Describe the structure of a typical virus.

Viruses are often considered non-living: they exist in an inert state outside of a host cell. They consist of a strand of nucleic acid, either DNA or RNA, surrounded by a protective protein coat (the capsid).

All viruses contain the following two components: 1) a nucleic acid genome and 2) a protein capsid that covers the genome. Together this is called the nucleocapsid. In addition, many animal viruses contain a 3) lipid envelope. The entire intact virus is called the virion. The structure and composition of these components can vary widely.