WGU D311 OA Microbiology Practice Exam 2026 UPDATE
1. Which of the following structures is primarily responsible for the high resistance of
endospores to environmental stress?
A. Peptidoglycan layer
B. Dipicolinic acid and calcium ions
C. Plasma membrane lipids
D. Ribosomal RNA proteins
Answer: B
Rationale: The core of an endospore contains dipicolinic acid complexed with calcium,
which helps dehydrate the spore and protect the DNA from heat and radiation.
2. In the Gram staining procedure, what is the function of the iodine solution?
A. Primary stain
B. Mordant
C. Counterstain
D. Decolorizer
Answer: B
,Rationale: Iodine acts as a mordant, forming a complex with crystal violet that gets
trapped in the thick peptidoglycan layer of Gram-positive bacteria.
3. Which metabolic pathway produces the most ATP per molecule of glucose oxidized?
A. Fermentation
B. Aerobic electron transport chain
C. The Krebs cycle
D. Glycolysis
Answer: B
Rationale: Aerobic respiration, specifically the electron transport chain combined with
chemiosmosis, produces significantly more ATP (approx 34) compared to other pathways.
4. A bacterium that grows best in the presence of oxygen but can also grow without it is
classified as a:
A. Obligate aerobe
B. Microaerophile
C. Facultative anaerobe
D. Aerotolerant anaerobe
Answer: C
Rationale: Facultative anaerobes prefer oxygen for aerobic respiration but possess the
machinery to switch to fermentation or anaerobic respiration if oxygen is absent.
, 5. Which enzyme is responsible for synthesizing a short RNA primer to initiate DNA
replication?
A. DNA polymerase III
B. Helicase
C. Ligase
D. Primase
Answer: D
Rationale: Primase synthesizes a short RNA primer that provides the 3’-OH group
necessary for DNA polymerase to begin adding nucleotides.
6. Horizontal gene transfer involving a bacteriophage is known as:
A. Transformation
B. Transduction
C. Conjugation
D. Binary fission
Answer: B
Rationale: Transduction occurs when a virus (bacteriophage) transfers bacterial DNA
from one host cell to another.
7. What is the primary component of the cell walls of most fungi?
A. Chitin
1. Which of the following structures is primarily responsible for the high resistance of
endospores to environmental stress?
A. Peptidoglycan layer
B. Dipicolinic acid and calcium ions
C. Plasma membrane lipids
D. Ribosomal RNA proteins
Answer: B
Rationale: The core of an endospore contains dipicolinic acid complexed with calcium,
which helps dehydrate the spore and protect the DNA from heat and radiation.
2. In the Gram staining procedure, what is the function of the iodine solution?
A. Primary stain
B. Mordant
C. Counterstain
D. Decolorizer
Answer: B
,Rationale: Iodine acts as a mordant, forming a complex with crystal violet that gets
trapped in the thick peptidoglycan layer of Gram-positive bacteria.
3. Which metabolic pathway produces the most ATP per molecule of glucose oxidized?
A. Fermentation
B. Aerobic electron transport chain
C. The Krebs cycle
D. Glycolysis
Answer: B
Rationale: Aerobic respiration, specifically the electron transport chain combined with
chemiosmosis, produces significantly more ATP (approx 34) compared to other pathways.
4. A bacterium that grows best in the presence of oxygen but can also grow without it is
classified as a:
A. Obligate aerobe
B. Microaerophile
C. Facultative anaerobe
D. Aerotolerant anaerobe
Answer: C
Rationale: Facultative anaerobes prefer oxygen for aerobic respiration but possess the
machinery to switch to fermentation or anaerobic respiration if oxygen is absent.
, 5. Which enzyme is responsible for synthesizing a short RNA primer to initiate DNA
replication?
A. DNA polymerase III
B. Helicase
C. Ligase
D. Primase
Answer: D
Rationale: Primase synthesizes a short RNA primer that provides the 3’-OH group
necessary for DNA polymerase to begin adding nucleotides.
6. Horizontal gene transfer involving a bacteriophage is known as:
A. Transformation
B. Transduction
C. Conjugation
D. Binary fission
Answer: B
Rationale: Transduction occurs when a virus (bacteriophage) transfers bacterial DNA
from one host cell to another.
7. What is the primary component of the cell walls of most fungi?
A. Chitin
