Video Transcript
Which of the following statements about antigen binding sites is true? (A) Antigen binding sites bind to a variety of antigens and are unique to each antibody. (B) Antigen binding sites bind to one specific antigen and are unique to each antibody. (C) Antigen binding sites bind to one specific antigen and are the same across all antibodies. Or (D) antigen binding sites are only found on some antibodies and have only one shape.
This question is asking us about antigen binding sites. So in order to answer this correctly, let’s first review what this is referring to. An antibody is usually depicted as a Y-shaped structure, and the tips of this Y contains specific antigen binding sites. These antigen binding sites recognize toxins, pathogens, or any foreign substance that can be damaging to the body. For every pathogen that is encountered, a unique and specific antibody is created in response.
Notice that this representation of an antigen binding site is circular. While this one is represented as a square, these unique binding sites only bind to their complementary-shaped antigen. So in this example, the circular antigen would only bind to the antigen binding site that’s a circle and would not bind to these other two antibodies. Once bound to its specific antigen, the antibody can go on to initiate further immune responses to eliminate the foreign substance that carries this antigen.
So the answer to our question “Which of the following statements about antigen binding sites is true?” is answer choice (B): antigen binding sites bind to one specific antigen and are unique to each antibody.
