macromolécules

Macromolecules are large organic molecules with high molecular weights, typically formed by the linkage of many repeating subunits called monomers. They arise through polymerization, in which monomers join via covalent bonds to produce long chains, branched networks, or cross‑linked structures. In biology, macromolecules carry out most cellular functions and provide the basis for genetic information, structure, and metabolism.

Natural macromolecules include proteins, nucleic acids, and polysaccharides. Proteins are polymers of amino acids folded into three‑dimensional structures that catalyze reactions and provide support. Nucleic acids such as DNA and RNA are polymers of nucleotides that store, transmit, and translate genetic information. Polysaccharides like starch, glycogen, and cellulose are polymers of sugars involved in energy storage and structural support. Synthetic macromolecules, produced industrially, include polymers such as polyethylene, polystyrene, and nylon, which form plastics, fibers, and gels. Lipids are not typically classified as polymers, but some lipid assemblies have polymeric features.

Macromolecules exhibit hierarchical structure. Linear, branched, or cross‑linked architectures influence properties such as solubility, melting point, and mechanical strength. In biopolymers, sequence and folding create functional three‑dimensional shapes. The bonds that link monomers—glycosidic, peptide, and phosphodiester—depend on the macromolecule type. Polymerization mechanisms include condensation (step‑growth) reactions and addition (chain‑growth) reactions, and in biology, biosynthesis uses specific enzymes to build polymers.

Because of their size and diversity, macromolecules underpin nearly all biological processes and many materials applications. They are central to genetics, metabolism, immune responses, and development, and they form the basis of plastics, textiles, hydrogels, and other advanced materials. Challenges associated with polymer waste and recycling are an important consideration in modern science and engineering.