Chapter 20.1 - Viruses

1
Chapter 20.1 - Viruses

• Part 1 Virus Structure and Function

2
The Discovery of Viruses

• Scientists were looking for the cause of a
  disease that was infecting TOBACCO plants.
• Causing tobacco mosaic disease.

3
The Experiment

• Filter a solution that causes the disease through
  a small filter that bacteria cannot get through.

4
The Results

• The filtered solution can still infect the
  tobacco plant.

5
The Conclusion

• The disease was caused by something smaller than
  a bacteria. They called it a virus.

6
The Discovery

• 1935Wendell 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.
7
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)

8
What is a Virus

• Parasitic (live off others)
• Disrupts the lives of the cells they invade
• Found in air, soil, and water

9
Structure of a virus
capsid
Nucleic acid
Tail
filaments
10
Influenza
11
Small pox
12
bacteriophage
13
Ebola
14
West Nile
15
HIV
16
Hepatitis C
17
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.

18
Role of Viruses

• Most viruses are pathogensdisease 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.

19
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.

20

• 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.

21
Why do people have more than one cold or the flu
more than once?

• These viruses mutate quickly so your body doesnt
  recognize them as the same thing.
• (there are more than 200 strains of the common
  cold)

22
Vaccine

• Substance prepared from inactive or weak viruses
  that cause your body to react and produce
  antibodies without making you sick.

23
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.

24
How do retroviruses reproduce?

• They have a way to convert RNA to DNA.
• The DNA is copied by the cells they invade.

25
HIVs structure
26
(No Transcript)
27
HIV attacks your bodys T cells
28
Virus docks by matching receptor shapes on host
cell surface.
HIV
Matches the receptor on host
Host cell
29
Because HIV mutates very quickly, it is difficult
to cure.