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 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

How Viruses Multiply - Viruses 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

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.