Final answer:
Antibodies are secreted forms of B cell receptors that can bind to specific antigens. They are produced by B cells in response to antigens and play a crucial role in the immune response. The diversity of antibody molecules is achieved through post-translational modifications.
Step-by-step explanation:
An antibody is a secreted form of a B cell receptor. The same genes encode both the secreted antibodies and the surface immunoglobulins, which are found on B cells. The antibodies have an antigen-binding site, which allows them to bind to specific antigens.
When a B cell encounters an antigen, it produces antibodies that are specific to that antigen. These antibodies can then bind to the antigen and mark it for destruction by other immune cells.
The diversity of antibody molecules is achieved through post-translational modifications of antibody polypeptide chains. These modifications can result in different amino acid sequences and structures, allowing antibodies to recognize and bind to a wide range of antigens.