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Biochemistry: Catabolism of Carbohydrates

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Biochemistry: Catabolism of Carbohydrates SEMMELWEIS PETER PAZMANY UNIVERSITY CATHOLIC UNIVERSITY Development of Complex Curricula for Molecular Bionics and Infobionics Programs within a consortial* framework** Consortium leader PETER PAZMANY CATHOLIC UNIVERSITY Consortium members SEMMELWEIS UNIVERSITY, DIALOG CAMPUS PUBLISHER The Project has been realised with the support of the European Union and has been co-financed by the European Social Fund *** **Molekuláris bionika és Infobionika Szakok tananyagának komplex fejlesztése konzorciumi keretben ***A projekt az Európai Unió támogatásával, az Európai Szociális Alap társfinanszírozásával valósul meg. .2011.09.13.. TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 1 http://semmelweis-egyetem.hu/www.se.hu BIOCHEMISTRY (BIOKÉMIA ) CATABOLISM OF CARBOHYDRATES (A SZÉNHIDRÁTOK LEBONTÁSA ) TRETTER LÁSZLÓ .2011.09.13.. TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 2 Biochemistry: Catabolism of carbohydrates http://semmelweis-egyetem.hu/www.se.hu CatabolismDEF: Part of intermediary metabolism dealing with the energy-yielding degradation of nutrient molecules Examples for catabolic processes Decomposition of glucose to pyruvate or lactate called: glycolysis Decomposition of fatty acids to acetyl-CoA called: beta oxidation Decomposition of glycogen to glucose: called glycogenolysis Decomposition of acetyl-CoA to carbon dioxide + water called: citric acid cycle Antonym of catabolism: anabolism CarbohydratesDEF: Aldehyde or ketone derivatives of polyhydric alcohols .2011.09.13.. TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 3 Biochemistry: Catabolism of carbohydrates http://semmelweis-egyetem.hu/www.se.hu CLASSIFICATION of CARBOHYDRATES MonosacharidesDEF: those carbohydrates that cannot be hydrolyzed into a simpler form subdivision: trioses, tetroses, pentoses, hexoses, heptoses depending upon the number of carbon atom subdivision: aldoses or ketoses depending upon the presence of of aldehyde or ketone group DisaccharidesDEF: hydrolysis of disaccharides yields 2 molecules of monosaccharides OligosaccharidesDEF: Hydrolysis yields 3-6 monosaccharide units PolysaccharidesDEF: Hydrolysis yields more than 6 monosaccharide units .2011.09.13.. TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 4 Biochemistry: Catabolism of carbohydrates http://semmelweis-egyetem.hu/www.se.hu Examples for monosaccharides Aldoses Ketoses Trioses (C3H6O3) Glycerose Dihydroxy- Synonym: acetone Glycer- aldehyde Tetroses (C4H8O4) Erythrose Erythrulose Pentoses (C5H10O5) Ribose Ribulose Hexoses (C6H12O6) Glucose Fructose Galactose Mannose .2011.09.13.. TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 5 Biochemistry: Catabolism of carbohydrates http://semmelweis-egyetem.hu/www.se.hu Table of contents: Glycolysis, the anaerobic decomposition of glucose Catabolism of non-glucose carbohydrates Regulation of carbohydrate catabolism .2011.09.13.. TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 6 Biochemistry: Catabolism of carbohydrates Glycolysis http://semmelweis-egyetem.hu/www.se.hu Glycolysis -reactions Learning objectives: Carbohydrates are major energy giving substrates for a living organism Glycolysis an universal pathway to decompose glucose even in the absence of oxygen At the end of the presentation students will be able: 1. To reproduce the most important steps of glycolysis 2. To understand the formation of ATP in the absence of oxygen 3. To demonstrate important principles of thermodinamics using examples taken from glycolysis .2011.09.13.. TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 7 Biochemistry: Catabolism of carbohydrates Glycolysis http://semmelweis-egyetem.hu/www.se.hu GlycolysisDEF -Anaerobic degradation of glucose to lactate or -Anaerobic degradation of glucose to pyruvate – a preparatory pathway for the aerobic metabolism of glucose -Can occur in every cell -Energy yielding pathway (2 ATP/glucose) In the absence of oxygen every cell would perform glycolysis and the end-product will be lactate thus glycolysis is the most universal metabolic pathway. .2011.09.13.. TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 8 Biochemistry: Catabolism of carbohydrates Glycolysis http://semmelweis-egyetem.hu/www.se.hu Glycolysis -reactions Overview of glycolysis Glucose C6 Hexose phosphates (C6) Triose phosphate Triose phosphate CO2 ATP + + H2O formation NADH+H NAD ATP Pyruvate Lactate Lactate + O2 (C3) Without O2 (C3) or blood no mitochondria .2011.09.13.. TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 9 Biochemistry: Catabolism of carbohydrates Glycolysis http://semmelweis-egyetem.hu/www.se.hu Glycolysis -reactions Overview of glycolysis 2 NAD+ 2 NADH+H+ In the absence of oxygen or mitochondria In the presence of oxygen and mitochondria .2011.09.13.. TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 10 Biochemistry: Catabolism of carbohydrates Glycolysis http://semmelweis-egyetem.hu/www.se.hu