Proteins- how structure relates to function

Proteins- how structure relates to function

1. amino acids

   • monomers
   • the sequence is determined by DNA triplet code
   • carboxyll group
   • R group
     • hydrophobic towards centre
     • hydrophilic towards edges
   • amino group
   • hydrogen

2. 1.primary structure

   • peptide bond between amino acids
     • condensation
     • Biuret test
       • positive-lilac
       • negative-stays blue
   • polypeptides
     • the sequence determines the ultimate shape and function
       • almost limitless number of combinations
       • charge
         • polar or non polar
     • polymerisation
       • TRna brings the amino acids into a ribosome

3. 2.secondary structure

   • hydrogen bonds
     • between NH hydrogen and CO oxygen in amino acids
     • cause 3D shape
       • alpha helix coil
         • parallel strands with helical axis
           • strong and stable
       • beta pleated sheet
         • antiparallel strands

4. 3.tertiary structure

   • twisted and folded more
   • disulfide bridges
     • strong
   • ionic bonds
     • weak
   • hydrogen bonds
     • very weak
   • motifs and domains

5. 4.quaternary structure

   • many polypeptide chains
   • prosthetic groups too

6. examples

   • enzymes
     • held by hydrogen bonds
     • active site made of amino acids in a specific shape
     • structural complimentarity
   • haemoglobin
     • wide range of amino acids
     • globular-soluble
       • mainly alpha helixes
         • haem prosthetic group
   • collagen
     • fibrous-insoluble
       • mainly left handed helixes
         • no prosthetic group
     • 35% glycine amino acid

7. Types

   • fibrous
   • globular
     • soluble

8. denaturing

   • changes the structure
     • changes the function
       • high degree of specificity
   • conditions
     • ph
     • temperature