Chapter 14.1 and 14.2: Glycolysis and Feeder Pathways CHEM 7784 Biochemistry Professor Bensley

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Text of Chapter 14.1 and 14.2: Glycolysis and Feeder Pathways CHEM 7784 Biochemistry Professor Bensley

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  • Chapter 14.1 and 14.2: Glycolysis and Feeder Pathways CHEM 7784 Biochemistry Professor Bensley
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  • CHAPTER 14.1 and 14.2 Glycolysis Process of harnessing energy from glucose via glycolysis Various pathways by which carbohydrates other than glucose enter glycolysis Todays Objectives: To learn and understand the
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  • Central Importance of Glucose Glucose is an excellent fuel Glucose is a versatile biochemical precursor Four major pathways of glucose utilization
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  • Glycolysis: The Big Picture Anaerobic process carried out by all cells but at different rates Converts hexose to two pyruvates Generates 2 ATP and 2 NADH For certain cells in the brain and eye, glycolysis is the only ATP generating pathway Glucose + 2 ADP + 2 NAD + + 2P i 2 Pyruvate + 2 ATP + 2 NADH + 2 H + + 2H 2 0
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  • Glycolysis: Importance Glycolysis is a sequence of ten enzyme- catalyzed reactions by which glucose is converted into pyruvate Two phases: First phase converts glucose to two G-3-P Second phase produces two pyruvate molecules Three possible fates for pyruvate
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  • Glycolysis: The Preparatory Phase
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  • Glycolysis: The Payoff Phase
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  • STEP 1 - The Hexokinase Reaction The first step, phosphorylation of glucose, is catalyzed by hexokinase in eukaryotes, and by glucokinase in prokaryotes This process uses the energy of ATP
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  • STEP 2 - Phosphohexose Isomerization An aldose can isomerize into ketose via an enediol intermediate Overall Glucose-6-Phosphate is converted to Fructose-6-Phosphate
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  • STEP 3 - The Second Priming Reaction; The First Commitment This is an irreversible step The product, fructose 1,6-bisphosphate is committed to become pyruvate and yield energy
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  • STEP 4 - Aldolases Cleave 6- Carbon Sugars Step four is the cleavage of Fructose 1,6- Bisphosphate
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  • STEP 5 - Triose Phosphate Interconversion DAP is converted enzymatically to GAP
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  • STEP 6 - Glyceraldehyde 3-Phosphate Dehydrogenase Reaction First step in the Payoff Phase of Glycolysis First energy-yielding step in glycolysis
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  • STEP 7 - First Substrate-Level Phosphorylation 1,3-bisphosphoglycerate is a high-energy compound that can donate the phosphate group to ADP to make ATP
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  • STEP 8 - Conversion of 3- Phosphoglycerate to 2-Phosphoglycerate This is a reversible isomerization reaction
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  • Mechanism of the Phosphoglycerate Mutase Reaction
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  • STEP 9 - Dehydration of 2-Phosphoglycerate The goal here is to create a better phosphoryl donor Loss of phosphate from 2-phosphoglycerate would merely give a secondary alcohol with no further stabilization
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  • STEP 10 - Second Substrate- Level Phosphorylation but loss of phosphate from phosphoenolpyruvate yields an enol that tautomerizes into ketone
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  • Feeder Pathways for Glycolysis