BIOD 171 Microbiology Module 6 Exam
ACTUAL EXAM 2026/2027 | Complete
Exam-Style Q&A | Verified Q&A | Pass
Guaranteed - A+ Graded
Table of Contents
Section 1: Viral Structure & Classification (Questions 1–10) ...... 2
Section 2: Viral Replication Cycles (Questions 11–20) ...... 2
Section 3: Viral Pathogenesis & Transmission (Questions 21–30) ...... 2
Section 4: Antiviral Therapies & Prevention (Questions 31–40) ...... 2
Section 5: Clinically Significant Viruses (Questions 41–50) ...... 2
Section 1: Viral Structure & Classification
Q1: A virus with an icosahedral capsid and no envelope is classified as:
A. An enveloped virus
B. A naked (non-enveloped) virus. [CORRECT]
C. A complex virus
D. A retrovirus
Correct Answer: B
Rationale: Viruses are classified based on the presence or absence of an envelope derived from host cell
membranes. Naked (non-enveloped) viruses possess only a protein capsid surrounding their nucleic acid
genome. The icosahedral symmetry provides structural stability and efficient packaging of the viral
genome. Examples include adenoviruses, poliovirus, and norovirus.
Q2: The Baltimore classification system categorizes viruses based on:
A. Their host species
B. Their genome type and replication strategy. [CORRECT]
C. Their capsid symmetry
D. Their geographic origin
,Correct Answer: B
Rationale: The Baltimore classification system, developed by David Baltimore in 1971, categorizes all
viruses into seven groups (I-VII) based on their nucleic acid type (DNA or RNA), strandedness (single or
double), sense (positive or negative), and replication strategy. This system reflects the fundamental
molecular mechanisms viruses use to express mRNA and replicate their genomes, providing a
framework for understanding viral replication and guiding antiviral drug development.
Q3: A virus with a single-stranded RNA genome that can function directly as mRNA belongs to Baltimore
Group:
A. Group III
B. Group IV. [CORRECT]
C. Group V
D. Group VI
Correct Answer: B
Rationale: Baltimore Group IV contains positive-sense single-stranded RNA (+ssRNA) viruses, whose
genome can be directly translated by host ribosomes upon entry into the cell. The viral RNA serves as
mRNA, producing a polyprotein that is cleaved to generate functional viral proteins. Examples include
picornaviruses (poliovirus, hepatitis A virus), coronaviruses (SARS-CoV-2), and flaviviruses (hepatitis C
virus, Zika virus).
Q4: The protein shell that surrounds and protects the viral genome is called the:
A. Envelope
B. Capsid. [CORRECT]
C. Spike
D. Matrix
Correct Answer: B
Rationale: The capsid is the protein shell composed of repeating protein subunits called capsomeres
that encloses and protects the viral nucleic acid genome. Capsids exhibit either icosahedral (20-sided) or
helical symmetry. The capsid provides structural integrity, protects the genome from nucleases, and
facilitates attachment to host cells through surface proteins.
Q5: Enveloped viruses acquire their lipid envelope from:
A. De novo synthesis in the cytoplasm
B. Budding through host cell membranes. [CORRECT]
, C. The viral genome
D. Bacterial cell walls
Correct Answer: B
Rationale: Enveloped viruses acquire their lipid bilayer envelope by budding through host cell
membranes, typically the plasma membrane, nuclear envelope, endoplasmic reticulum, or Golgi
apparatus. During budding, the virus incorporates host membrane lipids and viral glycoproteins that
project from the surface as spikes. These glycoproteins mediate attachment and entry into new host
cells. Examples include influenza virus, HIV, and herpesviruses.
Q6: A bacteriophage with a complex structure consisting of an icosahedral head, helical tail, and tail
fibers is characteristic of:
A. Filamentous phages
B. T-even phages such as T4. [CORRECT]
C. ssRNA phages
D. Enveloped phages
Correct Answer: B
Rationale: T-even bacteriophages, including T4, exhibit complex morphology with an icosahedral head
containing the dsDNA genome, a helical tail tube surrounded by a contractile tail sheath, baseplate, and
tail fibers. The tail fibers recognize specific receptors on the bacterial surface, and the contractile sheath
injects the viral DNA through the tail tube into the host cell. This complex structure is distinct from
simple icosahedral or helical viruses.
Q7: Viral glycoproteins embedded in the envelope function primarily in:
A. Genome replication
B. Attachment to host cell receptors and membrane fusion. [CORRECT]
C. Capsid assembly
D. Nucleic acid synthesis
Correct Answer: B
Rationale: Viral envelope glycoproteins are critical for host cell recognition and entry. They bind to
specific receptors on host cell surfaces, triggering conformational changes that mediate fusion of the
viral envelope with the host membrane or induce endocytosis. Examples include the HIV gp120/gp41
complex binding CD4 and CCR5/CXCR4, influenza hemagglutinin binding sialic acid, and SARS-CoV-2
spike protein binding ACE2.
