Virus General Structure

Viruses are the smallest infectious particles. In addition, viruses are obligate intracellular parasites, that is, they need living host cells to replicate. A virion is a complete, fully developed, infectious viral particle composed of nucleic acid surrounded by a coat called a capsid. In addition to it, some types of viruses may also have an envelope called an envelope. The presence or absence of this extra envelope classifies viruses into two groups: enveloped viruses and non-enveloped viruses.