BIO 171 BASIC MICROBIOLOGY
COMPREHENSIVE PRACTICE EXAM
2026/2027
1. Which of the following components is exclusively found in the cell walls of Acid-Fast
bacteria, providing them with high resistance to chemical disinfectants?
A. Teichoic acids
B. Mycolic acids
C. Lipopolysaccharides
D. Pseudomurein
Answer: B
Conceptual Explanation: Mycolic acids are long-chain fatty acids found in the cell walls of
Mycobacterium species, making them waxy and resistant to drying and chemicals.
2. In bacterial genetics, what is the specific role of the sigma factor in RNA polymerase?
A. It catalyzes the formation of phosphodiester bonds.
B. It assists in the unwinding of the DNA double helix.
C. It terminates transcription by forming a hairpin loop.
,D. It recognizes the specific promoter sequence to initiate transcription.
Answer: D
Conceptual Explanation: The sigma factor is a subunit of bacterial RNA polymerase that
ensures the enzyme binds to specific promoter regions to start transcription.
3. During the process of oxidative phosphorylation in bacteria, where is the electron
transport chain located?
A. Mitochondrial inner membrane
B. Outer membrane
C. Cytoplasmic membrane
D. Periplasmic space
Answer: C
Conceptual Explanation: Bacteria lack mitochondria; therefore, their electron transport
chain is situated in the cytoplasmic (plasma) membrane.
4. Which of the following best describes a ‘latent’ viral infection?
A. The virus replicates rapidly and causes immediate cell lysis.
B. The viral genome is integrated into the host DNA and replicates as a prophage.
C. The virus remains in equilibrium with the host without producing disease for long
periods.
D. The virus causes continuous low-level shedding without symptoms.
, Answer: C
Conceptual Explanation: Latent infections involve viruses that stay dormant within host
cells (like Herpes simplex) and can reactivate later.
5. Which molecule acts as the terminal electron acceptor in anaerobic respiration using
nitrate?
A. Oxygen
B. Nitrate (NO3-)
C. Pyruvate
D. Sulfate (SO4 2-)
Answer: B
Conceptual Explanation: In anaerobic respiration, inorganic molecules other than oxygen,
such as nitrate, serve as the final electron acceptor.
6. What is the primary function of the bacterial enzyme Gyrase?
A. Adding nucleotides to the 3’ end of DNA.
B. Ligating Okazaki fragments.
C. Relaxing supercoiling ahead of the replication fork.
D. Synthesizing RNA primers.
Answer: C
COMPREHENSIVE PRACTICE EXAM
2026/2027
1. Which of the following components is exclusively found in the cell walls of Acid-Fast
bacteria, providing them with high resistance to chemical disinfectants?
A. Teichoic acids
B. Mycolic acids
C. Lipopolysaccharides
D. Pseudomurein
Answer: B
Conceptual Explanation: Mycolic acids are long-chain fatty acids found in the cell walls of
Mycobacterium species, making them waxy and resistant to drying and chemicals.
2. In bacterial genetics, what is the specific role of the sigma factor in RNA polymerase?
A. It catalyzes the formation of phosphodiester bonds.
B. It assists in the unwinding of the DNA double helix.
C. It terminates transcription by forming a hairpin loop.
,D. It recognizes the specific promoter sequence to initiate transcription.
Answer: D
Conceptual Explanation: The sigma factor is a subunit of bacterial RNA polymerase that
ensures the enzyme binds to specific promoter regions to start transcription.
3. During the process of oxidative phosphorylation in bacteria, where is the electron
transport chain located?
A. Mitochondrial inner membrane
B. Outer membrane
C. Cytoplasmic membrane
D. Periplasmic space
Answer: C
Conceptual Explanation: Bacteria lack mitochondria; therefore, their electron transport
chain is situated in the cytoplasmic (plasma) membrane.
4. Which of the following best describes a ‘latent’ viral infection?
A. The virus replicates rapidly and causes immediate cell lysis.
B. The viral genome is integrated into the host DNA and replicates as a prophage.
C. The virus remains in equilibrium with the host without producing disease for long
periods.
D. The virus causes continuous low-level shedding without symptoms.
, Answer: C
Conceptual Explanation: Latent infections involve viruses that stay dormant within host
cells (like Herpes simplex) and can reactivate later.
5. Which molecule acts as the terminal electron acceptor in anaerobic respiration using
nitrate?
A. Oxygen
B. Nitrate (NO3-)
C. Pyruvate
D. Sulfate (SO4 2-)
Answer: B
Conceptual Explanation: In anaerobic respiration, inorganic molecules other than oxygen,
such as nitrate, serve as the final electron acceptor.
6. What is the primary function of the bacterial enzyme Gyrase?
A. Adding nucleotides to the 3’ end of DNA.
B. Ligating Okazaki fragments.
C. Relaxing supercoiling ahead of the replication fork.
D. Synthesizing RNA primers.
Answer: C
