Protein structure

• Define primary protein structure?

  • Definition: The sequence of amino acids in a polypeptide chain held together by peptide bonds
• Describe the importance of primary protein structure?

  • Importance: Determines the proteins shape and function. Any changes to this sequence (mutations) can change the protein's properties
• Describe the key features of primary protein structure?

  Key features:

  • Linear sequence
  • Peptide bond formed during condensation reaction between a hydrogen atom of the amine group of one amino acid and the hydroxyl group of the carboxylic acid of another amino acid
• Define the secondary protein structure?

  The folding or coiling of polypeptide chain into alpha-helices or beta-pleated sheets, stabilised by hydrogen bonds
• Describe the tertiary structure?

  • More bonds form between the different R groups to give the protein a 3D shape
  • R group interactions involve hydrogen bonds, disulfide bonds, ionic bonds and polar interactions
  • If proteins are made of a single polypeptide chain, this is their final overall structure
• Describe the quaternary protein structure? Describe an example?

  • Formed by the interaction of multiple polypeptide chains held together by bonds
  • Haemoglobin consists of four polypeptide chains ( two alpha and two beta) bonded together
  • Each chain surrounds an iron containing haem group. The haem group is referred to as the prosthetic group- the non- protein components required for protein function