Download - Chapter 20.1 - Viruses
Chapter 20.1 - Viruses
Part 1 – Virus Structure and Function
The Discovery of Viruses
Scientists were looking for the cause of a disease that was
infecting TOBACCO plants.Causing tobacco mosaic
disease.
The Experiment
Filter a solution that causes the disease through a small filter that bacteria cannot get through.
The Results
The filtered solution can still infect the tobacco plant.
The Conclusion
The disease was caused by something smaller than a bacteria. They called it a virus.
The Discovery
1935—Wendell Stanley discovered the structure of a virus and proved that they are NOT a
LIVING ORGANISM. 1946 Nobel Prize
winner. Extensive virus work..proved that they cause cancer.
What is a Virus
Complex, submicroscopic, organic particle. (20 nm, have carbon)
Not cellular, no cell parts. Do not carry out life functions on
their own. Reproduce only inside a living cell
(host cell)
What is a Virus
Parasitic (live off others)Disrupts the lives of the
cells they invadeFound in air, soil, and water
Structure of a virus capsid
Nucleic acid
Tail
filaments
Influenza
Small pox
bacteriophage
Ebola
West Nile
HIV
Hepatitis C
Structure of a Virus
A virus is a particle made up of a
nucleic acid core (either DNA
or RNA) and an outer protein coat called a capsid.
Some viruses also have an extra
outer layer called an envelope.
Role of Viruses
Most viruses are pathogens—
disease causing agents.Small pox, chicken pox, cold sores,
warts, AIDS, rabies, mumps, flu, measles, some forms of cancer and the common cold are caused by viruses.
How does the body handle viruses?
It is the job of the immune system to
fight diseases in the body. Your skin is one of the most important organs in this system because it keeps pathogens out of your body.
Once a virus is in your body, your main
defense is white blood cells. These cells are specialized to fight pathogens.
There are 2 main types of white blood
cells. T cells and B cells. B cells are normally more important for fighting viruses. Once a virus has entered your body, your B cells produce proteins called antibodies that will remember the virus and fight it off if the same virus enters your body again. This means that you normally never get the same viral infection twice.
Why do people have more than one cold or the flu more than once?
These viruses mutate quickly so your body doesn’t recognize them as the same thing.
(there are more than 200 strains of the common cold)
Vaccine
Substance prepared from
inactive or weak viruses that cause your body to react and produce antibodies without making you sick.
The HIV virus
HIV, the virus that causes AIDS, is in a class of viruses called retroviruses. These
viruses have RNA as their nucleic acid.
How do retroviruses reproduce?
They have a way to convert RNA to DNA.
The DNA is copied by the cells they invade.
HIV’s structure
HIV attacks your body’s T cells
Virus docks by matching receptor shapes on host cell surface.
HIV
Host cell
Matches the receptor on host
Because HIV mutates very quickly, it is difficult to cure.