Are Viruses Alive?

Viruses… Their Basic Structure Have a protein capsid (“head” region) DNA inside the capsid Some have a tail region and tail fibers

What do viruses look like? Have a protein capsid containing DNA Tail fibers allow virus to “land” on a host cell Injects DNA into host cell

Viral Dormancy Only activate their DNA once they have infected a host cell Can exist without a host for hours, days or longer! “Hijacks” and uses the host cell’s organelles to make new viral copies

Let’s Compare CELLS VIRUSES Prokaryotic or eukaryotic Outer cell membrane Can divide & reproduce independently Requires energy to survive Produces wastes Responds to stimuli Have no organelles No outer membrane Needs a host cell to make new viral copies No energy requirement Produces no wastes No response system

So… are there ANY similarities?? Both use DNA to make new copies This DNA can mutate Tiny (microscopic)

What happens once a virus enters a host cell? Let’s watch how phages attack bacterial cells… https://www.youtube.com/watch?v=YI3tsmFsrOg