Biochemistry

Protein

A polypeptide folded into a three-dimensional structure with biological function.

Definition

Proteins are folded polypeptide chains, often over 100 amino acids, performing structural, enzymatic, and signaling roles. Growth hormone (191 AAs) is a protein; semaglutide (31 AAs) is a peptide.

Related terms

PeptideA short chain of amino acids linked by peptide bonds — generally fewer than 50 amino acids.
PolypeptideA longer chain of amino acids, typically 50+ residues — the category between peptides and proteins.

Back to the full peptide glossary.