BIO111 Exam 2 Actual Exam V2 | BIO111 General Biology (BIO111
Exam 2) | University of California, Los Angeles
1. Which of the following best describes the function of an enzyme in a metabolic reaction?
A. Decreasing the activation energy of the reaction
B. Increasing the Gibbs free energy of the products
C. Changing the equilibrium constant to favor product formation
D. Acting as a permanent reactant in the chemical pathway
Answer: A
Rationale: Enzymes act as biological catalysts that speed up chemical reactions without
being consumed. They achieve this by lowering the activation energy barrier, allowing
substrates to reach the transition state more easily. This process does not change the
overall free energy (delta G) of the reaction.
2. How does ATP provide energy to drive endergonic reactions in a cell?
A. Through the process of energy coupling via phosphorylation
B. By absorbing heat from the surroundings
C. By decreasing the entropy of the cellular environment
D. By converting kinetic energy into potential energy stored in glucose
Answer: A
Rationale: ATP powers cellular work by coupling exergonic reactions to endergonic ones.
In many cases, this involves the transfer of a phosphate group from ATP to another
molecule, a process known as phosphorylation. The resulting phosphorylated intermediate
is more reactive and less stable, facilitating the chemical work.
3. Where does glycolysis occur in a eukaryotic cell?
A. Mitochondrial matrix
B. Cytosol
C. Inner mitochondrial membrane
D. Intermembrane space
Answer: B
,Rationale: Glycolysis is the first stage of cellular respiration and takes place entirely in the
cytosol. It does not require oxygen and is thought to be one of the most ancient metabolic
pathways. After glycolysis, the products move into the mitochondria if oxygen is present.
4. In the presence of oxygen, what is the net yield of ATP per molecule of glucose during
glycolysis?
A. 1 ATP
B. 32-34 ATP
C. 4 ATP
D. 2 ATP
Answer: D
Rationale: Glycolysis involves an initial energy investment phase where 2 ATP are used.
During the energy payoff phase, 4 ATP are produced via substrate-level phosphorylation.
Therefore, the net gain for the cell is 2 ATP molecules per glucose molecule.
5. Which molecule acts as the final electron acceptor in the electron transport chain of
aerobic respiration?
A. Water
B. Oxygen
C. Carbon dioxide
D. NAD+
Answer: B
Rationale: Oxygen is highly electronegative and serves as the terminal electron acceptor in
aerobic respiration. It accepts electrons at the end of the transport chain and combines
with hydrogen ions to form water. Without oxygen, the electron transport chain would stop
functioning, halting ATP production via oxidative phosphorylation.
6. What is the primary purpose of fermentation in cells?
A. To produce a large amount of ATP
B. To generate oxygen for the mitochondria
C. To oxidize glucose to CO2 and H2O
D. To regenerate NAD+ from NADH
Answer: D
Rationale: Fermentation occurs when oxygen is absent, preventing the electron transport
chain from recycling NADH. To allow glycolysis to continue producing a small amount of
, ATP, fermentation transfers electrons from NADH to an organic molecule like pyruvate or
acetaldehyde. This regenerates the NAD+ needed as an oxidizing agent in glycolysis.
7. During the light reactions of photosynthesis, what is the source of electrons for
Photosystem II?
A. Carbon dioxide
B. Glucose
C. NADPH
D. Water
Answer: D
Rationale: Photosystem II replaces its excited electrons by splitting water molecules into
protons, electrons, and oxygen. This process, known as photolysis, is the source of the
atmospheric oxygen we breathe. The electrons then travel through the electron transport
chain to Photosystem I.
8. In the Calvin cycle, which enzyme is responsible for ‘fixing’ CO2 onto RuBP?
A. ATP synthase
B. NADPH reductase
C. Phosphofructokinase
D. Rubisco
Answer: D
Rationale: Rubisco (ribulose bisphosphate carboxylase-oxygenase) is the enzyme that
catalyzes the first step of the Calvin cycle. It attaches a molecule of inorganic CO2 to the
five-carbon sugar RuBP. It is considered one of the most abundant and important proteins
on Earth.
9. What happens to the energy level of an electron as it moves through the electron transport
chain in mitochondria?
