Transcript CH.11 Sections 1-3

CH.11 Sections 1
Viruses
Viruses
 A virus
is a tiny non-living particle
that enters and reproduces inside a
host cell.
 A virus is like a parasite – in that it
needs a host in order to live.
Virus Shapes

Viruses vary in shape
Round
 Rod-shaped
 Shaped like bricks
 Shaped like threads
 Shaped like bullets
 Robot-like shape
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Bacteriophage – robot shaped- a virus that
infects bacteria.
Virus Size
Viruses are very tiny. They cannot be
seen with a compound microscope
 They are smaller than cells
 Measured using nanometers.
 1 nanometer is 1 billionth of a meter.

Structure of Viruses


All viruses have a similar structure
Viruses have two basic parts:
1. Protein Coat – protects the virus
- contains surface proteins that allow the
virus to attach to certain cells
- Lock and key – viruses can only attach
to a few certain cells
2. Inner Core made of genetic material
- contains instructions for making new
viruses
- Viruses
How Viruses Multiply

Active viruses enter cells and immediately
begin to multiply, leading to the quick death of
the invaded cells.
- Viruses
Hidden viruses “hide” for a while
inside host cells before becoming
active.
Viruses – Good or Bad?
Some viruses cause disease while others
are very useful – useful in gene therapy
 Some viruses like a cold or flu are often
short lived.
 HIV – is a deadly virus for which there is
no cure – eventually becomes AIDS.
 Viruses can affect other organisms other
than humans. Plants, dogs and cats can
all have viruses.

Some Common Infectious Viruses
Influenza – Flu
 Hepatitis
 AIDS
 Malaria
 Pneumonia
 Polio
 Strep
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Vaccines
A vaccine is a substance introduced into
the body to stimulate the production of
chemicals that destroy specific viruses or
bacteria.
 Vaccines are either dead or altered
viruses.
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