VIRUSES

1. VIRUSES • GIVE THE WORKSHEET A TRY!! • ANSWERS CAN BE FOUND IN CHAPTER 19 SECTION 2 on VIRUSES (you need to look at the WHOLE SECTION). HELPFUL START PAGE= 474

2. Bacteria & Viruses What’s the difference??

3. A little review…

4. A little review… • Prokaryotes are DIVERSE • shape, • the chemical nature of their cell walls, • the way they move, • and the way they obtain energy.

5. A little review… ARCHEABACTERIA EUBACTERIA NEWER bacteria It’s all around YOU In our intestines Water systems Land Has PEPTIDOGLYCAN in its cell wall • Live in EXTREME conditions. • Do NOT have PEPTIDOGLYCAN in their cell walls • Their DNA is so similar to Eukaryotes – possible ancestors • Example: Methanogens E. coli

6. Eubacteria come in all shapes… Bacilli (Rods) Cocci (Spherical) Spirilla (spiral) E. coli Streptococcus Spirillumvolutan

7. Eubacteria also differ in their… Cell Walls Movement Non movers Move slowly in their own secretion Have flagella that propel them along quickly! • Have really thick peptidoglycancovered OR • Thinner walls surrounded by a lipid layer

8. Eubacteria also differ in the way they eat… • Chemoheterotrophs- consumers • Photoheterotrophs- photosynthetic & consumers • Chemoautotrophs- use carbon compounds to make food w/out sunlight. • Photoautotrophs- do photosynthesis like green plants; no chloroplasts but have chlorophyll a

9. Eubacteria have different forms of release of energy • Obligate aerobes- have to have oxygen; do cell respiration • Obligate anaerobes- do fermentation; “allergic” to oxygen • Faculatative anaerobes- can do either one. • Can live just about anywhere.

10. IMPORTANCE OF BACTERIA • Producers that capture energy by photosynthesis. • Decomposers—breaking down nutrients • Ex. Nitrogen fixation • Human uses- • Remove poisons, break down petroleum, used to make yogurt, mine minerals, syntesize drugs • E.coliin our lower intestines, make vitamins we can’t get, further break down our food

11. Viruses: “Poison” – RNA or DNA surrounded by protein coat INFECTS BACTERIA

12. How viruses infect • Lytic Infection- • Virus “tricks” its way into cell- CAPSID • Cell replicates viral DNA • Cell assembles new viral proteins • Cell bursts or lyses from too many viruses. • Lysogenic infection- • Viral DNA is inserted into the DNA of the host cell, then just sits there until something triggers the lytic cycle. • When host cell replicates, the viral DNA is replicate with it.

13. Retroviruses • Nucleic acid is RNA instead of DNA • Some retroviruses cause cancer in animals (including humans). • HIV is a retrovirus (causes AIDS).

14. HIV • Human Immunodeficiency Virus • Why is it so dangerous? • No cure, only treatment • Attacks/Disables key cells in immune system (helper T cells) • Host no longer able to fight off infection • May remain latent for long periods. • Infected person may appear healthy but is contagious. • Lysogenic Phase (latent stage)- Viral DNA inserted into host cell’s DNA and copied prior to cell division. • Lytic Phase (active stage) – Viral Proteins rapidly reproducing and infecting many cells

15. Viruses vs Cells VIRUSES CELLS Reproduce Grow Can live without host cells Respond to their environments Obtain energy (autotrophs or heterotrophs Release energy (aerobic or anaerobically). • Are not made up of cells • Can’t live without host • Don’t respond to environment • Don’t obtain or use energy

16. Viruses and cells both • Reproduce • Have a genetic code (DNA or RNA) • Evolve

17. Common Viral Diseases • Rhinoviruses cause the common cold • HPV (Human papillomavirus) can cause cervical cancer in women • Herpes simplex viruses cause mouth and/or genital sores, lesions, and ulcers. • Influenza viruses cause the flu • HIV (Human Immunodeficiency Virus) causes AIDS and weakens the immune system

18. Rabies Chicken pox Hand, foot and mouth disease shingles

19. Controlling Viruses • PREVENT – with vaccines • TREAT – with rest and hydration for most viral infections • Antiviral drugs available for some viral infections (limited success) • Antibiotics DO NOT work on viruses. http://www.pbs.org/wgbh/nova/teachers/body/genetic-engineer-avian-flu.html

20. Controlling Viruses • Vaccines stimulate the immune system to create antibodies that recognize a certain virus. • Vaccines will NOT cure you if you are already sick. • These antibodies patrol your body and if they recognize that virus…they call in reinforcements and your immune system goes to battle!

21. How do we fight Illness? • Immune system- cells that inactivate or destroy pathogens • Nonspecific • Skin, mucus, sweat, tears • Inflammatory response • Fever • Specific • Hummoral Immunity • Acquired Immunity

22. Nonspecific Immunity • Skin • Mucus, saliva, tears contain lysozymes • Break down cell walls of bacteria • Inflammatory Response –happens if tissue damage • White blood cells: granulocytesthat engulf (EAT) pathogens • Infected tissue becomes painful and swollen • Fever • Chemicals released by immune system raise body temperature, so that pathogens can’t survive. • Heart rate increases, producing more white blood cells

23. Specific Immunity • Antigens trigger the response • Viruses, bacteria, and other pathogens that trigger immune response • “Self” and “Non-self” • Lymphocytes (T Cells and B Cells) • Tag, destroy and remember foreign bodies including pathogens

24. Acquired Immunity • The production of immunity against diseases • Vaccination • Injection of a weakened form of a pathogen to stimulate immune system • Antibiotics • Compounds that kill bacteria without harming host cells (prevent bacterial reproduction) • No effect on viruses