Chapter 5 (73-81) 5.1 Sugars as monomers I. What distinguishes one monosaccharide from another?• Carbohydrate molecular formula is (CH2O)n (n=#carb groups)• Carbohydrates don’t consist of carbon atoms bonded to water molecules. Instad, carbonyl (C=O), several hydroxyl (-OH), and several carbon-hydrogen (C-H)• Sugars provide chemical energy in cells and furnish some of the molecular building blocks required for the synthesis of larger, more complex compounds• Monosaccharides=simple sugars=monomers of carbohydrates• The presence of a carbonyl group along with multiple hydroxyl groups provides sugars with an array of reactive and hydrophilic functional groups• Carbon atoms present vary: carbons in a monosaccharide are #d consecutively, starting with the end nearest the carbonyl group• Trioses: 3carbon sugars• Pentose: 5carbons=Ribose:acts as a building block for nucleotides• Hexose: 6carbons=glucose that course through bloodstream• Vary in location of carbonyl group, total # of carbon atoms present, alternative ring forms, and in spatial arrangement of atoms• If structures differ so does function: even seemingly simple changes in structure-like location of a single hydroxyl group-can have enormous consequences forfunction 5.2 the structure of polysaccharides• Simple sugars can be covalently linked into chains of varying lengths=complex carbohydrates• Small length=small oligomers (oligosaccharides)• Large length=large polymers (polysaccharides)• Disaccharides: only two sugars are linked together• Structure and function of larger carbs depends on types of monomers involved and how they are linked together• Monosaccharides polymerize when a condensation reaction occurs b/w two hydroxyl groups, resulting in a covalent interaction called a glycosidic linkage• Glycosidic linkages hold monomers together and are analogous to the peptide bonds and phosphodiester linkages in proteins and nucleic acids• Bc glycosidic linkages form b/w hydroxyl groups and bc every monosaccharide contains at least 2 hydroxyls, the location and geometry of glycosidic linkagescan vary widely among polysaccharides I. Starch: a storage polysaccharide in plants• Starch: consists entirely of α-glucose monomers joined by glycosidic linkages• Linkages b/w C-1 and C-4 carbons causes a chain of glucose subunits to coil into a helix• Mixture of 2 such polysaccharides: amylose (unbranched molecule), amylopectin (branched molecule) II. Glycogen: a highly branched storage polysaccharide in animals• Glycogen performs the same storage role in animals that starch performs in plants.• Stored in liver and in muscles• When exercising enzymes break glycogen into glucose monomers which are processed in muscle cells to supply energy• A polymer of α-glucose and nearly identical to branched form of starch III. Cellulose: a structural polysaccharide in plants• Cellulose is the major component in the cell wall• Cellulose: a polymer of β-glucose monomers, joined by β-1, 4-glycosidic linkages• The geometry of the linkage is such that each glucose monomer in the chain is flipped in relation to the adjacent monomer• Flipped orientation is important:1. It generates a linear molecule2. Permits multiple hydrogen bonds to form b/w adjacent, parallel strands of cellulose IV. Chitin: a structural polysaccharide in fungi and animals• Chitin: a polysaccharide that stiffens the cell walls of fingi• Most important component of the external skeletons of insects and crustaceans• Similar to cellulose, but instead of consisting of glucose monomers the monosaccharide involved is one called Ν-acetyloglucosamine• Geometry of these bonds results in every other residue being flipped in orientation• NAG subunits form hydrogen bonds b/w adjacent strands resulting in a tough sheet hat provides stiffness and protection V. Peptidoglycan: a structural polysaccharide in bacteria• Gives bacterial cell walls strength and firmness (instead of cellulose)• Most complex polysaccharides• Long backbone formed by two typs of monosaccharides that alternate with each other and are linked by β-1, 4-glycosidic linkages• Short chain of amino acids is attached to one of the two sugar typs• When molecules of peptidoglycan align, peptide bonds link the amino acid chains on adjacent strands 5.3What do carbohydrates do?• Serve for synthesizing more complex molecules• Have diverse functions in cells: in addition to serving as precursors to larger molecules, they:1. Provide fibrous structural materials2. Indicate cell identity3. Store chemical