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What …

What …. have genetic material and can mutate and evolve, can not metabolize food, can not respond to stimuli, are not made up of cells, can only reproduce inside of a host cell, act as nonliving chemicals when outside a host cell,

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What …

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  1. What … • have genetic material and can mutate and evolve, • can not metabolize food, • can not respond to stimuli, • are not made up of cells, • can only reproduce inside of a host cell, • act as nonliving chemicals when outside a host cell, • form parasitic relationships with living organisms?

  2. Pseudo-Life Forms…Viruses

  3. Pseudo-Life Forms…Viruses Structure… Viruses contain an inner nucleic acid core (genetic material) and an outer protein coat (capsid).

  4. Enveloped Virus Lipid envelope Protein Receptors Enzymes Nucleic Acid (RNA) Capsid: core protein coat 25 nm Diagram of a Retrovirus or RNA carrying virus

  5. Naked Virus Capsid: core protein coat Nucleic Acid (DNA) Protein Receptors on tail fibers Diagram of a Bacteriophage or T4 DNA carrying virus

  6. Viruses …Structure • The virus may also contain some enzymes. • An outer envelope (membrane) that is derived from the cell membrane of the host • cell may surround the capsid. • The envelope contains viral protein spikes. • They are usually smaller than 200 nm.

  7. What is a Nanometer? Virus (20-50 nm) Tobacco Smoke (100 -1,000 nm) Bacteria ( 3,000-5,000 nm) Fungus Spores (5,000- 30,000 nm) Plant Pollen (10,000- 80,000 nm) Rain Droplet ( 600,000 – 10,000,000 nm)

  8. Object Characteristic Size person 1 m = 1000 mm grain of sand 1 mm human hair (thickness) .1 mm = 100 µm red blood cell 10 µm wavelength of light 1 µm = 1000 nm virus 100 nm atom .1 nm What is a Nanometer? 1 m  103 mm 106 µm  109nm ~ Viron size ranges from 20-200 nm

  9. 10 x smaller 1000 x smaller 100 x smaller

  10. Viruses… Structure • The genetic material in some viruses is DNA; in others it is RNA (as in retroviruses). • Both nucleic acids (NA) strands can be either a double (ds) or single (ss) stranded.

  11. Viruses…Reproduction …requires viruses to be in intimate contact with a specific host organisms and a specific type of cell within that host. This is called virus-host Specificity

  12. Viruses…Reproduction Examples: Influenza infects cells lining the respiratory tracts. Poliomyelitis virus infects nerve cells. Tobacco mosaic virus infects tobacco leaves.

  13. Viruses…Cycles Lytic Life Cycle… 1 - Adsorption 2 – Entry 3 – Replication 4 –Viron Assembly 5 –Lysis / Exit

  14. Viruses…Cycles Adsorption …requires the virus to enter a cell when either a part of the capsid or the spikes in the envelope match receptors in the host cell.

  15. Viruses…Cycles Lytic Cycle: Enveloped Virus 1 –Attachment or Adsorption

  16. Viruses…Cycles Lytic Cycle: Enveloped Virus 2 – Entry byFusion and Capsid Uncoating

  17. Viruses…Cycles Lytic Cycle: Enveloped Virus 2 – Entry byEndocytosis and Capsid Uncoating

  18. Viruses…Cycles Lytic Cycle: Enveloped Virus 3 & 4 –Enveloped Virus Replication & Assembly

  19. Viruses…Cycles Lytic Cycle: Enveloped Virus 5 –Lysis / Exit by Budding

  20. Viruses…Cycles Lytic Life Cycle of an Enveloped Virus…

  21. Viruses…Cycles Reinfection Some viruses, capable of causing cell fusion, may be transported from one cell to adjacent cells without being released, that is, they are transmitted by cell-to-cell contact whereby an infected cell fuses with an uninfected cell.

  22. Viruses…Cycles Lytic Cycle: Naked Virus 1 &2–Adsorption and Penetration

  23. Viruses…Cycles Lytic Cycle: Naked Virus 1 &2 –Adsorption and Injection

  24. Viruses…Cycles Adsorption and Injection…

  25. Viruses…Cycles Lytic Cycle: Naked Virus 3 & 4 – Replication & Assembly

  26. Viruses…Cycles Lytic Cycle: Naked Virus 5– Release via Cell Rupture

  27. Viruses…Cycles Lytic Life Cycle of Naked Virus…

  28. Viruses…Cycles Reinfection As many as 10,000 to 50,000 animal viruses may be produced by a single infected host cell.

  29. Viruses…Cycles Lysogenic Cycle ~ Replication without Immediate Host Death

  30. Viruses…Interrupting The Cycle How does a Vaccination Work? 1 –Injection of broken virus particles 2 –Body responds by making particles that recognize the virus and kiling to it - antibodies 3 –White blood cells collect and digest foreign particles covered in antibodies. Read pages 1063-1076

  31. Viruses…Interrupting The Cycle Neutralization of Viruses by Antibodies

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