Overview The Molecules of Life Within cells small organic molecules are joined together to form larger molecules Macromolecules are large molecules composed of thousands of covalently connected atoms ID: 1044896
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1. Chapter 5The Structure and Function of Macromolecules
2. Overview: The Molecules of LifeWithin cells, small organic molecules are joined together to form larger moleculesMacromolecules are large molecules composed of thousands of covalently connected atoms
3. Concept 5.1: Most macromolecules are polymers, built from monomersA polymer is a long molecule consisting of many similar building blocks called monomersThree of the four classes of life’s organic molecules are polymers:CarbohydratesProteinsNucleic acids
4. The Synthesis and Breakdown of PolymersMonomers form larger molecules by condensation reactions called dehydration reactionsPolymers are disassembled to monomers by hydrolysis, a reaction that is essentially the reverse of the dehydration reactionAnimation: Polymers
5. LE 5-2Short polymerUnlinked monomerDehydration removes a watermolecule, forming a new bondDehydration reaction in the synthesis of a polymerLonger polymerHydrolysis adds a watermolecule, breaking a bondHydrolysis of a polymer
6. Concept 5.2: Carbohydrates serve as fuel and building materialCarbohydrates include sugars and the polymers of sugarsThe simplest carbohydrates are monosaccharides, or single sugarsCarbohydrate macromolecules are polysaccharides, polymers composed of many sugar building blocks
7. SugarsMonosaccharides have molecular formulas that are usually multiples of CH2OGlucose is the most common monosaccharideMonosaccharides are classified by location of the carbonyl group and by number of carbons in the carbon skeleton
8. LE 5-3Triose sugars(C3H6O3)GlyceraldehydeAldosesKetoses Pentose sugars(C5H10O5)RiboseHexose sugars(C5H12O6)GlucoseGalactoseDihydroxyacetoneRibuloseFructose
9. Monosaccharides serve as a major fuel for cells and as raw material for building molecules Though often drawn as a linear skeleton, in aqueous solutions they form rings
10. LE 5-4Linear andring formsAbbreviated ringstructure
11. A disaccharide is formed when a dehydration reaction joins two monosaccharides This covalent bond is called a glycosidic linkageAnimation: Disaccharides
12. LE 5-5GlucoseMaltoseFructoseSucroseGlucoseGlucoseDehydrationreaction in thesynthesis of maltoseDehydrationreaction in thesynthesis of sucrose1–4glycosidiclinkage1–2glycosidiclinkage
13. The bulk of sucralose ingested does not leave the GI tract and is directly excreted in the feces. The small amount that is absorbed from the GI tract is removed from the blood stream by the kidneys and excreted in the urine. Sucralose is digestible by a number of microorganisms and is broken down once released into the environment.
14. PolysaccharidesPolysaccharides, the polymers of sugars, have storage and structural rolesThe structure and function of a polysaccharide are determined by its sugar monomers and the positions of glycosidic linkages
15. Storage PolysaccharidesStarch, a storage polysaccharide of plants, consists entirely of glucose monomersPlants store surplus starch as granules within chloroplasts and other plastids
16. LE 5-6aChloroplastStarch1 µmAmyloseStarch: a plant polysaccharideAmylopectin
17. Glycogen is a storage polysaccharide in animalsHumans and other vertebrates store glycogen mainly in liver and muscle cells
18. LE 5-6bMitochondriaGlycogen granules0.5 µmGlycogenGlycogen: an animal polysaccharide
19. Structural PolysaccharidesCellulose is a major component of the tough wall of plant cellsLike starch, cellulose is a polymer of glucose, but the glycosidic linkages differThe difference is based on two ring forms for glucose: alpha () and beta () Animation: Polysaccharides
20. LE 5-7a Glucosea and b glucose ring structuresb GlucoseStarch: 1–4 linkage of a glucose monomers.Cellulose: 1–4 linkage of b glucose monomers.
