BIOD 171
OBJECTIVE ASSESSMENT - EXAM
BIOD 171 Microbiology
Module 6 Exam
Portage Learning 2026/2027 Actual Exam
50 100% 2026/2027
QUESTIONS VERIFIED ANSWERS EDITION
TOPICS COVERED
* Virus Structure & Classification * Viral Pathogenesis
* Viral Replication Cycles * Antiviral Therapeutics
* Bacteriophage Biology * Vaccine Development
COVER PAGE - 1
BIOD 171 - 2026/2027 | Passing Score: 80% | Page 1 of 33
,SECTION 1 | Virus Structure and Classification | Q1-Q10 | BIOD 171 2026/2027
Q1 Question 1 of 50
A 34-year-old microbiology student examines a viral specimen under an electron
microscope and observes a spherical particle approximately 120 nm in diameter with a
lipid bilayer surrounding the protein capsid. Which structural component is responsible for
the host cell specificity observed in this enveloped virus?
A. The viral capsid proteins that form the icosahedral shell
B. The glycoprotein spikes embedded in the lipid envelope
C. The genomic RNA contained within the nucleocapsid
D. The matrix proteins located between the capsid and envelope
Correct Answer: B
Rationale:
The glycoprotein spikes (peplomers) on the viral envelope are responsible for recognizing and binding to
specific host cell receptors, determining tropism and host specificity. The capsid protects the genome but
does not mediate attachment. The genomic RNA contains the genetic code but does not directly interact
with host receptors. Matrix proteins provide structural support but are not the primary determinants of host
specificity.
Q2 Question 2 of 50
During a virology laboratory session, a professor presents three viral specimens: Tobacco
mosaic virus (TMV), Influenza A virus, and Human immunodeficiency virus (HIV). The
students are asked to classify each based on the presence or absence of an envelope.
Which of these viruses possesses a lipid envelope derived from the host cell membrane?
A. Tobacco mosaic virus only
B. Influenza A virus and HIV only
C. Tobacco mosaic virus and Influenza A only
D. All three viruses possess an envelope
Correct Answer: B
Rationale:
Influenza A virus and HIV are both enveloped viruses that acquire their lipid bilayer from the host cell
membrane during budding. Tobacco mosaic virus is a non-enveloped plant virus composed of a helical
capsid surrounding RNA, with no lipid envelope. The presence of an envelope significantly affects viral
stability, transmission routes, and susceptibility to disinfectants.
BIOD 171 - 2026/2027 | Passing Score: 80% | Page 2 of 33
,SECTION 1 | Virus Structure and Classification | Q1-Q10 | BIOD 171 2026/2027
Q3 Question 3 of 50
A clinical virologist is analyzing a newly discovered virus isolated from a patient with
respiratory illness. The virus contains a single-stranded RNA genome enclosed within a
helical nucleocapsid and is surrounded by a lipid envelope. According to the Baltimore
classification system, which class does this virus belong to?
A. Class I: Double-stranded DNA viruses
B. Class IV: Positive-sense single-stranded RNA viruses
C. Class V: Negative-sense single-stranded RNA viruses
D. Class VI: Retroviruses with reverse transcriptase
Correct Answer: C
Rationale:
Negative-sense single-stranded RNA viruses (Class V) include influenza, measles, and rabies viruses.
These viruses must carry their own RNA-dependent RNA polymerase because host cells cannot directly
transcribe negative-sense RNA into mRNA. Positive-sense RNA viruses (Class IV) can be directly
translated by host ribosomes. Class I contains DNA viruses like herpesviruses, and Class VI contains
retroviruses like HIV that use reverse transcriptase.
Q4 Question 4 of 50
In a comparative virology study, researchers measure the sizes of several viruses using
electron microscopy. They record the following diameters: Smallpox virus at 200 nm,
Paramyxovirus at 150 nm, and Poliovirus at 30 nm. When arranging these from largest to
smallest, which sequence is correct?
A. Poliovirus > Paramyxovirus > Smallpox virus
B. Paramyxovirus > Smallpox virus > Poliovirus
C. Smallpox virus > Paramyxovirus > Poliovirus
D. Smallpox virus > Poliovirus > Paramyxovirus
Correct Answer: C
Rationale:
Smallpox virus (Variola virus) is among the largest viruses at approximately 200 nm in diameter.
Paramyxoviruses such as measles and mumps viruses range from 100-150 nm. Poliovirus is one of the
smallest known animal viruses at approximately 30 nm. This size variation affects viral transmission,
filtration capabilities, and electron microscopy resolution requirements.
