Video Transcript
The diagram provided shows the
basic structure of an antibody. Which label indicates the variable
region of an antibody?
To answer this question, let’s
recall the different structures of an antibody. All antibodies are composed of two
heavy chains and two light chains. These chains are connected by
disulfide bridges, two of which on this diagram have been labeled with a Z. You might remember that antibodies
are very specific to the antigens that they recognize, which means that an antibody
can only bind to one specific antigen and that an antigen is simply any molecule or
substance that can trigger an immune response, for example, structures found on the
outer coat of a pathogen.
Antibodies are created in response
to these very specific antigen structures. To recognize their respective
pathogens by the antigens they present, antibodies contain two specific antigen
binding sites, one on each of the tips of their Y shape. Antibodies have a constant region,
which is the same for all antibodies and here has been labeled with a Y. Each antibody also has a variable
region, which is highly specific to a particular antigen. On this diagram, the variable
region has been labeled with an X.
Therefore, the correct answer to
our question “Which label indicates the variable region of an antibody?” is label
X.
