What section of an immunoglobulin does the FC portion comprise?

The FC portion of an immunoglobulin is indeed comprised only of the constant region of the heavy chain. The immunoglobulin structure consists of two heavy chains and two light chains, with each being further divided into variable and constant regions. The variable region is responsible for the antigen-binding specificity of the antibody, while the constant region, which includes the FC portion, determines the class of the immunoglobulin and its effector functions.

The FC region plays a crucial role in interacting with other components of the immune system, such as receptors on immune cells and complement proteins. This interaction is essential for carrying out immune responses, such as opsonization and antibody-dependent cellular cytotoxicity.

Understanding the structure of immunoglobulins is vital for immunology and serology, as it helps clarify how antibodies function in the immune system and how they can be manipulated for therapeutic purposes. Thus, recognizing that the FC portion encompasses only the constant region of the heavy chain is fundamental to comprehending the overall functionality of antibodies.