Virus life cycle

• Viruses are considered to be non living.

  Viruses can only replicate by invading host cells and using amino acids and ribosomes to replicate.
• Why can’t antibiotics kill viruses?

  • Bacteria can replicate outside of cells.
  • Antibiotics only destroy the cell wall of bacteria.
  • Viruses are inside of the cell meaning the antibiotics cannot destroy a virus.
• When RNA/DNA is injected into host cell, genes code for proteins to make the virus. They will use the host amino acids and ribosomes to make those proteins
• Lytic cycle


  • Virus will attach to receptors found on host cell.
  • Virus has inserted its DNA/RNA into the cell.
  • DNA/RNA replicates by using host ribosomes and amino acids.
  • Virus is able to make its protein coat and new viruses are assembled.
  • Host cell will burst (lysis).
  • New viruses released into your bloodstream and will bind to other host cell receptors.
  • Process repeats.
• Lysogenic cycle 


  • Virus attaches to host cell receptors and inserts its DNA/RNA into host cell.
  • Virus DNA/RNA becomes inserted into host DNA.
  • As host DNA replicated by mitosis the DNA of the host cell and DNA/RNA of the virus replicates.
  • Virus DNA/RNA will use ribosomes and amino acids from host cell to make protein coat.
  • New viruses assembled , host cell bursts(lysis).
  • Viruses are released.
• Advantage of lytic cycle


  • replication of new viruses is fast.
• Disadvantage of lytic cycle


  • host is immediately killed preventing viral genome from passing onto next generation of host cells.
• Advantage of lysogenic cycle


  • many more viruses can be made because viral genome is passed onto future generation of host cells.
• Disadvantage of lysogenic cycle


  • replication takes longer because it’s dependent on host cells replication by mitosis.
• APPLICATION- why would it be better to kill. bacteria using viruses rather than antibiotics?


  • By using viruses you avoid antibiotic resistance.
  • bacteria can be killed quicker with viruses.
  • when virus replicates it causes the bacterial cell to burst (lysis).
  • New viruses will be released and they will bind to receptors on bacterial cells.
  • Cycle repeats.