Virus: Structure

As you can see, all the viruses show some type of genetic material, either DNA or RNA, and a CAPSID or protein coat, surrounding the virus.
The capsid has three functions:

1. It protects the virus.

2. It contains special sites on its surface that allow the virus to attach to a host cell.

3. It provides proteins that enable the virus to penetrate the host cell membrane.

Virus: Structure

Viruses Compared to Eukaryotic Cells

Viruses are different from living cells.
Two eukaryotic cells - one a plant cell and the other an animal cell - are shown.
Eukaryotic cells contain membrane-bound organelles, such as a nucleus.