1. Proteins Review

2. Learning outcomes (e) Describe the structure of an amino acid and the formation and breakage of a peptide bond. (f) Explain the meaning of the terms primary structure, secondary structure, tertiary structure and quaternary structure of proteins, and describe the types of bonding (hydrogen, ionic, disulfide and hydrophobic interactions) which hold the molecule in shape. (g) Analyse the molecular structure of a protein with a quaternary structure e.g. haemoglobin, as an example of a globular protein, and of collagen as an example of a fibrous protein, and relate these structures to their functions.

3. Learning outcomes (e) Describe the structure of an amino acid and the formation and breakage of a peptide bond. (f) Explain the meaning of the terms primary structure, secondary structure, tertiary structure and quaternary structure of proteins, and describe the types of bonding (hydrogen, ionic, disulfide and hydrophobic interactions) which hold the molecule in shape. (g) Analyse the molecular structure of a protein with a quaternary structure e.g. haemoglobin, as an example of a globular protein, and of collagen as an example of a fibrous protein, and relate these structures to their functions.

4. Amino Acid

5. Zwitterion

6. Peptide Bond

7. Learning outcomes (e) Describe the structure of an amino acid and the formation and breakage of a peptide bond. (f) Explain the meaning of the terms primary structure, secondary structure, tertiary structure and quaternary structure of proteins, and describe the types of bonding (hydrogen, ionic, disulfide and hydrophobic interactions) which hold the molecule in shape. (g) Analyse the molecular structure of a protein with a quaternary structure e.g. haemoglobin, as an example of a globular protein, and of collagen as an example of a fibrous protein, and relate these structures to their functions.

8. Levels of protein structure Primary: The specific number and linear sequence of amino acids in a polypeptide chain Secondary: The regular coiling and folding of regions of the polypeptide chain held together by regularly spaced hydrogen bonds formed at the polypeptide backbone Tertiary: The further bending, twisting and folding of the secondary structure to give the precise 3-dimensional conformation of the protein Quaternary: The overall protein structure that results from the association of 2 or more polypeptides to form a functional protein

9. Bonds involved LvlBondsBetween 1PeptideAmino acids 2Hydrogen-N-H and –C=O groups on pp backbone 3Hydrogen bonds, hydrophobic interactions, ionic bonds, disulphide bonds R-groups of amino acid residues 4

10. Structure determines Function

11. Learning outcomes (e) Describe the structure of an amino acid and the formation and breakage of a peptide bond. (f) Explain the meaning of the terms primary structure, secondary structure, tertiary structure and quaternary structure of proteins, and describe the types of bonding (hydrogen, ionic, disulfide and hydrophobic interactions) which hold the molecule in shape. (g) Analyse the molecular structure of a protein with a quaternary structure e.g. haemoglobin, as an example of a globular protein, and of collagen as an example of a fibrous protein, and relate these structures to their functions.

12. Hemoglobin StructureFunction Tetrameric – 2 α chains and 2 β chains Quaternary structure allows co-operativity* Globular with hydrophilic R groups on surface Soluble, tpt protein for oxygen in blood Each polypeptide has 8 α helices and… - …a haem prosthetic group that can each bind 1 molecule of oxygen Tpt protein for oxygen

13. Collagen StructureFunction Primary: Gly-X-Y (Gly-Pro-HyPro/HyLys)- Secondary (special!): α chain- Quaternary: Tropocollagen- Within tropocollagen – extensive hydrogen bonding between –N-H and –C=O groups between polypeptides High tensile strength, important for a structural protein Between tropocollagen molecules – covalent cross-links at N and C termini Covalent bonds confer strength and rigidity Fibrils  FibresInsoluble fibrous protein

15. REMINDER Lecture Test is Term 2 Week 5, Monday!