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Viruses

Viruses. What is a Virus?. 1 nanometer (nm) = one billionth of a meter. 100 nm. Virus : A biological particle composed of nucleic acid and protein Intracellular Parasites : organism that must “live” inside a host. eukaryotics cells 10,000-100,000 nm. viroids 5-150 nm. viruses 50-200 nm.

anika-salazar
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Viruses

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  1. Viruses

  2. What is a Virus? 1 nanometer (nm) = one billionth of a meter 100 nm • Virus: A biological particle composed of nucleic acid and protein • Intracellular Parasites: organism that must “live” inside a host eukaryotics cells10,000-100,000 nm viroids5-150 nm viruses50-200 nm prokaryotics cells200-10,000 nm prion2-10 nm

  3. Reproduce Have nucleic acid Adapt to surroundings Have organization Not made of cells or organelles Can’t reproduce on own Don’t metabolize energy Don’t perform cellular processes Are viruses alive? No Yes

  4. Virus Parts • All Have: • 1) Capsid: coat of protein that surrounds nucleic acid • 2) Nucleic Acid: RNA or DNA • Some Have: • Tail Fibers: Used for attachment (not legs) • Shape & size varies

  5. Virus Video

  6. Viral Replication • Bacteriophages (viruses that attack bacteria) are often studied • Replication is similar with many animal viruses • Two “life” cycles: Lytic & Lysogenic Dozens of phage viruses attacking an E. coli bacteria cell The bacteria cell is destroyed and new viruses escape

  7. The Lytic Cycle 1st Step: Attachment • Virus lands on cell membrane • Virus attaches to a cell receptor • Virus acts as key; receptor acts as lock • No attachment = No infection

  8. The Lytic Cycle 2nd Step: Entry • Virus enzyme weakens cell membrane • Genetic material (DNA or RNA) enters host cell endocytosis

  9. The Lytic Cycle 3rd Step: Replication • Virus DNA/RNA uses ribosomes to make virus proteins • Virus proteins created by transcription/ translation transcription translation Viral DNA Viral RNA Viral Proteins

  10. The Lytic Cycle 4th Step: Assembly • New virus proteins are assembled in the cytoplasm

  11. The Lytic Cycle 5th Step: Release • Virus enzyme causes cell membrane to lyse (burst) • Viruses are released to find new host • Cycle repeats

  12. All stages on one slide Attachment Entry Replication & Assembly Release

  13. The Lysogenic Cycle 1st step: Attachment = Same as lytic cycle 2nd Step: Entry = Same as lytic cycle

  14. The Lysogenic Cycle • 3rd step: Replication • Provirus Created • Virus DNA combines with cell DNA • Infected cell divides by mitosis and copies the provirus • Each new cell will contain the provirus Virus DNA Pro-virus cell DNA Pro-virus Pro-virus

  15. The Lysogenic Cycle 4th Step: Assembly: Same, except many new viruses are assembled in many cells 5th Step: Release Same, except many cells burst releasing many more viruses

  16. The viral DNA become active and starts making new viral proteins The infected cells burst…releasing the new viruses

  17. HIV/AIDS

  18. ReView • True or False: All viruses have a capsid, nucleic acid, and tail fibers. • List 3 reasons why viruses may be living? Nonliving? • What is the virus capsid made from? • What type of organism do phages infect? • In order list the stages of the lytic/lysogenic cycles. • In which stage… • does the host cell explode? • are virus proteins built to make new viruses? • is a provirus created? • does a virus connect with the host cell’s receptors? • Which two objects make up a provirus? • Which virus “life” cycle is considered the most harmful? Why?

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