BIOL 3200 Exam 2 Actual Exam V3 | BIOL 3200 General Microbiology
(BIOL 3200 Exam 2) | Auburn University
1. Which of the following best describes the role of an enzyme in a microbial metabolic
reaction?
A. Enzymes increase the activation energy to slow down spontaneous reactions.
B. Enzymes change the net Gibbs free energy (ΔG) of a reaction.
C. Enzymes lower the activation energy required for a reaction to proceed.
D. Enzymes are consumed during the reaction to provide energy.
Answer: C
Rationale: Enzymes act as biological catalysts that lower the activation energy of a specific
chemical reaction. They do not alter the overall free energy change or the equilibrium of
the reaction itself. By providing an alternative pathway with a lower energy barrier, they
significantly increase the rate of biochemical processes.
2. In a redox reaction, the molecule that loses electrons is said to be:
A. Reduced
B. Oxidized
C. Phosphorylated
D. Hydrolyzed
Answer: B
Rationale: Oxidation is defined as the loss of one or more electrons from a molecule, atom,
or ion. This process is always coupled with a reduction reaction where another species
gains those electrons. In microbial metabolism, the oxidation of organic or inorganic
compounds provides the energy needed for cellular work.
3. The tendency of a compound to accept or donate electrons is expressed as its:
A. Activation energy
B. Standard reduction potential (E0’)
C. Entropy
D. Michaelis constant (Km)
Answer: B
,Rationale: The standard reduction potential is a measure of the affinity of a substance for
electrons. Substances with a more negative E0’ act as electron donors, while those with a
more positive E0’ act as electron acceptors. This concept is fundamental to understanding
the electron tower and the flow of energy in the electron transport chain.
4. Which electron carrier is primarily used in catabolic reactions to shuttle electrons to the
electron transport chain?
A. NADPH
B. NADH
C. ATP
D. FADH2
Answer: B
Rationale: NADH serves as the primary electron carrier for catabolic pathways like
glycolysis and the TCA cycle. It transports high-energy electrons to the electron transport
chain to generate a proton motive force. In contrast, NADPH is typically reserved for
biosynthetic or anabolic reactions.
5. How many net ATP molecules are produced per molecule of glucose during the Embden-
Meyerhof-Parnas (EMP) pathway?
A. 1
B. 38
C. 4
D. 2
Answer: D
Rationale: The EMP pathway, which is the most common form of glycolysis, consumes 2
ATP molecules during the preparatory phase. It subsequently generates 4 ATP molecules
through substrate-level phosphorylation in the payoff phase. This results in a net yield of 2
ATP and 2 NADH per glucose molecule.
6. The Entner-Doudoroff (ED) pathway is unique because it:
A. Produces more ATP than the EMP pathway.
B. Is only found in eukaryotes like yeast.
C. Produces one ATP, one NADH, and one NADPH per glucose.
D. Does not involve any oxidation-reduction steps.
Answer: C
, Rationale: The ED pathway is an alternative to glycolysis used by certain bacteria such as
Pseudomonas. It yields only 1 net ATP per glucose, which is half of what the EMP pathway
produces. However, it provides both NADH for energy and NADPH for biosynthesis, which
is advantageous for specific ecological niches.
7. What is the primary function of the Pentose Phosphate Pathway?
A. To generate large amounts of ATP via oxidative phosphorylation.
B. To provide precursors for nucleic acid synthesis and NADPH.
C. To oxidize pyruvate into acetyl-CoA.
D. To serve as the final electron acceptor in anaerobic respiration.
Answer: B
Rationale: The Pentose Phosphate Pathway is essential for producing ribose-5-phosphate,
which is a precursor for nucleotides. It is also the major source of NADPH, which provides
the reducing power for fatty acid and amino acid biosynthesis. While it can operate
alongside glycolysis, its primary goal is not ATP production.
8. During the transition step between glycolysis and the TCA cycle, pyruvate is converted into:
A. Acetyl-CoA
B. Oxaloacetate
C. Lactate
D. Citrate
Answer: A
Rationale: The pyruvate dehydrogenase complex catalyzes the oxidative decarboxylation
of pyruvate to form acetyl-CoA. This reaction releases one molecule of CO2 and reduces one
NAD+ to NADH per pyruvate. Acetyl-CoA then enters the TCA cycle by condensing with
oxaloacetate.
9. Which of the following is a direct product of one turn of the Citric Acid Cycle (TCA)?
A. 2 CO2, 3 NADH, 1 FADH2, and 1 GTP/ATP
B. 1 CO2, 2 NADH, 2 FADH2, and 2 ATP
C. 3 CO2, 1 NADH, 1 FADH2, and 4 ATP
D. 0 CO2, 4 NADH, 0 FADH2, and 1 ATP
Answer: A
Rationale: Each turn of the TCA cycle processes one acetyl-CoA molecule, releasing two
molecules of CO2. During this process, three NAD+ are reduced to NADH and one FAD is
(BIOL 3200 Exam 2) | Auburn University
1. Which of the following best describes the role of an enzyme in a microbial metabolic
reaction?
