The Lytic Cycle
Viral replication
- Being non-living, viruses do not undergo cell division
- All viruses are parasitic, meaning they can only reproduce by infecting living cells, referred to as host cells
- To replicate all viruses must:
- Attach to a specific attachment site on the host cell
- Inject their nucleic acid into the cytoplasm of the host cell
- Use the protein synthesis machinery of their host cell to produce viral proteins
- Assemble new viral particles
- Release the new viral particles from the host cell
- Viral replication occurs via a lytic pathway, but some viruses undergo a series of events known as the lysogenic pathway in between reproductive cycles
The lytic pathway
- This is named as such because the new virus particles are released during lysis (bursting) of the host cell
- This is caused by an enzyme called lysozyme which is coded for by the virus genetic material
- Lysis occurs after the production of fully functional virus particles called virions
- The steps of the lytic pathway are as follows:
- The virus attaches to the cell membrane of the host cell using attachment proteins
- The virus infects the host cell by injecting its DNA into the cytoplasm
- Next, the virus uses proteins and enzymes within the host cell to produce new virus particles in a process called biosynthesis
- Virus particles are assembled and matured into virions
- Finally, the host cell undergoes lysis, releasing the virions into the host organism to infect more cells
Lytic cycle diagram
Viruses use the protein synthesis machinery of host cells to replicate themselves in the lytic pathway