Download Chapter 21 Viruses

Viruses
A virus is a microscopic particle that
gets into a cell, takes over its functions,
and often destroys it while
reproducing.
Extremely small. Millions of virus can
fit into a bacteria.
Can change forms rapidly (mutates).
Can’t live on its own, must have a
.
host cell to reproduce
Viruses
They force their host to become
virus factories rather than
creating healthy cells.
Viruses genetic material can be
DNA or RNA
Living things vs Viruses
Both contain protein, genetic
material, and they can
reproduce. Viruses cannot
eat, grow, break-down food,
or use oxygen. They must
depend on their HOST Cell
Four Shapes of Viruses
• Crystals- polio virus
• Cylinders- tobacco moasic virus
• Spheres- influenza and HIV virus
•Spacecraft- attacks bacteria
only- Bacteriophage
Crystal shaped virus
Cylinder shaped virus
Sphere shaped virus
Spacecraft shaped virus
Spacecraft shaped virus-
Bacteriophage
HIV virus sphere shaped
One shape of Flu virus
Lytic Cycle
• Virus joins to host cell using similar
receptors.
• Virus injects its genetic material into the
cell (injects just like a needle).
• Virus genes take over the cell and make
viruses immediately. (virus factory).
• Virus breaks out of the cell (usually killing
it) and infecting many other healthy cells.
• Virus cycle begins again.
Lysogenic Cycle
• Virus joins to the host cell.
• Injects its genetic material.
• Lays dormant inside the host cell.
Does not make virus cells right away.
• Takes over the cell sometime later
and the Lytic Cycle begins.
• The cycle begins again.
Antibiotics vs Antiviral
Antibiotics – bacteria to fight
other bacteria. Kills good and bad.
Antiviral medicines stop the
reproductive cycle if viruses and are
not always 100% effective because
viruses change form so much.
Vaccinations
A killed or weakened pathogen
introduced into the body to
allow the body to gain
immunity (resistance) against
it. (polio, shingles, chickenpox,
rabies, etc.)
How to prevent viruses
The best way to prevent virus infections
is to not get them to begin with. Wash
hands often, do not use other personal
items, keep vaccinations up to date, and
just good general hygiene. Vaccination
is the best way and washing hands is
best low cost way to prevent viruses.