Viruses
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Viruses. Dead or alive?. Viral structure. Viruses are not cells. Basic structure: Protein coat Nucleic acid core (RNA or DNA) Lipoprotein coat (second coat – only in enveloped viruses). Virus Categories. DNA viruses – stable, do not mutate rapidly Single-stranded or double-stranded

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Viruses

Viruses

Dead or alive?


Viral structure
Viral structure

  • Viruses are not cells.

  • Basic structure:

    • Protein coat

    • Nucleic acid core (RNA or DNA)

    • Lipoprotein coat

      • (second coat – only in enveloped viruses)


Virus categories
Virus Categories

  • DNA viruses – stable, do not mutate rapidly

    • Single-stranded or double-stranded

    • Smallpox, Hepatitis B

  • RNA viruses – mutate rapidly, unstable

    • Single-stranded or double-stranded

    • HIV, Rhinovirus


Are viruses alive
Are viruses alive?

  • Only 1 characteristic of life: reproduction

  • Can only reproduce inside a host cell!

  • Process or reproduction = lytic cycle


Lytic cycle
Lytic Cycle

  • Virus attaches to host cell’s membrane and injects its nucleic acid into the host cell.

  • The viral nucleic acid takes over protein synthesis, creating new viruses.

  • The host cell bursts, lyses, releasing the newly formed viruses.


Before attachment

Attachment

Penetration and uncoating

Release

Assembly

Replication


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