A virion consists of one or more
nucleic acid genome molecules (single-stranded or double-stranded
RNA or
DNA) and coatings (a
capsid and possibly a
viral envelope). The virion may contain other
proteins (for example with
enzymatic activities) and/or
nucleoproteins.
Spikes Spikes (peplomers) can protrude from the capsid, as in the
Coronaviridae, the
Tectiviridae, and others. These are used to establish contact with the host cell. In viruses of the genus
Chlorovirus, the virions have a single spike that serves as an injection device; an extendable injection apparatus are found in virions of the family
Tectiviridae.
Viral envelope In many
virus species, the virion also has an outer membrane, the
viral envelope. The envelope includes a
lipid bilayer and surface
proteins, similar to the
cell membranes, that are usually used for the envelope construction when the virus is exiting the cell. This structure helps with attachment to the cell and also assists evading the
immune system of the host organism while the virion is searching for a cell to infect. == References ==