Microbiology Exam Review
1. Which structure allows bacteria to adhere to surfaces and form biofilms?
A. Flagella
B. Pili
C. Capsule
✅
D. Ribosomes
Answer: C. Capsule
Explanation: The capsule is a polysaccharide layer outside the cell wall that helps bacteria
adhere to surfaces and protects them from the immune system, making it crucial for biofilm
formation.
2. What is the primary function of the bacterial cell wall?
A. ATP production
B. Protein synthesis
C. Structural support and shape
✅
D. DNA replication
Answer: C. Structural support and shape
Explanation: The bacterial cell wall, mainly composed of peptidoglycan, maintains cell
shape and prevents lysis from osmotic pressure.
3. Which of the following best describes a Gram-negative bacterium?
A. Thick peptidoglycan layer, no outer membrane
B. Thin peptidoglycan layer, outer membrane present
C. Lacks peptidoglycan entirely
✅
D. Only contains lipopolysaccharide
Answer: B. Thin peptidoglycan layer, outer membrane present
Explanation: Gram-negative bacteria have a thin peptidoglycan layer between the plasma
membrane and an outer membrane that contains lipopolysaccharides.
4. Which microbial growth phase is characterized by no increase in cell number?
A. Log phase
B. Lag phase
C. Stationary phase
✅
D. Death phase
Answer: B. Lag phase
Explanation: During the lag phase, bacteria adapt to new environments and prepare for
cell division, but do not multiply.
,5. What structure do Gram-positive bacteria lack compared to
Gram-negative bacteria?
Answer: Outer membrane
Explanation: Gram-positive bacteria lack an outer membrane, which is present in
Gram-negative bacteria and contains lipopolysaccharides important for virulence.
6. What is the primary function of bacterial endospores?
Answer: Survival in harsh conditions
Explanation: Endospores are resistant structures that allow bacteria to withstand extreme
heat, desiccation, and chemicals.
7. Which stain is used to identify Mycobacterium tuberculosis?
Answer: Acid-fast stain
Explanation: The acid-fast stain targets the waxy mycolic acid in the cell walls of
Mycobacterium species.
8. What type of microorganism is a protozoan?
Answer: Eukaryotic
Explanation: Protozoa are single-celled eukaryotic organisms, meaning they have a
nucleus and organelles.
9. What component is found in fungal cell walls but not in bacterial cell
walls?
Answer: Chitin
Explanation: Fungi have cell walls made of chitin, while bacteria have peptidoglycan.
10. What term describes the time it takes for a bacterial population to
double?
, Answer: Generation time
Explanation: Generation time is the period required for one round of cell division, leading to
population doubling.
11. Which phase of bacterial growth shows no increase in cell number?
Answer: Lag phase
Explanation: During the lag phase, bacteria are metabolically active but not dividing.
12. What is the function of the ribosome in bacterial cells?
Answer: Protein synthesis
Explanation: Ribosomes are responsible for translating mRNA into proteins.
13. Which immune cells are the first responders during an infection?
Answer: Neutrophils
Explanation: Neutrophils are a type of white blood cell that quickly arrive at infection sites
to engulf pathogens.
14. What is the role of cytokines in the immune response?
Answer: Cell signaling
Explanation: Cytokines are signaling molecules that regulate immune responses,
inflammation, and cell communication.
15. What type of immunity is conferred by vaccination?
Answer: Artificial active immunity
Explanation: Vaccination introduces antigens to stimulate the immune system to produce
antibodies.
16. What does the term “opportunistic pathogen” refer to?
Answer: An organism that causes disease in weakened hosts
Explanation: These pathogens are normally harmless but can cause infections in
immunocompromised individuals.
1. Which structure allows bacteria to adhere to surfaces and form biofilms?
A. Flagella
B. Pili
C. Capsule
✅
D. Ribosomes
Answer: C. Capsule
Explanation: The capsule is a polysaccharide layer outside the cell wall that helps bacteria
adhere to surfaces and protects them from the immune system, making it crucial for biofilm
formation.
2. What is the primary function of the bacterial cell wall?
A. ATP production
B. Protein synthesis
C. Structural support and shape
✅
D. DNA replication
Answer: C. Structural support and shape
Explanation: The bacterial cell wall, mainly composed of peptidoglycan, maintains cell
shape and prevents lysis from osmotic pressure.
3. Which of the following best describes a Gram-negative bacterium?
A. Thick peptidoglycan layer, no outer membrane
B. Thin peptidoglycan layer, outer membrane present
C. Lacks peptidoglycan entirely
✅
D. Only contains lipopolysaccharide
Answer: B. Thin peptidoglycan layer, outer membrane present
Explanation: Gram-negative bacteria have a thin peptidoglycan layer between the plasma
membrane and an outer membrane that contains lipopolysaccharides.
4. Which microbial growth phase is characterized by no increase in cell number?
A. Log phase
B. Lag phase
C. Stationary phase
✅
D. Death phase
Answer: B. Lag phase
Explanation: During the lag phase, bacteria adapt to new environments and prepare for
cell division, but do not multiply.
,5. What structure do Gram-positive bacteria lack compared to
Gram-negative bacteria?
Answer: Outer membrane
Explanation: Gram-positive bacteria lack an outer membrane, which is present in
Gram-negative bacteria and contains lipopolysaccharides important for virulence.
6. What is the primary function of bacterial endospores?
Answer: Survival in harsh conditions
Explanation: Endospores are resistant structures that allow bacteria to withstand extreme
heat, desiccation, and chemicals.
7. Which stain is used to identify Mycobacterium tuberculosis?
Answer: Acid-fast stain
Explanation: The acid-fast stain targets the waxy mycolic acid in the cell walls of
Mycobacterium species.
8. What type of microorganism is a protozoan?
Answer: Eukaryotic
Explanation: Protozoa are single-celled eukaryotic organisms, meaning they have a
nucleus and organelles.
9. What component is found in fungal cell walls but not in bacterial cell
walls?
Answer: Chitin
Explanation: Fungi have cell walls made of chitin, while bacteria have peptidoglycan.
10. What term describes the time it takes for a bacterial population to
double?
, Answer: Generation time
Explanation: Generation time is the period required for one round of cell division, leading to
population doubling.
11. Which phase of bacterial growth shows no increase in cell number?
Answer: Lag phase
Explanation: During the lag phase, bacteria are metabolically active but not dividing.
12. What is the function of the ribosome in bacterial cells?
Answer: Protein synthesis
Explanation: Ribosomes are responsible for translating mRNA into proteins.
13. Which immune cells are the first responders during an infection?
Answer: Neutrophils
Explanation: Neutrophils are a type of white blood cell that quickly arrive at infection sites
to engulf pathogens.
14. What is the role of cytokines in the immune response?
Answer: Cell signaling
Explanation: Cytokines are signaling molecules that regulate immune responses,
inflammation, and cell communication.
15. What type of immunity is conferred by vaccination?
Answer: Artificial active immunity
Explanation: Vaccination introduces antigens to stimulate the immune system to produce
antibodies.
16. What does the term “opportunistic pathogen” refer to?
Answer: An organism that causes disease in weakened hosts
Explanation: These pathogens are normally harmless but can cause infections in
immunocompromised individuals.
