Final answer:
The constant regions of antibodies contain binding sites for complement factors and phagocytic cells. The variable regions of antibodies bind to specific antigens. The hypervariable regions form a surface that complements the surface of the bound antigen.
Step-by-step explanation:
The constant regions of antibodies contain binding sites for complement factors and binding to phagocytic cells during antibody-mediated opsonization.
The variable regions of antibodies, located in the Fab (fragment of antigen binding) region, are responsible for binding to specific antigens.
The hypervariable regions, also known as complementarity determining regions (CDRs), form a surface complementary to the three-dimensional surface of a bound antigen.