Question

What is the difference between an epitope and an antigen? Does an antibody bind onto the epitope or the antigen?

Answer 1

Hint: Antigen-antibody interaction, also known as antigen-antibody reaction, is a chemical event in which antibodies produced by white blood cells' B cells interact with antigens during an immune response. Agglutination is the process through which antigens and antibodies interact. It is the body's basic mechanism for protecting itself from complex foreign substances such as infections and their chemical poisons. Antibodies bind to antigens in the blood, binding them precisely and with a high affinity to form an antigen-antibody complex.

Complete answer:
Part A-

ANTIGEN	EPITOPE
A material that reacts with antibody molecules and antigen receptors on lymphocytes is known as an antigen. An immunogen is an antigen that the body recognizes as non-self and activates the adaptive immune system.	Epitopes are the parts or pieces of an antigen that bind to receptors on B-lymphocytes and T-lymphocytes, as well as free antibody molecules.
The antigen elicits an antibody response in the host; however, the antibody only binds to the epitope, not the whole protein.	The region of the antigen to which antibodies bind is called an epitope (also known as the antigenic determinant).
Antigens are produced in normal cells as a result of cell metabolism or as a result of viral or intracellular bacterial infection.	The \[3\]-D shape taken by the interaction of discontiguous amino acid residues forms a conformational epitope.
Proteins, peptides, and polysaccharides make up antigens. Antigens can be found in any part of bacteria or viruses, including the surface protein, coat, capsule, toxins, and cell wall.	Epitopes are normally made up of a series of amino acids that contribute in antibody binding, and their interaction is determined by the epitope's fundamental structure.
Antibodies are made up of two heavy chains and two light chains that are linked together to form a "Y" shaped molecule.	An epitope is a protein fragment of five to six amino acids in length.
Types of antigens-exogenous, endogenous, autoantigens	Types of epitopes- continuous and discontinuous

Part B- antibody binds to epitope.
When an antibody binds to a protein, it doesn't necessarily attach to the entire protein. Instead, it binds to an epitope, which is a portion of the protein. An epitope is a five- or six-amino-acid sequence of amino acids.
The part of an antibody that binds to the epitope referred to as a paratope. Although epitopes are often non-self-proteins, they can sometimes be sequences originating from the host that can be identified (as in autoimmune disorders). The net strength of all contacts with an antigen determines the avidity of any specific antibody molecule. IgG, IgE, and IgD antibodies bind epitopes with greater affinity than IgM antibodies. Each IgM molecule, on the other hand, can interact with up to ten epitopes per antigen, giving it increased avidity.

Note:
When these antigens are introduced, B cells produce a new antibody with a unique paratope (a location where the antibody interacts to the antigen) to bind to a specific epitope. Each B cell lymphocyte produces a unique antibody against a specific epitope. Antigen-antibody interaction, also known as antigen-antibody reaction, is a chemical event in which antibodies produced by white blood cells' B cells interact with antigens during an immune response. Agglutination is the process through which antigens and antibodies interact.