<prompt> Which part is responsible for the class of immunoglobulin?Heavy chainLight chainBothNone  <response>: Ans. is a i.e. Heavy chain There are five immunoglobulin classes isotypes of antibody molecules found in serum: IgG, IgM, IgA, IgE and IgD. They are distinguished by the type of heavy chain they contain. IgG molecules possess heavy chains known as g-chains; IgMs have m-chains; IgAs have a-chains; IgEs have e-chains; and IgDs have d-chains. The variation in heavy chain polypeptides allows each immunoglobulin class to function in a different type of immune response or during a different stage of the bodys defense. 