Glycolysis -reactions Preparatory phase of glycolysis 2 ATP invested and Hexose chain is converted into triose phosphates .2011.09.13.. TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 11 Biochemistry: Catabolism of carbohydrates Glycolysis http://semmelweis-egyetem.hu/www.se.hu Important reactions of the preparatory phase ATP requiring reactions of glycolysis ΔG’o= -16.7 kJ/mol irreversible Hexokinase Glucokinase ΔG’o= -14.2 kJ/mol Irreversible Phosphofructokinase-1 Rate limiting step of glycolysis .2011.09.13.. TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 12 Biochemistry: Catabolism of carbohydrates Glycolysis http://semmelweis-egyetem.hu/www.se.hu Important reactions of the preparatory phase Hexokinase and glucokinase are isoenzymes IsoenzymesDEF: Enzymes catalyzing the same reaction But differ: In amino acid sequence Vmax, and/or KM in regulation Hexokinases are localized in the peripheral tissues Glucokinase is localized in the liver Hexokinases show high affinity for glucose Glucokinase show low affinity for glucose Their regulation is different .2011.09.13.. TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 13 Biochemistry: Catabolism of carbohydrates Glycolysis http://semmelweis-egyetem.hu/www.se.hu Important reactions of the payoff phase Inorganic phosphate incorporation NADH formation High energy acyl-phosphate group formation on the 1st C atom ΔG’o= 6.3 kJ/mol reversible The acyl-phosphate group is transferred to ADP Substrate level phosphorylation ΔG’o= -18.5 kJ/mol reversible From the high energy enol-phosphate bond the phosphoryl group is transferred to ADP Substrate level phosphorylation ΔG’o= -31.4 kJ/mol irreversible .2011.09.13.. TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 14 Biochemistry: Catabolism of carbohydrates Glycolysis http://semmelweis-egyetem.hu/www.se.hu Energetic balance of glycolysis Preparatory phase 2 ATP invested - 2 Payoff phase 2x2 ATP produced (1 hexose 2 triose) +4 Summary Net ATP production +2 Substrate level phosphorylationDEF: Formation of ATP by phosphoryl group transfer from a compound having high energy bound Examples for substrate level phosphorylation: in glycolysis: phosphoglycerate kinase reaction pyruvate kinase reaction in citric acid cycle: succinate thiokinase reaction Antonym of substrate level phosphorylation: oxidative phosphorylation .2011.09.13.. TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 15 Biochemistry: Catabolism of carbohydrates Glycolysis http://semmelweis-egyetem.hu/www.se.hu Glycolysis - Summary Glycolysis – the most important decomposition pathway of the most important carbohydrate - glycolysis produces energy even in the absence of oxygen - every higher eukaryotic cells are able to perform glycolysis - 2 mol of ATP produced from 1 mol of glucose - in the presence of oxygen and mitochondria glycolysis is continued in the citric acid cycle - glycolysis has reversible and irreversible steps - the irreversible reactions of glycolysis are catalyzed by hexokinase (glucokinase in liver), phosphofructokinase and pyruvate kinase .2011.09.13.. TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 16 Biochemistry: Catabolism of carbohydrates Catabolism of non-glucose carbohydrates http://semmelweis-egyetem.hu/www.se.hu Catabolism of non-glucose carbohydrates Introduction Carbohydrates are major energy giving substrates for living organism Besides glucose other carbohydrates (e.g. fructose and galactose) are also taken up by the organism, which sugars can be catabolized or can participate in the synthesis of other molecules Glycogen is a special storage form of glucose with a function in the maintenance of blood sugar level and in the energy supply of the muscle cells. .2011.09.13.. TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 17 Biochemistry: Catabolism of carbohydrates Catabolism of non-glucose carbohydrates http://semmelweis-egyetem.hu/www.se.hu Learning objectives At the end of the presentation students will be able: To understand the pathways used by individual carbohydrates to join to the mainstream of the metabolism To understand that consumption of different carbohydrates could change physiological pathways and could have pathological consequences as well. .2011.09.13.. TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 18 Biochemistry: Catabolism of carbohydrates Catabolism of non-glucose carbohydrates http://semmelweis-egyetem.hu/www.se.hu Fructose metabolism Availability of fructose: Natural sources: fruit juices, honey, disaccharide sucrose Food industry: High Fructose Corn Syrup Importance: Mainly changed to glucose in the liver and used in the body Pathological significance: hereditary fructose intolerance (fructose accumulation plus hypoglycemia), obesity .2011.09.13.. TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 19 Biochemistry: Catabolism of carbohydrates Catabolism of non-glucose carbohydrates http://semmelweis-egyetem.hu/www.se.hu Entry of fructose into glycolysis 1. In liver – major organ of fructose catabolism Important: fructose
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