nnn76 Flashcards

1
Q

Are viruses considered to be cells? Would they be included in any of the 6 kingdoms in the
classification system?

A

Viruses are not considered to be cells. Cells are the basic unit of life, as in, all living things
consist of at least one or more cells. Because of this, viruses would not be found in the
classification system of living things and would not be found in any of the 6 kingdoms.

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2
Q

Compare and contrast a virus to a cell. What would be some differences? What are some
similarities?

A

Viruses share similarities with a cell in that all cells possess a nucleic acid (either RNA or DNA
with a virus) – cells possess both RNA and DNA. Because of this, like cells, viruses have the
ability to mutate and ‘evolve’ because of their genetic material.
A key difference from a virus to a cell is that a virus does not possess a cell membrane. Every
cell on the planet has a cell membrane. In addition, viruses do not possess any organelles and
as a result they are reliant on host organisms to carry out important processes such as
replication and protein synthesis.

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3
Q

Describe the general structure/components of a virus?

A

A virus consists of a nucleic acid and a protein coat (capsid).
In some cases a virus may contain an additional envelope – comprised of lipid and
protein
Viruses do not have a cell membrane, a nucleus, or organelles.

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4
Q

It is debated whether viruses are living or non-living. Give 2 reasons why they would be
considered living and 2 reasons why they would be considered non-living.

A

Living:
they contain nucleic acid – the molecule of life
they can mutate and evolve (respond to environment)
they do have the ability to replicate/reproduce….just not by themselves
Non-living:
they are inactive without a host
they do not have a cell membrane or cell wall
they cannot replicate without host machinery
they do not respire (they do not utilize energy)
they do not move or grow

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5
Q

“Viruses are specific”. Explain this statement. (Viral Specificity)

A

Viruses are specific to a small range of hosts because of their genetic similarities. A
viruses genetic material is more similar to its host than it is to other viruses.
Plant viruses infect plants etc.

Note*: the idea is that the host cell will translate the genetic material of the virus to make
viral proteins (tricks the host cell into ‘reading’ the viral genetic material)
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6
Q

How does the body respond to an antigen?

A

An antigen is a substance that prompts the generation of antibodies and can cause an immune
response.

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7
Q

Arrange the following stages of the lytic cycle in order. Provide a brief explanation for each stage
ASSEMBLY (maturation), REPLICATION (biosynthesis), RELEASE, ATTACHMENT, PENETRATION

A

 1. Attachment to the cell
 2. Penetration (injection) of viral DNA or RNA
 3. Replication (Biosynthesis) of new viral proteins and nucleic acids
 4. Assembly (Maturation) of the new viruses
 5. Release of the new viruses into the environment (cell lyses)

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8
Q

If someone is infected with a virus that enters the lysogenic cycle, why may they not have any
symptoms initially? Be specific in your response.

A

When a virus enters the lysogenic cycle, a dormant/latent phase, the virus integrates itself into
the hosts DNA. Because of this, the hosts DNA remains intact and the host cell can carry out
normal function (or relatively normal).
A part of the normal life cycle of a cell is cell division, a process where the cell makes an identical
copy of itself. When the host cell divides it will make a copy of its own DNA, and in this case, the
viral DNA as well. If this occurs many times, then the host organism will contain many cells that
have this viral DNA.
With viral infections, the host will only experience symptoms when they begin to experience cell
death (lysis). When the virus enters the lytic cycle it degrades the host cells DNA which will
greatly impact normal cell function. Then, the virus will replicate in great numbers eventually
causing the cell to lyse (burst).

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