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VIRUSES
PA State Standards:
What are VIRUSES?
1) A nucleic acid (DNA
or RNA) surrounded
by a coat of protein.
2) Viruses are not
considered to be alive
(they are not in one of
the five kingdoms).
Nonliving Properties of Viruses
1) Not made of Cells (no organelles or cell
functions).
2) Can’t grow or reproduce on their own
(reproduce inside the cells of other
organisms).
3) Can be crystallized & stored for years.
Examples of Viruses:
Bacteriophage
Capsid
Head
DNA
Tail
Tail Fibers
Examples of Viruses:
Influenza Virus
Capsid
RNA
Protein
spikes
What is a parasite


An organism that
attaches itself and
feeds off of another
organism.
A parasite does harm
to the organism it is
attached to
Hookworm
What is a host


The organism that is harmed or hurt by the
parasite
Example: You are the host to a mosquito
Bacteriophage Reproductive
Cycle
1- Attach
Virus attaches to cell.
Use tail to attach to
cell membrane of cell.
Bacteriophage
Bacteria
2- Invade
Viral DNA invades cell
Virus injects nucleic
acid into the cell.
Viral DNA slides into host cell
Viral DNA penetrates cell
membrane/cell wall
3- Copy
a) Virus’ nucleic acid
attaches to DNA of
the cell.
Bacterial DNA
Viral DNA
3- Copy
b) DNA copies and
makes new viruses
Virus takes control of
cell & makes new
virus particles.
Bacteria is forced to make
more & more viruses
4- Release
Cell bursts releasing hundreds
of new viruses
Bacteriophage Reproductive Cycle
5- VIRUSES & DISEASE
1)
HUMANS
a) Colds
b) A.I.D.S.
Aquired Immune Deficiency
Syndrome
H.I.V. –
Human Immunodeficiency
Virus
5- VIRUSES & DISEASE
1)
HUMANS
c) Polio
Iron Lung
F.D.R.
Deformed Leg
Caused by Polio
5- VIRUSES & DISEASE
2) ANIMALS
Rabies
5- VIRUSES & DISEASE
3) PLANTS
Tobacco Mosaic Virus
How are viruses transmitted?

Direct contact


Vectors 

Touching, body fluids, etc.
mosquitoes, flies, etc
Airborne

Spread by the air
Terms to know:




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What happens when a disease spreads fast in a
certain area?
An epidemic
What system in your body is used to help stop
you from getting sick?
The immune system
What is a small amount of a virus injected into
your body to give you immunity called?
A vaccine
CREDITS
http://www.cat.cc.md.us/courses/bio141/lecguide/unit2/
viruses/lysosum.html