1. Protects the nucleic acid from the effects of enzymes and chemicals when the virus is outside the host cell.
2. Help to introduce the viral DNA or RNA into a host cell by binding to the cell surface and assisting in penetration of the viral nucleic acid.
3. Parts of the viral capsids and envelops stimulate the immune system to produce antibodies that can neutralize viruses and protect the host cells against future infections (concept of vaccines).
Kavungya answered the question on March 12, 2019 at 13:24