Polypeptide
Also known as: polypeptide chain
A single continuous chain of many amino acids linked by peptide bonds — the backbone of both long peptides and proteins.
A polypeptide is one unbranched chain of amino-acid residues joined by peptide bonds. The term emphasises the chain itself, regardless of whether it is short enough to be called a peptide or long and folded enough to be called a protein.
A protein may consist of one polypeptide or several assembled together. Where "peptide" implies a short, defined sequence, "polypeptide" is the neutral term for the chain of any length.
RELATED TERMS
Peptide Bond
The covalent amide bond linking amino acids into a peptide chain — the defining structural feature of every peptide.
Protein
A large biological molecule of one or more long amino-acid chains; peptides are the same chemistry at shorter length.
Amino Acid
The building-block molecules of peptides and proteins; each contributes one residue to the chain.
Amino-Acid Sequence
The specific order of amino-acid residues in a peptide — its "primary structure" — which dictates shape and activity.
Secondary & Tertiary Structure
The levels of peptide/protein organisation: sequence (primary), local folds (secondary), 3-D shape (tertiary), assembly (quaternary).
Educational content, not medical advice. All products supplied for research purposes only — not for human consumption.