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Large Biological Molecules: Proteins, Nucleic Acids, Carbs, Lipids Structure & Functions

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

  2. You Must Know • The role of dehydration synthesis in the formation of organic compounds and hydrolysisin 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 denaturingimpact that heat and pH can have on protein structure

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

  4. + H2O + + H2O +

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

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

  7. Overview of protein functions

  8. Overview of protein functions

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

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

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

  12. 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.

  13. 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

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

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

  16. Chaperoninsassist in proper folding of proteins

  17. Protein structure and function are sensitive to chemical and physical conditions • Unfolds or denaturesif pHand temperature are not optimal

  18. change in structure = change in function

  19. II. Nucleic Acids Function: store hereditary info

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

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

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

  23. III. Carbohydrates • 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) Differ in position & orientation of glycosidic linkage

  24. The structure and classification of some monosaccharides

  25. Linear and ring forms of glucose

  26. Carbohydrate synthesis

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

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

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

  30. Structural polysaccharides: cellulose & chitin (exoskeleton)

  31. IV. Lipids • 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 Hydrophilic head Hydrophobic tail

  32. Cholesterol, a steroid

  33. The structure of a phospholipid

  34. Hydrophobic/hydrophilic interactions make a phospholipid bilayer

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