MICROBIOLOGY MIDTERM EXAM JERSEY
COLLEGE VERSION 2 QUESTIONS AND
CORRECT ANSWERS (VERIFIED ANSWERS)
PLUS RATIONALES 2025
1. What structure do bacteria use for motility?
A. Capsule
B. Ribosome
C. Flagellum
D. Pili
Flagella are tail-like structures that rotate to propel bacteria through their
environment.
2. Which of the following is not a function of the bacterial cell wall?
A. Maintains cell shape
B. Protein synthesis
C. Prevents osmotic lysis
,D. Protects against environmental stress
Protein synthesis occurs in the ribosomes, not in the cell wall.
3. Which of the following is a gram-positive bacterium?
A. Escherichia coli
B. Neisseria gonorrhoeae
C. Staphylococcus aureus
D. Salmonella typhi
Staphylococcus aureus has a thick peptidoglycan cell wall, staining purple
during Gram staining.
4. What is the function of plasmids in bacteria?
A. Respiration
B. Carry non-essential genes such as antibiotic resistance
C. Protein synthesis
D. Energy production
Plasmids are small DNA molecules that often carry genes for antibiotic
resistance or toxins.
5. Which of the following is considered an obligate intracellular parasite?
A. Bacteria
B. Viruses
C. Fungi
D. Protozoa
Viruses must enter a host cell to replicate and cannot reproduce
independently.
,6. What component is unique to the cell walls of Gram-positive bacteria?
A. Outer membrane
B. Teichoic acids
C. Endotoxin
D. Lipopolysaccharide
Teichoic acids are found only in Gram-positive bacteria and help maintain
wall structure.
7. Which bacterial shape is spiral?
A. Coccus
B. Bacillus
C. Spirillum
D. Vibrio
Spirillum bacteria have a twisted, spiral shape.
8. What is the purpose of the acid-fast stain?
A. Detect endospores
B. Identify Mycobacterium species
C. Visualize flagella
D. Determine cell wall thickness
Mycobacterium species have waxy cell walls that retain carbol fuchsin dye
after acid-alcohol treatment.
9. Which phase of bacterial growth involves rapid cell division?
A. Lag phase
B. Stationary phase
, C. Log (exponential) phase
D. Death phase
During the log phase, bacteria multiply at an exponential rate.
10. What type of organism can grow with or without oxygen?
A. Obligate aerobe
B. Facultative anaerobe
C. Microaerophile
D. Obligate anaerobe
Facultative anaerobes can adjust their metabolism to use oxygen when
available.
11. Which of the following is a characteristic of endotoxins?
A. Secreted by live cells
B. Found in Gram-negative bacteria
C. Composed of proteins
D. Produced by Gram-positive bacteria only
Endotoxins are part of the lipopolysaccharide in Gram-negative outer
membranes.
12. The term “nosocomial infection” refers to an infection:
A. Caused by antibiotics
B. Acquired in a healthcare setting
C. From contaminated food
D. Present at birth
COLLEGE VERSION 2 QUESTIONS AND
CORRECT ANSWERS (VERIFIED ANSWERS)
PLUS RATIONALES 2025
1. What structure do bacteria use for motility?
A. Capsule
B. Ribosome
C. Flagellum
D. Pili
Flagella are tail-like structures that rotate to propel bacteria through their
environment.
2. Which of the following is not a function of the bacterial cell wall?
A. Maintains cell shape
B. Protein synthesis
C. Prevents osmotic lysis
,D. Protects against environmental stress
Protein synthesis occurs in the ribosomes, not in the cell wall.
3. Which of the following is a gram-positive bacterium?
A. Escherichia coli
B. Neisseria gonorrhoeae
C. Staphylococcus aureus
D. Salmonella typhi
Staphylococcus aureus has a thick peptidoglycan cell wall, staining purple
during Gram staining.
4. What is the function of plasmids in bacteria?
A. Respiration
B. Carry non-essential genes such as antibiotic resistance
C. Protein synthesis
D. Energy production
Plasmids are small DNA molecules that often carry genes for antibiotic
resistance or toxins.
5. Which of the following is considered an obligate intracellular parasite?
A. Bacteria
B. Viruses
C. Fungi
D. Protozoa
Viruses must enter a host cell to replicate and cannot reproduce
independently.
,6. What component is unique to the cell walls of Gram-positive bacteria?
A. Outer membrane
B. Teichoic acids
C. Endotoxin
D. Lipopolysaccharide
Teichoic acids are found only in Gram-positive bacteria and help maintain
wall structure.
7. Which bacterial shape is spiral?
A. Coccus
B. Bacillus
C. Spirillum
D. Vibrio
Spirillum bacteria have a twisted, spiral shape.
8. What is the purpose of the acid-fast stain?
A. Detect endospores
B. Identify Mycobacterium species
C. Visualize flagella
D. Determine cell wall thickness
Mycobacterium species have waxy cell walls that retain carbol fuchsin dye
after acid-alcohol treatment.
9. Which phase of bacterial growth involves rapid cell division?
A. Lag phase
B. Stationary phase
, C. Log (exponential) phase
D. Death phase
During the log phase, bacteria multiply at an exponential rate.
10. What type of organism can grow with or without oxygen?
A. Obligate aerobe
B. Facultative anaerobe
C. Microaerophile
D. Obligate anaerobe
Facultative anaerobes can adjust their metabolism to use oxygen when
available.
11. Which of the following is a characteristic of endotoxins?
A. Secreted by live cells
B. Found in Gram-negative bacteria
C. Composed of proteins
D. Produced by Gram-positive bacteria only
Endotoxins are part of the lipopolysaccharide in Gram-negative outer
membranes.
12. The term “nosocomial infection” refers to an infection:
A. Caused by antibiotics
B. Acquired in a healthcare setting
C. From contaminated food
D. Present at birth
