Final answer:
The statement is true; the heavy chains of an antibody are made up of both variable and constant regions, where the variable regions contribute to antigen specificity and the constant regions define the class and effector functions of the antibody.
Step-by-step explanation:
The statement that heavy chains of an antibody comprise portions of both the constant and variable regions is true. Antibodies consist of four polypeptide chains; two heavy chains and two light chains. The heavy chains of an antibody contain one variable domain (VH) and three or four constant domains (CH1, CH2, CH3, and C₄) depending on the class of the antibody. The variable regions of both heavy and light chains are involved in antigen recognition, forming the antigen-binding sites, which determine the specificity of the antibody for a particular antigen. The constant domains of the heavy chains not only determine the antibody's class or isotype, such as IgG, IgM, IgA, IgD, and IgE, but also influence the physical properties, functional forms, and the effector mechanisms that will be activated upon binding.