What does an icosahedral capsid consist of?

Explanation

Capsid: The coat is the outer covering of a viral particle which consists of a capsid and envelope. The capsid is the protective coat of protein surrounding the core. Capsid is composed of identical repeating subunits called capsomers (capsomeres). The number of capsomers is specific to a particular kind of virus. Icosahedral capsid: When the capsomers are arranged in 20 triangles, it is called icosahedral (polyhedral or spherical). In a bacteriophage capsid, there are 12 vertices and 20 faces. Two types of capsomeres constitute the icosahedral capsid: Pentagonal (pentons) at the vertices Hexagonal (hexons) at the faces. There are always twelve pentons, but the number of hexons varies among virus groups.