WGU D311 Microbiology OA Exam Prep (2026) UPDATE
1. Which of the following structures is unique to Gram-negative bacteria and contains Lipid A,
which acts as an endotoxin?
A. Outer membrane
B. Peptidoglycan layer
C. Plasma membrane
D. Teichoic acids
Answer: A
Rationale: The outer membrane of Gram-negative bacteria contains lipopolysaccharide
(LPS), of which Lipid A is the toxic component released during cell death.
2. Which phase of the bacterial growth curve is characterized by a period of little to no cell
division as the bacteria adapt to a new environment?
A. Log phase
B. Death phase
C. Stationary phase
D. Lag phase
Answer: D
,Rationale: The lag phase is an initial period where metabolic activity is high but there is no
increase in cell number as the population adjusts.
3. In which process is a portion of DNA transferred from one bacterium to another through a
bacteriophage?
A. Transformation
B. Conjugation
C. Translation
D. Transduction
Answer: D
Rationale: Transduction involves the transfer of bacterial DNA via a viral vector
(bacteriophage).
4. What is the primary function of ribosomes in both prokaryotic and eukaryotic cells?
A. Lipid synthesis
B. ATP production
C. DNA replication
D. Protein synthesis
Answer: D
Rationale: Ribosomes are the site of translation, where mRNA is read to assemble amino
acids into proteins.
, 5. A scientist observes a bacterium that requires oxygen to grow but at lower concentrations
than are present in the atmosphere. How is this organism classified?
A. Obligate aerobe
B. Facultative anaerobe
C. Aerotolerant anaerobe
D. Microaerophile
Answer: D
Rationale: Microaerophiles require oxygen for growth but are inhibited by typical
atmospheric levels (21%).
6. Which of the following is an example of an innate immune defense?
A. Production of memory B cells
B. Phagocytosis by macrophages
C. Generation of specific antibodies
D. Activation of cytotoxic T cells
Answer: B
Rationale: Innate immunity is non-specific and includes physical barriers and phagocytic
cells like macrophages.
7. What is the mechanism of action for the antibiotic Penicillin?
A. Inhibition of cell wall synthesis
1. Which of the following structures is unique to Gram-negative bacteria and contains Lipid A,
which acts as an endotoxin?
A. Outer membrane
B. Peptidoglycan layer
C. Plasma membrane
D. Teichoic acids
Answer: A
Rationale: The outer membrane of Gram-negative bacteria contains lipopolysaccharide
(LPS), of which Lipid A is the toxic component released during cell death.
2. Which phase of the bacterial growth curve is characterized by a period of little to no cell
division as the bacteria adapt to a new environment?
A. Log phase
B. Death phase
C. Stationary phase
D. Lag phase
Answer: D
,Rationale: The lag phase is an initial period where metabolic activity is high but there is no
increase in cell number as the population adjusts.
3. In which process is a portion of DNA transferred from one bacterium to another through a
bacteriophage?
A. Transformation
B. Conjugation
C. Translation
D. Transduction
Answer: D
Rationale: Transduction involves the transfer of bacterial DNA via a viral vector
(bacteriophage).
4. What is the primary function of ribosomes in both prokaryotic and eukaryotic cells?
A. Lipid synthesis
B. ATP production
C. DNA replication
D. Protein synthesis
Answer: D
Rationale: Ribosomes are the site of translation, where mRNA is read to assemble amino
acids into proteins.
, 5. A scientist observes a bacterium that requires oxygen to grow but at lower concentrations
than are present in the atmosphere. How is this organism classified?
A. Obligate aerobe
B. Facultative anaerobe
C. Aerotolerant anaerobe
D. Microaerophile
Answer: D
Rationale: Microaerophiles require oxygen for growth but are inhibited by typical
atmospheric levels (21%).
6. Which of the following is an example of an innate immune defense?
A. Production of memory B cells
B. Phagocytosis by macrophages
C. Generation of specific antibodies
D. Activation of cytotoxic T cells
Answer: B
Rationale: Innate immunity is non-specific and includes physical barriers and phagocytic
cells like macrophages.
7. What is the mechanism of action for the antibiotic Penicillin?
A. Inhibition of cell wall synthesis
