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Why are viruses dangerous? Host Lysogenic Cycle Parasitic Relationships Viruses Lytic Cycle Shapes of Viruses Viruses • Not cells b/c no cytoplasm or organelles. • Basic structure is some form of genetic material in a protein coat. • Invades a cell and destroys it Viruses Cont. • Found everywhere Ex. 5 billion in 1 drop of blood. • Ever changing Ex. Colds, flu, and AIDS What do viruses look like? Virus Shapes Crystals Ex. Polio virus Spheres Ex. Influenza and HIV virus Virus Shapes Cont. Cylinders • Tobacco Mosaic virus Spacecraft • Attacks only bacteria. How do viruses survive in the environment? Host • Viruses don’t eat, grow, breathe, or perform biological functions. • Viruses reproduce inside a host cell. • Viruses have parasitic relationships. • They reprogram the cell. So, how does the virus get inside the host? And, what does it do there? Reproduce! The Lytic Cycle 1. The virus finds a host. 2. Enters the cell or genes are injected. 3. Genes reprogram the host cell into a virus “factory”. 4. New viruses break out to find a new host cell. Lysogenic Cycle • Inactive virus genes that wait inside the cell until after the host cell divides. • Changes in environment and stress can cause the virus to become active. Immune System • White blood cells attack and engulf anything that is not suppose to be in the body. • A “plan of attack” is kept in the body in case you get the same virus again. Ex. Killer T Cells and Helper B Cells Vaccines • Edward Jenner developed the first vaccine in the late 1700’s. It was for small pox. • A vaccine is a weakened or inactive virus used to develop immunity against viruses. Explain why virus are so dangerous. Use terms and concepts we discussed in class today.
