BIOD 171 MODULE 6 ESSENTIAL
MICROBIOLOGY ACTUAL TEST BANK
QUESTIONS SOLUTIONS GRADED A PLUS
PREMIUM STUDY RESOURCE
●● What is an obligate intracellular parasite?
Answer: viruses cannot replicate unless inside a living host cell. As a
parasite, a virus depends on its living host to provide the framework
(proteins, etc) to replicate—to make additional copies of itself.
●● What is a viral capsid?
Answer: a membrane-like protective structure that contains genetic
material similar to nucleus of eukaryotic cells.
●● What is the viral envelope, and what does the presence (or absence)
of it tell you about the type of virus?
Answer: The envelope surrounds the viral capsid, is derived from the
host cell membrane and serves as an additional barrier to the external
environment. The overwhelming majority of animal viruses are
enveloped whereas the majority of plant or bacteria-infecting viruses are
not.
●● What type of microscope would be used to study the shape of a viral
capsid?
,Answer: Due to its size (~30-150 nm) most viral capsids must be
visualized via electron microscopy.
●● How does the viral envelope both aid in cell entry as well as hide it
from being detected by the immune system?
Answer: The viral envelope contains the necessary proteins required for
interaction with host cells. As the envelope is derived from the host cell
membrane, this camouflages the virus and lowers the likelihood of
immune detection by making it appear similar to the normal biological
host cell.
●● What must happen before viral replication of its genome can occur?
Answer: For all viruses, the genome is replicated following attachment
and entry, never before.
●● Describe the basic steps of the viral life cycle.
Answer: 1. Attachment: Viral receptors bind to host proteins on the
surface of the cell.2. Entry: The virus fuses with the host membrane and
enters the cell3. Uncoating: (where applicable) the viral capsid
disassembles4. Replication: The viral genome provides the 'blueprint' to
make copies of itself5. Exit: New viruses are produced and leave the
cell6. New infection: Newly produced viruses leave the host cell and go
on to infect new cells. The process outlined above now restarts.
●● What is a bacteriophage?
Answer: A virus that infects bacteria
, ●● What structural aspects make bacteriophages distinct from viruses
that infect either animals or plants?
Answer: Bacteriophages possess an icosahedral capsid head group and a
helical tail. Attached to the tail are fibrous extensions or 'legs' that aid in
binding host cells. Notably, this particular structural arrangement has not
been observed among viruses that infect either animals or plants.
●● Which viral replicative process results in the destruction of the host
cell?
Answer: The lytic replication cycle occurs when a bacteriophage
replicates within a host until it ruptures, effectively destroying the host
bacterial cell. The phrase lytic stems from 'lysis', meaning to rupture or
disintegrate (breakdown) a cell.
●● Describe the appearance of a bacterial culture infected with virus at
the time of infection versus later once viral replication is occurring at a
high rate.
Answer: During the initial inoculation of virus and bacteria, the media
has a high degree of turbidity (cloudiness). However, as the lytic cycle
progresses and more and more bacterial cells are destroyed, the culture
media turns from turbid to clear, as turbidity is a function of the number
of intact bacterial cells present in the media. Thus, as bacterial cell
numbers decrease due to lysis, the media becomes clearer.
MICROBIOLOGY ACTUAL TEST BANK
QUESTIONS SOLUTIONS GRADED A PLUS
PREMIUM STUDY RESOURCE
●● What is an obligate intracellular parasite?
Answer: viruses cannot replicate unless inside a living host cell. As a
parasite, a virus depends on its living host to provide the framework
(proteins, etc) to replicate—to make additional copies of itself.
●● What is a viral capsid?
Answer: a membrane-like protective structure that contains genetic
material similar to nucleus of eukaryotic cells.
●● What is the viral envelope, and what does the presence (or absence)
of it tell you about the type of virus?
Answer: The envelope surrounds the viral capsid, is derived from the
host cell membrane and serves as an additional barrier to the external
environment. The overwhelming majority of animal viruses are
enveloped whereas the majority of plant or bacteria-infecting viruses are
not.
●● What type of microscope would be used to study the shape of a viral
capsid?
,Answer: Due to its size (~30-150 nm) most viral capsids must be
visualized via electron microscopy.
●● How does the viral envelope both aid in cell entry as well as hide it
from being detected by the immune system?
Answer: The viral envelope contains the necessary proteins required for
interaction with host cells. As the envelope is derived from the host cell
membrane, this camouflages the virus and lowers the likelihood of
immune detection by making it appear similar to the normal biological
host cell.
●● What must happen before viral replication of its genome can occur?
Answer: For all viruses, the genome is replicated following attachment
and entry, never before.
●● Describe the basic steps of the viral life cycle.
Answer: 1. Attachment: Viral receptors bind to host proteins on the
surface of the cell.2. Entry: The virus fuses with the host membrane and
enters the cell3. Uncoating: (where applicable) the viral capsid
disassembles4. Replication: The viral genome provides the 'blueprint' to
make copies of itself5. Exit: New viruses are produced and leave the
cell6. New infection: Newly produced viruses leave the host cell and go
on to infect new cells. The process outlined above now restarts.
●● What is a bacteriophage?
Answer: A virus that infects bacteria
, ●● What structural aspects make bacteriophages distinct from viruses
that infect either animals or plants?
Answer: Bacteriophages possess an icosahedral capsid head group and a
helical tail. Attached to the tail are fibrous extensions or 'legs' that aid in
binding host cells. Notably, this particular structural arrangement has not
been observed among viruses that infect either animals or plants.
●● Which viral replicative process results in the destruction of the host
cell?
Answer: The lytic replication cycle occurs when a bacteriophage
replicates within a host until it ruptures, effectively destroying the host
bacterial cell. The phrase lytic stems from 'lysis', meaning to rupture or
disintegrate (breakdown) a cell.
●● Describe the appearance of a bacterial culture infected with virus at
the time of infection versus later once viral replication is occurring at a
high rate.
Answer: During the initial inoculation of virus and bacteria, the media
has a high degree of turbidity (cloudiness). However, as the lytic cycle
progresses and more and more bacterial cells are destroyed, the culture
media turns from turbid to clear, as turbidity is a function of the number
of intact bacterial cells present in the media. Thus, as bacterial cell
numbers decrease due to lysis, the media becomes clearer.
