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Station 4

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Reporting Category 1
Cell Structure and
Function
Station 4
Viruses:
Structure, Replication, and Disease
Essential Question
Why is it necessary for a virus to invade
a living cell to make copies of itself?
Viruses do not have the capability to
reproduce as living cells do. A virus
must make use of a cell’s functions,
parts, and enzymes in order to
replicate itself.
Pre-Review Question
• Is a virus considered to be alive?
NO
Pre-Review Question
• Which of the following do viruses and cells
have in common?
A. They both contain nucleic acids.
B. They both have mitochondria.
C. They can both be multicellular.
D. They both have a capsid.
Lab Activities
• You will now go to the lab and complete
the activities for today’s topics.
1. Locate the Structures of Viruses and Cells sheet at this
station. Carefully examine the structures of the plant cell,
animal cell, bacteriophage virus, and influenza virus. Draw the
chart in your journal and fill it in.
Structures found in a virus
Both
Structures found in a cell
1. Locate the Structures of Viruses and Cells sheet at this
station. Carefully examine the structures of the plant cell,
animal cell, bacteriophage virus, and influenza virus. Draw the
chart in your journal and fill it in.
Structures found in a virus Both
Structures found in a cell
Protein Coat
Vesicles
cytoplasm
Tail (bacteriophage)
Nucleus
nucleolus
Fibers
Vacuoles
Cell wall
Capsid
Centrosomes
Membrane envelope
Cell membranes
Nucleic Acid
lysosomes
Mitochondria
Golgi complex
Endoplasmic reticulum
Chloroplasts (plants)
2. Discuss with your partner:
Scientists consider viruses to be nonliving. Based
on the information you used to fill in the Venn
diagram, would you support or refute this
statement? Explain your position.
According to the information in the Venn diagram,
the only structure or component that a virus and a
cell have in common is nucleic acid. The virus
lacks all the other cellular structures, and without
them, it cannot exist, thrive, and reproduce on its
own. Thus unlike living cells, viruses do not
reproduce: They replicate by controlling the DNA
and protein production of a living cell.
3. Discuss with your partner:
Some disinfectants claim that they are effective at
killing viruses. Does your knowledge of the
structures and functions of a virus support or refute
this claim? Explain your position.
Viruses do not exhibit characteristics of a living
organism and are therefore considered to be
nonliving. The product’s claim that it “kills” viruses
is questionable, since only living things can be
killed. A virus’ structure may be destroyed,
rendering the virus incapable of entering a living
cell to make copies of itself, but it is inaccurate to
say a virus can be killed.
4. Locate the Lytic Infection Cycle sheet and the
envelope labeled Lytic Infection cards. Place the
cards in the proper sequence on the Lytic Infection
Cycle sheet to represent how a virus can infect a
living cell and cause the cell to
replicate the virus.
• Draw, label and
describe only the last
stage of the lytic cycle
and the last stage of
the lysogenic cycle.
5. Discuss with your partner:
Not all viruses replicate through lytic infection. Some
viruses replicate by another method, called lysogenic
infection. In this method, as in lytic infection, the virus
injects DNA into the host cell, and the virus DNA combines
with the DNA of the host cell. This may not cause any
damage to the cell for weeks, months, or years. Then the
virus DNA begins a process of replication similar to that
found in lytic infection. The human immunodeficiency virus
(HIV) replicates by the lysogenic infection method,
attacking the cells of our immune system. Why do you think
a person infected with HIV has difficulty fighting infections?
See next slide for answer.
5 cont.
HIV replicates by lysogenic infection, meaning
that the virus’s DNA and the immune system cell’s
DNA combine. Once the virus has replicated, it
breaks out of the host cell by a process called lysis.
The newly replicated viruses repeat the process
with other immune system cells, destroying them
and eventually weakening the immune system to
the point that it is unable to fight off infections.
6. Discuss with your partner:
Locate the model of HIV at this station. Carefully
examine the model without removing any of its
parts. If a scientist tried to use this model to
understand the structure and function of HIV, what
limitations would he/she have?
Answers may vary. Possible responses listed below.
The model may not represent all of the virus’s structures.
There is no means to test the model in a laboratory setting.
It is not possible to see how the model behaves with a host
cell.
I need to remember………
• Viruses lack the cell structures necessary for
reproduction.
• Viruses are considered nonliving.
• Viruses can replicate by two methods—lytic infection
and lysogenic infection.
• Lysogenic infections occur when the nuclear material
of the virus combines with the DNA of a cell before
replication of the virus begins.
• Viruses and cells have one structure in common,
nucleic acids.
• HIV is a virus that infects and destroys immune
system cells.
Post Review Questions
• Can a virus attack any cell in your body?
No, it only attacks cells with specific
protein markers.
Post Review Questions
In which cycle can the virus remain
dormant for a long time?
Lytic
or
Lysogenic
Post Review Questions
Name the type of cell attacked by the
following viruses.
HIV - T Cells
Hepatitis C – Liver Cells
Flu – Epithelial cells of the respiratory
system
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