Protein structure diagram 1

Primary structure: Amino acids join together in condensation reactions in a specific sequence. The peptide bonds form between amino acids resulting in a polypeptide.

Secondary structure: Amino acids which are 'close' to one another bond through weak hydrogen bonds, forming some common alpha-helices and beta-sheets.

Tertiary structure: Amino acids which are 'distant' bond together through hydrogen bonds, sulphur bonds and ionic bonds. This forms a unique 3D shape.

Quaternary structure: Here many polypeptide chains join together and some prosthetic groups may also add on. Prosthetic group are non-protein, and include the iron containing haem group in haemoglobin.