Viruses Flashcards
Viruses are
are non-cellular infectious particles that straddle the boundary between ‘living’ and ‘non-living’
but not living as cant reproduce on its own
They are relatively simple in structure; much smaller than
prokaryotic cells (with diameters between 20 and 300 nm)
Structurally they have:
A nucleic acid core (their genomes are either DNA or RNA, and can be single or double-stranded)
A protein coat called a ‘capsid’
Some viruses have an outer layer called an
Lipid envelope formed usually from the membrane-phospholipids of a cell they were made in
helps protect the virus from the host’s immune system.
All viruses are parasitic in that they can only
reproduce by infecting living cells and using their protein-building machinery (ribosomes) to produce new viral particles
Attachment proteins are present on the surface of the capsid. The virus uses the attachment proteins to
to bind to host cells in order to infect them
The enzyme reverse transcriptase is a enzyme that is found in only some viruses and bacteria and
catalyses the formation of a double strand of DNA from a single strand on RNA.