Fundamentals of Microbiology

1.5.2 Viral Structure

Nucleic acid

Virus contains a single kind of nucleic acid, either DNA or RNA which is the genetic material. The nucleic acid can be single stranded or double stranded. The nucleic acid can be linear or circular.

Capsid and Envelope

The nucleic acid of a virus is surrounded by a protein coat called the capsid. Each capsid is composed of protein subunits called capsomeres, which can be a single type of protein or several types. The capsid of some viruses is enclosed by an envelope consisting of lipids, proteins and carbohydrates. Some envelopes are covered with carbohydrate – protein complexes called spikes.