Virus Power Point


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Virus Power Point

  1. 1. Viruses Chp 21
  2. 2. Viruses <ul><li>Viruses possess only a portion of the properties of “living” organisms </li></ul><ul><ul><li>Segments of DNA or RNA wrapped in a protein coat called a capsid </li></ul></ul><ul><ul><ul><li>No Metabolism </li></ul></ul></ul><ul><ul><ul><li>Must reproduce within cells </li></ul></ul></ul>
  3. 3. Key Concepts <ul><li>Non-cellular infectious agents </li></ul><ul><li>Composed of nucleic acid, DNA or RNA and protein </li></ul>Cytoplasm, cell membrane, etc. Nucleic acid core, protein covering, some have envelope Structure Independently by cell division Only within host cell Reproduction DNA DNA or RNA Nucleic Acid Yes Yes Mutation Yes No Metabolism Yes No Homeostasis Yes No Growth Cell Virus Characteristic of Life
  4. 4. All viruses have 2 main parts: <ul><li>DNA or RNA - genetic info </li></ul><ul><li>Capsid - a protein encasement </li></ul>
  5. 5. Viral Shapes <ul><li>General Structure: </li></ul><ul><ul><li>Helical- rod-shaped protein coat wound helically around nucleic acid core </li></ul></ul><ul><ul><li>Polyhedral- many-sided coat </li></ul></ul><ul><ul><li>Enveloped- envelope around virus is made mostly of membrane remnants from previously infected cell </li></ul></ul>
  6. 6. Helical Virus , , Enveloped Virus Adenovirus (Polyhedral)
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  8. 8. <ul><li>The influenza virus has an envelope derived from the host cell. It consists of proteins, lipids and glycoproteins. The envelope helps the virus evade the host cell’s immune system. </li></ul>
  9. 9. Virus leaving host cell enveloped by host cell membrane
  10. 10. Grouping Viruses <ul><li>Grouped according to: </li></ul><ul><ul><li>Presence of capsid and envelope - shape </li></ul></ul><ul><ul><li>RNA or DNA, single or double stranded - structure </li></ul></ul>HIV Icosahedral, enveloped RNA Retroviruses Rabies Helical, enveloped RNA Rhabdoviruses Influenza A B C Helical, enveloped RNA Myxoviruses Polio, hepatitis, cancer Icosohedral, non-env RNA Picornaviruses Small pox, cow pox Complex brick, enveloped DNA Poxviruses Herpes simplex, chicken ox, mono, shingles Icosohedral, enveloped DNA Herpesviruses Resp. & intestinal infections Icosohedral, non-env DNA Adenoviruses Warts, cancer Icosohedral, non-env DNA Papovaviruses Example Shape and Structure Nucleic Acid Viral Group
  11. 11. Viral Multiplication Cycles <ul><li>5 Steps </li></ul><ul><ul><li>Attachment </li></ul></ul><ul><ul><li>Penetration </li></ul></ul><ul><ul><li>Replication </li></ul></ul><ul><ul><li>Assembly </li></ul></ul><ul><ul><li>Release </li></ul></ul><ul><li>Lytic pathway </li></ul><ul><ul><li>Host cell lysis relatively immediate </li></ul></ul><ul><li>Lysogenic pathway </li></ul><ul><ul><li>Viral DNA integrates into bacterial chromosomes, there is a period of dormancy. </li></ul></ul>
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  14. 14. Disease Causing Viruses <ul><li>Emerging Viruses </li></ul><ul><ul><li>Viruses that evolve in a geographically isolated area and are pathogenic (disease causing) to humans </li></ul></ul><ul><li>Viruses and Cancer </li></ul><ul><ul><li>Viruses are capable of altering growth properties of humans cells they infect by triggering oncogene expression (HPV) </li></ul></ul>
  15. 15. Prions and Viroids <ul><li>Prions </li></ul><ul><ul><li>Infectious protein conformations containing no genetic material. They can cause normal proteins to assume an abnormal shape preventing proper function (Mad Cow Disease) </li></ul></ul><ul><li>Viroids </li></ul><ul><ul><li>Tiny, circular molecules of RNA </li></ul></ul><ul><ul><ul><li>No protein or membrane coat </li></ul></ul></ul><ul><ul><ul><li>Important infectious disease agents in plants </li></ul></ul></ul>