1 / 24

Viruses

Viruses. Biology 4(C). Viruses. Learning objectives Know the structure of viruses Compare viruses to cells Understand viral reproduction Understand the role of viruses in diseases. Do viruses fulfill the characteristics of life? Viruses cannot reproduce on their own

adonai
Download Presentation

Viruses

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Viruses Biology 4(C)

  2. Viruses Learning objectives • Know the structure of viruses • Compare viruses to cells • Understand viral reproduction • Understand the role of viruses in diseases

  3. Do viruses fulfill the characteristics of life? • Viruses cannot reproduce on their own • Need host machinery (ribosomes) • Viruses cannot metabolize energy • Need host energy • No, not considered biotic (a living thing) • What is a Virus?

  4. Capsid – protein shell that protects genetic information of virus • Viral Structure - Bacteriophage

  5. Genetic information – strands of DNA or RNA used to make viral proteins inside infected hosts • Viral Structure - Bacteriophage

  6. Tail – protein shaft that contracts to inject viral genetic information into host • Viral Structure - Bacteriophage

  7. Tail fibers – proteins that attach to the outside of a host • Viral Structure - Bacteriophage

  8. Membranous envelope – lipids that attach and fuse to hosts • Viral Structure – Other Types

  9. Viruses • DNA or RNA • Need a host to replicate • Never contain organelles • Do not convert energy Cellular Life • Only DNA • Can reproduce independently • Eukaryotes contain organelles • Convert energy to perform tasks • Viruses vs. Cellular Life

  10. Viruses need a host to reproduce • Goal: create more copies of their genetic material • Two methods • Lytic Cycle • Lysogenic Cycle • Viral Reproduction

  11. Lytic Cycle • Attaches to host • Injects genetic material into host • Cellular machinery duplicates genetic material and creates viral proteins (capsids, tail fibers) • New viruses are assembled • New viruses exit the cell by bursting the cellular membrane • End result – more viruses made, cell dies • Viral Reproduction – Lytic Cycle

  12. Attachment Lytic Cycle • Viral Reproduction – Lytic Cycle Entry Release Replication Assembly

  13. Lysogenic Cycle • Attaches to host • Injects genetic material into host • Viral genetic material is inserted into host genome • Viral genetic material lies dormant • When cell reproduces, new copies have viral genetic information • End result – more viral genome made, cell lives • Viral Reproduction – Lysogenic Cycle

  14. Lysogenic Cycle • Viral Reproduction – Lysogenic Cycle Attachment Entry Separation Insertion Reproduction

  15. Viral Reproduction Lytic Cycle • New viruses made • Cellular host dies Lysogenic Cycle • Genome copies made • Cellular host lives Viruses can use both cycles Infect many cells with lysogenic Create many viruses at once with lytic

  16. Lytic & Lysogenic Cycles • Viral Reproduction

  17. Some animal viruses exit without lysing the host • Envelopes that fuse to the host cell’s plasma membrane • Viral Reproduction in Animals Images by Matt Gonda [Public domain]

  18. AIDS – acquired immune deficiency syndrome • Describes loss of immune system because of HIV • Caused by HIV - human immunodeficiency virus • makes helper T cells useless • Prevention • No vaccine • Limit transmission (use condoms) • Avoid transmission (use clean needles) • Viral Diseases - AIDS

  19. Viral Diseases – AIDS – HIV Replication

  20. Viral Diseases - AIDS Graoh by Jurema Oliveira [GFDL]

  21. Initial infection • Helper T cells rapidly decline • Viral genome rapidly increases • Clinical latency • Viral genomes lay mostly dormant in infected cells • AIDS • Rate of viral creation outweighs helper T cell creation • Death • Immune system too weak to fight common pathogens • Viral Diseases - AIDS

  22. Influenza (the flu) • Causes fever, fatigue, and respiratory infections • More severe than common cold, can be deadly • Viral Diseases - Influenza • Caused by a variety of influenza viruses • Change often, new vaccines yearly • Can blend with bird and swine strains to produce new viruses • Prevention • Seasonal vaccine • Limit transmission (wash hands) Image by NIAD [Public Domain]

  23. The Common Cold • Causes fever, fatigue, and respiratory infections • Less severe than influenza • Caused by a variety rhinoviruses • Over 200 different virus strains • Prevention • No vaccine • Limit transmission (wash hands) • Viral Diseases – Common Cold Image by Robin S [GNU]

  24. Hepatitis A • Causes inflammation of liver, jaundice appearance • Rarely results in liver failure • Caused by a hepatitis A virus • Carried through infected food or water • Prevention • Vaccine • Limit transmission (wash hands, food) • Viral Diseases – Hepatitis A Image by The CDC [Public Domain]

More Related