Virion

Virion (plural viria, virions or virions) refers exclusively to the extracellular form of a virus. In this form, a virus is transferred from one cell to the next. Its biological properties are not taken into account here.

Virions are typically 19 × 50 nm in size, varying in width between 18 and 20 nm and in length between 48 and 53 nm

Virions (as well as viruses that reproduce by means of foreign cells) do not belong to living beings (organisms), since they do not have their own metabolism.

A virion consists of one or more nucleic acid molecules, which can be surrounded by a protein capsule, the capsid. Capsids are always composed of symmetrically arranged building blocks called capsomers. The complex of capsid and nucleic acid is called nucleocapsid.

The genomic nucleic acid is present either as DNA or as RNA and can consist of a single strand or a double strand.

A virion can also have other proteins, such as those with enzymatic activities. These generally contribute to the main mass of the virion.

Some virions are additionally characterized by an outer lipid membrane, a viral envelope originating from the membrane of the host cell. Viral glycoproteins are incorporated into this lipid envelope, which has an enzymatic, a transmembrane and an extracellular part.

Virions (like viruses) do not belong to the category of organisms (living beings), as they do not have their own metabolism.

1. Hof H (2019). General virology. In: Hof H, Schlüter D, Dörries R, eds Duale Reihe Medizinische Mikrobiologie. 7th, completely revised and expanded edition. Stuttgart: Thieme p 168-171