Unit 2 – Biodiversity - Virus

A Virus Viruses are NOT organisms: They do not have cellular structure and are not classified into the six kingdoms They are successful at invading the cells of organisms They can only reproduce using the metabolism (energy) of the host cell They consist of strand of DNA/RNA Surrounded by a protective protein called a capsid Viruses have a variety of shapes These shapes are determined by the type and arrangement of proteins in the capsid.

A virus Cannot replicate without a host Origin is thought to be fragments of nucleic acid which had escaped from their original cell Survives by becoming a parasite on specific hosts. This suggests that viruses and their hosts probably evolved together This would make a virus and a host more closely related than a particular virus with other viruses

Example of Viral Reproduction Attachment: The T4 phage is a complex virus that attaches to a specific receptor site on a host's cell wall (eg. E. coli). Weak chemical bonds form between the attachment and receptor sites adhering (sticking to) the virus to the host

2. Entry (Penetration) : T4 injects it nucleic acid (DNA) into the host cell. The viral DNA passes through the core and into the cell. The capsid remains outside. 3. Replication: The host protein synthesis is stopped by viral degradation of host DNA. The host’s metabolism will replicate the viral DNA (or RNA)

4. Assembly: Spontaneous assembly of new virus particles occurs. 5. Lysis and Release: The host cell plasma membrane and cell wall lyses (breaks open) releasing the new virus particles. The host cell dies.

https://www.youtube.com/watch?v=HhhRQ4t95OI