Tertiary structure
The 3D fold of a single peptide chain — how it arranges in space.
A peptide or protein's tertiary structure is its three-dimensional fold — how the linear amino acid chain (primary structure) and local secondary-structure elements (alpha-helices, beta-sheets) arrange in space to form a functional molecule. Tertiary structure is held together by side-chain interactions: hydrogen bonds, hydrophobic clustering, salt bridges, and disulphide bonds between cysteines. Most peptides under ~30 amino acids don't fold into a stable tertiary structure in solution — they're flexible. Larger peptides and proteins do fold, and the specific fold determines biological function.
- GlossaryPeptide
A short chain of amino acids — typically 2 to ~50 — joined by peptide bonds.
- GlossaryAmino acid sequence
The ordered list of amino acids in a peptide, written N-terminus to C-terminus.
- GlossaryDisulphide bond
A covalent S-S bond between two cysteine residues — stabilises peptide / protein structure.