BIOL 3200 Exam 2 Actual Exam V2 | BIOL 3200 General Microbiology
(BIOL 3200 Exam 2) | Auburn University
1. Enzymes facilitate chemical reactions by doing which of the following?
A. Increasing the temperature of the reaction environment
B. Lowering the activation energy required for the reaction
C. Decreasing the change in Gibbs free energy (delta G)
D. Increasing the concentration of the substrate molecules
Answer: B
Rationale: Enzymes act as biological catalysts by lowering the activation energy of a
reaction, allowing it to proceed more rapidly. They bind specifically to substrates at the
active site to stabilize the transition state. Importantly, enzymes do not change the overall
free energy change of the reaction or the equilibrium constant.
2. Which of the following processes generates the most ATP during the complete oxidation of
glucose in a chemoheterotrophic bacterium?
A. Glycolysis
B. Oxidative Phosphorylation
C. The Tricarboxylic Acid (TCA) Cycle
D. Fermentation
Answer: B
Rationale: Oxidative phosphorylation utilizes the electron transport chain and ATP
synthase to produce the majority of ATP. While glycolysis and the TCA cycle produce a
small amount of ATP via substrate-level phosphorylation, the bulk is generated through the
proton motive force. In aerobic respiration, this process typically yields around 34 ATP per
glucose molecule.
3. In the Entner-Doudoroff (ED) pathway, what is the net yield of ATP per molecule of
glucose?
A. 1 ATP
B. 2 ATP
C. 4 ATP
D. 38 ATP
Answer: A
,Rationale: The Entner-Doudoroff pathway is an alternative to glycolysis used by some
bacteria like Pseudomonas. It yields only 1 net ATP per glucose molecule, along with 1
NADH and 1 NADPH. This is less energy-efficient than the Embden-Meyerhof-Parnas
pathway, which yields 2 net ATP.
4. Which molecule serves as the primary electron carrier that feeds electrons directly into
Complex I of the mitochondrial-like bacterial electron transport chain?
A. FADH2
B. Cytochrome c
C. NADPH
D. NADH
Answer: D
Rationale: NADH is the primary electron donor for the first complex of the electron
transport chain. It releases two electrons and one proton, becoming oxidized to NAD+. This
transfer initiates the movement of electrons through the chain, facilitating proton pumping
across the membrane.
5. What is the terminal electron acceptor in aerobic respiration?
A. Nitrate (NO3-)
B. Sulfate (SO4 2-)
C. Oxygen (O2)
D. Carbon Dioxide (CO2)
Answer: C
Rationale: Aerobic respiration is defined by the use of molecular oxygen as the final
electron acceptor at the end of the electron transport chain. Oxygen has a high reduction
potential, making it a very efficient electron sink. When oxygen accepts electrons and
protons, it is reduced to form water.
6. Which enzyme is responsible for the fixation of CO2 in the Calvin-Benson cycle?
A. Nitrogenase
B. ATP Synthase
C. Phosphofructokinase
D. Ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO)
Answer: D
Rationale: RuBisCO is the key enzyme that catalyzes the carboxylation of ribulose-1,5-
bisphosphate with CO2. This reaction is the first step in the Calvin cycle, which is used by
, many autotrophic bacteria to build organic molecules. It is often considered the most
abundant enzyme on Earth due to its central role in biomass production.
7. During fermentation, what is the primary purpose of reducing pyruvate to lactic acid or
ethanol?
A. To generate additional ATP through substrate-level phosphorylation
B. To regenerate NAD+ from NADH so glycolysis can continue
C. To produce gas for the expansion of the cell
D. To lower the pH of the environment to kill competitors
Answer: B
Rationale: Fermentation does not produce additional ATP beyond what is made in
glycolysis. Its critical role is to oxidize NADH back into NAD+ by using an organic molecule
like pyruvate as an electron acceptor. Without this regeneration, the cell would run out of
NAD+ and glycolysis would stop, leading to cell death.
8. Which of the following is a characteristic of anoxygenic photosynthesis?
A. Oxygen is produced as a byproduct
B. Bacteriochlorophylls are used as the primary light-harvesting pigments
C. Water is used as the electron donor
D. It only occurs in eukaryotic algae
Answer: B
Rationale: Anoxygenic photosynthesis is performed by groups like purple and green sulfur
bacteria. Unlike oxygenic photosynthesis, it uses bacteriochlorophylls and does not
produce oxygen because water is not the electron donor. Instead, these organisms typically
use hydrogen sulfide or organic compounds to provide electrons.
