PORTAGE LEARNING BIOD 171 MODULE 6 EXAM QUESTIONS WITH COMPLETE SOLUTIONS VERIFIED GRADED A+
True or False: viruses can be classified as prokaryotic or eukaryotic
False. Viruses are neither prokaryotic or eukaryotic
What is an obligate intracellular parasite?
viruses cannot replicate unless i...
True or False: viruses can be classified as prokaryotic or eukaryotic
False. Viruses are neither prokaryotic or eukaryotic
What is an obligate intracellular parasite?
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?
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?
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?
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?
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?
For all viruses, the genome is replicated following attachment and entry, never before.
, Describe the basic steps of the viral life cycle.
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?
A virus that infects bacteria
What structural aspects make bacteriophages distinct from viruses that infect
either animals or plants?
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?
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.
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.
To what family of viruses does rubella come from and how is it transmitted?
Rubella virus belongs to a family of viruses called Togaviridae. Rubella is transmitted
via air-borne particles such as when a person coughs.
What is the common name for rubeola, and is it a DNA or RNA virus?
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