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Chapter 14.1 and 14.2: Glycolysis and Feeder Pathways

Chapter 14.1 and 14.2: Glycolysis and Feeder Pathways. CHEM 7784 Biochemistry Professor Bensley. CHAPTER 14.1 and 14.2 Glycolysis. Today’s Objectives : To learn and understand the. Process of harnessing energy from glucose via glycolysis

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Chapter 14.1 and 14.2: Glycolysis and Feeder Pathways

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

  2. CHAPTER 14.1 and 14.2Glycolysis Today’s Objectives: To learn and understand the • Process of harnessing energy from glucose via glycolysis • Various pathways by which carbohydrates other than glucose enter glycolysis

  3. Central Importance of Glucose • Glucose is an excellent fuel • Glucose is a versatile biochemical precursor • Four major pathways of glucose utilization

  4. 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+ + 2Pi  2 Pyruvate + 2 ATP + 2 NADH + 2 H+ + 2H20

  5. Glycolysis: Importance • Glycolysis is a sequence of ten enzyme-catalyzed reactions by which glucose is converted intopyruvate • Two phases: • First phase converts glucose to two G-3-P • Second phase produces two pyruvate molecules • Three possible fates for pyruvate

  6. Glycolysis: The Preparatory Phase

  7. Glycolysis: The Payoff Phase

  8. 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

  9. STEP 2 - Phosphohexose Isomerization • An aldose can isomerize into ketose via an enediol intermediate • Overall – Glucose-6-Phosphate is converted to Fructose-6-Phosphate

  10. 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

  11. STEP 4 - Aldolases Cleave 6-Carbon Sugars • Step four is the cleavage of Fructose 1,6-Bisphosphate

  12. STEP 5 - Triose Phosphate Interconversion • DAP is converted enzymatically to GAP

  13. STEP 6 - Glyceraldehyde 3-Phosphate Dehydrogenase Reaction • First step in the “Payoff Phase” of Glycolysis • First energy-yielding step in glycolysis

  14. 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

  15. STEP 8 - Conversion of 3-Phosphoglycerate to 2-Phosphoglycerate • This is a reversible isomerization reaction

  16. Mechanism of the PhosphoglycerateMutase Reaction

  17. 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 …

  18. STEP 10 - Second Substrate-Level Phosphorylation … but loss of phosphate from phosphoenolpyruvate yields an enol that tautomerizes into ketone

  19. Feeder Pathways for Glycolysis

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