polypeptidy

Polypeptidy are polymers consisting of amino acid residues linked by peptide bonds. They are the basic building blocks of proteins and, depending on length and structure, may act as functional peptides on their own.

They are synthesized in cells by ribosomes through translation of genetic information encoded in mRNA. Each residue contributes an amino group and a carboxyl group; successive residues are joined by a peptide bond in a condensation reaction, releasing a molecule of water. The chain has an N-terminal and a C-terminal end, and its sequence determines its properties.

Primary structure refers to the linear sequence of amino acids. Secondary structures arise from hydrogen bonding within the chain and include alpha helices and beta sheets. Tertiary structure describes the overall three-dimensional folding of a single polypeptidy, while quaternary structure refers to the assembly of multiple polypeptidy chains into a functional complex.

Functions of polypeptidy are diverse. They form enzymes that catalyze biochemical reactions, structural proteins like collagen and keratin, transport proteins such as hemoglobin, and signaling or immune proteins. Shorter polypeptidy can act as hormones or neuropeptides, while longer chains often serve as functional domains within larger proteins.

Post-translational modifications and degradation are important aspects of polypeptidy biology. Many are modified after synthesis (for example, by phosphorylation or glycosylation), influencing activity, localization, or interactions. They are also subject to proteolytic cleavage and turnover. The term polypeptidy is often used synonymously with polypeptides, particularly in non-English technical contexts.