The hierarchy of protein structure

• Primary structure

  The sequence of amino acids,

  particularly in respect to properties of their R groups, formed by peptide bonds
• Secondary structure


  Due to hydrogen bonding between the main groups of neighbouring amino acids folding begins to occur. The bonds/structures that form are alpha helix and beta pleated sheets.
• Tertiary structure

  -tertiary structures can contain more hydrogen bonds between main groups and R groups resulting in more folding. -R groups containing sulfur atoms in close proximity could form a disulphide bridge

  -many of the carboxyl and amine groups are charged therefore if they are near, as they are oppositely charged, it will form ionic bonds. -hydrophobic R groups will cluster together to form a hydrophobic region with distance to water
• Tertiary structure 


  Due to additional folding due to all of the bonds in the diagram to the left. A tertiary structure protein will form a unique fibrous or 3D globular shape
• Fibrous


  -similar to cellulose as a structural polysaccharide, COLLOGEN

  -repeating units of glycine and proline provide structural regularity and therefore strength to this fibrous protein

  -collagen also has many repeating chains that offer strength for this structurally fibrous protein
• Globular proteins


  -similar to enzymes, peptide hormones like insulin are globular in structure

  -insulin is kept inactive in the pancreas by being joined in a dimer

  -when these dimers are separate, the insulin becomes activated lowering blood glucose
• Quaternary structure 


  When more than one polypeptide chain need to combine to perform a certain function- often associated with external groups, i.e HAEM/iron … e.g. haemoglobin