Draw a well-labelled diagram of an antibody molecule.

(N/A) An antibody molecule is $Y$-shaped and consists of four polypeptide chains: two small chains called light chains and two longer chains called heavy chains. The structure is represented as $H_2L_2$. The chains are held together by disulfide bonds $(-S-S-)$. Each antibody molecule has two antigen-binding sites located at the tips of the $Y$-shaped structure,which are specific to particular antigens.