Lecture 7 Carbohydrates PDF

Carbohydrates  Saccharides (sugars) Monosaccharides Cx(H2O)x Glucose (C6H12O6) Tri- = 3 Fructose (C6H12O6) Tetr- = 4 Pent- = 5 Ribo...

Carbohydrates  Saccharides (sugars) Monosaccharides Cx(H2O)x Glucose (C6H12O6) Tri- = 3 Fructose (C6H12O6) Tetr- = 4 Pent- = 5 Ribose (C5H10O5) X= Hex- =6 Galactose (C6H12O6) Hept- = 7 Oct- = 8 Glyceraldehyde (C3H6O3) Aldehydes = Aldoses Ketones = Ketoses Different Sizes The -oses 3 Carbons 4 Carbons 5 Carbons 6 Carbons D-Glyceraldehyde Triose D-Threose Tetrose D-Ribose Pentose D-Glucose Hexose  Common Sugars Aldose and Ketose Aldehyde Ketone { } D-Glucose D-Fructose Aldose Ketose  Simple Sugars Aldopentose Aldohexose Ketohexose Aldohexose Aldohexose  Carbonyl on the End 11/5/2024 RY 11/5/2024 RY 11/5/2024 RY  Carbonyl Inner-Carbon 11/5/2024 RY 11/5/2024 RY  Asymmetric Carbons The Glyceraldehydes Asymmetric Carbon D- Configuration Mirror Images L- Configuration L-Glyceraldehyde D-Glyceraldehyde Multiple Asymmetric Centers Glucose D-configuration D-Glucose Enantiomers Mirror Images D-configuration L-configuration D-Glucose L-Glucose Diastereomers Same chemical type & size, non-mirror images Same Configuration Different Configurations Same Configuration D-Glucose D-Gulose Epimers Diastereomers differing in configuration of one carbon only D-Glucose D-Galactose Cyclization of Sugars New Asymmetric Center In Close Spatial Proximity The New Asymmetric Carbon Is Called Anomeric Cyclization of Sugars 11/5/2024 RY  Anomers 11/5/2024 RY 11/5/2024 RY Common Furanoses Fructose and Ribose β-D-Fructofuranose β-D-Ribofuranose  Oxidation of sugars: Reducing sugars All monosaccharides and some disaccharides: lactose, maltose (at least one anomeric carbon is free = can be converted into an aldehyde form) are reducing sugars A sugar is classified as a reducing sugar only if it has an open-chain form with an aldehyde group (ketoses can tautomerize in solution to form an aldehyde group)  Basis of Fehling’s Reaction = Glucose is Reducing Glucose oxidase test => biosensors? EOC Problem 15: an exercise in recognizing reducing sugars. 11/5/2024 RY 11/5/2024 RY Disaccharides Comprised of two sugars Sucrose (glucose + fructose) Lactose (glucose + galactose) Maltose (glucose + glucose) Formation of Glycosidic Bond..Polysaccharides: Written from Non- Reducing to Reducing End 11/5/2024 RY Disaccharides α1, β2 Diglycosidic Links 6 1 5 4 1 5 2 2 3 4 3 6 Glucose Fructose Sucrose α-D-glucopyranosyl-(1→2)-β-D-fructofuranoside Disaccharides Lactose and Maltose Glucose Glucose Glucose 6 Galactose 6 6 5 6 4 1 5 5 2 4 1 4 1 5 3 2 2 4 1 3 3 2 3 β-1,4 Glycosidic Bond α-1,4 Glycosidic Bond Lactose Maltose β-D-galactopyranosyl-(1→4)-D-glucose α-D-glucopyranosyl-(1→4)-D-glucose Oligosaccharides Play roles in cellular identity Typically 3 to 9 residues Usually attached to other biopolymers (lipids, proteins)  Oligosaccharides attached to proteins may be N-linked (through asparagine) or O-linked (though serine or threonine): O-linked sugars are added only in the Golgi apparatus N-linked sugars are attached starting in the endoplasmic reticulum and then completed in the Golgi Polysaccharides (glycans) Cellulose Glycogen Amylose Amylopectin Chitin The functions for polysaccharides are varied. They include energy storage, structural strength, and lubrication. 11/5/2024 RY Polysaccharides Sugar Polymers With Glycosidic Bonds α-1-4 Glycosidic Links 4 1 4 1 4 1 Glucose Glucose Glucose Amylose - component of starch, unbranched homopolysaccharide  β-1,4 Glycosidic Links Glucose Glucose Cellulose: unbranched homopolysaccharide Structure of amylopectin and glycogen, branched homopolysaccharides Amylopectin: branches after every 30-50 residues Glycogen: branches after every 8-12 residues Hemicellulose: branched heteropolysaccharide, contains both D- and L-sugars Monomers: xylose, mannose, galactose, rhamnose, arabinose Chitin, much like cellulose, but with acetylamine group at C2 Dextran? Agar?  Glycosaminoglycans (mucopolysaccharides) Ex: keratan sulfate, heparin, hyaluronic acid, and chondroitin sulfate Each of them contains a repeating unit of a disaccharide that contains at least one negatively charged residue Proteoglycans => the polysaccharide compounds are linked to proteins, but differ from glycoproteins in having a much larger contingent of sugar residues and, further, the sugars are considerably more chemically modified