1. Molecular Biology 2.4 Proteins

2. Made of C, H, O and N Proteins are large molecules constructed of many amino acids Most abundant organic compound found in living cells

3. Most important macromolecule in the body… Proteins Rule Everything! Functions? Structural parts  nails, hair, cell membrane, and cartilage Pigments  skin, eyes, and chlorophyll Hormones and receptors Muscle contractions Immunity-Antibodies Enzymes Cytoskeleton Blood clotting Transport of nutrients/gases Cell adhesion Cell membrane transport Packing of DNA

4. Total energy gain is 4 Calories/gram. (however, energy gain is not their main function).

5. Amino acids are linked together by condensation reactions to form polypeptides. The building blocks of proteins are amino acids.

6. Amino Acids Centre carbon atom Bonded to: Hydrogen (H) Amine group (-NH 2 ) Carboxyl group (-COOH) R- group (different in each amino acid)

7. Amino acids are linked together by condensation reactions to form polypeptides. The amino acids are bonded together by peptide bonds to form proteins.

8. The bond that is formed from the acid group (COOH) and the amino group (NH 2 ) Water is eliminated = condensation reaction Proteins are frequently called polypeptides (many peptide bonds).

9. The smallest polypeptide consists of 20 amino acids (less than that called an “oligopeptide)  Insulin contains 2 polypeptides: 21 amino acids and 30 amino acids  Human titin has 34 350 amino acids

10. There are 20 different amino acids used by ribosomes to make polypeptides

11. Draw molecular diagrams to show the formation of a peptide bond: Locate the Amine, Carboxyl, and R-groups Show the formation of a peptide bond between 2 amino acid Try to draw an oligopeptide with all 4 SerineGlutamic acid Alanine Glycine

12. Did you notice? The amine and carboxyl are used in the peptide bonds Chain of atoms linked with single bonds form backbone H attached to N by single bond O attached to C by double bond The R-groups remain SerineGlutamic acid Alanine Glycine

13. The amine and carboxyl group are used in the condensation reaction The R-groups give the polypeptide its character The R-groups provide an amazing range of proteins

14. Some proteins contain amino acids not contained in the list of 20. This is due to modification after a polypeptide has been made. Example: hydroxyproline in collagen

15. Patterns, trends, discrepancies: most but not all organisms assemble polypeptides from the same amino acids. We can exclude the possibility that this trend is due to chance… What reasons would account for almost all organisms using the same 20 amino acids?  These were the ones produced before life  These are the ideal  All life evolved from a single ancestral species

16. Amino acids can be linked together in any sequence giving a huge range of possible polypeptides

17. Calculate the possibilities Number of Amino Acids in the Chain Number of possible sequences 120 1 220 2 400 3 8000 4 64 000 000

18. Shapes –  primary (linear)  secondary (β-pleated sheets and α-helix)  tertiary (bent-coiled)  quaternary (compact with a specific structure).

19. You can unfold a protein (de-nature) by exposing the protein to heat, radiation or a change in pH. (i.e. frying an egg, baking a cake, UV exposure, x-rays).

20. Questions 1. What 2 functional groups do all amino acids have in common? 2. Draw a generic formation of a peptide bond. Identify the amino terminus, carboxyl terminus, and peptide bond. 3. Define primary structure. 4. Name the 2 types of secondary structure. What type of bond stabilizes this structure? 5. Distinguish between polypeptide and protein. 6. Why do proteins have more diverse functional roles than carbohydrates?