Chapter 16 Notes
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This 3 page Class Notes was uploaded by Cassidy Zirko on Saturday March 19, 2016. The Class Notes belongs to BCH 110 at University of Montana taught by Scott Samuels in Spring 2016. Since its upload, it has received 11 views. For similar materials see Intro Biology for Biochemist in Biology at University of Montana.
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Date Created: 03/19/16
Chapter 16: Carbohydrates 16.3 Some Important Oligosaccharides Oligomers of sugars disaccharides formed by linking two monosaccharides units by glyosidic bonds What makes Sucrose an Important Compound? o Sucrose able sugar from sugarcane and sugar beets o Monosaccharide units alpha D glucose and betaDfructose o Alpha C1 carbon of glucose is linked to beta C2 carbon of fructose in a glyosidic linkage o Sucrose is not reducing sugar because both anomeric groups are involved in glycosidic linkages o Free glucose is reducing sugar free fructose can give positive test (ketone rather than aldehyde in opening chain form) o When sucrose is consumed hydrolyzed to glucose and fructose degraded by metabolic processes to provide energy o Some artificial sweeteners derived from sucrose, less dangerous o Splenda differs from sucrose because of three hydroxyl groups replaced with chlorines and configuration at carbon 4 of sixmembered pyranose is inverted galactose derivative o Hydroxyl groups replaced by chlorine are bonded to carbon 1 and 6 of fructose and carbon4 of galactose o Sucralose is not metabolize by bond does not provide calories safe sugar substitute Are any other Disaccharides important to us? o Lactose disaccharide with betadglucose o Galactose is C4 epimer of glucose only difference from glucose is C4 configuration is inverted o Anomeric carbon of glucose not involved in glycosidic linkage o 2 anomeric forms of lactose designated by glucose residue o Lactose is reducing sugar because the group at the anomeric carbon of glucose portion is not involved in a glyosidic linkage free to react with oxidizing agents o Maltose disaccharide from hydrolysis of starch Had two residues of Dglucose in a alpha (14) linkage Differences from cellobiose by glycosidic linkage Mammals can digest maltose but not cellobiose Maltose is used in milk and beer 16.4 Structures and Functions of Polysaccharides Polysaccharide many monosaccharides are linked together Occur in organisms that are compose of very few types of monosaccharide compontes Homopolysaccharide only one type of monomer Heteropolysaccharide more than one type of monomer Glucose is most common monomer Polysaccharides include specification of which monomers are present and sequence of monomers Requires type of glycosidic linkage Cellulose and chitin polysaccharides with beta glycosidic linkages structural materials Starch and glycogen polysaccharides with alpha glycosidic linkages serve as carbs storage polymers in plants and animals How Do Cellulose and Starch differ From Each other? o Cellulose is major structural component in plants o Linear homopholysaccharide of betaDglucose, all residues are linked in a beta 14 glycosidic bond o Individual chains are hydrogen bonded together o Animals cant hydrolyze cellulose o Cellulases hydrolyze cellulose by attacking the alpha and beta linkages between glucose Is there more than one form of starch? o Importance of carbs as energy sources is that there are uses for some polysaccharides in metabolism o Starches polymers of alphadglucose that occurs in plant cells o Types of starches can be distinguished from one another by chain branching o Starches are storage molecules mechanism for releasing glucose from starch when organism needs energy o Alpha and beta amylase attack alpha 14 linkages o Amylose can be completely degraded to glucose and maltose How is Glycogen related to starch? o Glycogen branched chain polymer of alphadglucose o Has chain of alpha 14 linkages with alpha 16 linkages at branch points o Main difference is that glycogen is more highly branched o Every glycogen molecule there is a protein called glycogenin o Number of branch points is important more branched polysaccharide more water soluble o Organism needs energy quickly glycogen phosphorylase has more potential targets if there are more branches quicker mobilization of glucose What is Chitin? o Polysaccharide that is similar to cellulose in both structure and function, also has linear homopolysaccharide with all the residues linked in beta 14 linkages o Differs from cellulose because of monosaccharide unit o Has Nacetylbetadglucosamine o Plays structural role and has mechanical strength because of how the individual strands are held together by hydrogen bonds o Component of exoskeletons of invertebrates, occurs in cell walls What roles do Polysaccharides play in structure of cell walls? o Heteropolysaccharides are major components of bacterial cell walls o Distinguishing feature polysaccharides are cross linked by peptides o Cross links of bacterial cell walls have small peptides o Tetrapeptides are cross linked by another small peptide and have five amino acids o Occurrence of d amino acids and nactylmuramic acid shows a biochemical and structural difference between prokaryotes and eukaryotes o Extensive cross linking produces three dimensional network of mechanical strength o Peptidoglycan formed by cross linking of polysaccharides by peptides o Pectin polymer made up of dgalacturonic acid derivative of galactose o Extracted from plants because of commercial importance o Lignin polymer of coniferyl alcohol tough and durable material Do Polysaccharides play any specific roles in connective tissues? o Glycosaminoglycans polysaccharide based on repeating disaccharide where one of the sugars is an amino sugar and one of them has negative charge o Polysaccharides involved in wide variety of cell functions 16.5 Glycoproteins Have carb residue and polypeptide chain Antibodies bind to and immobilize antigens Carbs are important in antigenic determinants portions of an antigenic molecule that antibodies recognize and to which they bind How are Carbs important in the immune response? o Super important in determinates of blood groups o A,B, AB, O blood groups o Distinctions between groups depend on oligosaccharide portions of glycoprotiens on surface of blood cells o All blood types oligosaccharides contains sugar Lfuctose o Type A has NAcetylglactosamine on the nonreducing end of oligosaccharide o Type B alphadGlactose o Type O has neither terminal residues present o AB has both terminal residues o Glydoprotiens are also in eukaryotic cell membranes o Proteoglycans glycoproteins with high carbohydrate content o Constantly being synthesized and broken down
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