1. CH.11 Sections 1
Viruses

2. 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.

3. Virus Shapes Viruses vary in shape
Round
Rod-shaped
Shaped like bricks
Shaped like threads
Shaped like bullets
Robot-like shape
Bacteriophage – robot shaped- a virus that infects bacteria.

5. 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.

6. 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

8. How Viruses Multiply
- Viruses
Active viruses enter cells and immediately begin to multiply, leading to the quick death of the invaded cells.

9. - Viruses
Hidden viruses “hide” for a while inside host cells before becoming active.

10. 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.

11. Some Common Infectious Viruses
Influenza – Flu
Hepatitis
AIDS
Malaria
Pneumonia
Polio
Strep

12. 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.