Carbohydrates. Structure and functions of di, Slides of Bioorganic Chemistry

Download Carbohydrates. Structure and functions of di and more Slides Bioorganic Chemistry in PDF only on Docsity! Carbohydrates. Structure and functions of di- and polysaccharides Ministry of Public Health of Ukraine Ukrainian Medical Stomatological Academy Department of biological and bioorganic chemistry Assoc. Prof. Bilets M.V. Lecture plan  Structure and properties of sucrose, lactose, maltose.  Classification of polysaccharides.  Structure, biological role of starch.  Structure and biological role of glycogen.  Structure and biological role of cellulose.  Heteropolysaccharides. Glycosaminoglycans. Proteoglycans. Lactose  Lactose is known as milk sugar because it occurs in the milk of humans, cows, and other mammals. In fact, the natural synthesis of lactose occurs only in mammary tissue, whereas most other carbohydrates are plant products. Human milk contains about 7.5% lactose, and cow’s milk contains about 4.5%. This sugar is one of the lowest ranking in terms of sweetness, being about one-sixth as sweet as sucrose.  Lactose is a reducing sugar composed of one molecule of D- galactose and one molecule of D-glucose joined by a β-1,4- glycosidic bond (the bond from the anomeric carbon of the first monosaccharide unit being directed upward). The two monosaccharides are obtained from lactose by acid hydrolysis or the catalytic action of the enzyme lactase.  Many adults and some children suffer from a deficiency of lactase. These individuals are said to be lactose intolerant because they cannot digest the lactose found in milk. A more serious problem is the genetic disease galactosemia, which results from the absence of an enzyme needed to convert galactose to glucose. https://chem.libretexts.org/Courses/Sacramento_City_College/SCC%3A_Chem_309_- _General_Organic_and_Biochemistry_(Bennett)/Text/14%3A_Carbohydrates/14.6%3A_Disaccharideshttp://www.chups.jussieu.fr/polys/biochimie/SGLbioch/POLY.Chp.1.5.html Sucrose  Sucrose, is known as beet sugar, cane sugar, table sugar, or simply sugar.  The sucrose molecule is unique among the common disaccharides in having an α-1,β-2-glycosidic (head-to-head) linkage. Because this glycosidic linkage is formed by the OH group on the anomeric carbon of α-D-glucose and the OH group on the anomeric carbon of β-D- fructose, it ties up the anomeric carbons of both glucose and fructose.  This linkage gives sucrose certain properties that are quite different from those of maltose and lactose. As long as the sucrose molecule remains intact, neither monosaccharide “uncyclizes” to form an open- chain structure. Thus, sucrose is incapable of mutarotation and exists in only one form both in the solid state and in solution. In addition, sucrose does not undergo reactions that are typical of aldehydes and ketones. Therefore, sucrose is a nonreducing sugar.  The hydrolysis of sucrose in dilute acid or through the action of the enzyme sucrase (also known as invertase) gives an equimolar mixture of glucose and fructose. This 1:1 mixture is referred to as invert sugar because it rotates plane-polarized light in the opposite direction than sucrose. The widespread use of sucrose is a contributing factor to obesity and tooth decay. Carbohydrates such as sucrose, are converted to fat when the caloric intake exceeds the body’s requirements, and sucrose causes tooth decay by promoting the formation of plaque that sticks to teeth. https://chem.libretexts.org/Courses/Sacramento_City_College/SCC%3A_Chem_309_- _General_Organic_and_Biochemistry_(Bennett)/Text/14%3A_Carbohydrates/14.6%3A_ Disaccharideshttp://www.chups.jussieu.fr/polys/biochimie/SGLbioch/POLY.Chp.1.5.htm l Polysaccharides  Polysaccharides (glycans), are long chain polymeric carbohydrates composed of monosaccharide units ( more than 20) bound together by glycosidic linkages. This carbohydrate can react with water (hydrolysis) using enzymes as catalyst, which produces constituent sugars (monosaccharides, or oligosaccharides). They range in structure from linear to highly branched. Examples include storage polysaccharides such as starch, glycogenand structural polysaccharides such as cellulose.  Polysaccharides can be broadly classified into two classes:  Homo-polysaccharides – are made up of one type of monosaccharide units. ex: cellulose, starch, glycogen.  Hetero-polysaccharides – are made up of two or more types of monosaccharide units. ex. hyaluronic acid and they provide extracellular support for organisms. https://www.slideshare.net/ArunimaSur/classification-of-polysaccharides-gluconeogenesis-and- glucogenolysis Cellulose  Cellulose is a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked β-D- glucose units.  Cellulose, a fibrous carbohydrate found in all plants, is the structural component of plant cell walls.  Like amylose, cellulose is a linear polymer of glucose. It differs, however, in that the glucose units are joined by β-1,4-glycosidic linkages, producing a more extended structure than amylose. This extreme linearity allows a great deal of hydrogen bonding between OH groups on adjacent chains, causing them to pack closely into fibers. As a result, cellulose exhibits little interaction with water or any other solvent. Because cellulose does not have a helical structure, it does not bind to iodine to form a colored product.  