CHAPTER 6 NOTES.docx - 6.1 The Search for the Elusive Virus Early Discoveries Pasteur developed a vaccine for rabies Coined the term virus(Latin for

CHAPTER 6 NOTES.docx - 6.1 The Search for the Elusive Virus...

This preview shows page 1 - 3 out of 7 pages.

6.1: The Search for the Elusive VirusEarly DiscoveriesPasteur developed a vaccine for rabies-Coined the term “virus” (Latin for poison)Ivanovski and Beijernick: tobacco disease caused by a virusLoeffler and Frosch: foot-and-mouth disease caused by a virusFilterable virus:Infectious fluids were passed through filters designed to trap bacteriaThe cell-free filtered fluid remained infectiousThis proved that an agent smaller than bacteria (a virus) was the cause of disease6.2: The Position of Viruses in the Biological SpectrumViruses on the Biological SpectrumViruses can infect every type of cell:-Bacteria-Algae-Fungi-Protozoa-Plants-AnimalsUnique Properties of VirusesInfectious particles-Rather than organismsActive or inactive-Rather than alive or deadObligate intracellular parasites:-Cannot multiply unless they invade a specific host cell-Must instruct the genetic and metabolic machinery of the host cell to make and release new viruses6.3: The General Structure of VirusesViral Size RangeUltramicroscopic size:-Smaller than the average bacterium-Electron microscopes are required to detect themoParvoviruses: 20 nm in diameteroMimiviruses: 450 nm in length – larger than some small bacteriaoCylindrical viruses: 800 nm long, but 15 nm in diameterViral Components: Capsids, Envelopes, and Nucleic AcidsViruses bear no resemblance to cells-Lack protein-synthesizing machinery Need only those parts required to invade and control a host cell:-External coating-Core containing nucleic acidsCapsid:-Shell surrounds the nucleic acid-Nucleocapsid: capsid and nucleic acid together
Envelope:-Usually a modified piece of the host cell membraneNaked viruses:-Consist only of a nucleocapsidSpikes:-Found on both naked and enveloped viruses-Project from either the nucleocapsid or envelope-Allow viruses to dock with their host cellsVirion:-Fully formed virus able to establish infection in a hostThe Viral Capsid: The Protective Outer ShellCapsomeres:-Identical protein subunits that spontaneously self assemble to form the capsidHelical capsid:-Rod-shaped capsomeres that form a continuous helix around the nucleic acidIcosahedral capsid:-Three-dimensional, 20-sided figure with 12 evenly spaced cornersComplex capsids:-Found in bacteriophage, the viruses that infect bacteria-Have multiple types of proteins-Take shapes that are not symmetricalThe Viral EnvelopeComposed of the membrane system of the host.-Cell membrane or nuclear membrane-Regular membrane proteins are replaced with viral proteins-Spikes: protruding glycoproteins essential for attachment to the host cellNucleic Acids: At the Core of a VirusGenome:the full complement of DNA and RNA carried by a cell.

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture