Protein
Also known as: proteins · macromolecule
A large biological molecule of one or more long amino-acid chains; peptides are the same chemistry at shorter length.
A protein is a biological macromolecule built from one or more long chains of amino acids folded into a specific three-dimensional shape. Proteins do most of the structural and functional work in cells — as enzymes, receptors, antibodies and scaffolding.
The distinction from a peptide is essentially length: peptides are short chains (roughly up to 50 residues) while proteins are longer and usually fold into complex shapes. The underlying chemistry — amino acids joined by peptide bonds — is identical.
RELATED TERMS
Peptide Bond
The covalent amide bond linking amino acids into a peptide chain — the defining structural feature of every peptide.
Amino Acid
The building-block molecules of peptides and proteins; each contributes one residue to the chain.
Polypeptide
A single continuous chain of many amino acids linked by peptide bonds — the backbone of both long peptides and proteins.
Secondary & Tertiary Structure
The levels of peptide/protein organisation: sequence (primary), local folds (secondary), 3-D shape (tertiary), assembly (quaternary).
Amino-Acid Sequence
The specific order of amino-acid residues in a peptide — its "primary structure" — which dictates shape and activity.
Educational content, not medical advice. All products supplied for research purposes only — not for human consumption.