Structural Levels

• How many structural levels do proteins have?

  four
• Are proteins big and complicated molecules?

  yes
• how can you describe the structure of proteins?

  in four 'level'
• what are the 4 levels?

  a protein's primary, secondary, tertiary and quaternary structures
• What is a protein's primary structure?


  This is the sequence of amino acids in the polypeptide chain
• What is a protein's secondary structure?


  • The polypeptide chain doesn't remain flat and straight
  • Hydrogen bonds form between the amino acids in the chain
  • This makes it automatically coil into an alpha helix or fold into a beta pleated sheet - this is the SECONDARY STRUCTURE
• What is a protein's tertiary structure?


  • the coiled or folded chain of amino acids is often coiled and folded further
  • more bonds form between different parts of the polypeptide chain (including hydrogen bonds and ionic bonds)
  • Disulfide bridges also form whenever two molecules of the amino acid CYSTEINE come close together - the sulfur atom in one cysteine bonds to the sulfur atom in the other
  • FOR PROTEINS MADE FROM A SINGLE POLYPEPTIDE CHAIN, THE TERTIARY STRUCUTE FORMS THEIR FINAL 3D STRUCTURE
• What are IONIC BONDS?


  Attractions between negative and positive charges on different parts of the molecule
• why is the tertiary strucutre important for proteins made from a SINGLE polypeptide chain?

  the tertiary structure forms their final 3D structure
• what is a protein's quaternary structure?

  • Some proteins are made of several different polypeptide chains held together by bonds
  • The quaternary structure is the way these polypeptide chains are assembled toggether
  • for proteins made from more than one polypeptide chain the quaternary structure is the protein's final 3D structure
• give examples of proteins with more than one polypeptide chain ?

  haemoglobin insulin collagen]