BIOD 171 - 2026/2027 | Passing Score: 80% | Page 3 of 33
, SECTION 1 | Virus Structure and Classification | Q1-Q10 | BIOD 171 2026/2027
Q5 Question 5 of 50
A first-year nursing student asks her microbiology instructor whether viruses should be
classified as prokaryotic or eukaryotic organisms based on their enclosed genetic material.
Which response accurately describes the biological classification of viruses?
A. Viruses are classified as prokaryotic because they lack membrane-bound organelles
B. Viruses are classified as eukaryotic because their genome is enclosed within a capsid
C. Viruses are neither prokaryotic nor eukaryotic and are not considered living cells
D. Viruses are classified based on their host: plant viruses are eukaryotic and bacteriophages are
prokaryotic
Correct Answer: C
Rationale:
Viruses are acellular entities that are neither prokaryotic nor eukaryotic. They lack cellular machinery for
metabolism, cannot reproduce independently, and do not possess ribosomes or other organelles. While
they contain genetic material enclosed in a capsid, this structural similarity to a nucleus does not confer
cellular status. Viruses are obligate intracellular parasites that require host cells to replicate.
Q6 Question 6 of 50
A pathologist examines a viral preparation from a patient with hemorrhagic fever and
identifies a filamentous virus approximately 80 nm in diameter and up to 14,000 nm in
length. The virus contains a negative-sense single-stranded RNA genome. Which family
does this virus most likely belong to?
A. Orthomyxoviridae, which includes influenza viruses
B. Filoviridae, which includes Ebola and Marburg viruses
C. Paramyxoviridae, which includes measles and mumps viruses
D. Rhabdoviridae, which includes rabies virus
Correct Answer: B
Rationale:
Filoviruses such as Ebola and Marburg are characterized by their distinctive filamentous or thread-like
morphology, with lengths reaching up to 14 micrometers. They are negative-sense RNA viruses that
cause severe hemorrhagic fever with high mortality rates. Orthomyxoviruses are spherical and much
smaller. Paramyxoviruses are pleomorphic but not filamentous. Rhabdoviruses are bullet-shaped.
BIOD 171 - 2026/2027 | Passing Score: 80% | Page 4 of 33
OBJECTIVE ASSESSMENT - EXAM
BIOD 171 Microbiology
Module 6 Exam
Portage Learning 2026/2027 Actual Exam
50 100% 2026/2027
QUESTIONS VERIFIED ANSWERS EDITION
TOPICS COVERED
* Virus Structure & Classification * Viral Pathogenesis
* Viral Replication Cycles * Antiviral Therapeutics
* Bacteriophage Biology * Vaccine Development
COVER PAGE - 1
BIOD 171 - 2026/2027 | Passing Score: 80% | Page 1 of 33
,SECTION 1 | Virus Structure and Classification | Q1-Q10 | BIOD 171 2026/2027
Q1 Question 1 of 50
A 34-year-old microbiology student examines a viral specimen under an electron
microscope and observes a spherical particle approximately 120 nm in diameter with a
lipid bilayer surrounding the protein capsid. Which structural component is responsible for
the host cell specificity observed in this enveloped virus?
A. The viral capsid proteins that form the icosahedral shell
B. The glycoprotein spikes embedded in the lipid envelope
C. The genomic RNA contained within the nucleocapsid
D. The matrix proteins located between the capsid and envelope
Correct Answer: B
Rationale:
The glycoprotein spikes (peplomers) on the viral envelope are responsible for recognizing and binding to
specific host cell receptors, determining tropism and host specificity. The capsid protects the genome but
does not mediate attachment. The genomic RNA contains the genetic code but does not directly interact
with host receptors. Matrix proteins provide structural support but are not the primary determinants of host
specificity.
Q2 Question 2 of 50
During a virology laboratory session, a professor presents three viral specimens: Tobacco
mosaic virus (TMV), Influenza A virus, and Human immunodeficiency virus (HIV). The
students are asked to classify each based on the presence or absence of an envelope.
Which of these viruses possesses a lipid envelope derived from the host cell membrane?
A. Tobacco mosaic virus only
B. Influenza A virus and HIV only
C. Tobacco mosaic virus and Influenza A only
D. All three viruses possess an envelope
Correct Answer: B
Rationale:
Influenza A virus and HIV are both enveloped viruses that acquire their lipid bilayer from the host cell
membrane during budding. Tobacco mosaic virus is a non-enveloped plant virus composed of a helical
capsid surrounding RNA, with no lipid envelope. The presence of an envelope significantly affects viral
stability, transmission routes, and susceptibility to disinfectants.
