Transcript Slide 1
Chapter 20 Pathogens •harmful to living organisms •Disease causing 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 cellThis 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 Viruses are tiny particles of DNA or RNA that are coated with protein. Sometimes they contain an envelope made of membrane. Flu They can’t reproduce on their own and they won’t survive long outside a living cell. RNA virusretrovirus HIV Ebola • RNA viruses can change more rapidly than RNA single strand vs DNA viruses-WHY? double strand • 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. Lytic Cycle 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. In some lysogenic viruses, a change in the environment can cause the provirus to begin the lytic ___ cycle resulting in the destruction of the cell. 1 5 2 4 3 3 4 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 Tcells then It causes the disease AIDS Smallpox, Chickenpox, flu, and warts are also caused by viruses. Adenoviruses cause the common cold. They attack cells in your respiratory system. 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 NIC 9. Viruses are ___, that is, they• cause disease. Rabies PATHOGENI C 17. Viruses have a protein coat or ___ that contains either RNA or DNA. • CAPSID 18. The AIDS and rabies viruses are examples of viruses that contain ___. Rabies • RN A and mononucleosis are examples of •viruses that DNA contain ___. Chicken Pox Virus Mono Virus Warts virus