Q.An antibody is ...............

An antibody is Y-shaped, made of two identical heavy chains and two identical light chains joined by disulphide bonds; the arm tips (variable regions) form two antigen-binding sites, and the stem (constant region) det...

Antibody = Y-shaped protein of 2 heavy + 2 light chains, with two antigen-binding sites at the arm tips.

An antibody (immunoglobulin) is a Y-shaped glycoprotein made of four polypeptide chains: two identical, longer heavy (H) chains and two identical, shorter light (L) chains, held together by disulphide bridges. Each of the four chains has a variable (V) region — at the tips of the Y's two arms — whose amino-acid sequence differs between antibodies and gives each antibody its specific antigen-binding site (the paratope); since there are two identical arms, each antibody molecule can bind two antigen molecules simultaneously. The remaining constant (C) region of the chains forms the stem of the Y and is largely the same within a given antibody class; it determines the antibody's class (IgG, IgM, IgA, IgD or IgE) and its biological effector functions. …