1. Proteins

2. You need to know that: Proteins have a variety of functions within all living organisms. The general structure of an amino acid Condensation reactions form peptide bonds Amino acids link together to form polypeptides. The relationship between primary, secondary, tertiary and quaternary structure, and protein function. The biuret test for proteins.

3. Proteins Enzymes, carrier molecules, hormones, antibodies, cell membrane Over 50 % of a cells dry weight is Protein Basic Unit Molecule ▫Amino acids - 20 amino acids found in living systems

4. Amino acid structure AA-AADipeptide AA-AA-AA-AA-AAPolypeptide Bond between Amino acids - Peptide Bond

5. Amino acid structure

6. Levels of Structure 1. Primary 2. Secondary 3. Tertiary 4. Quaternary

7. Primary Level of Structure The linear sequence of Amino acids This is determined by the genetic code built into DNA of a gene

9. How amino acids combin e ↓ + H 2 O

10. Linking of amino acids This is a hydrolysis reaction The bond formed is a peptide bond

11. Secondary Level of Structure When the a chain of polypeptides takes on a specific orientation in space 2 Main Types ▫Alpha Helix ▫Beta Pleated Sheet

13. Tertiary Level of Structure Final 3 dimensional configuration Held together by many different bonds: ▫peptide ▫ionic ▫hydrogen ▫Covalent ▫Disulphide -S – S-

15. Quaternary Level of Structure When 2 or more proteins come together to form a functional unit

18. Biuret test for protein Place test solution in a test tube. Add equal volume of sodium hydroxide, (Biuret A) at room temp. Add few drops very dilute (0.05%) copper(II) sulphate solution, (Biuret B) and mix gently. Purple colouration = peptide bonds and so a protein. If it remains blue = no protein.

19. Questions What type of bond links amino acids together? What type of reaction is involved in linking amino acids together? What 4 different components make up an amino acid? Name the 2 bonds involved in holding together the primary structure of a protein. Name the bonds involved in holding together the secondary structure of a protein.

20. Denatured Temperature pH salt concentrations heavy metals