Viral Structure

Generally speaking, what are two main components of viruses?

A genome encased in proteins.

• The viral genome can come in the form of DNA or RNA and it can be double stranded or single stranded.
• The proteins that surround viruses are called capsids and can take several forms (helical, icosahedral or complex).

What is an envelope?

Some viruses also have a protective outer covering in addition to the capsid. This envelope is host derived; meaning that by budding from the infected cell, viruses take with them some of the host's envelope - sort of like a vesicle but outside of the cell - which can include host cell membrane glycoproteins, phospholipids, etc.

Figure 7.2: The structural elements of a virus: this illustration shows the key components of a virus. For the curious, the virus depicted is HIV (the red dots represent reverse transcriptase, an enzyme unique to the viral family Retroviridae which is capable of converting RNA to DNA).