Carbohydrate Chemistry PDF

Carbohydrate Chemistry Carbohydrates Definition C:H:O CH2OH C : H2O 1: 2:1 HC OH 1 : 1 CH2OH Glycerol CHO CH2OH HC OH C=O CH2OH CH2OH Glyceraldehde...

Carbohydrate Chemistry Carbohydrates Definition C:H:O CH2OH C : H2O 1: 2:1 HC OH 1 : 1 CH2OH Glycerol CHO CH2OH HC OH C=O CH2OH CH2OH Glyceraldehde Dihydroxyacetone  Carbohydrates classifications 1) Monosacchrides: simplest carbohydrates may be: a) Polyhydroxyaldhydes (aldoses) b) Polyhydroxyketones (ketoses)  2) Disacchrides : contain 2 monosacchride 3) Oligosacchrides: 3-10 monosacchride units bound by glycosidic bonds 4) Polysacchrides: larger, containing hundreds monosacchrides 12/16/2023 3  Carbohydrates structure The OH groups in CHO allows interaction with aqueous environment Derivatives of CHO contain N, S and P CHO can also combine with lipids to form glycolipids or proteins to form glycoproteins (Glycoconjugates) 12/16/2023 4  Monosaccharides No. of carbons Aldehyde (Aldose) Ketone (Ketose) 3 Trioses Glyceraldehyde Dihydroxyacetone 4 Tetroses Erythrose Erythulose 5 Pentoses Ribose Ribulose Glucose, Galactose, 6 Hexoses Fructose Mannose  Monosaccharides Aldehyde Ketone CHO CH2OH Trioses H C OH C=O CH2OH CH2OH Glyceraldehde Dihydroxyacetone CHO CH2OH H C OH C=O Tetroses H C OH OH C H CH2OH CH2OH Erythrose Erythrulose  Monosaccharides Aldehyde Ketone CHO CH2OH 2 H C OH C=O 3 Pentoses H C OH H C OH 4 H C OH H C OH 5 CH2OH CH2OH Ribose Ribulose  Monosaccharides Aldehydes Ketone Hexoses Properties of Monosaccharides Physical Properties Chemical Properties 1. Soluble in water 1. Oxidation 2. Show optical activity 2. Reduction 3. Ring or Cyclic structure 3. Reaction with H2SO4 4. Show optical isomerism 4. Osazone formation  Monoscchrides Optically active (rotate polarized light), contain at least 1 asymmetric carbon (chiral center) Stereoisomers (Isomers): cpds with same chemical formula but different structures. CHO have: 1- Enantiomers 2- Epimers 3- Anomers 12/16/2023 10  Monosacchrides Enantiomers: They can exist in D, L conformation according to OH-orientation of farthest chiral carbon from carbonyl D, L forms are ENANTIOMERS (mirror images) D-form is physiologically important 12/16/2023 11  Monoscchrides Epimers: Sugar molecules that differ in configuration at only one of several chiral centers are called epimers. For example, D-mannose C2 epimer of D-glu D-galactose C4 epimer of D-glu 12/16/2023 12  Monosacchrides Anomers: The aldhyde or ketone will form a cyclic ring either: a) five member ring called furanose b) six membered ring called pyranose These rings can reopen and close Fisher projections allowing rotation to occur, leading to 2 configuration α and β This carbon is anomeric carbon and α and β are anomers Haworth projectons Right downwards 12/16/2023 Left upwards 13  Disaccharides 2 monosaccrides will form disacchrides by glycosidic bond e.g. 1- Sucrose: glucose + fructose, 2-Lactose: galactose + glucose. 3-Maltose: glucose + glucose. 12/16/2023 14 12/16/2023 15  Reducing and non-reducing sugars Reducing sugars: contain a reactive carbonyl group, they are readily oxidized to diverse products. Reduce metal ions as Cu+2 to insoluble products e.g. Glucose, maltose, and lactose Non-reducing sugars: Sucrose, which are not readily oxidized because both anomeric carbon atoms are fixed in a glycosidic linkage 12/16/2023 16  Polysacchrides Homopolysacchrides: composed of single monosacchride building block e.g glycogen Heteropolysacchride: different building blocks e.g glycosaminoglycans Glycogen Starch GAGs 12/16/2023 17  Glycogen Major form of stored CHO in animals Polymer of α(1,4) glucose linkage Highly branched by α(1,6) linkage every 8-10 residues Very compact, allow storage of energy in small volume, low osmolarity 12/16/2023 18 12/16/2023 Glycogen 19  Starch Major form of storage in plant Similar structure as glycogen but less extensively branched (20-30 residues) Unbranched starch called amylose Branched called amylopectin 12/16/2023 20 Starch  Cellulose (structural polysaccharide)  Structure: Long straight non-branching chains of b-D-glucose linked by b-(1-4) glucosidic bond.  Properties: insoluble in water & cannot be digested by humans due to absence of hydrolase enzymes that can attack b-linkage.  Its presence in diet is important, because it cannot be digested, so it will increase the bulk of stool & stimulate the intestinal movement & prevent constipation.  Proteoglycans Also called glycosaminoglycans. These molecules are long unbranched polysaccharides containing a repeating disaccharide unit + specific protein called core proteins. These are predominantly in ECM, CT of multicellular animals The disaccharide units contain either of two modified sugars: A)N-acetylgalactosamine (GalNAc) or N-acetylglucosamine (GlcNAc) B) uronic acid such as glucuronate C) some contain sulphate groups 12/16/2023 23  Examples of GAGs Hyaluronan Chondroitin sulphate Heparin 12/16/2023 24  Hyaluronan: Composed of D-glucuronate + GlcNAc linkage is b(1, 3) Localization: synovial fluid, vitreous humor, ECM of loose connective tissue 12/16/2023 25  Chondroitin 4- and 6-sulfates Composed of D-glucuronate + GalNAc-4- or 6-sulfate linkage is b(1, 3) (the figure contains GalNAc 4-sulfate Cartilage, bone, heart valves 12/16/2023 26