Polypeptider

Polypeptider are linear chains of amino acids linked by peptide bonds. They form the fundamental building blocks of proteins and occur in a wide range of lengths and properties. The specific sequence of amino acids—encoded by genes—governs the chemical behavior, folding, and biological function of the polypeptide. Depending on length and context, a chain may be regarded as a short oligopeptide, a longer polypeptide, or a complete protein if it adopts a stable three‑dimensional structure.

Polypeptider are synthesized in cells by ribosomes through translation of messenger RNA. Amino acids are added one by one to a growing chain, which is then folded and often modified. Many polypeptides undergo processing after synthesis, such as cleavage, glycosylation, or formation of disulfide bonds, and some are secreted or integrated into membranes.

Structure: The primary structure is the linear amino acid sequence. Local folding produces secondary structures like alpha helices and beta sheets. Further folding yields the tertiary structure, and, for multisubunit assemblies, the quaternary structure. A protein is typically a functional polypeptide or a complex of multiple polypeptides.

Functions: Polypeptider carry out catalytic, regulatory, structural, signaling, and defense roles. They can act as hormones, enzymes, receptors, antimicrobial agents, or subunits of larger protein complexes. Function depends on sequence and three‑dimensional shape, which in turn reflects the genetic and cellular context.

Notes: Terms vary—oligopeptider refer to short chains; there is no strict length boundary between polypeptider and proteins. Some polypeptider remain unstructured in solution, while others form stable folds. Post-translational modifications and proteolytic processing can regulate activity and localization.