9. In the electron transport chain, the movement of electrons is coupled with the pumping of
protons to create a:
A. Concentration of glucose
B. Substrate-level phosphorylation gradient
C. Proton motive force (PMF)
D. Magnetic field across the cell wall
Answer: C
Rationale: As electrons move through the electron transport chain, energy is released and
used to pump protons (H+) across the cytoplasmic membrane. This creates an
(BIOL 3200 Exam 2) | Auburn University
1. Enzymes facilitate chemical reactions by doing which of the following?
A. Increasing the temperature of the reaction environment
B. Lowering the activation energy required for the reaction
C. Decreasing the change in Gibbs free energy (delta G)
D. Increasing the concentration of the substrate molecules
Answer: B
Rationale: Enzymes act as biological catalysts by lowering the activation energy of a
reaction, allowing it to proceed more rapidly. They bind specifically to substrates at the
active site to stabilize the transition state. Importantly, enzymes do not change the overall
free energy change of the reaction or the equilibrium constant.
2. Which of the following processes generates the most ATP during the complete oxidation of
glucose in a chemoheterotrophic bacterium?
A. Glycolysis
B. Oxidative Phosphorylation
C. The Tricarboxylic Acid (TCA) Cycle
D. Fermentation
Answer: B
Rationale: Oxidative phosphorylation utilizes the electron transport chain and ATP
synthase to produce the majority of ATP. While glycolysis and the TCA cycle produce a
small amount of ATP via substrate-level phosphorylation, the bulk is generated through the
proton motive force. In aerobic respiration, this process typically yields around 34 ATP per
glucose molecule.
3. In the Entner-Doudoroff (ED) pathway, what is the net yield of ATP per molecule of
glucose?
A. 1 ATP
B. 2 ATP
C. 4 ATP
D. 38 ATP
Answer: A
,Rationale: The Entner-Doudoroff pathway is an alternative to glycolysis used by some
bacteria like Pseudomonas. It yields only 1 net ATP per glucose molecule, along with 1
NADH and 1 NADPH. This is less energy-efficient than the Embden-Meyerhof-Parnas
pathway, which yields 2 net ATP.
4. Which molecule serves as the primary electron carrier that feeds electrons directly into
Complex I of the mitochondrial-like bacterial electron transport chain?
A. FADH2
B. Cytochrome c
C. NADPH
D. NADH
Answer: D
Rationale: NADH is the primary electron donor for the first complex of the electron
transport chain. It releases two electrons and one proton, becoming oxidized to NAD+. This
transfer initiates the movement of electrons through the chain, facilitating proton pumping
across the membrane.
5. What is the terminal electron acceptor in aerobic respiration?
A. Nitrate (NO3-)
B. Sulfate (SO4 2-)
C. Oxygen (O2)
D. Carbon Dioxide (CO2)
Answer: C
Rationale: Aerobic respiration is defined by the use of molecular oxygen as the final
electron acceptor at the end of the electron transport chain. Oxygen has a high reduction
potential, making it a very efficient electron sink. When oxygen accepts electrons and
protons, it is reduced to form water.
6. Which enzyme is responsible for the fixation of CO2 in the Calvin-Benson cycle?
A. Nitrogenase
B. ATP Synthase
C. Phosphofructokinase
D. Ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO)
Answer: D
Rationale: RuBisCO is the key enzyme that catalyzes the carboxylation of ribulose-1,5-
bisphosphate with CO2. This reaction is the first step in the Calvin cycle, which is used by
, many autotrophic bacteria to build organic molecules. It is often considered the most
abundant enzyme on Earth due to its central role in biomass production.
7. During fermentation, what is the primary purpose of reducing pyruvate to lactic acid or
ethanol?
A. To generate additional ATP through substrate-level phosphorylation
B. To regenerate NAD+ from NADH so glycolysis can continue
C. To produce gas for the expansion of the cell
D. To lower the pH of the environment to kill competitors
Answer: B
Rationale: Fermentation does not produce additional ATP beyond what is made in
glycolysis. Its critical role is to oxidize NADH back into NAD+ by using an organic molecule
like pyruvate as an electron acceptor. Without this regeneration, the cell would run out of
NAD+ and glycolysis would stop, leading to cell death.
8. Which of the following is a characteristic of anoxygenic photosynthesis?
A. Oxygen is produced as a byproduct
B. Bacteriochlorophylls are used as the primary light-harvesting pigments
C. Water is used as the electron donor
D. It only occurs in eukaryotic algae
Answer: B
Rationale: Anoxygenic photosynthesis is performed by groups like purple and green sulfur
bacteria. Unlike oxygenic photosynthesis, it uses bacteriochlorophylls and does not
produce oxygen because water is not the electron donor. Instead, these organisms typically
use hydrogen sulfide or organic compounds to provide electrons.
9. In the electron transport chain, the movement of electrons is coupled with the pumping of
protons to create a:
A. Concentration of glucose
B. Substrate-level phosphorylation gradient
C. Proton motive force (PMF)
D. Magnetic field across the cell wall
Answer: C
Rationale: As electrons move through the electron transport chain, energy is released and
used to pump protons (H+) across the cytoplasmic membrane. This creates an
