Understanding Large Biological Molecules: Proteins and Nucleic Acids

1. Chapter 5 The Structure and Function of Large Biological Molecules

2. You Must Know • The role of dehydration synthesisin the formation of organic compounds and hydrolysis in the digestion of organic compounds. • How to recognize the 4 biologically important organic compounds (carbs, lipids, proteins, nucleic acids) by their structural formulas. • The cellular functions of all four organic compounds. • The 4 structural levels of proteins • How proteins reach their final shape (conformation) and the denaturing impact that heat and pH can have on protein structure

3. ie. amino acid  peptide  polypeptide  protein larger smaller

4. + H2O + + H2O +

6. I. Proteins Myoglobin protein • “Proteios” = first or primary • 50% dry weight of cells • Contains: C, H, O, N, S

7. Protein Functions (+ examples) • Enzymes (lactase) • Defense (antibodies) • Storage (milk protein = casein) • Transport (hemoglobin) • Hormones (insulin) • Receptors • Movement (motor proteins) • Structure (keratin)

8. Overview of protein functions

9. Overview of protein functions

10. Four Levels of Protein Structure • Primary • Amino acid (AA) sequence • 20 different AA’s • peptide bonds link AA’s

11. Amino Acid • R group = side chains • Properties: • hydrophobic • hydrophilic • ionic (acids & bases) • “amino” : -NH2 • “acid” : -COOH

14. Four Levels of Protein Structure (continued) • Secondary • Gains 3-D shape (folds, coils) by H-bonding • Alpha (α) helix, Beta (β) pleated sheet

15. Basic Principles of Protein Folding Hydrophobic AA buried in interior of protein (hydrophobic interactions) Hydrophilic AA exposed on surface of protein (hydrogen bonds) Acidic + Basic AA form salt bridges (ionic bonds). Cysteines can form disulfide bonds.

16. Four Levels of Protein Structure (continued) • Tertiary • Bonding between side chains (R groups) of amino acids • H bonds, ionic bonds, disulfide bridges, van der Waals interactions

17. Four Levels of Protein Structure (continued) • Quaternary • 2+ polypeptides bond together

18. amino acids  polypeptides  protein Bonding (ionic & H) can create asymmetrical attractions

19. Chaperonins assist in proper folding of proteins

20. Protein structure and function are sensitive to chemical and physical conditions • Unfolds or denatures if pH and temperature are not optimal

21. change in structure = change in function

22. II. Nucleic Acids Function: store hereditary info

23. Nucleotides: monomer of DNA/RNA Nucleotide = Sugar + Phosphate + Nitrogen Base

24. Nucleotide phosphate A – T G – C Nitrogen base 5-C sugar

26. Information flow in a cell:DNA  RNA  protein

27. III. Carbohydrates Differ in position & orientation of glycosidic linkage • Fueland building material • Include simple sugars (fructose) and polymers (starch) • Ratio of 1 carbon: 2 hydrogen: 1 oxygen or CH2O • monosaccharide disaccharide  polysaccharide • Monosaccharides = monomers (eg. glucose, ribose) • Polysaccharides: • Storage (plants-starch, animals-glycogen) • Structure (plant-cellulose, arthropod-chitin)

28. The structure and classification of some monosaccharides

29. Linear and ring forms of glucose

30. Carbohydrate synthesis

31. Cellulose vs. Starch Two Forms of Glucose:  glucose &  glucose

32. Cellulose vs. Starch • Starch =  glucose monomers • Cellulose =  glucose monomers

33. Storage polysaccharides of plants (starch) and animals (glycogen)

34. Structural polysaccharides: cellulose & chitin (exoskeleton)

35. II. Lipids Hydrophilic head Hydrophobic tail • Fats (triglyceride): store energy • Glycerol + 3 Fatty Acids • saturated, unsaturated, polyunsaturated • Steroids: cholesterol and hormones • Phospholipids: lipid bilayer of cell membrane • hydrophilic head, hydrophobic tails

38. Cholesterol, a steroid

39. The structure of a phospholipid

40. Hydrophobic/hydrophilic interactions make a phospholipid bilayer