Video Transcript
The diagram shows a lymphocyte releasing antibodies in response to a pathogen. Which of the following is correct about the structure of antigens and antibodies? Our choices are: Antigens have a complementary shape to the antibody they attack. Antibodies have a complementary shape to a specific antigen they attack. Antigens and antibodies have the same shape. Antibodies have a complementary shape to all antigens. And antigens have a complementary shape to a wide range of antibodies.
Defining some of the key terms in this question will help us to determine which of the answer choices is correct. A lymphocyte is a type of immune cell. Some of them produce antibodies. The lymphocyte in our diagram is represented in blue. A pathogen is anything that triggers an immune response. The pathogen in our diagram is represented in orange. An antibody is a special protein created by a lymphocyte that attaches to a specific antigen. In the diagram, you can see the antibodies on the surface of the lymphocyte and being released from the surface of the lymphocyte.
An antigen is the specific part of a pathogen that an antibody is designed to attach to. You can see the antigens on the outside of the pathogen in our diagram. Some even already have antibodies attached. Note that both the antigen and the antibody are described as specific. When a lymphocyte makes antibodies, they’re designed only to attach to one type of antigen. Now that we fully understand our diagram, let’s review the answer choices again.
Antigens have a complementary shape to the antibody they attack. Antibodies are special proteins that the immune system uses to attack antigens, not the other way around. This statement is not correct.
Antibodies have a complementary shape to a specific antigen they attack. Since one antibody attaches to one specific antigen, they can be said to be complementary. This statement is true.
Antigens and antibodies have the same shape. Antigens and antibodies have complementary shapes. This means that they fit together like the pieces of a puzzle. They’re not shaped exactly the same. This statement is not correct.
Antibodies have a complementary shape to all antigens. We already know that antibodies are made specifically for one antigen. This answer is incorrect.
Antigens have a complementary shape to a wide range of antibodies. Once again, we already defined antigens and antibodies as having a specific relationship. So an antigen cannot have a complementary shape to a wide range of antibodies, and this statement is also false.
So the statement that is correct about the structure of antigens and antibodies is that antibodies have a complementary shape to a specific antigen they attack.
