MCB 3020C Exam 2 V3 | MCB 3020C General
Microbiology | Actual Q&A with Rationale
(MCB3020C Exam 2) | University of Central Florida
1. During the process of glycolysis, what is the net gain of ATP molecules produced per
glucose molecule via substrate-level phosphorylation?
A. 4 ATP
B. 38 ATP
C. 2 ATP
D. 0 ATP
Correct Answer: C
Explanation: Glycolysis involves an energy investment phase followed by an energy payoff
phase. Although four ATP molecules are generated in total, two are consumed during the
initial phosphorylation of glucose. Therefore, the net metabolic yield is two ATP molecules
for every one molecule of glucose processed.
2. Which of the following terminal electron acceptors is utilized during anaerobic respiration
by certain bacteria like Pseudomonas?
A. Pyruvate
B. Oxygen (O2)
C. Nitrate (NO3-)
,D. Water (H2O)
Correct Answer: C
Explanation: Anaerobic respiration is characterized by the use of inorganic molecules
other than oxygen as the final electron acceptor in the electron transport chain. Nitrate is a
common acceptor that is reduced to nitrite or nitrogen gas depending on the organism’s
enzymatic capability. Aerobic respiration, by contrast, strictly requires oxygen as the
terminal acceptor.
3. In the microbial growth curve, during which phase are bacteria most susceptible to
antibiotics like penicillin that target cell wall synthesis?
A. Lag phase
B. Stationary phase
C. Log (Exponential) phase
D. Death phase
Correct Answer: C
Explanation: The log phase is characterized by rapid cell division and active synthesis of
new cell components including peptidoglycan. Antibiotics that inhibit cell wall synthesis,
such as beta-lactams, are most effective when the bacteria are actively growing and
building their walls. During stationary or lag phases, the metabolic activity and rate of
synthesis are insufficient for these drugs to exert their maximum lethal effect.
, 4. What is the primary function of the enzyme DNA Gyrase during bacterial DNA replication?
A. Unwinding the double helix
B. Relieving torsional strain and supercoiling
C. Synthesizing RNA primers
D. Joining Okazaki fragments
Correct Answer: B
Explanation: DNA Gyrase, a type II topoisomerase, functions by introducing negative
supercoils into the DNA molecule. This action counteracts the positive supercoiling that
occurs ahead of the replication fork as helicase unwinds the strands. Without the activity of
DNA gyrase, the DNA would become overwound, causing the replication fork to stall.
5. Which component of the Lac operon acts as a sensor for the presence of lactose by binding
to the repressor protein?
A. Allolactose
B. cAMP
C. Glucose
D. Tryptophan
Correct Answer: A
Explanation: Allolactose is an isomer of lactose that serves as the inducer for the lac
operon. When lactose is present in the cell, it is converted to allolactose, which then binds
Microbiology | Actual Q&A with Rationale
(MCB3020C Exam 2) | University of Central Florida
1. During the process of glycolysis, what is the net gain of ATP molecules produced per
glucose molecule via substrate-level phosphorylation?
A. 4 ATP
B. 38 ATP
C. 2 ATP
D. 0 ATP
Correct Answer: C
Explanation: Glycolysis involves an energy investment phase followed by an energy payoff
phase. Although four ATP molecules are generated in total, two are consumed during the
initial phosphorylation of glucose. Therefore, the net metabolic yield is two ATP molecules
for every one molecule of glucose processed.
2. Which of the following terminal electron acceptors is utilized during anaerobic respiration
by certain bacteria like Pseudomonas?
A. Pyruvate
B. Oxygen (O2)
C. Nitrate (NO3-)
,D. Water (H2O)
Correct Answer: C
Explanation: Anaerobic respiration is characterized by the use of inorganic molecules
other than oxygen as the final electron acceptor in the electron transport chain. Nitrate is a
common acceptor that is reduced to nitrite or nitrogen gas depending on the organism’s
enzymatic capability. Aerobic respiration, by contrast, strictly requires oxygen as the
terminal acceptor.
3. In the microbial growth curve, during which phase are bacteria most susceptible to
antibiotics like penicillin that target cell wall synthesis?
A. Lag phase
B. Stationary phase
C. Log (Exponential) phase
D. Death phase
Correct Answer: C
Explanation: The log phase is characterized by rapid cell division and active synthesis of
new cell components including peptidoglycan. Antibiotics that inhibit cell wall synthesis,
such as beta-lactams, are most effective when the bacteria are actively growing and
building their walls. During stationary or lag phases, the metabolic activity and rate of
synthesis are insufficient for these drugs to exert their maximum lethal effect.
, 4. What is the primary function of the enzyme DNA Gyrase during bacterial DNA replication?
A. Unwinding the double helix
B. Relieving torsional strain and supercoiling
C. Synthesizing RNA primers
D. Joining Okazaki fragments
Correct Answer: B
Explanation: DNA Gyrase, a type II topoisomerase, functions by introducing negative
supercoils into the DNA molecule. This action counteracts the positive supercoiling that
occurs ahead of the replication fork as helicase unwinds the strands. Without the activity of
DNA gyrase, the DNA would become overwound, causing the replication fork to stall.
5. Which component of the Lac operon acts as a sensor for the presence of lactose by binding
to the repressor protein?
A. Allolactose
B. cAMP
C. Glucose
D. Tryptophan
Correct Answer: A
Explanation: Allolactose is an isomer of lactose that serves as the inducer for the lac
operon. When lactose is present in the cell, it is converted to allolactose, which then binds
