BIOS 242 MICROBIOLOGY
COMPREHENSIVE EXAM QUESTIONS
AND ANSWERS
1. Which component of the Gram-negative cell wall is responsible for the induction of septic
shock by triggering a massive immune response?
A. Teichoic acid
B. Peptidoglycan cross-links
C. Lipopolysaccharide (Lipid A)
D. Periplasmic proteins
Answer: C
Conceptual Explanation: Lipid A, the lipid component of Lipopolysaccharide (LPS) in
Gram-negative bacteria, acts as an endotoxin that can trigger systemic inflammation and
septic shock.
2. In the process of bacterial DNA replication, which enzyme is responsible for relieving
torsional strain (supercoiling) ahead of the replication fork?
A. DNA Helicase
,B. DNA Polymerase III
C. DNA Gyrase (Topoisomerase II)
D. Primase
Answer: C
Conceptual Explanation: DNA Gyrase travels ahead of the replication fork and introduces
negative supercoils to neutralize the positive supercoiling caused by helicase unwinding
the DNA.
3. What is the net yield of ATP molecules produced per glucose molecule through substrate-
level phosphorylation during the Glycolysis pathway alone?
A. 38 ATP
B. 4 ATP
C. 36 ATP
D. 2 ATP
Answer: D
Conceptual Explanation: While 4 ATP are produced during the payoff phase, 2 ATP are
consumed in the preparatory phase, resulting in a net gain of 2 ATP per glucose.
4. A bacterium that grows optimally at human body temperature (37 degrees Celsius) is
classified as a:
A. Psychrophile
, B. Mesophile
C. Thermophile
D. Hyperthermophile
Answer: B
Conceptual Explanation: Mesophiles are organisms that grow best in moderate
temperatures, typically between 20 and 45 degrees Celsius, covering the human body
temperature.
5. Which of the following best describes the ‘Log Phase’ of a bacterial growth curve?
A. Exponential growth where metabolic activity is at its peak.
B. The rate of cell division equals the rate of cell death.
C. Cells are adjusting to the environment and synthesizing enzymes.
D. Nutrients are exhausted and waste products accumulate, leading to death.
Answer: A
Conceptual Explanation: The Log (exponential) phase is characterized by rapid cell
division and is the time when bacteria are most susceptible to antibiotics like penicillin.
6. During specialized transduction, which of the following events occurs?
A. A specific piece of bacterial DNA adjacent to the prophage insertion site is transferred.
B. Random bacterial DNA is packaged into a phage head.
COMPREHENSIVE EXAM QUESTIONS
AND ANSWERS
1. Which component of the Gram-negative cell wall is responsible for the induction of septic
shock by triggering a massive immune response?
A. Teichoic acid
B. Peptidoglycan cross-links
C. Lipopolysaccharide (Lipid A)
D. Periplasmic proteins
Answer: C
Conceptual Explanation: Lipid A, the lipid component of Lipopolysaccharide (LPS) in
Gram-negative bacteria, acts as an endotoxin that can trigger systemic inflammation and
septic shock.
2. In the process of bacterial DNA replication, which enzyme is responsible for relieving
torsional strain (supercoiling) ahead of the replication fork?
A. DNA Helicase
,B. DNA Polymerase III
C. DNA Gyrase (Topoisomerase II)
D. Primase
Answer: C
Conceptual Explanation: DNA Gyrase travels ahead of the replication fork and introduces
negative supercoils to neutralize the positive supercoiling caused by helicase unwinding
the DNA.
3. What is the net yield of ATP molecules produced per glucose molecule through substrate-
level phosphorylation during the Glycolysis pathway alone?
A. 38 ATP
B. 4 ATP
C. 36 ATP
D. 2 ATP
Answer: D
Conceptual Explanation: While 4 ATP are produced during the payoff phase, 2 ATP are
consumed in the preparatory phase, resulting in a net gain of 2 ATP per glucose.
4. A bacterium that grows optimally at human body temperature (37 degrees Celsius) is
classified as a:
A. Psychrophile
, B. Mesophile
C. Thermophile
D. Hyperthermophile
Answer: B
Conceptual Explanation: Mesophiles are organisms that grow best in moderate
temperatures, typically between 20 and 45 degrees Celsius, covering the human body
temperature.
5. Which of the following best describes the ‘Log Phase’ of a bacterial growth curve?
A. Exponential growth where metabolic activity is at its peak.
B. The rate of cell division equals the rate of cell death.
C. Cells are adjusting to the environment and synthesizing enzymes.
D. Nutrients are exhausted and waste products accumulate, leading to death.
Answer: A
Conceptual Explanation: The Log (exponential) phase is characterized by rapid cell
division and is the time when bacteria are most susceptible to antibiotics like penicillin.
6. During specialized transduction, which of the following events occurs?
A. A specific piece of bacterial DNA adjacent to the prophage insertion site is transferred.
B. Random bacterial DNA is packaged into a phage head.
