Question

Describe the structure of an antibody molecule. MUST refer to four specific features of its primary, secondary, tertiary, and quaternary structure and how they are important for its function.

Answer 1

• Structure of an antibody:~ The structure of antibody molecule is - determined by the primary, secondary , tertiary and quaternary organization of the protein. The primary structure ie the amino acid - sequence, accounts for the variable and constant regions of the heavy and light chains. The - Secondary structure is formed by folding of the extended polypeptide chain back and forth upon itself into an antiparrallel ß pleated Sheet. The Chains are then folded into a tertiary structure of compact globular - domains, which are connected to neighboring domains by continuations of the polypeptide- chain that lie outside the ß pleated Sheets. 7 N y antigen binding - Site (): Lightenin (-) = hea Chain fig: - Antibody.

quaterne Finally the globular domains of adjacent heavy and light polypeptide chains interact in the aternary structure forming functional domain that bind antigen. Both light and heavy chain in a are made up of repeating segment A light chain consist of one variable (W) and the constant (cc) domain. Similarly - heavy chain consist of one variable (VH) and three or four constant (CH) domain. like CCHI, CH2D CH3,C44) etc. function: IgG > IgG is the only type of immuno- globulin that can pass through the placenta, enabiling the mother to transfer her immunity to the fetus. - Ig A Provide bar Igm → Take part in body immunity by - antigen agutination ; bacteriolysis etc. ega 7 Provide barrier to microbes for I entering in the body. iv. Ig & Rescue body from allergy v. Ig D > Act as a antigen acceptor of L B timphocyte.