STRUCTURE OF VIRUS

Structure of Virus

 

All viruses contain nucleic acid, either DNA or RNA ( but not both ), and a protein coat known as CAPSID

Capsid - is the protein shell that encloses that nucleic acid : with it enclosed the nuclei acid, it is called the nucleocapsid.

This shell is composed of protein organized in subunits known as copsomers. Viral capsids normally have a helical or polyhedral structure or combination of both.

The Capsids has three function.

a. it protects the nucleic acid from digestion by enzyme

b. contains special site on its surface that allow the virus to attach to a host cell,

c. provide protein that enable the virus to penetrate the host cell membrane and, in some cases, to inject the infectious nucleic acid into cells cytoplasm.