ACTUAL EXAM 2026/2027 | Complete
Exam-Style Q&A | Verified Q&A | Pass
Guaranteed - A+ Graded
Table of Contents
Section 1: Viral Structure & Classification (Questions 1–10) ...... 2
Section 2: Viral Replication Cycles (Questions 11–20) ...... 2
Section 3: Viral Pathogenesis & Transmission (Questions 21–30) ...... 2
Section 4: Antiviral Therapies & Prevention (Questions 31–40) ...... 2
Section 5: Clinically Significant Viruses (Questions 41–50) ...... 2
Section 1: Viral Structure & Classification
Q1: A virus with an icosahedral capsid and no envelope is classified as:
A. An enveloped virus
B. A naked (non-enveloped) virus. [CORRECT]
C. A complex virus
D. A retrovirus
Correct Answer: B
Rationale: Viruses are classified based on the presence or absence of an envelope derived from host cell
membranes. Naked (non-enveloped) viruses possess only a protein capsid surrounding their nucleic acid
genome. The icosahedral symmetry provides structural stability and efficient packaging of the viral
genome. Examples include adenoviruses, poliovirus, and norovirus.
Q2: The Baltimore classification system categorizes viruses based on:
A. Their host species
B. Their genome type and replication strategy. [CORRECT]
C. Their capsid symmetry
D. Their geographic origin
,Correct Answer: B
Rationale: The Baltimore classification system, developed by David Baltimore in 1971, categorizes all
viruses into seven groups (I-VII) based on their nucleic acid type (DNA or RNA), strandedness (single or
double), sense (positive or negative), and replication strategy. This system reflects the fundamental
molecular mechanisms viruses use to express mRNA and replicate their genomes, providing a
framework for understanding viral replication and guiding antiviral drug development.
Q3: A virus with a single-stranded RNA genome that can function directly as mRNA belongs to Baltimore
Group:
A. Group III
B. Group IV. [CORRECT]
C. Group V
D. Group VI
Correct Answer: B
Rationale: Baltimore Group IV contains positive-sense single-stranded RNA (+ssRNA) viruses, whose
genome can be directly translated by host ribosomes upon entry into the cell. The viral RNA serves as
mRNA, producing a polyprotein that is cleaved to generate functional viral proteins. Examples include
picornaviruses (poliovirus, hepatitis A virus), coronaviruses (SARS-CoV-2), and flaviviruses (hepatitis C
virus, Zika virus).
Q4: The protein shell that surrounds and protects the viral genome is called the:
A. Envelope
B. Capsid. [CORRECT]
C. Spike
D. Matrix
Correct Answer: B
Rationale: The capsid is the protein shell composed of repeating protein subunits called capsomeres
that encloses and protects the viral nucleic acid genome. Capsids exhibit either icosahedral (20-sided) or
helical symmetry. The capsid provides structural integrity, protects the genome from nucleases, and
facilitates attachment to host cells through surface proteins.
Q5: Enveloped viruses acquire their lipid envelope from:
A. De novo synthesis in the cytoplasm
B. Budding through host cell membranes. [CORRECT]
, C. The viral genome
D. Bacterial cell walls
Correct Answer: B
Rationale: Enveloped viruses acquire their lipid bilayer envelope by budding through host cell
membranes, typically the plasma membrane, nuclear envelope, endoplasmic reticulum, or Golgi
apparatus. During budding, the virus incorporates host membrane lipids and viral glycoproteins that
project from the surface as spikes. These glycoproteins mediate attachment and entry into new host
cells. Examples include influenza virus, HIV, and herpesviruses.
Q6: A bacteriophage with a complex structure consisting of an icosahedral head, helical tail, and tail
fibers is characteristic of:
A. Filamentous phages
B. T-even phages such as T4. [CORRECT]
C. ssRNA phages
D. Enveloped phages
Correct Answer: B
Rationale: T-even bacteriophages, including T4, exhibit complex morphology with an icosahedral head
containing the dsDNA genome, a helical tail tube surrounded by a contractile tail sheath, baseplate, and
tail fibers. The tail fibers recognize specific receptors on the bacterial surface, and the contractile sheath
injects the viral DNA through the tail tube into the host cell. This complex structure is distinct from
simple icosahedral or helical viruses.
Q7: Viral glycoproteins embedded in the envelope function primarily in:
A. Genome replication
B. Attachment to host cell receptors and membrane fusion. [CORRECT]
C. Capsid assembly
D. Nucleic acid synthesis
Correct Answer: B
Rationale: Viral envelope glycoproteins are critical for host cell recognition and entry. They bind to
specific receptors on host cell surfaces, triggering conformational changes that mediate fusion of the
viral envelope with the host membrane or induce endocytosis. Examples include the HIV gp120/gp41
complex binding CD4 and CCR5/CXCR4, influenza hemagglutinin binding sialic acid, and SARS-CoV-2
spike protein binding ACE2.