21. LE 5-8CellulosemoleculesCellulose microfibrilsin a plant cell wallCell wallsMicrofibrilPlant cells0.5 µmb Glucosemonomer
22. Enzymes that digest starch by hydrolyzing alpha linkages can’t hydrolyze beta linkages in celluloseCellulose in human food passes through the digestive tract as insoluble fiberSome microbes use enzymes to digest celluloseMany herbivores, from cows to termites, have symbiotic relationships with these microbes
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24. Chitin, another structural polysaccharide, is found in the exoskeleton of arthropodsChitin also provides structural support for the cell walls of many fungiChitin can be used as surgical thread
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26. Concept 5.3: Lipids are a diverse group of hydrophobic moleculesLipids are the one class of large biological molecules that do not form polymersThe unifying feature of lipids is having little or no affinity for waterLipids are hydrophobic becausethey consist mostly of hydrocarbons, which form nonpolar covalent bondsThe most biologically important lipids are fats, phospholipids, and steroids
27. FatsFats are constructed from two types of smaller molecules: glycerol and fatty acidsGlycerol is a three-carbon alcohol with a hydroxyl group attached to each carbonA fatty acid consists of a carboxyl group attached to a long carbon skeletonAnimation: Fats
28. LE 5-11aDehydration reaction in the synthesis of a fatGlycerolFatty acid(palmitic acid)
29. Fats separate from water because water molecules form hydrogen bonds with each other and exclude the fatsIn a fat, three fatty acids are joined to glycerol by an ester linkage, creating a triacylglycerol, or triglyceride
30. LE 5-11bEster linkageFat molecule (triacylglycerol)
31. Fatty acids vary in length (number of carbons) and in the number and locations of double bondsSaturated fatty acids have the maximum number of hydrogen atoms possible and no double bondsUnsaturated fatty acids have one or more double bondsThe major function of fats is energy storage
32. Fats made from saturated fatty acids are called saturated fatsMost animal fats are saturatedSaturated fats are solid at room temperatureA diet rich in saturated fats may contribute to cardiovascular disease through plaque deposits
33. LE 5-12aSaturated fat and fatty acid.Stearic acid
34. Fats made from unsaturated fatty acids are called unsaturated fatsPlant fats and fish fats are usually unsaturatedPlant fats and fish fats are liquid at room temperature and are called oils
35. LE 5-12bUnsaturated fat and fatty acid.Oleic acidcis double bondcauses bending
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37. Enzymes in your digestive system, called lipases, help digest (or break down) fat. When taken with meals, XENICAL attaches to the lipases and blocks them from breaking down some of the fat you have eaten.The undigested fat cannot be absorbed and is eliminated in your bowel movements. By working this way, XENICAL helps block about one-third of the fat in the foods you eat from being absorbed by your body. The most commonly reported side effects of Xenical include stomach pain and discomfort, gas, an urgent need to move the bowels, fatty or oily stools, oily rectal discharge, diarrhea, and a loss of bowel control. You're more likely to have these side effects with higher doses of medicine and with a high-fat diet.
38. PhospholipidsIn a phospholipid, two fatty acids and a phosphate group are attached to glycerol The two fatty acid tails are hydrophobic, but the phosphate group and its attachments form a hydrophilic head
39. LE 5-13Structural formulaSpace-filling modelPhospholipid symbolHydrophilicheadHydrophobictailsFatty acidsCholinePhosphateGlycerolHydrophobic tailsHydrophilic head
40. When phospholipids are added to water, they self-assemble into a bilayer, with the hydrophobic tails pointing toward the interiorThe structure of phospholipids results in a bilayer arrangement found in cell membranesPhospholipids are the major component of all cell membranes
41. LE 5-14WATERHydrophilicheadHydrophobictailsWATER
42. SteroidsSteroids are lipids characterized by a carbon skeleton consisting of four fused ringsCholesterol, an important steroid, is a component in animal cell membranesAlthough cholesterol is essential in animals, high levels in the blood may contribute to cardiovascular disease
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44. Concept 5.4: Proteins have many structures, resulting in a wide range of functionsProteins account for more than 50% of the dry mass of most cellsProtein functions include structural support, storage, transport, cellular communications, movement, and defense against foreign substances[Animations are listed on slides that follow the figure]
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46. Enzymes are a type of protein that acts as a catalyst, speeding up chemical reactions
47. LE 5-16Substrate(sucrose)Enzyme(sucrose)FructoseGlucose
48. PolypeptidesPolypeptides are polymers of amino acidsA protein consists of one or more polypeptides
49. Amino Acid MonomersAmino acids are organic molecules with carboxyl and amino groupsAmino acids differ in their properties due to differing side chains, called R groupsCells use 20 amino acids to make thousands of proteins
50. LE 5-UN78AminogroupCarboxylgroupa carbon
51. Amino Acid PolymersAmino acids are linked by peptide bondsA polypeptide is a polymer of amino acidsPolypeptides range in length from a few monomers to more than a thousandEach polypeptide has a unique linear sequence of amino acids
