SCI 251 Final Exam V2 | SCI 251
Microbiology with Intervention Skill-Based
(ISB) Experiential Learning | Q&A with
Rationale (SCI251 Final Exam) |
Nightingale College
1. A nurse is reviewing the characteristics of a patient’s bacterial infection. Which structure is
uniquely present in Gram-positive cell walls and helps stabilize the peptidoglycan layer?
A. Lipopolysaccharide
B. Outer membrane
C. Teichoic acid
D. Periplasmic space
Correct Answer: C
Rationale: Teichoic acids are polyalcohols that are embedded within the thick
peptidoglycan layers of Gram-positive bacteria. They play a significant role in cell wall
maintenance and provide an overall negative charge to the cell surface. Gram-negative
bacteria lack teichoic acids but possess an outer membrane containing lipopolysaccharides.
2. During which phase of the bacterial growth curve are microorganisms most susceptible to
the action of beta-lactam antibiotics like penicillin?
A. Lag phase
,B. Death phase
C. Stationary phase
D. Log phase
Correct Answer: D
Rationale: The log phase, or exponential growth phase, is when bacteria are dividing most
rapidly and synthesizing new cell walls. Beta-lactam antibiotics function by inhibiting
peptidoglycan synthesis, which occurs primarily during active division. Therefore, the
drugs are most effective when the population is in this specific metabolic state.
3. A healthcare provider is preparing equipment for sterilization using an autoclave. What are
the standard parameters required to ensure the destruction of bacterial endospores?
A. 121 degrees C for 15 minutes at 15 psi
B. 100 degrees C for 10 minutes at 5 psi
C. 160 degrees C for 2 hours at 0 psi
D. 72 degrees C for 15 seconds at 10 psi
Correct Answer: A
Rationale: Autoclaving utilizes pressurized steam to achieve temperatures higher than
boiling to kill all forms of microbial life, including spores. The standard operational setting
is 121 degrees Celsius at 15 pounds per square inch (psi) for at least 15 minutes. This
process is considered the most reliable method for sterilization in a clinical setting.
, 4. In the context of bacterial genetics, which process involves the transfer of DNA from a
donor cell to a recipient cell through a sex pilus?
A. Transformation
B. Transduction
C. Transposition
D. Conjugation
Correct Answer: D
Rationale: Conjugation is the direct transfer of genetic material, often plasmids, between
two bacterial cells that are temporarily joined. This process requires a physical connection
mediated by a structure called a sex pilus. It is a major mechanism by which antibiotic
resistance genes spread through bacterial populations.
5. Which class of antibodies is the most abundant in the serum and is the only one capable of
crossing the placenta to provide passive immunity to a fetus?
A. IgG
B. IgM
C. IgA
D. IgE
Correct Answer: A
Microbiology with Intervention Skill-Based
(ISB) Experiential Learning | Q&A with
Rationale (SCI251 Final Exam) |
Nightingale College
1. A nurse is reviewing the characteristics of a patient’s bacterial infection. Which structure is
uniquely present in Gram-positive cell walls and helps stabilize the peptidoglycan layer?
A. Lipopolysaccharide
B. Outer membrane
C. Teichoic acid
D. Periplasmic space
Correct Answer: C
Rationale: Teichoic acids are polyalcohols that are embedded within the thick
peptidoglycan layers of Gram-positive bacteria. They play a significant role in cell wall
maintenance and provide an overall negative charge to the cell surface. Gram-negative
bacteria lack teichoic acids but possess an outer membrane containing lipopolysaccharides.
2. During which phase of the bacterial growth curve are microorganisms most susceptible to
the action of beta-lactam antibiotics like penicillin?
A. Lag phase
,B. Death phase
C. Stationary phase
D. Log phase
Correct Answer: D
Rationale: The log phase, or exponential growth phase, is when bacteria are dividing most
rapidly and synthesizing new cell walls. Beta-lactam antibiotics function by inhibiting
peptidoglycan synthesis, which occurs primarily during active division. Therefore, the
drugs are most effective when the population is in this specific metabolic state.
3. A healthcare provider is preparing equipment for sterilization using an autoclave. What are
the standard parameters required to ensure the destruction of bacterial endospores?
A. 121 degrees C for 15 minutes at 15 psi
B. 100 degrees C for 10 minutes at 5 psi
C. 160 degrees C for 2 hours at 0 psi
D. 72 degrees C for 15 seconds at 10 psi
Correct Answer: A
Rationale: Autoclaving utilizes pressurized steam to achieve temperatures higher than
boiling to kill all forms of microbial life, including spores. The standard operational setting
is 121 degrees Celsius at 15 pounds per square inch (psi) for at least 15 minutes. This
process is considered the most reliable method for sterilization in a clinical setting.
, 4. In the context of bacterial genetics, which process involves the transfer of DNA from a
donor cell to a recipient cell through a sex pilus?
A. Transformation
B. Transduction
C. Transposition
D. Conjugation
Correct Answer: D
Rationale: Conjugation is the direct transfer of genetic material, often plasmids, between
two bacterial cells that are temporarily joined. This process requires a physical connection
mediated by a structure called a sex pilus. It is a major mechanism by which antibiotic
resistance genes spread through bacterial populations.
5. Which class of antibodies is the most abundant in the serum and is the only one capable of
crossing the placenta to provide passive immunity to a fetus?
A. IgG
B. IgM
C. IgA
D. IgE
Correct Answer: A