A. Enzymes increase the activation energy to slow down spontaneous reactions.
B. Enzymes change the net Gibbs free energy (ΔG) of a reaction.
C. Enzymes lower the activation energy required for a reaction to proceed.
D. Enzymes are consumed during the reaction to provide energy.
Answer: C
Rationale: Enzymes act as biological catalysts that lower the activation energy of a specific
chemical reaction. They do not alter the overall free energy change or the equilibrium of
the reaction itself. By providing an alternative pathway with a lower energy barrier, they
significantly increase the rate of biochemical processes.
2. In a redox reaction, the molecule that loses electrons is said to be:
A. Reduced
B. Oxidized
C. Phosphorylated
D. Hydrolyzed
Answer: B
Rationale: Oxidation is defined as the loss of one or more electrons from a molecule, atom,
or ion. This process is always coupled with a reduction reaction where another species
gains those electrons. In microbial metabolism, the oxidation of organic or inorganic
compounds provides the energy needed for cellular work.
3. The tendency of a compound to accept or donate electrons is expressed as its:
A. Activation energy
B. Standard reduction potential (E0’)
C. Entropy
D. Michaelis constant (Km)
Answer: B
,Rationale: The standard reduction potential is a measure of the affinity of a substance for
electrons. Substances with a more negative E0’ act as electron donors, while those with a
more positive E0’ act as electron acceptors. This concept is fundamental to understanding
the electron tower and the flow of energy in the electron transport chain.
4. Which electron carrier is primarily used in catabolic reactions to shuttle electrons to the
electron transport chain?
A. NADPH
B. NADH
C. ATP
D. FADH2
Answer: B
Rationale: NADH serves as the primary electron carrier for catabolic pathways like
glycolysis and the TCA cycle. It transports high-energy electrons to the electron transport
chain to generate a proton motive force. In contrast, NADPH is typically reserved for
biosynthetic or anabolic reactions.
5. How many net ATP molecules are produced per molecule of glucose during the Embden-
Meyerhof-Parnas (EMP) pathway?
A. 1
B. 38
C. 4
D. 2
Answer: D
Rationale: The EMP pathway, which is the most common form of glycolysis, consumes 2
ATP molecules during the preparatory phase. It subsequently generates 4 ATP molecules
through substrate-level phosphorylation in the payoff phase. This results in a net yield of 2
ATP and 2 NADH per glucose molecule.
6. The Entner-Doudoroff (ED) pathway is unique because it:
A. Produces more ATP than the EMP pathway.
B. Is only found in eukaryotes like yeast.
C. Produces one ATP, one NADH, and one NADPH per glucose.
D. Does not involve any oxidation-reduction steps.
Answer: C
, Rationale: The ED pathway is an alternative to glycolysis used by certain bacteria such as
Pseudomonas. It yields only 1 net ATP per glucose, which is half of what the EMP pathway
produces. However, it provides both NADH for energy and NADPH for biosynthesis, which
is advantageous for specific ecological niches.
7. What is the primary function of the Pentose Phosphate Pathway?
A. To generate large amounts of ATP via oxidative phosphorylation.
B. To provide precursors for nucleic acid synthesis and NADPH.
C. To oxidize pyruvate into acetyl-CoA.
D. To serve as the final electron acceptor in anaerobic respiration.
Answer: B
Rationale: The Pentose Phosphate Pathway is essential for producing ribose-5-phosphate,
which is a precursor for nucleotides. It is also the major source of NADPH, which provides
the reducing power for fatty acid and amino acid biosynthesis. While it can operate
alongside glycolysis, its primary goal is not ATP production.
8. During the transition step between glycolysis and the TCA cycle, pyruvate is converted into:
A. Acetyl-CoA
B. Oxaloacetate
C. Lactate
D. Citrate
Answer: A
Rationale: The pyruvate dehydrogenase complex catalyzes the oxidative decarboxylation
of pyruvate to form acetyl-CoA. This reaction releases one molecule of CO2 and reduces one
NAD+ to NADH per pyruvate. Acetyl-CoA then enters the TCA cycle by condensing with
oxaloacetate.
9. Which of the following is a direct product of one turn of the Citric Acid Cycle (TCA)?
A. 2 CO2, 3 NADH, 1 FADH2, and 1 GTP/ATP
B. 1 CO2, 2 NADH, 2 FADH2, and 2 ATP
C. 3 CO2, 1 NADH, 1 FADH2, and 4 ATP
D. 0 CO2, 4 NADH, 0 FADH2, and 1 ATP
Answer: A
Rationale: Each turn of the TCA cycle processes one acetyl-CoA molecule, releasing two
molecules of CO2. During this process, three NAD+ are reduced to NADH and one FAD is