52. Determining the Amino Acid Sequence of a PolypeptideThe amino acid sequences of polypeptides were first determined by chemical methodsMost of the steps involved in sequencing a polypeptide are now automated
53. Protein Conformation and FunctionA functional protein consists of one or more polypeptides twisted, folded, and coiled into a unique shapeThe sequence of amino acids determines a protein’s three-dimensional conformationA protein’s conformation determines its function
54. Four Levels of Protein StructureThe primary structure of a protein is its unique sequence of amino acidsSecondary structure, found in most proteins, consists of coils and folds in the polypeptide chainTertiary structure is determined by interactions among various side chains (R groups)Quaternary structure results when a protein consists of multiple polypeptide chains
55. LE 5-20Amino acidsubunitsb pleated sheet+H3NAmino end helix
56. Primary structure, the sequence of amino acids in a protein, is like the order of letters in a long word Primary structure is determined by inherited genetic informationAnimation: Primary Protein Structure
57. LE 5-20aAmino acidsubunitsCarboxyl endAmino end
58. The coils and folds of secondary structure result from hydrogen bonds between repeating constituents of the polypeptide backboneTypical secondary structures are a coil called an alpha helix and a folded structure called a beta pleated sheetAnimation: Secondary Protein Structure
59. LE 5-20bAmino acidsubunitsb pleated sheet helix
60. Tertiary structure is determined by interactions between R groups, rather than interactions between backbone constituentsThese interactions between R groups include hydrogen bonds, ionic bonds, hydrophobic interactions, and van der Waals interactionsStrong covalent bonds called disulfide bridges may reinforce the protein’s conformationAnimation: Tertiary Protein Structure
61. LE 5-20dHydrophobicinteractions andvan der WaalsinteractionsPolypeptidebackboneDisulfide bridgeIonic bondHydrogenbond
62. Quaternary structure results when two or more polypeptide chains form one macromoleculeCollagen is a fibrous protein consisting of three polypeptides coiled like a ropeHemoglobin is a globular protein consisting of four polypeptides: two alpha and two beta chainsAnimation: Quaternary Protein Structure
63. LE 5-20eb Chainsa ChainsHemoglobinIronHemeCollagenPolypeptide chainPolypeptidechain
64. Sickle-Cell Disease: A Simple Change in Primary StructureA slight change in primary structure can affect a protein’s conformation and ability to function Sickle-cell disease, an inherited blood disorder, results from a single amino acid substitution in the protein hemoglobin
65. LE 5-21aRed bloodcell shapeNormal cells arefull of individualhemoglobinmolecules, eachcarrying oxygen.10 µm10 µmRed bloodcell shapeFibers of abnormalhemoglobin deformcell into sickleshape.
66. LE 5-21bPrimarystructureSecondaryand tertiarystructures123Normal hemoglobinValHisLeu4Thr5Pro6GluGlu7PrimarystructureSecondaryand tertiarystructures123Sickle-cell hemoglobinValHisLeu4Thr5Pro6ValGlu7QuaternarystructureNormalhemoglobin(top view)aaaaFunctionMolecules donot associatewith oneanother; eachcarries oxygen.QuaternarystructureSickle-cellhemoglobinFunctionMolecules interact withone another tocrystallize intoa fiber; capacityto carry oxygenis greatly reduced.Exposedhydrophobicregionb subunitb subunit
67. What Determines Protein Conformation?In addition to primary structure, physical and chemical conditions can affect conformationAlternations in pH, salt concentration, temperature, or other environmental factors can cause a protein to unravelThis loss of a protein’s native conformation is called denaturationA denatured protein is biologically inactive
68. LE 5-22DenaturationRenaturationDenatured proteinNormal protein
69. Concept 5.5: Nucleic acids store and transmit hereditary informationThe amino acid sequence of a polypeptide is programmed by a unit of inheritance called a geneGenes are made of DNA, a nucleic acid
70. The Roles of Nucleic AcidsThere are two types of nucleic acids:Deoxyribonucleic acid (DNA)Ribonucleic acid (RNA)DNA directs synthesis of messenger RNA (mRNA) and, through mRNA, controls protein synthesisProtein synthesis occurs in ribosomes
71. LE 5-25NUCLEUSDNACYTOPLASMmRNAmRNARibosomeAminoacids Synthesis ofmRNA in the nucleus Movement ofmRNA into cytoplasmvia nuclear pore Synthesis of proteinPolypeptide
72. The Structure of Nucleic AcidsNucleic acids are polymers called polynucleotidesEach polynucleotide is made of monomers called nucleotidesEach nucleotide consists of a nitrogenous base, a pentose sugar, and a phosphate group
73. LE 5-26a5¢ end3¢ endNucleosideNitrogenousbasePhosphategroupNucleotide Polynucleotide, ornucleic acidPentosesugar
74. Nucleotide MonomersIn DNA, the sugar is deoxyriboseIn RNA, the sugar is ribose
75. Nucleotide PolymersNucleotide polymers are linked together, building a polynucleotideAdjacent nucleotides are joined by covalent bonds- phosphodiester bondsThese links create a backbone of sugar-phosphate units with nitrogenous bases as appendagesThe sequence of bases along a DNA or mRNA polymer is unique for each gene
76. The DNA Double HelixA DNA molecule has two polynucleotides spiraling around an imaginary axis, forming a double helixOne DNA molecule includes many genesThe nitrogenous bases in DNA form hydrogen bonds in a complementary fashion: A always with T, and G always with C