viral replication

• bacteriophage virus - infects bacteria
• influenza virus - infects eukaryotic cells
• bacteriophage fibres attach to a bacterial cell to inject its nucleic acid into bacteria
• bacteriophage contains DNA

  influenza contains RNA
• Stages of viral replication:

  1. attachment (adsorption)
  2. penetration
  3. synthesis: replication and protein production
  4. assembly
  5. release (lysis)
• Attachment

  • virus attaches to the host cell by specific binding of its spikes to the cell surface receptors
  • attachment proteins on virus have a complimentary shape to the receptors
• Penetration

  • virus is engulfed into a vesicle
  • its envelope and capsid break down --> envelope is uncoated
  • uncoating frees the viral DNA/RNA into the host's cytoplasm
• Synthesis

  • the cell synthesises the basic components of a new virus, under the control of viral genes
  • basic components = RNA molecules, capsomeres, spikes
• Assembly

  • the nucleocapsid is formed from the new RNA and capsomeres
  • viral spike proteins are inserted into the cell membrane to make the viral envelope
• Release

  • the new viruses bud off the cell membrane, carrying away an envelope with spikes.
  • virus bursts out the cell