates a proton gradient across the inner
mitochondrial membrane. This gradient provides the potential energy necessary for ATP
synthase to phosphorylate ADP into ATP. This process, known as oxidative
phosphorylation, accounts for approximately 90% of the ATP generated during respiration.
6. What causes muscle soreness during intense exercise when oxygen levels are low?
A. Ethanol production
B. Pyruvate oxidation
C. Excess CO2 buildup
D. Lactic acid fermentation
Correct Answer: D
Explanation: When oxygen is scarce, cells switch from aerobic respiration to lactic acid
fermentation to regenerate NAD+. This process converts pyruvate into lactate, which can
accumulate in muscle tissues. The buildup of lactate and associated acidity contributes to
muscle fatigue and soreness.
, 7. What are the two primary electron carriers used in cellular respiration?
A. ATP and ADP
B. NADH and FADH2
C. NADPH and ATP
D. CO2 and H2O
Correct Answer: B
Explanation: NADH and FADH2 act as high-energy electron shuttles that transport
electrons from the Krebs cycle to the electron transport chain. They are the reduced forms
of the coenzymes NAD+ and FAD. Their oxidation provides the energy needed to drive the
proton pumps in the mitochondria.
8. Which phase of cellular respiration releases the most carbon dioxide?
A. Glycolysis
B. Chemiosmosis
C. The Krebs Cycle
D. Electron Transport Chain
Correct Answer: C
Explanation: The Krebs cycle is responsible for the complete oxidation of the carbon
atoms originally found in glucose. As the cycle turns, carbon is released in the form of CO2
as a metabolic waste product. This CO2 eventually diffuses out of the cell and into the
bloodstream for exhalation.
9. What is the relationship between oxidation and reduction in a redox reaction?
A. Oxidation is the gain of electrons; reduction is the loss
B. Oxidation creates energy; reduction uses energy
C. Oxidation adds oxygen; reduction removes oxygen
D. Oxidation is the loss of electrons; reduction is the gain
Correct Answer: D
Explanation: In biological systems, redox reactions involve the transfer of electrons from
one molecule to another. The molecule that loses electrons is said to be oxidized, while the
one receiving them is reduced. These two processes always occur simultaneously in a
coupled fashion.
10. What is the direct source of energy that powers ATP synthase?
A. The H+ concentration gradient
with Rationale (BIOL101 Exam 2) | Liberty University
1. Where does glycolysis occur within a eukaryotic cell?
A. Cytosol
B. Mitochondrial matrix
C. Inner mitochondrial membrane
D. Chloroplast stroma
Correct Answer: A
Explanation: Glycolysis is the initial stage of cellular respiration and takes place in the
cytosol of the cell. This process involves the metabolic breakdown of glucose into two
molecules of pyruvate. It is considered an ancient metabolic pathway because it does not
require oxygen to function.
2. What is the net gain of ATP molecules produced during the process of glycolysis?
A. 2 ATP
B. 36 ATP
C. 4 ATP
D. 32 ATP
Correct Answer: A
Explanation: Although glycolysis produces a total of four ATP molecules, two are
consumed during the initial energy investment phase. This results in a net yield of two ATP
molecules available for the cell’s immediate use. This net gain represents a small fraction of
the total energy stored in a glucose molecule.
3. In aerobic respiration, what is the role of oxygen?
A. To serve as a source of carbon
B. To provide energy for the proton pump
C. To catalyze the conversion of glucose
D. To act as the final electron acceptor
Correct Answer: D
Explanation: Oxygen is highly electronegative and functions as the final electron acceptor
at the end of the electron transport chain. It combines with low-energy electrons and
,hydrogen ions to form water as a byproduct. Without oxygen, the entire transport chain
stops, preventing the regeneration of NAD+ and FAD.
4. Which molecule enters the Krebs cycle (Citric Acid Cycle) to begin the process?
A. Glucose
B. Pyruvate
C. Acetyl CoA
D. Oxaloacetate
Correct Answer: C
Explanation: Before entering the Krebs cycle, pyruvate is oxidized into a two-carbon
fragment called an acetyl group. This group is then attached to Coenzyme A, forming Acetyl
CoA. This molecule delivers the acetyl group to the four-carbon oxaloacetate to begin the
cycle.
5. Where is the majority of ATP synthesized during cellular respiration?
A. Glycolysis
B. Krebs Cycle
C. Fermentation
D. Electron Transport Chain and Chemiosmosis
Correct Answer: D
Explanation: The electron transport chain creates a proton gradient across the inner
mitochondrial membrane. This gradient provides the potential energy necessary for ATP
synthase to phosphorylate ADP into ATP. This process, known as oxidative
phosphorylation, accounts for approximately 90% of the ATP generated during respiration.
6. What causes muscle soreness during intense exercise when oxygen levels are low?
A. Ethanol production
B. Pyruvate oxidation
C. Excess CO2 buildup
D. Lactic acid fermentation
Correct Answer: D
Explanation: When oxygen is scarce, cells switch from aerobic respiration to lactic acid
fermentation to regenerate NAD+. This process converts pyruvate into lactate, which can
accumulate in muscle tissues. The buildup of lactate and associated acidity contributes to
muscle fatigue and soreness.
, 7. What are the two primary electron carriers used in cellular respiration?
A. ATP and ADP
B. NADH and FADH2
C. NADPH and ATP
D. CO2 and H2O
Correct Answer: B
Explanation: NADH and FADH2 act as high-energy electron shuttles that transport
electrons from the Krebs cycle to the electron transport chain. They are the reduced forms
of the coenzymes NAD+ and FAD. Their oxidation provides the energy needed to drive the
proton pumps in the mitochondria.
8. Which phase of cellular respiration releases the most carbon dioxide?
A. Glycolysis
B. Chemiosmosis
C. The Krebs Cycle
D. Electron Transport Chain
Correct Answer: C
Explanation: The Krebs cycle is responsible for the complete oxidation of the carbon
atoms originally found in glucose. As the cycle turns, carbon is released in the form of CO2
as a metabolic waste product. This CO2 eventually diffuses out of the cell and into the
bloodstream for exhalation.
9. What is the relationship between oxidation and reduction in a redox reaction?
A. Oxidation is the gain of electrons; reduction is the loss
B. Oxidation creates energy; reduction uses energy
C. Oxidation adds oxygen; reduction removes oxygen
D. Oxidation is the loss of electrons; reduction is the gain
Correct Answer: D
Explanation: In biological systems, redox reactions involve the transfer of electrons from
one molecule to another. The molecule that loses electrons is said to be oxidized, while the
one receiving them is reduced. These two processes always occur simultaneously in a
coupled fashion.
10. What is the direct source of energy that powers ATP synthase?
A. The H+ concentration gradient
