1. V IRUSES Biology 11 A. MacAskill

2. W HAT IS A VIRUS ? Virus is the Latin word for Poison A Virus does not fit the six kingdom classification They lack the characteristics of living cells Unlike all true organisms (even the most simple bacteria) viruses have no cellular structure No Cell Membrane No organelles

3. V IRUS CHARACTERISTICS Viruses have both non-living and living characteristics: Non-living: Alone a virus is life-less Living: Capable of reproduction with a host cell Viruses do not require energy – or carry out other common life processes such as growth, respiration and metabolism

4. B ASIC V IRUS S TRUCTURE Very very small - measured in nanometers (nm) Two main parts: Protein coat (a.k.a. capsid) Core (contains DNA or RNA) Viruses can be different shapes Virus are specific to their host

5. H ELICAL E XAMPLE – T OBACCO M OSAIC V IRUS

6. P OLYHEDRAL E XAMPLE : R HINOVIRUS ( COMMON COLD )

7. C OMPLEX E XAMPLE : B ACTERIOPHAGE Virus which attacks Bacteria

8. V IRAL REPLICATION : LYTIC C YCLE

9. L YTIC OR L YSOGENIC C YCLE

10. H OW C AN H UMANS A VOID V IRAL I NFECTIONS ? Vaccines: solutions that are prepared from viral components or inactivated viruses An individual is injected with viral components, their body creates anti-bodies as if the virus is real. These anti-bodies stay with us and as a result, a vaccinated person is immune to that disease

11. U NDERSTANDING VIRUSES : V IDEO During the video, answer the questions which were given!