The tertiary structure of a polypeptide (or protein containing only one polypeptide) refers to its shape, or more precisely the complete description its molecules' positions in three-dimensional space. This shape results after hydrogen bonding has joined amino acids from different locations on the polypeptide and protein folding has produced a nonlinear protein shape.
The tertiary structure of a polypeptide will determine its chemical properties on a larger scale; however, the polypeptide's tertiary structure follows uniquely from its primary structure (i.e., the order of amino acids). As a result, inferring the tertiary structure of a protein from its primary structure poses a research problem of the first order for a wide range of biological applications, and one that is still far from fully understood.