A. It decreases at each step
B. It stays the same
C. It increases at each step
D. It fluctuates randomly
Answer: A
Rationale: As electrons move through the electron transport chain, they drop in free
energy. This energy release is used by the protein complexes to pump protons (H+) from
Exam 2) | University of California, Los Angeles
1. Which of the following best describes the function of an enzyme in a metabolic reaction?
A. Decreasing the activation energy of the reaction
B. Increasing the Gibbs free energy of the products
C. Changing the equilibrium constant to favor product formation
D. Acting as a permanent reactant in the chemical pathway
Answer: A
Rationale: Enzymes act as biological catalysts that speed up chemical reactions without
being consumed. They achieve this by lowering the activation energy barrier, allowing
substrates to reach the transition state more easily. This process does not change the
overall free energy (delta G) of the reaction.
2. How does ATP provide energy to drive endergonic reactions in a cell?
A. Through the process of energy coupling via phosphorylation
B. By absorbing heat from the surroundings
C. By decreasing the entropy of the cellular environment
D. By converting kinetic energy into potential energy stored in glucose
Answer: A
Rationale: ATP powers cellular work by coupling exergonic reactions to endergonic ones.
In many cases, this involves the transfer of a phosphate group from ATP to another
molecule, a process known as phosphorylation. The resulting phosphorylated intermediate
is more reactive and less stable, facilitating the chemical work.
3. Where does glycolysis occur in a eukaryotic cell?
A. Mitochondrial matrix
B. Cytosol
C. Inner mitochondrial membrane
D. Intermembrane space
Answer: B
,Rationale: Glycolysis is the first stage of cellular respiration and takes place entirely in the
cytosol. It does not require oxygen and is thought to be one of the most ancient metabolic
pathways. After glycolysis, the products move into the mitochondria if oxygen is present.
4. In the presence of oxygen, what is the net yield of ATP per molecule of glucose during
glycolysis?
A. 1 ATP
B. 32-34 ATP
C. 4 ATP
D. 2 ATP
Answer: D
Rationale: Glycolysis involves an initial energy investment phase where 2 ATP are used.
During the energy payoff phase, 4 ATP are produced via substrate-level phosphorylation.
Therefore, the net gain for the cell is 2 ATP molecules per glucose molecule.
5. Which molecule acts as the final electron acceptor in the electron transport chain of
aerobic respiration?
A. Water
B. Oxygen
C. Carbon dioxide
D. NAD+
Answer: B
Rationale: Oxygen is highly electronegative and serves as the terminal electron acceptor in
aerobic respiration. It accepts electrons at the end of the transport chain and combines
with hydrogen ions to form water. Without oxygen, the electron transport chain would stop
functioning, halting ATP production via oxidative phosphorylation.
6. What is the primary purpose of fermentation in cells?
A. To produce a large amount of ATP
B. To generate oxygen for the mitochondria
C. To oxidize glucose to CO2 and H2O
D. To regenerate NAD+ from NADH
Answer: D
Rationale: Fermentation occurs when oxygen is absent, preventing the electron transport
chain from recycling NADH. To allow glycolysis to continue producing a small amount of
, ATP, fermentation transfers electrons from NADH to an organic molecule like pyruvate or
acetaldehyde. This regenerates the NAD+ needed as an oxidizing agent in glycolysis.
7. During the light reactions of photosynthesis, what is the source of electrons for
Photosystem II?
A. Carbon dioxide
B. Glucose
C. NADPH
D. Water
Answer: D
Rationale: Photosystem II replaces its excited electrons by splitting water molecules into
protons, electrons, and oxygen. This process, known as photolysis, is the source of the
atmospheric oxygen we breathe. The electrons then travel through the electron transport
chain to Photosystem I.
8. In the Calvin cycle, which enzyme is responsible for ‘fixing’ CO2 onto RuBP?
A. ATP synthase
B. NADPH reductase
C. Phosphofructokinase
D. Rubisco
Answer: D
Rationale: Rubisco (ribulose bisphosphate carboxylase-oxygenase) is the enzyme that
catalyzes the first step of the Calvin cycle. It attaches a molecule of inorganic CO2 to the
five-carbon sugar RuBP. It is considered one of the most abundant and important proteins
on Earth.
9. What happens to the energy level of an electron as it moves through the electron transport
chain in mitochondria?
A. It decreases at each step
B. It stays the same
C. It increases at each step
D. It fluctuates randomly
Answer: A
Rationale: As electrons move through the electron transport chain, they drop in free
energy. This energy release is used by the protein complexes to pump protons (H+) from
