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. Structure… Viruses contain an inner nucleic acid core (genetic material) and an outer protein coat (capsid).

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

5. Protein Receptors on tail fibers Capsid: core protein coat Nucleic Acid (DNA) Diagram of a Bacteriophage or T4 DNA carrying virus Naked 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. ObjectCharacteristic Size person1 m = 1000 mm grain of sand1 mm human hair (thickness).1 mm = 100 µm red blood cell10 µm wavelength of light1 µm = 1000 nm virus100 nm atom.1 nm What is a Nanometer? 1 m  10 3 mm  10 6 µm  10 9 nm ~ Viron size ranges from 20-200 nm

10. 10 x smaller 100 x smaller 1000 x smaller

11. 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.

12. 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

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

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

15. …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. Viruses…Cycles Adsorption

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

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

18. 2 – Entry by Endocytosis and Capsid Uncoating Lytic Cycle: Enveloped Virus Viruses…Cycles

19. 3 & 4 –Enveloped Virus Replication & Assembly Lytic Cycle: Enveloped Virus Viruses…Cycles

20. 5 – Lysis / Exit by Budding Lytic Cycle: Enveloped Virus Viruses…Cycles

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

22. 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. Viruses…Cycles

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

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

25. Adsorption and Injection… Viruses…Cycles

26. 3 & 4 – Replication & Assembly Lytic Cycle: Naked Virus Viruses…Cycles

27. 5– Release via Cell Rupture Lytic Cycle: Naked Virus Viruses…Cycles

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

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

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

31. 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 Viruses…Interrupting The Cycle

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