Chapter 5 The Structure and Function of Macromolecules

1. Chapter 5The Structure and Function of Macromolecules 3 themes are emphasized Hierarchy of structural levels Emergent properties Form fits function

2. Polymers • Monomers- units that comprise a polymer • Polymer- long molecule consisting of many similar or identical building blocks linked by covalent bonds

3. Polymer formation • Condensation reaction- linking of monomers through the loss of a water molecule (dehydration reaction)

4. Polymer formation • One molecules provides the hydroxyl group (-OH) and the other the hydrogen (-H). • Requires energy and enzymes

5. Polymer disassembly • Hydrolysis- dissemble polymers • Water is added to break a bond • Ex: digestion- food polymers broken down by enzymes

7. Classes of Polymers • Carbohydrates • Lipids • Proteins • Nucleic Acids • Other

8. Carbohydrates • Monomers called monosaccharides • Cellular use: energy, energy storage, structure • (C, 2H, O)n • Monosaccharides, disaccharides, and polysaccharides

9. Monosaccharides • Glucose • Aldehydes and ketones • Linear and ring forms

11. Disaccharides • 2 monosaccharides, sucrose = glucose+fructose • Joined by a condensation synthesis called a glycosidic linkage.

13. Polysaccharides • Several hundred or more monosaccharides • Energy storage: starch and glycogen • Structural: cellulose and chitin

14. Starch • Storage of polysaccaharides in plants, made up glucose monomers • Provides a way to store surplus glucose, energy can be withdrawn by hydrolysis • Humans have enzymes that can hydrolyze plant starch. High sources of starch found in potatoes, grains (wheat, corn, rice).

15. Glycogen • Used by animals to store glucose. • More extensively branched than plant starch. • Stored mainly in liver and muscle cells. Humans can only store enough energy for about a day.

16. Cellulose • Polysaccharide used by plants from structure. • Similar to starch except in the location of the glucose bond: • Starch- alpha linkage, helical shape • Cellulose- beta linkage, straight shape • Opposing hydroxyl groups bond with other strands, creating strong fibers.

18. Why don’t humans eat grass?

20. Chitin • structural polysaccharide used by arthropods (insects, spiders, crustaceans) to build their exoskeleton • Also used by fungi rather than cellulose for their cell walls. • Similar to cellulose except has a nitrogen appendage to the glucose.

22. Lipids • Fats • Not polymers but Large molecules, composed of smaller molecules, assembled by dehydration reactions • Not soluble in water. C-H bonds are non polar

23. Triglycerides • Fat molecule = Triacylglycerol (or triglyceride) • Triacyglycerol= Glycerol + 3 fatty acids • Linked by ester linkage (condensation reaction) • Oils and fats

24. Animal fat vs. Plant and Fish fat • Saturated fat vs unsaturated fat • Animal fat- usually saturated- solid at room temperature • Plant and fish fat- usually unsaturated- liquid at room temperature

26. Fat- what is it good for? • Fat- stores energy • 1 gram of fat stores 2x energy as starch • Stored in adipose cells • Cushions vital organs • Provide insulation

27. Phospholipids • 2 fatty acids + phosphate group + glycerol

28. Phospholipids • Various molecules attach to the phosphate group  • Tails are hydrophobic • Heads are hydrophilic • What do they do in water?

29. Phospholipids • When added to water- they self assemble so that they shield their hydrophobic tails • Micelle- phospholipid droplet, phosphate heads on the outside, tails are restricted to the water-free interior • Phospholipid bilayer- major component of cell membranes

30. Steroids • Four interlocking carbon rings • Regulatory molecules- sex hormones • Cholesterol-precursor of many steroids • Cholesterol is a component of cell membranes • Cholesterol can contribute to atherosclerosis

32. Proteins • Monomers called amino acids • 20 different amino acids • Joined by peptide linkage • Chains of amino acids- polypeptide • Function as support, storage, transport, signaling, defense, movement, and catalysts • C, H, O, N, S • Make up 50% of cellular DRY weight

33. Tens of thousands different types in humans • Enzymes- regulate metabolism, accelerate chemical reactions

34. Amino Acid Structure • Contains 3 functional groups • Amino, carboxyl and R groups • Polar, nonpolar, charged and uncharged

37. Amino acid linkage • Peptide bond- covalent bond catalyzed by a dehydration reaction

39. Amino end: N-terminus Carboxyl end: C-terminus

41. “Polypeptide” vs “Protein” • Protein- one or more polypeptides twisted, folded, and coiled.

42. Four Levels of Protein Organization • Primary- sequence of amino acids

44. Sequence determines function • 20 different amino acids • Lysozyme- protein that helps fight bacteria • 129 amino acids long • 20129 possible combinations • Sickle cell disease is caused by one protein substitution in the structure of hemoglobin.

45. Four Levels of Protein Organization • Primary- sequence of amino acids • Secondary- coils or folds

46. Secondary- coils and folds • Result from hydrogen bonding on the backbone of the chain (not the R groups) • Oxygen and nitrogen are electronegative with partial negative charges. • Hydrogen molecules attached to Nitrogen have partial positive charges.

47. Secondary coil • Alpha helix- delicate coil held together by hydrogen bonding between every fourth amino acid

48. Secondary Fold • Beta pleated sheet- two or more parallel chains. Held together by hydrogen bonds of the backbone.

50. Four Levels of Protein Organization • Primary- sequence of amino acids • Secondary- coils or folds • Tertiary- R group interaction