Chapter 20 harmful to living organisms Disease causing Pathogens

Viruses The word virus means toxin or poison A virus cannot live, grow, or reproduce outside of a host cell Each virus only attaches to a specific cell- This cell is called a target cell The protein coat of the virus acts as a “key” and can only fit certain receptor sites “lock” on specific cells

Virus Structure- Viruses come in a variety of shapes All have: capsid-protein coat & DNA or RNA Some have envelope-like a cell membrane Glycoproteins- “name tags” on cell Bacteria

Flu HIVEbola Viruses are tiny particles of DNA or RNA that are coated with protein. Sometimes they contain an envelope made of membrane. They can’t reproduce on their own and they won’t survive long outside a living cell. RNA virus- retrovirus

RNA viruses can change more rapidly than DNA viruses-WHY? Diseases such as chicken pox, measles by DNA viruses people tend to only get once Diseases such as influenza by RNA viruses people tend to get these diseases more than once. RNA single strand vs double strand

1.Viruses attach to the host cell membrane. 2.They inject their DNA (instruction for making more viruses) inside the cell. 3.They use the cell’s machinery to reproduce 4.They rupture (burst) the host cell, killing host cell. Lytic Cycle

In some lysogenic viruses, a change in the environment can cause the provirus to begin the ___ cycle resulting in the destruction of the cell. lytic

Some viruses can hide their DNA or RNA inside the host cell for many years before they begin to kill cells! HIV retrovirus ( ) virus attacks white blood cells called T-cells. Destroys T-cells. Once no more T- cells then It causes the disease AIDS Adenoviruses cause the common cold. They attack cells in your respiratory system. Smallpox, Chickenpox, flu, and warts are also caused by viruses.

How do we get rid of these diseases? Antibiotics WILL NOT get rid of a virus Why? There is no way to cure a cold or fix a disease caused by a virus (medicines only relieve the symptoms) Vaccines give you immunity to the virus Vaccines-weakened virus, parts of virus, similar virus

Transmission HIV: through bodily fluids (blood, semen, breast milk) Sharing needles, sex, bloodstream Sneezing, sitting on same toilet?? No needs to come in contact with bloodstream

9. Viruses are ___, that is, they cause disease. PATHOGE NICPATHOGE NIC

9. Viruses are ___, that is, they cause disease. PATHOGEN ICPATHOGEN IC Rabies

17. Viruses have a protein coat or ___ that contains either RNA or DNA. CAPSIDCAPSID

18. The AIDS and rabies viruses are examples of viruses that contain ___. RN ARN A Rabies

19. Warts, chickenpox, and mononucleosis are examples of viruses that contain ___. DNADNA Warts virus Chicken Pox Virus Mono Virus