Concept 5 Review

Polypeptide Folding

As polypeptides are synthesized by the sequential addition of amino acids (primary structure), they begin to fold in several ways.

The 4 levels of protein structure

Polypeptides are assembled in several stages. The first stage, called primary structure, is the sequential assembly of amino acids into a chain. These chains may be as short as two or as long as many hundreds of amino acids.

While lengthening of the primary chain is proceeding, folding begins, leading initially to secondary structure, followed by further folding into tertiary structure. Quaternary structure, found in some proteins, results from the association of multiple folded polypeptide chains.