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Viruses
Three Learning Objectives.
1. What is a virus?
2. What are the two basic parts of a
virus?
3. How do viruses reproduce?
1. What is a Virus?
1. A simple microscopic parasite
that infects bacteria, plants, and
animals.
2. Often a major cause of disease
3. Consist of a core of RNA or DNA
surrounded by a protein coat.
Did you write that
down?
They are not truly alive.
Viruses can’t:
 metabolize
nutrients
 produce and eliminate wastes
 Reproduce
(unless they are inside another organism’s
cells)
They are not considered living cells.
Some human diseases
caused by viruses are:
AIDS
Hepatitis
Chicken pox
Flu (Influenza)
Common cold
Mononucleosis
Fever blisters
Polio
Measles
Smallpox
Ebola
Warts
2. What are the two basic
parts of a virus?
The two basic parts of a virus are:


a small collection of genetic material (DNA or RNA)
an outer protective protein coat called a capsid.
2. What are the two basic
parts of a virus?
The two basic parts of a virus are:


a small collection of genetic material (DNA or RNA)
an outer protective protein coat called a capsid.
Did you write that
down?
Everyone knows Franklin
D. Roosevelt was afflicted
by a virus.
In the summer of
1921 at the age of
39 he was stricken
with polio.
What was
the worst viral epidemic
in US History?
Between the years of 1918-1919
In the US 675,000 people died,
(43,000 servicemen mobilized for WWI died)
Globally between 20 –40 million
3. How does a virus
reproduce?
As stated earlier a virus can only
reproduce in a living cell.
This complicated series of five
steps is called the Lytic life cycle.
Lytic life cycle
1. The virus attaches to a host cell.
2. The virus inserts its DNA into the cell.
3. The viral DNA takes over the cell's
machinery.
4. The host cell produces more and more
viruses.
5. The host cell splits open releasing the
viruses which leads to the cells death.
Lytic life cycle
1. The virus attaches to a host cell.
2. The virus inserts its DNA into the cell.
3. The viral DNA takes over the cell's
machinery.
4. The host cell produces more and more
viruses.
5. The host cell splits open releasing the
viruses which leads to the cells death.
Two examples of common viruses:
Polio
Common Cold
Polio
FAVORITE HANGOUT:
Intestine and nervous
system
LIKES:
Moving to the brain and
spinal cord, where it can
cause paralysis
DISLIKES:
The vaccine developed in
1954 that has tamed it
throughout most of the
world
Common Cold
FAVORITE HANGOUT:
Mucus linings of the
respiratory tract
LIKES:
DISLIKES:
Body temperatures above
102, hand washing,
Helpful cites
Glossary: http://wwwmicro.msb.le.ac.uk/MBChB/VirGloss.html
http://www.mansfield.ohiostate.edu/~sabedon/biol3025.htm
http://www.microbeworld.org/htm/aboutmicro/microbe
s/types/virus.htm
http://www.microbeworld.org/htm/aboutmicro/microbe
s/types/virus.htm