Final answer:
Complementarity determining regions (CDRs) are closely related to antigen-binding sites. The CDRs form the antigen-binding site of a T cell receptor (TCR) or an antibody, but the term 'antigen-binding site' includes other surrounding regions as well.
Step-by-step explanation:
Complementarity determining regions (CDRs) and antigen-binding sites are closely related but not exactly the same.
The antigen-binding site of a T cell receptor (TCR) or an antibody is formed by the CDRs. The CDRs are specific parts of the variable domains of the receptor or antibody chains that have unique patterns of amino acids, allowing them to bind to target antigens.
While the CDRs form the antigen-binding site, the term 'antigen-binding site' refers to the entire surface on the receptor or antibody that interacts with the antigen. It includes the CDRs as well as other surrounding regions.