controlof carbon(bio)

controlof carbon(bio) - GLUCOSE: Chapters 15 & 20...

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1 1 Control of Carbohydrate Metabolism Balanced Anabolism and Catabolism Plant Carbohydrate Metabolism 2 GLUCOSE: SUPPLY AND DEMAND Daily Demand: ~ 160 g (120 g for brain) Supply: ~ 20 g Body fluids ~ 190 g Glycogen Hierarchy of Metabolism 1- Glucose, other monosaccharides 2- Glucogen 3- Fatty acids 4- Ketone Bodies 5- Protein 3 Citric acid Cycle Nucleotide biosynthesis Endogenous glycogen Dietary carbohydrates Gluconeogenesis 4 MOBILIZATION OF GLUCOSE FROM GLYCOGEN Major storage form of animal glucose LIVER glycogen: 1 day glucose reservoir BRAIN uses glucose (not fatty acid) as fuel Mainly in liver (up to 10% of dry weight) and muscle (1-2%) α 1 J 4 Glycosidic bonds α 1 J 6 Glycosidic branches every 8-10 glucose molecules Stored in cytosolic β -granules ~55,000 glucose molecules 2000 non reducing ends 20-40 of these granules form rosettes 5 MOBILIZATION OF GLUCOSE FROM GLYCOGEN 6 GLYCOGEN PHOSPHORYLASE Shift of three glucose molecules to nearby non-reducing end Single glucose is released Attacks α 1 > 4 glycosidic bond at non-reducing end Glucose 1 – P Cannot be used in glycolysis P i DEBRANCHING ENZYME Glucose 2 Enzymes Liberate Glucose
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2 7 Strategy of Phosphoglucomutase: Shift the Phosphate Ser Ser Ser Glucose-6-P Glucose-1-P Glucose-1,6- bisphoshate phospho glucomutase Similar to phosphoglycerate kinase 8 GLUCOSE MOBILIZATION Muscle Muscle : Glycogen ± Gluc 1-P ± indirectly enters glycolysis Liver Liver : Glycogen ±± Gluc 6-P ± Glucose ± blood - Supplies brain with glucose - Requires liver-specific gluc 6-phosphatase 9 Alternative Oxidation of Glucose: Pentose Phosphate Pathway - Rapidly dividing cells - Anabolic tissues Important Products: 1. Ribose 5-phosphate DNA/RNA synthesis 2. NADPH Prevents oxidative damage from free radicals A reactant mostly in anabolic reactions 10 Oxidative Reactions : Pentose Phosphate Pathway 1 Glucose 6-phosphate Yields 2 NADPH 1 Ribose 5-phosphate 1 CO 2 11 Non-oxidative Reactions: Pentose Phosphate Pathway É Recycle pentose phosphates to Glucose 6-phosphate In animal cells (Plants use Calvin Cycle) 12 GLUCONEOGENESIS Helps maintain constant blood glucose level Mainly in liver and kidney Not significant in heart, skeletal muscle or brain Usually starts with pyruvate or lactate Lactate + NAD + Pyruvate + NADH 7 steps from Glycolysis are reversed - 3 Steps are unique = By - Pass Reactions Replace 3 irreversible steps of glycolysis IF Glycolysis Reversed : Δ G ’o = + 84 kJ/mol Gluconeogenesis: Δ G ’o = - 38 kJ/mol LDH
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3 13 Gycolysis Gluconeogenesis Regulations 14 1. PYRUVATE to PHOSPHOENOLPYRUVATE A. mitochondria B. cytosol Malate Shuttle 15 Two Ways to Make PEP IF Pyruvate Predominates IF Lactate Predominates Malate Shuttle Provides NADH To Cytosol NADH Already In Cytosol 16 2 3 17 GLYCOGEN SYNTHESIS Glucose-6-P Gluc-1 -P phosphoglucomutase Glucose-1-P UDP-Glucose UDP-glucose pyrophosphorylase
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controlof carbon(bio) - GLUCOSE: Chapters 15 & 20...

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