Lecture 5 Sept 9, 2005 MARMLEULES #1 arbohydrates Lecture outline: - Polymers -arbohydrates monomers and polymers And Lipids - Lipids Principles of Building Polymers: - biological polymers are built from simple small units called monomers - addition of each monomeric unit occurs with the removal of a water molecule A condensation dehydration reaction - ends are chemically distinct directionality of synthesis - requires energy input for polymerization; uses carrier molecules to activate monomers MDULAR DESIGN SIMPLIITY AND VERSATILITY ASSEMBLY-LINE MENTALITY Don t have to make every structure from scratch Simplified chemistry, repeating link Dehydration Synthesis
-XXXX- -YYY- -ZZZZZ- Dehydration Synthesis make by taking water away -XXXX- YYY-ZZZZZ- Monomers Polymer ydrolysis death by water Endless variety of Polymers rder of Monomers Different Amounts of each monomer -XXXX- YYY-ZZZZZ- -YYY-XXXX- ZZZZZ- -XXXX- ZZZZZ- YYY- -ZZZZZ- YYY-ZZZZZ- Monomers form larger molecules by condensation reactions called dehydration reactions Polymers can disassemble by ydrolysis 1 2 3 4 1 2 3 Short polymer Unlinked monomer ydrolysis adds a water molecule, breaking a bond 2 Dehydration removes a water molecule, forming a new bond 2 1 2 3 4 1 2 3 Figure 5.2A Longer polymer (a) Dehydration reaction in the synthesis of a polymer Figure 5.2B (b) ydrolysis of a polymer
Monomers Polymers Monomers: ARBYDRATES Sugars and Sugar Derivatives Polymers: Monosaccharides Simple Sugars Glucose Fructose Ribose ligosaccharides Informational structures Polysaccharides Long chains of monomers storage starch: amylose amylopectin glycogen structure Fiber: cellulose NSAARIDES = arbohydrate Monomers = = 1 arbonyl - aldehyde or ketone R-- R 1 --R 2 All ther ARBNS each have NE alcohol group Aldo sugar R- Expect them to be YDRPILI Keto sugar Monosaccharides Vary in length Aldoses Ketoses 3, 4, 5, 6 or 7 carbons Triose sugars ( 3 6 3 ) Pentose sugars ( 5 10 5 ) exose sugars ( 6 12 6 ) Glyceraldehyde Ribose Glucose Dihydroxyacetone Galactose
Also differ by SPATIAL GEMETRY Plane of symmetry Right handed D form Left handed L form arbon with 4 different functional groups hiral or asymmetric carbon = handed carbon Stereoisomers not the same Not chiral hiral hiral hiral hiral Not chiral Spatial Geometry yields a variety of forms Aldoses Ketoses Triose sugars ( 3 6 3 ) Pentose sugars ( 5 10 5 ) exose sugars ( 6 12 6 ) Glyceraldehyde Ribose Glucose Dihydroxyacetone Galactose 8 Forms!
5 and 6 arbon Sugars IRULARIZE in Water To FRM RINGS 1 6 2 6 2 Fischer projection aworth projection 2 3 4 5 6 4 5 3 5 2 1 4 3 2 1 4 2 6 5 3 2 1 Figure 5.4 (a) Linear and ring forms. hemical equilibrium between the linear and ring structures greatly favors the formation of rings. To form the glucose ring, carbon 1 bonds to the oxygen attached to carbon 5. ircularization causes another chiral carbon monomeric sugars coupled together by NDENSATIN REATIN α-d-glucose β-d-glucose (a) Dehydration reaction in the synthesis of maltose. The bonding of two glucose units forms maltose. The glycosidic link joins the number 1 carbon of one glucose to the number 4 carbon of the second glucose. Joining the glucose monomers in a different way would result in a different disaccharide. (b) Dehydration reaction in the synthesis of sucrose. Sucrose is a disaccharide formed from glucose and fructose. Notice that fructose, though a hexose like glucose, forms a five-sided ring. Figure 5.5 2 Glucose 2 Glucose 2 2 2 2 Glucose 2 Fructose Glycosidic bond 2 2 1 4 1 glycosidic 4 linkage Maltose 2 2 1 2 1 glycosidic 2 linkage 2 Sucrose
Disaccharides, ligosaccharides and Polysaccharides (two) (few) (many) ynthesis Requires Energy Input Breakdown Does not Require Energy Input DiSaccharides Sucrose (glucose+ fructose) Sugar Lactose (glucose+galactose) Sugar Maltose (glucose+glucose) ane Milk Beer ligosaccharides Dextran (short chain of glucose) Digested Starch Furans (short chain of fructose) nions Polysaccharides Long chains of Millions of monomers most common polymers made NLY of GLUSE monomers Storage reserves: Starch amylose amylopectin, glycogen hloroplast Starch Mitochondria Giycogen granules 0.5 µm Structure: cellulose 1 µm Glycogen Amylose Amylopectin Figure 5.6 (b) Glycogen: an animal polysaccharide
