D311 Microbiology OA Exam 2026/2027 –
100+ Verified Questions & Answers |
Vaccines, Pathogens, Staining, Immunity |
WGU
D311 Microbiology OA Exam Q&A (2025/2026 Edition)
Section 1: Microbial World and Cell Structure (Questions 1-15)
1. Which of the following microorganisms lacks a true nucleus and membrane-bound
organelles?
- A) Protozoa
- B) Fungi
- C) Bacteria
- D) Helminths
Answer: C) Bacteria
> Explanation: Bacteria are prokaryotes, meaning their genetic material is not enclosed within a
nuclear membrane and they lack organelles like mitochondria.
2. Which of the following structures is used by bacteria for motility?
- A) Pili
- B) Capsule
- C) Fimbriae
- D) Flagella
Answer: D) Flagella
> Explanation: Flagella are whip-like structures that provide motility to bacterial cells.
3. A Gram-negative cell wall contains which of the following?
- A) Thick peptidoglycan
,- B) Teichoic acid
- C) No outer membrane
- D) Lipopolysaccharide (LPS)
Answer: D) Lipopolysaccharide (LPS)
> Explanation: Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane
containing lipopolysaccharide (LPS).
4. What is the defining characteristic of eukaryotes?
- A) They are always multicellular
- B) They have a nucleus
- C) They lack membrane-bound organelles
- D) They reproduce only asexually
Answer: B) They have a nucleus
> Explanation: Eukaryotic cells are defined by the presence of a true nucleus and
membrane-bound organelles.
5. A key structural difference between Gram-positive and Gram-negative bacteria is:
- A) Gram-positive bacteria have an outer membrane
- B) Gram-negative bacteria have a thick peptidoglycan layer
- C) Gram-positive bacteria have teichoic acids in their cell wall
- D) Gram-negative bacteria lack lipopolysaccharide
Answer: C) Gram-positive bacteria have teichoic acids in their cell wall
> Explanation: Teichoic acids are unique to Gram-positive cell walls.
6. Why are viruses considered acellular?
- A) They lack a cell wall
- B) They cannot reproduce without a host
- C) They are too small to see
- D) They contain DNA but not RNA
Answer: B) They cannot reproduce without a host
, > Explanation: Viruses are acellular because they lack cellular structure and cannot reproduce
independently—they must infect a host cell to replicate.
7. What occurs during the log phase of bacterial growth?
- A) Bacteria are adapting to the environment
- B) Bacteria are dying at a rapid rate
- C) Bacteria are dividing at their maximum rate
- D) Bacterial growth equals bacterial death
Answer: C) Bacteria are dividing at their maximum rate
> Explanation: The log (exponential) phase is characterized by maximum, constant cell division.
8. Which microorganism can cause vaginal yeast infections and oral thrush?
- A) Bacteria
- B) Viruses
- C) Fungi
- D) Protozoa
Answer: C) Fungi
> Explanation: Candida species (fungi) are responsible for vaginal yeast infections and oral
thrush.
9. Which eukaryote is responsible for producing antibiotics to ward off bacterial competitors?
- A) Protozoa
- B) Algae
- C) Fungi
- D) Helminths
Answer: C) Fungi
> Explanation: Many fungi produce antibiotic substances to inhibit bacterial growth in their
environment.
100+ Verified Questions & Answers |
Vaccines, Pathogens, Staining, Immunity |
WGU
D311 Microbiology OA Exam Q&A (2025/2026 Edition)
Section 1: Microbial World and Cell Structure (Questions 1-15)
1. Which of the following microorganisms lacks a true nucleus and membrane-bound
organelles?
- A) Protozoa
- B) Fungi
- C) Bacteria
- D) Helminths
Answer: C) Bacteria
> Explanation: Bacteria are prokaryotes, meaning their genetic material is not enclosed within a
nuclear membrane and they lack organelles like mitochondria.
2. Which of the following structures is used by bacteria for motility?
- A) Pili
- B) Capsule
- C) Fimbriae
- D) Flagella
Answer: D) Flagella
> Explanation: Flagella are whip-like structures that provide motility to bacterial cells.
3. A Gram-negative cell wall contains which of the following?
- A) Thick peptidoglycan
,- B) Teichoic acid
- C) No outer membrane
- D) Lipopolysaccharide (LPS)
Answer: D) Lipopolysaccharide (LPS)
> Explanation: Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane
containing lipopolysaccharide (LPS).
4. What is the defining characteristic of eukaryotes?
- A) They are always multicellular
- B) They have a nucleus
- C) They lack membrane-bound organelles
- D) They reproduce only asexually
Answer: B) They have a nucleus
> Explanation: Eukaryotic cells are defined by the presence of a true nucleus and
membrane-bound organelles.
5. A key structural difference between Gram-positive and Gram-negative bacteria is:
- A) Gram-positive bacteria have an outer membrane
- B) Gram-negative bacteria have a thick peptidoglycan layer
- C) Gram-positive bacteria have teichoic acids in their cell wall
- D) Gram-negative bacteria lack lipopolysaccharide
Answer: C) Gram-positive bacteria have teichoic acids in their cell wall
> Explanation: Teichoic acids are unique to Gram-positive cell walls.
6. Why are viruses considered acellular?
- A) They lack a cell wall
- B) They cannot reproduce without a host
- C) They are too small to see
- D) They contain DNA but not RNA
Answer: B) They cannot reproduce without a host
, > Explanation: Viruses are acellular because they lack cellular structure and cannot reproduce
independently—they must infect a host cell to replicate.
7. What occurs during the log phase of bacterial growth?
- A) Bacteria are adapting to the environment
- B) Bacteria are dying at a rapid rate
- C) Bacteria are dividing at their maximum rate
- D) Bacterial growth equals bacterial death
Answer: C) Bacteria are dividing at their maximum rate
> Explanation: The log (exponential) phase is characterized by maximum, constant cell division.
8. Which microorganism can cause vaginal yeast infections and oral thrush?
- A) Bacteria
- B) Viruses
- C) Fungi
- D) Protozoa
Answer: C) Fungi
> Explanation: Candida species (fungi) are responsible for vaginal yeast infections and oral
thrush.
9. Which eukaryote is responsible for producing antibiotics to ward off bacterial competitors?
- A) Protozoa
- B) Algae
- C) Fungi
- D) Helminths
Answer: C) Fungi
> Explanation: Many fungi produce antibiotic substances to inhibit bacterial growth in their
environment.
