Concept 5 Review

Primary Structure

Primary structure refers to the sequence of amino acids in a polypeptide, without any reference to how the molecule folds up in three-dimensional space.

Primary structure is often written as a sequence of amino acids using three-letter, or one-letter, abbreviations: N-ala-glu-asp-C, or AEN, for example.

Because all polypeptides are synthesized starting at the N-terminal amino acid, it is customary to describe primary structure with the N-terminus on the left, and the carboxyl, or C-terminus, on the right.