Download Viruses Part 1

Viruses, like 98% of all
parasites, are very Host
specific.
What are parasites?
What are hosts?
What are pathogens?
Viruses can ONLY
survive & reproduce in
very specific cells of very
specific organisms!
Different viruses can
infect Plants, or Animals,
or even specific microbes.
Viruses come in many different shapes,
often they have geometric shapes.
Bacteriophage or Phage
Can infect only a particular species of bacteria
Why do Virologists
like to work with
Bacteriophages?
What do you think
the binding site
would be???
Viruses are subcellular
No cell parts / organelles
More like a piece of a
chromosome =
A group of genes (DNA
or RNA) wrapped in a
protein coat (capsid)
Are viruses alive???
On borderline between
life and non-living.
Viruses are so small
they could NOT be
seen until the
Electron Microscope
was invented (1930’s)
Compare the size of a
Virus to
Prokaryotic cell to
Eukaryotic cell
Viruses are
obligate
parasites
They do NOT
do most Life
Functions
They have only
one goal – to
reproduce
Like a Lock and Key, each virus can
infect ONLY cells with the very specific
binding site, or certain protein in the cell
membrane, that the virus protein can
attach to or “unlock” the passage into
the cell!
For example, HIV can only infect the T4, (or CD-4) Lymphocyte.
Unfortunately for humans, the T-4
lymphocyte is the “Field Commander”
of our Immune System, which is why
HIV is so devastating to humans.
Could HIV infect a cat?
Feline Leukemia is “AIDS” in cats!
Lysogenic
Viruses