BIOS 242 Fundamentals of Microbiology
Complete Midterm Exam Review (Qns & Ans)
2025
1. Which of the following structures allow bacteria to adhere to
surfaces and host tissues?
- A. Flagella
- B. Pili
- C. Ribosomes
- D. Endospores
ANS : B. Pili
Rationale : Pili are hair-like appendages that facilitate
bacterial attachment to surfaces and host cells, aiding in
colonization.
©2025
,2. Which phase of bacterial growth is characterized by rapid cell
division?
- A. Lag phase
- B. Log phase
- C. Stationary phase
- D. Death phase
ANS : B. Log phase
Rationale : During the log (exponential) phase, bacteria grow
and divide at their maximum rate due to optimal environmental
conditions.
3. What is the primary purpose of performing a Gram stain in
microbiology?
- A. To visualize bacterial spores
- B. To differentiate bacteria based on cell wall composition
- C. To detect motility in bacteria
- D. To identify bacterial metabolism
ANS : B. To differentiate bacteria based on cell wall
composition
Rationale : The Gram stain differentiates bacteria into Gram-
positive and Gram-negative groups based on their peptidoglycan
layer thickness.
©2025
, ---
Fill-in-the-Blank Questions
4. The ____, are small, circular pieces of DNA in bacteria that
often carry antibiotic resistance genes.
ANS : Plasmids
Rationale : Plasmids are extrachromosomal DNA elements
that can transfer between bacteria, spreading resistance traits.
5. Viruses that infect bacteria are known as ____.
ANS : Bacteriophages
Rationale : Bacteriophages are specialized viruses that infect
bacterial cells and can play roles in genetic exchange.
6. The enzyme ____, is produced by some bacteria to break
down hydrogen peroxide into water and oxygen.
ANS : Catalase
Rationale : Catalase protects bacteria from oxidative damage
by neutralizing hydrogen peroxide.
---
©2025
Complete Midterm Exam Review (Qns & Ans)
2025
1. Which of the following structures allow bacteria to adhere to
surfaces and host tissues?
- A. Flagella
- B. Pili
- C. Ribosomes
- D. Endospores
ANS : B. Pili
Rationale : Pili are hair-like appendages that facilitate
bacterial attachment to surfaces and host cells, aiding in
colonization.
©2025
,2. Which phase of bacterial growth is characterized by rapid cell
division?
- A. Lag phase
- B. Log phase
- C. Stationary phase
- D. Death phase
ANS : B. Log phase
Rationale : During the log (exponential) phase, bacteria grow
and divide at their maximum rate due to optimal environmental
conditions.
3. What is the primary purpose of performing a Gram stain in
microbiology?
- A. To visualize bacterial spores
- B. To differentiate bacteria based on cell wall composition
- C. To detect motility in bacteria
- D. To identify bacterial metabolism
ANS : B. To differentiate bacteria based on cell wall
composition
Rationale : The Gram stain differentiates bacteria into Gram-
positive and Gram-negative groups based on their peptidoglycan
layer thickness.
©2025
, ---
Fill-in-the-Blank Questions
4. The ____, are small, circular pieces of DNA in bacteria that
often carry antibiotic resistance genes.
ANS : Plasmids
Rationale : Plasmids are extrachromosomal DNA elements
that can transfer between bacteria, spreading resistance traits.
5. Viruses that infect bacteria are known as ____.
ANS : Bacteriophages
Rationale : Bacteriophages are specialized viruses that infect
bacterial cells and can play roles in genetic exchange.
6. The enzyme ____, is produced by some bacteria to break
down hydrogen peroxide into water and oxygen.
ANS : Catalase
Rationale : Catalase protects bacteria from oxidative damage
by neutralizing hydrogen peroxide.
---
©2025
