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Viruses – Chp. 25

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  1. Viruses – Chp. 25

  2. Pathogen – any organism that causes disease. Exs.) virus, bacteria, protozoan. Some Examples of VIRUS Illnesses : Polio, Chicken Pox, Shingles, Hepatitis, Flu, AIDS, Common Cold.

  3. Are Viruses Living or Non-Living?? : - Scientists debate this because viruses do not require food, oxygen, water……yet they can reproduce (note – they only reproduce inside a living host cell).

  4. Bacteriophage – viruses that only attack bacteria. Ex.) T-4 virus T-4 Virus – a famous virus in scientific circles. • It only attacks bacteria – it is safe to humans. • It is easy to grow in petri dishes and cost is minimal. • Because of the above factors, T-4 makes a good research specimen. • T-4 is famous because it has been widely studied. Most of our early knowledge about viruses came from studying T-4.

  5. Virus Structure – made up of a coat and a core. • Coat is outer protective covering made of protein. • Core is made up of the genetic material DNA or RNA.

  6. Lytic Cycle – reproductive cycle for regular viruses. See figure 25-5 on page 492 in book.

  7. Stages of Lytic Cycle: • Attachment – virus latches onto cell. • Entry – virus injects its DNA into cell. • Replication – virus DNA takes over the cell’s machinery and directs it to make virus parts. • Assembly – virus parts get put together. • Release – newly made viruses break out of cell and can now go and attack more cells. (note – the cell dies in the process).

  8. Lysogenic Cycle – reproductive cycle for LATENT viruses.

  9. Latent Viruses – infect you now, but do not make you sick for a period of time. Exs.) HIV, Herpes, Shingles.

  10. 3 Major Ways That Germs are Transmitted • Airborne Transmission – enter the body with the air breathed in. Exs.) smallpox, chicken pox, polio, measles, flu, common cold. Prevention – vaccines, avoid sick people, cover your mouth when sneezing and coughing.

  11. 2. Food and Water Transmission – most effect stomach and intestines. Gets into food/water from intestinal wastes. Exs.) hepatitis A, salmonella, botulism, E. coli. Prevention – good hygiene, wash hands, check canned food for damage, keep foods refrigerated/frozen, cook meats/eggs well done, have drinking water tested.

  12. 3. Contact Transmission– shaking hands, kissing, touching, sex, sharing cups, towels, etc. • Watch wounds of all kinds Prevention – practice safe sex, good hygiene, disinfect wounds.

  13. Chapter 25 - Bacteria

  14. Classification Kingdoms of Bacteria

  15. Archaebacteria – rare – only found in a few places on earth. Exs.) in the boiling water of hot springs, in very salty waters where no other bacteria thrive, at the ocean vents where water is superheated.

  16. Eubacteria – “true” bacteria – common, everyday bacteria. They are found just about everywhere, including in and on our bodies.

  17. Prokaryotic Cells (Prokaryotes) = Bacteria • Thought to be the oldest cells on earth. • Do not have a true nucleus that houses the DNA. Bacterial DNA just floats unprotected inside the cell. • Very simple structure. They do not have any parts that are seen in more complex cells. • ***BACTERIA ARE THE ONLY CELLS ON EARTH THAT ARE PROKARYOTIC.***

  18. Bacterial Shapes – Used for Identification • 1. Coccus (Cocci) • 2. Bacillus (Bacilli) • 3. Spirillum (Spirilla)

  19. Coccus (Cocci) – round, sphere shaped. • Diplococcus – 2 joined in a pair. • Staphylococcus – clumps/clusters of cells…many cause “staph” infection. • Streptococcus – strips/chains of cells…. cause “strep” throat. • Tetrad – 4 cells arranged in a square.

  20. 2. Bacillus (Bacilli) – elongated rod shapes • Diplobacillus – 2 joined. • Streptobacillus – strips/chains.

  21. 3. Spirillum (Spirilla) – bent rods like a boomerang, or corkscrew shaped. Spirilla only occur in the single form, they do not join together in any way. See top of page 470 in book.

  22. Nutrition in Bacteria Autotrophs – “Cyanobacteria” – SOME bacteria are photosynthetic and can make there own food. Heterotrophs – MOST bacteria rely on other organisms to make food for them. 2 types: • Saprophytes – get food from dead organisms….many of these bacteria compete with us for our food and spoil it. • Parasites – get food from living cells. These are the pathogens that infect us and make us sick.

  23. Respiration in Bacteria Obligate Aerobes – require oxygen and cannot live without it…….most bacteria. Obligate Anaerobes – do not grow in the presence of oxygen. They use other gases such as methane or they conduct fermentation. Facultative Bacteria – live with or without oxygen. They grow faster with oxygen.

  24. Factors That Affect the Growth of Bacteria • Temperature : • 79 – 100 degrees Fahrenheit – optimum growth range for many bacteria. • Refrigeration/cooking inhibits bacteria. • Body uses fever as defense mechanism to kill off temperature sensitive bacteria. 2. Moisture: • Bacteria are 90% water and dryness makes them inactive • We dry many foods to preserve them such as pasta, dried fruit and beans, cereal, rice, potatoes.

  25. Factors That Affect the Growth of Bacteria 3. Radiation – sunlight and ultraviolet light kills bacteria by mutating their DNA. • We put ultraviolet lights in operating rooms to kill germs. 4. Chemicals – many kill bacteria. Exs.) chlorine, vinegar (acetic acid) to pickle foods, sugar, salt, artificial preservatives.

  26. Bacteria Reproduction and Survival Binary Fission = simple cell division….the bacterium splits in 2. • This is how bacteria REPRODUCE when growth conditions are good.

  27. Bacteria Reproduction and Survival Spore Formation – Bacterium makes a tough protein wrapper to protect only its DNA when conditions are not good. This is called a SPORE. • This is how bacteria SURVIVE when conditions are not suited for growth. Spores can survive quite harsh conditions.