Primary Structure

Introduction to Protein Structure

Primary Structure

Proteins, like peptides, are composed of amino acids joined togeather via amide linkages (for the details see the peptide structure section). The only difference between peptides, polypeptides and proteins is the number of amino acid residues in the chain. The relationship between residue count and these terms is somewhat arbitrary. Generally, peptides are small 10 or 20 residues; polypeptides might range up to 50 or 60 residues, with anything larger considered a protein. Then again, some biochemists use the term polypeptide more or less interchangeably; as I stated, the terms are somewhat flexible!