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  1. 1. 1! Metabolism of Carbohydrates The Energy Metabolism of Glucose Entry of other Carbohydrates into Glycolysis Pyruvate Metabolism Biosynthesis of Carbohydrates Regulation of Carbohydrate Metabolism 2! Metabolism of carbohydrates 3! Carbohydrate metabolism 4! Energy metabolism of glucose Glycogen (animals) Starch (plants) Glucose Pyruvate Acetyl CoA Lactate Ethanol Ribose-5-phosphate + NADPH + H+ Disaccharides ATP + NADH + H+ catabolism anabolism phosphogluconate pathway glycolysis gluconeo- genesis aerobic anaerobic,muscles anaerobic,yeast 5! Glycolysis 6! First five reactions of glycolysis glucose glucose-6-P fructose-6-P fructose-1,6-bisP glyceraldehyde-3-P dihydroxyacetone-P ATP ADP ATP ADP 6 carbon stage Requires energy
  2. 2. 7! Reactions of glycolysis 1,3-bisphosphoglycerate 3-phosphoglycerate 2-bisphosphoglycerate phosphoenolpyruvate pyruvate glyceraldehyde-3-P ATP ADP ATP ADP NAD+ NADH + H+ H2O Pi 3 carbon stage Double this since two pyruvate are made. 8! Overall glycolysis glucose 2 ADP + 2 PO4 = + 2 NAD+! 2 pyruvate + 2 NADH + 2 H2O + 2 ATP! 10 enzymes! 9! Entry of other carbohydrates into glycolysis 10! Entry of other carbohydrates into glycolysis maltase invertase (bacteria) sucrase (animals) lactase 11! Entry of other carbohydrates into glycolysis 12! Entry of other carbohydrates into glycolysis
  3. 3. 13! Entry of other carbohydrates into glycolysis Galactose Galactose-1-phosphate UDP-galactose UDP-glucose Glucose-1-phosphate Glucose-6-phosphate galactokinase galactose-1- phosphate uridyl transferase UDP-galactose -4-epimerase UDP-glucose pyrophosphorylase Phospho- glucomutase 14! Pyruvate metabolism 15! Fermentation 16! Lactate fermentation 17! Alcohol fermentation Used by anaerobic bacteria to obtain additional energy from glucose. 18! Biosynthesis of carbohydrates
  4. 4. 19! Biosynthesis of carbohydrates Skeletal muscles Glycogen glucose-6-P exercise rest glucose-6-P pyruvate lactate Liver Glycogen glucose-6-P glucose-6-P pyruvate lactate glucose Muscles lack enzyme needed to convert pyruvate to glucose-6-P. Must be sent to liver. Blood 20! Gluconeogenesis Oxaloacetate Phosphoenolpyruvate Pyruvate Pyruvate Malate Malate Oxaloacetate Lactate Pyruvate Pyruvate Oxaloacetate Phosphoenol pyruvate Stage I mitochondria 21! Gluconeogenesis Glycogen Glucose UDP-glucose + UDP H O 2 Pi ATP H O 2 Pi Fructose-1,6-bisphosphate Glyceraldehyde-3-phosphate Phosphoenolpyruvate 3-Phosphoglycerate 2-Phosphoglycerate Glucose-1-phosphate Glucose-6-phosphate Fructose-6-phosphate ATP Stage III Stage II 22! Gluconeogenesis The process is sometimes called ‘reverse glycolysis’ but that is a misnomer. Only seven of the ten steps in glycolysis are reversible. The three steps to be bypassed are: 1. glucose + ATP glucose-6-phosphate + ADP 3. fructose-6-phosphate + ATP fructose-1,6 -bisphosphate + ADP 10. PEP + ADP pyruvate + ATP 23! Gluconeogenesis 24! Gluconeogenesis
  5. 5. 25! Gluconeogenesis 26! Gluconeogenesis Fructose-6-phosphate Fructose-1,6-bisphosphate ATP H2O Pi phospho- fructokinase fructose-1,6- bisphosphatase gluconeogenesis glycolysis 27! Gluconeogenesis glucose-6-phosphate + H2O glucose + Pi glucose-6- phosphatase 28! Synthesis of disaccharides and polysaccharides 29! Activation of glucose and galactose 30! Synthesis of UDP-galactose
  6. 6. 31! Synthesis of glycogen Glucose, activated and tagged by attachment of UDP, is added to the nonreducing ends of an existing glycogen. Glycogen synthase catalyzes the formation of a new ! (1 4) glycosidic linkage. UDP-glucose + (glucose)n + H2O (glucose)n+1 + UDP 32! Synthesis of starch Similar to glycogen formation except glucose is activated by ADP, not UDP. Starch synthase catalyzes the addition of glucose to an existing starch molecule by formation of ! (1 4) glycosidic linkage. ADP-glucose + (glucose)n (glucose)n+1 + ADP 33! Synthesis of lactose This disaccharide is actively synthesized in the mammary glands of mammals. It is produced by combining activated galactose with glucose using lactose synthase. A "(1 4) linkage results. UDP-galactose + glucose UDP + lactose 34! Synthesis of sucrose Sucrose is present in most fruits and vegetables. It is produced by a two step process. UDP-glucose + fructose-6-phosphate sucrose-6-phosphate + UDP sucrose + Pi sucrose-6- phosphate synthase phosphatase H2O 35! Synthesis of cellulose Cellulose- major structural polysaccharide in cell walls of plants and some bacteria. It’s synthetic route is similar to starch except a "(1 4) linkage is produced. UDP-glucose or GDP-glucose + (glucose)n UDP or GDP + (glucose)n+1 36! Regulation of glycolysis
  7. 7. 37! Regulation of glycolysis glucose glucose 6-phosphate fructose 6-phosphate fructose 1,6-bisphosphate phosphoenolpyruvate pyruvate feedback inhibition