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VIRUSES

In the 1890s, scientists made groundbreaking discoveries about diseases caused by viruses. They extracted sap from diseased leaves and applied it to healthy plants, leading to the conclusion that an agent smaller than bacteria was responsible for the illnesses. This research culminated in the coining of the term "virus," derived from Latin meaning slime or poisonous liquid. Modern definitions recognize viruses as infectious agents that consist of a protein shell (capsid), nucleic acid core (either DNA or RNA), and, in some cases, an envelope that helps them enter host cells.

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VIRUSES

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  1. 21 SEP 12 24 SEP 12 VIRUSES

  2. How did scientists come up with the term VIRUS? In the 1890s, two scientists independently investigate the cause of the disease.

  3. How did scientists come up with the term VIRUS? The scientists extracted sap from unhealthy leaves and put it on the leaves of normal, healthy plants

  4. How did scientists come up with the term VIRUS? They filtered the sap to remove bacteria and then repeated the tests.

  5. How did scientists come up with the term VIRUS? Their conclusion was that something smaller than bacteria were causing the disease.

  6. VIRUS Latin – Slime; poisonous liquid Modern – Agent that causes infectious disease

  7. If viruses are smaller than bacteria, how big do you think they are?

  8. What are the main components of a virus? Capsid – Protein Shell Viruses are simple agents Nucleic Acid Core Envelope – Outer Membrane Surface Receptors

  9. Capsids PROTEINS Isoleucine Ile, I Proline, Pro, P Asparagine, Asn, N Threonine, Thr, T Glutamic acid, Glu, E Serine, Ser, S Amino Acids

  10. Helical Viruses Tobacco Mosaic Virus

  11. Polyhedral Viruses Adenovirus

  12. Complex Viruses T4 Bacteriophages

  13. Influenza Virus T4 Bacteriophage Tobacco Mosaic Virus RNA DNA Head RNA Capsid Tail sheath Tail fiber Surface proteins Capsid proteins

  14. Nucleic Acid Core DNA Deoxyribonucleic acid Adenine Guanine Thymine Cytosine

  15. Nucleic Acid Core RNA Ribonucleic acid Adenine Guanine Uracil Cytosine

  16. Nucleic Acid Core Viruses genomes can be either double stranded or single stranded.

  17. Nucleic Acid Core Viruses can only have one type of nucleic acid. It must be DNA or RNA, not both!

  18. Envelope Helps get the virus into the host cell.

  19. Envelope Acquired from the host cell.

  20. Envelope Is sensitive and can be disrupted by desiccation, heat, and exposure to detergents.

  21. Receptors Help the virus recognize the host cell.

  22. Receptors Are very specific – have a key and lock relationship.

  23. Capsid Protein Shell Nucleic Acid DNA or RNA Envelope Membrane around virus Receptors Proteins that help virus get into proper host

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