MICROBIOLOGY PORTAGE LEARNING MODULE 6 EXAM QUESTIONS WITH COMPLETE SOLUTIONS VERIFIED LATEST UPDATE
Can viruses be classified as either prokaryotic or eukaryotic microorganisms?
No, viruses are neither prokaryotic or eukaryotic.
What is an obligate intracellular parasite?
An obligate intr...
Can viruses be classified as either prokaryotic or eukaryotic microorganisms?
No, viruses are neither prokaryotic or eukaryotic.
What is an obligate intracellular parasite?
An obligate intracellular parasites do not carry out metabolism or build their own
components like nucleic acids or proteins. The virus depends on its host to provide the
framework to replicate.
What is a viral capsid?
The capsid is a membrane-like protective structure that contains the genetic material,
similar to the nucleus of a eukaryotic cell.
What is the viral envelope, and what does the presence (or absence) of it tell you
about the type of virus?
Viral envelopes are a lipid coating surrounding the capsid formed from budding from
host cells and taking parts of its lipid membrane in the process. It serves as an
additional barrier to the external environment. Most animal viruses are enveloped while
most plant or bacteria infecting viruses are not.
What type of microscope would be used to study the shape of a viral capsid?
Electron microscopy due to its size which is about 30-15nm.
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 cell
3. Uncoating: (where applicable) the viral capsid disassembles
4. Replication: The viral genome provides the 'blueprint' to make copies of itself
5. Exit: New viruses are produced and leave the cell
6. 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 bacteriophage is simply a virus (phage) 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 comes from the Togaviridae family. It is transmitted through aerosols from the
respiratory tract such as a cough.
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