Structural Polysaccharides ellulose Is also a polymer of glucose Glycogen (or Amylopectin) But has different glycosidic linkages than starch olysaccharides of glucose chains in n a(1->4) linkage, with a(1->6) ranches We can readily digest starches but cannot digest cellulose ellulose is indigestable to animals ows and termites have microbes in their stomachs to facilitate this process 4 2 4 2 1 α glucose β glucose (a) α and β glucose ring structures Starches: α glycosidic linkage down 2 1 4 2 2 2 1 4 4 1 1 (b) Starch: 1 4 linkage of α glucose monomers Figure 5.9 ellulose: β glycosidic linkage up Figure 5.7 A 2 2 1 4 2 (c) ellulose: 1 4 linkage of β glucose monomers 2
ellulose ß(1->4) linkage Amylose a(1->4) linkage ell walls ellulose microfibrils in a plant cell wall Microfibril About 80 cellulose molecules associate to form a microfibril, the main architectural unit of the plant cell wall. 0.5 µm Plant cells Figure 5.8 Parallel cellulose molecules are held together by hydrogen bonds between hydroxyl groups attached to carbon atoms 3 and 6. 2 2 2 2 2 2 2 2 2 2 2 2 β Glucose monomer A cellulose molecule is an unbranched β glucose polymer. ellulose molecules Polysaccharides although hydrophillic are generally Insoluble in water Starch Polymer forms Secondary Structures Polymer hydrogen bonding to Itself polymer effect -orders too much water around polymer -Polymer tends to hydrogen bond to itself -Polymer falls out of solution
If Denature Secondary Structure an FRE polymer to stay ydrated Sugar Derrivatives (Break ydrogen Bonds of Polymer with Itself) Water will ydrogen bond With Polymer RESULT IS BUND WATER GEL Disrupt Secondary Structures -remain ydrated! haracteristics? Some ther Sugar Derivatives or Modified Sugars Missing one or more components: Questions?. 5 carbon RIBSE and DEXYRIBSE missing one alcohol a.. Glycerol - 3 arbon Sugar with alcohol in place of an aldehyde b.. Sugar amines, Sugar acids have amine or carboxylic acid group or something else in place of an alcohol - - - - - - - - - - c.
Figure 5.11 (b) Fat molecule (triacylglycerol) LIPIDS hydrophobic character Fatty Acid: carboxylic acid with LNG hydrocarbon chain F.A differ by: Triglycerides Phospholipids Steroids FATS ILS -long term storage depot MEMBRANES Membranes ormones ther hain length saturation Fatty Acids and Glycerol Fats Are constructed from two types of smaller molecules, a single glycerol and usually three fatty acids Fatty acid (palmitic acid) Glycerol (a) Dehydration reaction in the synthesis of a fat Ester linkage Triglycerides: 3 fatty acids linked to Glycerol by NDENSATIN SYNTESIS
Triglycerides Properties in Water FATS Solid WY? ILS Liquid Insoluble! All hydrophobic Saturated Unsaturated or Polyunsaturated Like Fig 3-2 Saturated fatty acids ave the maximum number of hydrogen atoms possible ave no double bonds Unsaturated fatty acids ave one or more double bonds Do not Stack well leic acid Stearic acid Figure 5.12 (b) Unsaturated fat and fatty acid cis double bond causes bending Figure 5.12 (a) Saturated fat and fatty acid Stack nicely
Polar (charged) ead Very ydrophobic Tail monolayer Free Fatty Acids ydrolyzed Triglycerides micelle Fatty Acids amphipathic Phospholipids Glycerol linked to 2 fatty acids Fig 3-27 Phospholipid structure onsists of a hydrophilic head and hydrophobic tails ydrophilic head 2 + 2 P 2 2 N( 3 ) 3 holine Phosphate Glycerol Phosphate ead Group Glycerol Fatty acid tails Fatty acid tails Figure 5.13 ydrophobic tails (a) Structural formula Fatty acids (b) Space-filling model ydrophil head ydropho tails (c) Phospholipid symbol
Phospholipid Bilayer Phospholipid ead Groups ydrophillic!! Polar groups Form Boundaries Sheet WATER utside ydrophilic head Polar eadgroups ydrophobic tail Nonpolar FA tails Polar eadgroups 3-D Ball (Sphere) Inside ure 5.14 WATER Vesicle or Liposome ross
Summary Principles of Building Polymers Directional assembly from simple units Requires energy input ondensation dehydration reactions ormones: Signal molecules arbohydrates monosaccharides polysaccharides Lipids Triglycerides phospholipids steroids Next Time: Proteins More Macromolecules Nucleic Acids