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Chapter 17

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  1. Chapter 17 Viruses & prokaryotes

  2. 17-1 Viruses • What is a virus? • How do viral life cycles differ? • What is the relationship between viruses and their hosts?

  3. What is a virus? • A virus is a noncellular particle made up of genetic material and protein that can invade living cells • First discovered in 1935 by an American scientist named Wendell Stanley • It was called the tobacco mosaic virus or TMV

  4. TMV on tobacco plant http://healthyhomegardening.com/Disease.php?pid=15

  5. http://concerncrisis.blogspot.com/2008/03/tobacco-mosaic-virus-tmv.htmlhttp://concerncrisis.blogspot.com/2008/03/tobacco-mosaic-virus-tmv.html

  6. Structure of a virus • Composed of a core of DNA or RNA surrounded by a protein coat called a capsid • Capsid protects the genetic material • The core contains several genes to several hundred genes

  7. http://micro.magnet.fsu.edu/cells/virus.html

  8. More complex structures are in viruses called bacteriophages – viruses that invade bacteria • Has a head region (capsid), a nucleic acid core, and a tail • Some have tail fibers that allow them to attach to the bacteria

  9. http://micro.magnet.fsu.edu/cells/virus.html

  10. Viruses are rod-shaped, tadpole-shaped, helical and cubelike shaped • Vary in size from 20 to 400 nanometers • A nanometer is one billionth of a meter

  11. http://learnsomescience.com/microbiology/viruses-viroids-and-prions/http://learnsomescience.com/microbiology/viruses-viroids-and-prions/

  12. Specificity of a virus • Specific viruses infect specific organisms • Plant virus cannot infect an animal • Only mammal viruses that do not infect other animals and vise versa • Viruses for every type of organism

  13. http://www.wellesley.edu/Chemistry/Chem101/dna-viruses/viruses.htmlhttp://www.wellesley.edu/Chemistry/Chem101/dna-viruses/viruses.html

  14. Life cycle of a Lytic Virus • In order to reproduce, viruses must invade, or infect, a living host cell • They also invade in different ways… • One way is done by lytic viruses where when they invade the cell bursts or lyses

  15. Life cycle of a lytic virus http://dvm5.blogspot.com/2010/11/classification-of-viruses.html

  16. Infection • A virus is activated by contact with the right host cell (chance) • It then injects its DNA into the cell

  17. Life cycle of a lytic virus http://dvm5.blogspot.com/2010/11/classification-of-viruses.html

  18. Growth • The RNA polymerase of the host cell creates messenger RNA of the virus DNA • This mRNA then takes over the host cell • Some proteins turn off the creation of molecules for the cell

  19. Life cycle of a lytic virus http://dvm5.blogspot.com/2010/11/classification-of-viruses.html

  20. Replication • It then uses the host cell to make thousands of copies of its own protein coat and DNA • The host cell is then filled with viral DNA molecules • These three steps can happen in 25 minutes

  21. Life cycle of a lytic virus http://dvm5.blogspot.com/2010/11/classification-of-viruses.html

  22. The infected cell then lyses (bursts) and releases hundreds of virus particles • These particles than infect other cells • The host cell is lysed and destroyed so this process is called lytic infection

  23. http://en.wikipedia.org/wiki/Lytic_cycle

  24. Lysogenic Infection • Lysogenic infection-the virus does not reproduce and lyse its host cell • The DNA of the virus enters the cell and is inserted into the DNA of the host cell • The viral DNA is then known as a prophage

  25. Prophage activity • Blocks entry of other viruses and may even add useful DNA to the host cell’s DNA • Eventually it will remove itself from the DNA and create new virus particles

  26. http://en.wikipedia.org/wiki/Lytic_cycle

  27. Retroviruses • Retroviruses contain RNA as their genetic information • When they enter the cell they produce a DNA copy • This then enters into the host cells DNA

  28. http://ucdbiotech.wordpress.com/2009/10/13/be-on-the-alert-the-first-ever-gammaretrovirus-capable-of-infecting-human-hosts-has-been-identified/http://ucdbiotech.wordpress.com/2009/10/13/be-on-the-alert-the-first-ever-gammaretrovirus-capable-of-infecting-human-hosts-has-been-identified/

  29. Viruses and Living Cells • Viruses must infect living cells to carry out their functions • Viruses are parasites-an organism that depends entirely upon another living organism for its existence in such a way that it harms that organism

  30. http://westernrifleshooters.blogspot.com/2011/02/interview-with-stanley-kurtz.htmlhttp://westernrifleshooters.blogspot.com/2011/02/interview-with-stanley-kurtz.html

  31. Are viruses alive? • Viruses are not made of cells • They can grow, reproduce, regulate gene expression, an evolve • It is up for debate

  32. Virus video

  33. 17-2 Prokaryotic Cells Bacteria Intro video http://hyperphysics.phy-astr.gsu.edu/hbase/biology/imgbio/cellprokaryote6.gif

  34. Prokaryotes • Cells that do not have a nucleus http://en.wikipedia.org/wiki/Prokaryote

  35. Eubacteria http://calexa.weebly.com/eubacteria.html

  36. Cyanobacteria http://user.uni-frankfurt.de/~schauder/cyanos/cyanos.html

  37. Archaeabacteria • Methanogens – archaeabacteria that produces methane gas http://en.wikipedia.org/wiki/Archaea

  38. Prochlorobacteria http://jk169.k12.sd.us/proteobacteria.htm

  39. Bacteria (E. Coli) • One-celled prokaryotes http://en.wikipedia.org/wiki/Bacteria

  40. They do not contain the complex range of membrane enclosed organelles that are found in most eukaryotic cells http://www.weblife.org/humanure/images/fig3-1.jpg

  41. Eubacteria Structure • generally surrounded by a cell wall made of carbohydrates • there is a cell membrane which surrounds the cytoplasm • long whip like flagella protrude from the membrane through the cell wall

  42. Eubacteria http://upload.wikimedia.org/wikipedia/commons/thumb/5/5a/Average_prokaryote_cell-_en.svg/494px-Average_prokaryote_cell-_en.svg.png

  43. They use photosynthesis to get energy http://www.biologie.uni-hamburg.de/b-online/library/webb/BOT311/Cyanobacteria/CyanoHyellaStella300Crop.jpg

  44. Fresh and saltwater, land, hot water, arctic, grow on snow http://lyxia.us/wp-content/uploads/2012/08/cyanobacteria-1.jpg

  45. Methanogens are archaebactria that produce methane gas http://www.daviddarling.info/images/methanogens_large.jpg

  46. prochlorobacteriamore related to chloroplasts http://jk169.k12.sd.us/images/Escherichia_coli1355024.300a[1].jpg

  47. Bacteria Identification • cell shape • Cell Wall • Bacterial Movement • How the obtain energy

  48. Bacterial shape https://benchprep.com/blog/ap-biology-diversity-of-organisms-kingdoms-part-i/

  49. Gram Staining • There are two types of dye, The bacterial cells with only one thick layer of carbohydrate and protein molecules outside the cell membrane took up the crystal violet. The bacterial cells that have lipid and carbohydrate molecules appear red under the microscope and are gram negative

  50. Gram Staining http://en.wikipedia.org/wiki/Gram_staining