chainelongation

Chain elongation is the general process by which a molecular chain grows through the successive addition of monomer units or building blocks. It is a central concept across disciplines such as polymer chemistry, biochemistry, and metabolism. Growth typically begins at an initiating site to form a reactive chain end, followed by propagation and, in many systems, termination or regulation.

In polymer science, chain elongation refers to chain-growth polymerization, where an active center adds monomer units one by one. Initiation, propagation, and termination define the main stages. Some systems pursue controlled or “living” polymerization to achieve precise chain lengths and architectures. Real-world examples include the formation of polyethylene, polystyrene, and polyacrylates, with chain length influencing properties such as molecular weight, viscosity, and mechanical strength.

In biology, chain elongation describes translation elongation during protein synthesis. The ribosome catalyzes peptide bond formation as aminoacyl-tRNA is delivered to the growing chain by elongation factors and energy from GTP hydrolysis. The cycle—tRNA selection, peptide bond formation, and translocation—repeats for each amino acid until a stop codon is encountered, producing a polypeptide.

In metabolism, chain elongation also occurs in fatty acid biosynthesis, where acyl chains are extended by two-carbon units, typically using malonyl-CoA. Enzyme complexes such as elongases or fatty acid synthase mediate these additions, with the resulting chain length influencing lipid function and membrane properties.