People cannot digest cellulose, but it is as important in the diet as fiber. Fiber improves intestinal motility, gives a feeling of satiety and promotes the formation of feces and accelerates its excretion from the body. In addition, the cage helps to remove toxic substances from the body. https://www.easybiologyclass.com/polysaccharides-structure-classification-and-examples- biochemistry-lecture-notes/ Heteropolysaccharides.  In general, heteropolysaccharides (heteroglycans) contain two or more different monosaccharide units. Although a few representatives contain three or more different monosaccharides, most naturally occurring heteroglycans contain only two different ones and are closely associated with lipid or protein. The major heteropolysaccharides include the connective-tissue polysaccharides, the blood group substances, glycoproteins (combinations of carbohydrates and proteins) such as gamma globulin, and glycolipids (combinations of carbohydrates and lipids), particularly those found in the central nervous system. heteropolysaccharide component sugars functions distribution hyaluronic acid D-glucuronic acid and N- acetyl-D-glucosamine lubricant, shock absorber, water binding connective tissue, skin chondroitin-4-sulfate D-glucuronic acid and N- acetyl-D-galactosamine-4- O-sulfate calcium accumulation, cartilage and bone formation cartilage heparin D-glucuronic acid, L- iduronic acid, N-sulfo-D- glucosamine anticoagulant mast cells, blood gamma globulin N-acetyl-hexosamine, D- mannose, D-galactose antibody blood blood group substance D-glucosamine, D- galactosamine, L-fucose, D-galactose blood group specificity cell surfaces, especially red blood cells Glycosaminoglycans  Glycosaminoglycans (GAGs) or mucopolysaccharides are long linear polysaccharides consisting of repeating disaccharide units (i.e. two-sugar units). The repeating two-sugar unit consists of a uronic sugar (glucuronic or iduronic acid) and an amino sugar (glucosamine or galactosamine), with the exception of keratan, where in the place of the uronic sugar it has galactose. Because GAGs are highly polar and attract water, they are used in the body as a lubricant or shock absorber.  Mucopolysaccharidoses are a group of metabolic disorders in which abnormal accumulations of glycosaminoglycans occur because of enzyme deficiencies. https://www.researchgate.net/figure/Structure-of-the-different-glycosaminoglycan- chains_fig2_12681530 Proteoglycans  Proteoglycans are proteins that consists of a "core protein" with one or more covalently attached glycosaminoglycan (GAG) chain(s). The chains are long, linear carbohydrate polymers that are negatively charged under physiological conditions due to the occurrence of sulfate and uronic acid groups. Proteoglycans occur in connective tissue.  Proteoglycans (PG) are a major component of the extracellular matrix of connective tissue, the "filler" substance existing between cells in an organism. They form large complexes, both to other proteoglycans, to hyaluronan, and to fibrous matrix proteins, such as collagen.  The combination of proteoglycans and collagen form cartilage, a sturdy tissue that is usually heavily hydrated (mostly due to the negatively charged sulfates in the glycosaminoglycan chains of the proteoglycans).  PG are involved in binding cations (such as sodium, potassium and calcium) and water, and also regulating the movement of molecules through the matrix.  PG can affect the activity and stability of proteins and signalling molecules within the matrix.  PG can serve as lubricants, by creating a hydrating gel that helps withstand high pressure. https://pediaa.com/difference-between-proteoglycan-and- glycoprotein/ Sources of information  https://chem.libretexts.org/Courses/Sacramento_City_College/SCC%3A_Chem_309_- _General_Organic_and_Biochemistry_(Bennett)/Text/14%3A_Carbohydrates/14.6%3A_Disacchari des  http://www.chups.jussieu.fr/polys/biochimie/SGLbioch/POLY.Chp.1.5.html  https://www.slideshare.net/ArunimaSur/classification-of-polysaccharides-gluconeogenesis-and- glucogenolysis  https://www.sciencedirect.com/topics/neuroscience/glycogen  https://www.easybiologyclass.com/polysaccharides-structure-classification-and-examples- biochemistry-lecture-notes/#starch-structure  https://www.easybiologyclass.com/polysaccharides-structure-classification-and-examples-biochemistry-lecture- notes/  https://www.researchgate.net/figure/Structure-of-the-different-glycosaminoglycan- chains_fig2_12681530  https://www.researchgate.net/figure/Fig-1-Structure-of-Hyaluronic-acid-molecule-HA_fig1_23656785  https://pediaa.com/difference-between-proteoglycan-and-glycoprotein/ Biological and Bioorganic Chemistry. In 2 books. Book 1. Bioorganic Chemistry. Textbook/B.S.Zimenkovsky, I.V. Nizhenkovska et.al.; edited by B.S.Zimenkovsky, I.V.Nizhenkovska. – Kyiv:AUS Medicine Publishing, 2020.- 288 p. Semyonova T.V. Bioorganic chemistry: Manual /Semyonova T.V. – Simferopol, 2004. –128p. Jelena Dodonova. Bioorganic chemistry (Set of lectures)/ Jelena Dodonova. - Vilnius, 2016.-301 p.