What shapes can viruses have and what structure determined that shape?

Question

What shapes can viruses have and what structure determined that shape?

Answer 1

Viral shape is largely determined by the capsid, a structure composed of capsomeres that protects the viral genome. Capsids can be classified as:

1. Helical: these are long and cylindrical in shape
2. Icosahedral: these viruses look spherical though in reality have regular geometric patterns
3. Head-and tail: (complex) head similar to icosahedral viruses and tail similar to helical viruses

Furthermore, many viruses possess a lipid bilayer envelope surrounding the capsid, containing glycoproteins and host cell proteins. These can further alter the shape and function of the virus. Not all viruses are enveloped however