Summary:
- A virus particle consists of DNA or RNA within a protective protein coat called a capsid.
- The shape of the capsid may vary from one type of virus to another.
- Some viruses have an envelope of phospholipids and proteins.
- The envelope is made from portions of the host’s cell membrane.
- It surrounds the virus and helps protect the virus from the host's immune system.
- The capsid of the virus shown in Figure below is icosahedral.
- Viral structures are built of repeated identical protein subunits.
- This makes the icosahedron the easiest shape to assemble.