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C disulfide bonds
Antibodies are proteins found in the blood and lymph that are secreted by the plasma cells arising from the B-lymphocytes.
B-lymphocytes are white blood cells with a non-granular cytoplasm that are produced and matured in the bone marrow (primary lymphoid organ).
B-lymphocytes migrate to secondary lymphoid organs like spleen, tonsils, lymph nodes, etc., when they mature and come in contact with trapped antigens. They undergo cell division and differentiation to form plasma cells which secrete antibodies.
Each antibody is made up of two short light (L) peptide chains and two long heavy (H) peptide chains (H
2L
2) joined to each other by disulfide bonds.
Disulfide bonds are covalent linkages between the sulphur-containing side chains of cysteine amino acids.
The peptide chains are arranged in a Y shaped structure. Each chain in the antibody has both constant and variable regions. The amino acid sequence and conformation of the variable region keeps changing from one type of antibody to the other. The conformation and amino acid sequence of the constant region remains the same. The unique antigen binding site in each antibody that is compatible with specific antigens is composed of the variable regions of both the heavy and the light chains.
Phosphodiester bonds are most commonly seen in the backbone of nucleic acids such as RNA and DNA.
Figure : Phosphodiester bond
Hydrogen bonds have a hydrogen atom located between a pair of other atoms having a high affinity for electrons.
Hydrogen bonds do not hold the peptide chains of an antibody together.
Condensation of two monosaccharides results in the formation of a glycosidic bond.
Figure : Glycosidic bond