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The structure & function of large biological macromolecules
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The structure & function of large biological macromolecules

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  1. The structure & function of large biological macromolecules Campbell and Reece CHAPTER 5

  2. Macromolecules are Polymers • polymer: long molecule consisting of many similar, sometimes identical, building blocks linked by covalent bonds • monomer: the smaller units that make up a polymer

  3. Many Monomers Make a Polymer

  4. Making Polymers • 2 monomers joined by dehydration reaction

  5. Disassembling Polymers • hydrolysis reaction breaks apart 2 monomers in a polymer

  6. Diversity of Polymers • possible varieties of macromolecules infinite • only use 40 -50 monomers • small molecules common to all organisms are ordered into species unique macromolecules

  7. Carbohydrates • Simple Carbohydrates • Sugars • Monosaccharides • Disaccharides • Complex Carbohydrates • Polysaccharides

  8. Monosaccharides • multiples of the unit CH2O • glucose most common monosaccharide

  9. Monosaccharide Diversity • depending on position of the carbonyl group in a sugar it is classified as either: • aldose (aldehyde sugar) • ketose (ketone sugar)

  10. Monosaccharide Diversity • 3 to 7 carbons • hexose: 6 carbons long • pentose: 5 carbons • triose: 3 carbons

  11. Monosaccharide Diversity • most hexoses and pentoses form rings in aqueous solutions • used in cellular respiration (especially glucose) • serve as raw materials for synthesis of amino acids and fatty acids • if not immediately used in these ways used to build disaccharides or polysaccharides

  12. Forms of Glucose Alpha Glucose Beta Glucose

  13. Disaccharides • reaction: 2 monosaccharides joined in a glycosidic linkage • covalent bond formed by dehydration reaction

  14. Disaccharides • 2 glucose = maltose (malt sugar) • glucose + galactose • glucose + fructose = sucrose (table sugar) • sucrose: form plants use to transport sugars from leaves  roots & other nonphotosynthetic parts of plant

  15. Polysaccharides • polymers of hundreds to thousands of monosaccharides joined by glycosidic linkages • function determined by its sugar monomers & positions of glycosidic linkages • 2 types: • storage of monosaccharides to be used for energy when needed • building material

  16. Storage Polysaccharides • Plants store glucose (the monomers)as starch (the polymer) • represents stored energy

  17. Starch • most is made of α glucose monomers joined in 1-4 linkages • simplest form of starch (amylose) is unbranched • complex starch, amylopectin, has 1-6 linkage

  18. Storage Polysaccharides • Animals: store glucose (the monomers) as glycogen (the polymer) in 1-4 & 1-6 linkages • stored mainly in liver & muscle cells • humans store about 1 days supply of glucose this way

  19. Structural Polysaccharides • Cellulose: most abundant organic cpd on Earth • is polymer of β glucose (makes every monomer of glucose “upside down” from its neighbors)

  20. Starch & Cellulose Starch Cellulose • many are mostly helical • digested by enzymes breaking its α linkages • never branched • has –OH groups available for H-bonds • digested by enzymes breaking its β linkages

  21. Cellulose • digested by very few organisms (don’t have enzymes to do it) • in humans: passes thru GI tract abrading walls & stimulating mucus secretion along the way  smoother passage of food thru • not technically a nutrient but is important

  22. “Insoluble Fiber” = Cellulose

  23. Cellulose • Cows: have bacteria and protists in their guts that have enzymes that can digest cellulose  nutrients that can be used by cow • Termites unable to digest cellulose in wood it eats have prokaryotes & protists to break it down and so termite can use nutrients

  24. Termite Life Cycle

  25. Termites

  26. Chitin • another structural polysaccharide • used by arthropods to build exoskeletons • exoskeletons: made of chitin + calcium carbonate

  27. Chitin • also in many fungi cell walls • monomer has N group attached

  28. Lipids • large group of hydrophobic molecules • do not have true monomers • Includes: • Waxes • Steroids • Some Pigments • Oils, Fats • Phospholipids

  29. Fats • large molecules assembled from smaller molecules by a dehydration reaction • 2 parts: • Glycerol • Fatty Acid

  30. Glycerol

  31. Fatty Acids • long (16-18) chain of carbons (hydrophobic) • @ one end carboxyl group (hence fatty acid)

  32. Triglyceride • 3 fatty acids + glycerol

  33. Saturated & Unsaturated

  34. Saturated Fats • include most animal fats • most are solids @ room temperatures

  35. Unsaturated Fats • fats of plants, fish • usually liquid @ room temperature

  36. Hydrogenated Vegetable Oil • seen on some food labels • means that unsaturated fats have been synthetically converted to saturated fats to keep from separating

  37. Plaques • deposits of saturated & trans fats (hydrogenated vegetable oils with trans double bonds) in muscularis of arteries

  38. Plaques • lead to atherosclerosis (leading cause of heart attacks) by decreasing resilience of vessel & impeding blood flow

  39. Trans Fats • USDA now requires nutritional labels to include amount of trans fats • some cities & Denmark ban restaurants from using trans fats

  40. Essential Fatty Acids • cannot be synthesized in body so must be included in diet • include: omega-3 fatty acids: • required for normal growth in children • probably protect against cardiovascular disease in adults

  41. Omega-3 Fatty Acids

  42. Energy Storage • 1 g fat has 2x chemical potential energy as 1 g of polysaccharide • plants (generally immobile) can store majority of their energy in polysaccharides except vegetable oils extracted from their seeds

  43. Functions of Fat • Plants: storage of energy • Animals: • storage of energy • protect organs • insulation

  44. Phospholipids • essential component of cell membranes

  45. Phospholipids • when added to water self-assemble into lipid bilayers

  46. Steroids • lipids characterized by a carbon skeleton made of 4 fused rings • cholesterol & sex hormones have functional groups attached to these fused rings