WGU D311 Microbiology OA Exam Prep 2026 UPDATE
1. Which component is unique to the cell walls of bacteria and not found in Archaea or
Eukarya?
A. Cellulose
B. Peptidoglycan
C. Chitin
D. Phospholipids
Answer: B
Rationale: Peptidoglycan is a unique structural polymer found only in bacterial cell walls,
consisting of sugars and amino acids.
2. Which of the following describes a bacterium that requires oxygen but at lower
concentrations than those found in the atmosphere?
A. Microaerophile
B. Facultative anaerobe
C. Obligate aerobe
D. Aerotolerant anaerobe
Answer: A
,Rationale: Microaerophiles require oxygen for survival but are poisoned by high
concentrations of atmospheric oxygen.
3. In the Gram stain procedure, what is the role of iodine?
A. Primary stain
B. Counterstain
C. Mordant
D. Decolorizer
Answer: C
Rationale: Iodine acts as a mordant, forming a complex with crystal violet that gets
trapped in the thick peptidoglycan layer of Gram-positive cells.
4. Which metabolic pathway produces the most ATP during cellular respiration?
A. Electron Transport Chain
B. Fermentation
C. Glycolysis
D. Krebs Cycle
Answer: A
Rationale: The electron transport chain, through oxidative phosphorylation, generates
significantly more ATP (approx. 32-34) than glycolysis or the Krebs cycle.
, 5. Which type of horizontal gene transfer involves the uptake of ‘naked’ DNA from the
environment?
A. Transduction
B. Transformation
C. Conjugation
D. Translation
Answer: B
Rationale: Transformation is the process where a competent bacterial cell takes up free
DNA fragments from its surroundings.
6. Which enzyme is responsible for unwinding the DNA double helix during replication?
A. Helicase
B. RNA Polymerase
C. DNA Polymerase
D. Ligase
Answer: A
Rationale: Helicase breaks the hydrogen bonds between the two strands of the DNA
molecule to unzip the double helix.
7. What is the primary function of ribosomes in a cell?
A. Lipid synthesis
1. Which component is unique to the cell walls of bacteria and not found in Archaea or
Eukarya?
A. Cellulose
B. Peptidoglycan
C. Chitin
D. Phospholipids
Answer: B
Rationale: Peptidoglycan is a unique structural polymer found only in bacterial cell walls,
consisting of sugars and amino acids.
2. Which of the following describes a bacterium that requires oxygen but at lower
concentrations than those found in the atmosphere?
A. Microaerophile
B. Facultative anaerobe
C. Obligate aerobe
D. Aerotolerant anaerobe
Answer: A
,Rationale: Microaerophiles require oxygen for survival but are poisoned by high
concentrations of atmospheric oxygen.
3. In the Gram stain procedure, what is the role of iodine?
A. Primary stain
B. Counterstain
C. Mordant
D. Decolorizer
Answer: C
Rationale: Iodine acts as a mordant, forming a complex with crystal violet that gets
trapped in the thick peptidoglycan layer of Gram-positive cells.
4. Which metabolic pathway produces the most ATP during cellular respiration?
A. Electron Transport Chain
B. Fermentation
C. Glycolysis
D. Krebs Cycle
Answer: A
Rationale: The electron transport chain, through oxidative phosphorylation, generates
significantly more ATP (approx. 32-34) than glycolysis or the Krebs cycle.
, 5. Which type of horizontal gene transfer involves the uptake of ‘naked’ DNA from the
environment?
A. Transduction
B. Transformation
C. Conjugation
D. Translation
Answer: B
Rationale: Transformation is the process where a competent bacterial cell takes up free
DNA fragments from its surroundings.
6. Which enzyme is responsible for unwinding the DNA double helix during replication?
A. Helicase
B. RNA Polymerase
C. DNA Polymerase
D. Ligase
Answer: A
Rationale: Helicase breaks the hydrogen bonds between the two strands of the DNA
molecule to unzip the double helix.
7. What is the primary function of ribosomes in a cell?
A. Lipid synthesis