BIOD 171 - 2026/2027 | Passing Score: 80% | Page 2 of 33
,SECTION 1 | Virus Structure and Classification | Q1-Q10 | BIOD 171 2026/2027
Q3 Question 3 of 50
A clinical virologist is analyzing a newly discovered virus isolated from a patient with
respiratory illness. The virus contains a single-stranded RNA genome enclosed within a
helical nucleocapsid and is surrounded by a lipid envelope. According to the Baltimore
classification system, which class does this virus belong to?
A. Class I: Double-stranded DNA viruses
B. Class IV: Positive-sense single-stranded RNA viruses
C. Class V: Negative-sense single-stranded RNA viruses
D. Class VI: Retroviruses with reverse transcriptase
Correct Answer: C
Rationale:
Negative-sense single-stranded RNA viruses (Class V) include influenza, measles, and rabies viruses.
These viruses must carry their own RNA-dependent RNA polymerase because host cells cannot directly
transcribe negative-sense RNA into mRNA. Positive-sense RNA viruses (Class IV) can be directly
translated by host ribosomes. Class I contains DNA viruses like herpesviruses, and Class VI contains
retroviruses like HIV that use reverse transcriptase.
Q4 Question 4 of 50
In a comparative virology study, researchers measure the sizes of several viruses using
electron microscopy. They record the following diameters: Smallpox virus at 200 nm,
Paramyxovirus at 150 nm, and Poliovirus at 30 nm. When arranging these from largest to
smallest, which sequence is correct?
A. Poliovirus > Paramyxovirus > Smallpox virus
B. Paramyxovirus > Smallpox virus > Poliovirus
C. Smallpox virus > Paramyxovirus > Poliovirus
D. Smallpox virus > Poliovirus > Paramyxovirus
Correct Answer: C
Rationale:
Smallpox virus (Variola virus) is among the largest viruses at approximately 200 nm in diameter.
Paramyxoviruses such as measles and mumps viruses range from 100-150 nm. Poliovirus is one of the
smallest known animal viruses at approximately 30 nm. This size variation affects viral transmission,
filtration capabilities, and electron microscopy resolution requirements.
BIOD 171 - 2026/2027 | Passing Score: 80% | Page 3 of 33
, SECTION 1 | Virus Structure and Classification | Q1-Q10 | BIOD 171 2026/2027
Q5 Question 5 of 50
A first-year nursing student asks her microbiology instructor whether viruses should be
classified as prokaryotic or eukaryotic organisms based on their enclosed genetic material.
Which response accurately describes the biological classification of viruses?
A. Viruses are classified as prokaryotic because they lack membrane-bound organelles
B. Viruses are classified as eukaryotic because their genome is enclosed within a capsid
C. Viruses are neither prokaryotic nor eukaryotic and are not considered living cells
D. Viruses are classified based on their host: plant viruses are eukaryotic and bacteriophages are
prokaryotic
Correct Answer: C
Rationale:
Viruses are acellular entities that are neither prokaryotic nor eukaryotic. They lack cellular machinery for
metabolism, cannot reproduce independently, and do not possess ribosomes or other organelles. While
they contain genetic material enclosed in a capsid, this structural similarity to a nucleus does not confer
cellular status. Viruses are obligate intracellular parasites that require host cells to replicate.
Q6 Question 6 of 50
A pathologist examines a viral preparation from a patient with hemorrhagic fever and
identifies a filamentous virus approximately 80 nm in diameter and up to 14,000 nm in
length. The virus contains a negative-sense single-stranded RNA genome. Which family
does this virus most likely belong to?
A. Orthomyxoviridae, which includes influenza viruses
B. Filoviridae, which includes Ebola and Marburg viruses
C. Paramyxoviridae, which includes measles and mumps viruses
D. Rhabdoviridae, which includes rabies virus
Correct Answer: B
Rationale:
Filoviruses such as Ebola and Marburg are characterized by their distinctive filamentous or thread-like
morphology, with lengths reaching up to 14 micrometers. They are negative-sense RNA viruses that
cause severe hemorrhagic fever with high mortality rates. Orthomyxoviruses are spherical and much
smaller. Paramyxoviruses are pleomorphic but not filamentous. Rhabdoviruses are bullet-shaped.
BIOD 171 - 2026/2027 | Passing Score: 80% | Page 4 of 33
