,BIOD171/BIOD 171 Module 6 Exam | Essential Microbiology
with Lab | Portage Learning | Q & A | 2026/2027 Edition (PDF)
1. Which of the following best describes why viruses are not classified as living organisms?
A) They contain genetic material
B) They can replicate inside a host cell
C) They lack cellular machinery for independent metabolism and reproduction
D) They have a protein capsid
Correct Answer: They lack cellular machinery for independent metabolism and reproduction
Rationale: Viruses are acellular infectious agents that lack the cellular machinery required for
independent metabolism and reproduction. They are obligate intracellular parasites that must hijack a
host cell's machinery to replicate, which is why they are not considered living organisms.
2. Which of the following correctly identifies the two basic components of a virus?
A) DNA and RNA
B) Genomic material and a capsid
C) A nucleus and a cell wall
D) A lipid bilayer and ribosomes
Correct Answer: Genomic material and a capsid
Rationale: A virus consists of two basic components: genomic material, which can be either DNA or RNA,
and a capsid, a membrane-like protective structure that contains the genetic material. Some viruses may
also have an envelope surrounding the capsid.
3. Which structure surrounds the capsid of some viruses?
A) Cell wall
B) Envelope
C) Nucleus
,D) Ribosome
Correct Answer: Envelope
Rationale: The envelope is a lipid bilayer that surrounds the capsid of some viruses. It is derived from the
host cell membrane and may contain viral glycoproteins. The presence or absence of an envelope is an
important characteristic for virus classification.
4. Which of the following statements about viral classification is TRUE?
A) Viruses are classified as prokaryotic
B) Viruses are classified as eukaryotic
C) Viruses are neither prokaryotic nor eukaryotic
D) Viruses are classified as both prokaryotic and eukaryotic
Correct Answer: Viruses are neither prokaryotic nor eukaryotic
Rationale: Although viruses may contain their genome within an enclosed space, they are considered
neither eukaryotic nor prokaryotic. Viruses are acellular and lack the cellular structure and machinery
that define both prokaryotic and eukaryotic organisms.
5. What is an obligate intracellular parasite?
A) A virus that can replicate independently
B) A virus that cannot replicate unless inside a living host cell
C) A bacterium that lives inside another cell
D) A parasite that lives on the surface of a host cell
Correct Answer: A virus that cannot replicate unless inside a living host cell
Rationale: An obligate intracellular parasite is a virus that cannot replicate unless it is inside a living host
cell. The virus depends on its living host to provide the framework (proteins, etc.) to replicate and make
additional copies of itself.
, 6. Which of the following is NOT a characteristic of a viral capsid?
A) It is a protective structure
B) It contains genetic material
C) It is composed of lipids
D) It is similar to the nucleus of a eukaryotic cell
Correct Answer: It is composed of lipids
Rationale: The capsid is a protein coat, not composed of lipids. The capsid is a membrane-like protective
structure that contains the genetic material, similar to the nucleus of a eukaryotic cell. The envelope,
not the capsid, is composed of lipids.
7. A virus that infects bacteria is specifically called a:
A) Retrovirus
B) Bacteriophage
C) Prion
D) Viroid
Correct Answer: Bacteriophage
Rationale: A bacteriophage, often shortened to phage, is a virus that specifically infects bacterial cells.
These viruses are important tools in molecular biology and have potential therapeutic applications.
8. The viral replication cycle in which the host cell is immediately destroyed is called the:
A) Lysogenic cycle
B) Lytic cycle
C) Latent cycle
D) Productive cycle
with Lab | Portage Learning | Q & A | 2026/2027 Edition (PDF)
1. Which of the following best describes why viruses are not classified as living organisms?
A) They contain genetic material
B) They can replicate inside a host cell
C) They lack cellular machinery for independent metabolism and reproduction
D) They have a protein capsid
Correct Answer: They lack cellular machinery for independent metabolism and reproduction
Rationale: Viruses are acellular infectious agents that lack the cellular machinery required for
independent metabolism and reproduction. They are obligate intracellular parasites that must hijack a
host cell's machinery to replicate, which is why they are not considered living organisms.
2. Which of the following correctly identifies the two basic components of a virus?
A) DNA and RNA
B) Genomic material and a capsid
C) A nucleus and a cell wall
D) A lipid bilayer and ribosomes
Correct Answer: Genomic material and a capsid
Rationale: A virus consists of two basic components: genomic material, which can be either DNA or RNA,
and a capsid, a membrane-like protective structure that contains the genetic material. Some viruses may
also have an envelope surrounding the capsid.
3. Which structure surrounds the capsid of some viruses?
A) Cell wall
B) Envelope
C) Nucleus
,D) Ribosome
Correct Answer: Envelope
Rationale: The envelope is a lipid bilayer that surrounds the capsid of some viruses. It is derived from the
host cell membrane and may contain viral glycoproteins. The presence or absence of an envelope is an
important characteristic for virus classification.
4. Which of the following statements about viral classification is TRUE?
A) Viruses are classified as prokaryotic
B) Viruses are classified as eukaryotic
C) Viruses are neither prokaryotic nor eukaryotic
D) Viruses are classified as both prokaryotic and eukaryotic
Correct Answer: Viruses are neither prokaryotic nor eukaryotic
Rationale: Although viruses may contain their genome within an enclosed space, they are considered
neither eukaryotic nor prokaryotic. Viruses are acellular and lack the cellular structure and machinery
that define both prokaryotic and eukaryotic organisms.
5. What is an obligate intracellular parasite?
A) A virus that can replicate independently
B) A virus that cannot replicate unless inside a living host cell
C) A bacterium that lives inside another cell
D) A parasite that lives on the surface of a host cell
Correct Answer: A virus that cannot replicate unless inside a living host cell
Rationale: An obligate intracellular parasite is a virus that cannot replicate unless it is inside a living host
cell. The virus depends on its living host to provide the framework (proteins, etc.) to replicate and make
additional copies of itself.
, 6. Which of the following is NOT a characteristic of a viral capsid?
A) It is a protective structure
B) It contains genetic material
C) It is composed of lipids
D) It is similar to the nucleus of a eukaryotic cell
Correct Answer: It is composed of lipids
Rationale: The capsid is a protein coat, not composed of lipids. The capsid is a membrane-like protective
structure that contains the genetic material, similar to the nucleus of a eukaryotic cell. The envelope,
not the capsid, is composed of lipids.
7. A virus that infects bacteria is specifically called a:
A) Retrovirus
B) Bacteriophage
C) Prion
D) Viroid
Correct Answer: Bacteriophage
Rationale: A bacteriophage, often shortened to phage, is a virus that specifically infects bacterial cells.
These viruses are important tools in molecular biology and have potential therapeutic applications.
8. The viral replication cycle in which the host cell is immediately destroyed is called the:
A) Lysogenic cycle
B) Lytic cycle
C) Latent cycle
D) Productive cycle
