1. Homework for next week Green q 1,2,3 p29 Do evaluation points from Biuret Practical Revise test on all work next week Bring evidence you have revised please

2. 3.1.2 Protein structure The relationship between primary, secondary, tertiary and quaternary structure to function in proteins

3. Revise Structure of amino acid Formation of a peptide bond

4. C amino group carboxylic acid group R group is different in different amino acids) Amino Acid Structure text p.26

5. Peptide bonds and dipeptides

6. Peptides

7. Polypeptides When more amino acids are added to a dipeptide, a polypeptide chain is formed. A protein consists of one or more polypeptide chains folded into a highly specific 3D shape. There are up to four levels of structure in a protein: primary, secondary, tertiary and quaternary. Each of these play an important role in the overall structure and function of the protein.

8. Protein structure Text p.26

9. The structure of proteins

10. Protein structure cont.. Secondary structure Hydrogen Bonds occur between the NH and C=O of the peptide bond, between different amino acids in the chain 1 hydrogen bond is weak The chain coils up into a helix shape (called ALPHA HELIX) (Beta pleated sheet is a different shape of secondary structure – again held by H bonds) Protein may have none, just alpha helix, just beta pleated sheet or both forms of secondary structure Alpha helixBeta pleated sheet

12. Tertiary structure Further folding to give a complex 3d shape known as tertiary structure Shape is called GLOBULAR Depends on the a.a. sequence 3 types of bonds holding tertiary structure in place: 1 disulphide bonds – strong (between S in adjacent ‘R’ groups) 2 ionic between carboxyl and amino groups not involved in peptide bonds. Weaker than covalent, broken by extremes of pH 3 hydrogen bonds -numerous, weak animation

13. Sulphur-containing amino acid Active site The tertiary structure of an enzyme

14. Quaternary structure 2 or more polypeptide chains joined together Same types of bond hold it as tertiary structure (all 3) There can be non- protein (prosthetic) groups e.g. haem group containing iron E.g. haemoglobin Haemoglobin Molecule

15. Globular protein 3˚ Metabolic eg. Enzymes, hormones

16. Fibrous protein eg. Keratin (hair), collagen (tendons).

17. Levels of protein structure LevelDescriptionBondsBetween groups Primary 1 o Sequence of amino acids PeptideAmino and carboxylic acid Secondary 2 o Alpha helix Beta sheet Hydrogen bondsC=O and N-H Tertiary 3 o Folding Globular shape Disulphide (Ionic) (Hydrogen) Amino acids with sulphur in Quaternary 4 o More than 1 polypeptide joined together As tertiary

18. Protein structure

19. 3.1.2 Protein structure The relationship between primary, secondary, tertiary and quaternary structure to function in proteins A student model

20. Use a highlighter to show what is ON YOUR SYLLABUS (get it out!)