Protein Structure

Protein Structure

1. Two groups

   • Globular Proteins
     • Take part in reactions
     • Enzymes
     • Roughly spherical
   • Fibrous Proteins
     • Have structural roles
       • Such as giving strength or elasticity
     • E.g. Collagen and keratin

2. Made up of amino acids

   • Join together in a condensation reaction
     • Chain of amino acids is called a polypeptide
       • Proteins consist of one or more polypeptide
     • 2 amino acids form a dipeptide
   • 20 different amino acids
     • Join together in any order
       • Infinite number of different protein molecules

3. Contain carbon, hydrogen, oxygen and nitrogen. They often contain sulfur and phosphorus

4. Four levels

   • Primary Structure
     • The sequence of amino acids in the polypeptide
   • Secondary Structure
     • The twisting and folding of the polypeptide chain to form an alpha helix or beta pleated sheet, held together by hydrogen bonds
   • Tertiary Structure
     • The complex twisting and folding of the polypeptide chain to give a 3 dimensional shape. Held together by bonds between the R groups
       • Hydrogen bonds, ionic bonds, covalent bonds, disulfide bonds
   • Quaternary Structure
     • The presence of more than one polypeptide chain in a protein. The polypeptide chain are held together by bonds between R groups AND/OR the presence of non-protein prosthetic groups in the working protein

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