Question

I. Antibodies are highly glycosylated proteins

II. Antibodies are made up of 2 identical heavy chains and 2 identical light chains

III. N-terminal end of light and heavy chain interacts with the antigen

IV. N-terminal end of the heavy chain interacts with the antigen

V. C-terminal end of light and heavy chain, interacts with the antigen

Choose the option which identifies the incorrect statements:

• A. III,V
• B. I, III
• C. I, III, IV
• D. IV, V

Answer 1

The correct option is D IV, V

Antibodies are Y-shaped tetra peptide molecules that are basically made of globulin (gamma) proteins .These are highly glycosylated and are stimulated by the antigens. Antigens are the foreign substances which after enetring the body, act as a stimulus to produce more antibodies.

There are basically five types of antibodies IgG, IgA, IgD, IgE, and IgM that are produced by the body to counteract any foreign invaders.

Each antibody molecule is made up of four polypeptide chains held together by disulphide bonds (-S-S-).
- 2 identical light chains called L, 220 amino acids.
- 2 identical heavy chains called H, 440 amino acids.
Hence, an antibody is represented as H${}_2$L${}_2$.

Further, these light and heavy chains are further subdivided into variable and constant regions; variable regions of both chains contain the antigen binding site, where the antigen attaches itself to the antibodies. As antibodies are proteins and are made up of amino acids, so every polypeptide chain has a specific direction of the sequence of amino acids, it starts from the amino terminal (N-terminal) and ends in the carboxy terminal (C-terminal). Amino terminals (N) of both heavy and light chains are at the variable side of the antibody where the antigen comes and binds.