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Energy Harvesting Pathways

Energy Harvesting Pathways. Glycolysis & Cellular Respiration. energy harvest, storage & transfers Figure 7.1. energy transfers. two ways to transfer metabolic energy from one molecule to another as free energy during coupled exergonic/ endergonic reactions

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Energy Harvesting Pathways

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  1. Energy Harvesting Pathways Glycolysis & Cellular Respiration

  2. energy harvest, storage & transfersFigure 7.1

  3. energy transfers • two ways to transfer metabolic energy from one molecule to another • as free energy during coupled exergonic/ endergonic reactions • as “high energy” electrons during reduction/oxidation reactions

  4. reduction reactions transfer energy Figure 7.2 of course, some usable energy is lost in the transfer

  5. NAD+ accepts reducing equivalents (H & e-)Figure 7.4 (NADH+H+) + 1/2 O2 => NAD+ + H2O DG = -52.4 kcal·mol-1

  6. NAD+/NADH shuttles reducing equivalentsFigure 7.3

  7. retrieving energy from storage • glucose is the most common metabolic fuel • other fuel molecules use the same catabolic pathway • when glucose is completely oxidized (burned) C6 +6O2 => 6CO2+6H2O + energy • DG= -686 kcal/mol • when glucose is oxidized metabolically C6 +6O2 => 6CO2+6H2O + energy ~ half of released energy is transferred to ATP

  8. stages of glucose oxidationFigure 7.5

  9. retrieving energy from storage • glucose is oxidized by a series of regulated metabolic pathways • glycolysis (cytoplasmic) • yields ATP, NADH & • two 3C pyruvates • cellular respiration (mitochondrial) • converts pyruvate to CO2 & H2O, and • yields ATP, and • absolutely requires O2

  10. fermentation: partial oxidation of glucose in the absence of oxygen OR, if O2 is short Figure 7.5

  11. Cell Resp/Ferment LocationsTable 7.1

  12. free energy changes duringglycolysisFigure 7.7

  13. Investment, Isomerase,Harvest I,Harvest IIFigure 7.6

  14. glycolysis products:NADH (2)ATP (2)pyruvate (2)Figure 7.7

  15. retrieving energy from storage • glycolysis • a ten-step metabolic pathway • in the cytoplasm • cellular respiration • NADH & pyruvate go to the mitochondrion • pyruvate is oxidized, and • decarboxylated • COOH functional group (carboxyl) is released as COO (CO2)

  16. coenzyme A cycleFigure 7.8

  17. citric acid cycle,tricarboxylic acid (TCA) cycle, Kreb’s cycleFigure 7.8

  18. retrieving energy from storage • pyruvate oxidation produces acetyl-CoA which enters the citric acid cycle • 2C acetate joins 4C oxaloacetate => 6C citric acid • atoms are rearranged • CO2 is released • intermediates are oxidized • ATP is formed • more oxidation & rearrangement

  19. final enzymatic disassembly of glucose by acyclic acetate burner with energy capturing accessoriesFigure 7.8

  20. energy yield of glycolysis and citric acid cycleFigure 7.9

  21. retrieving energy from storage • the major energy product of glycolysis and citric acid cycle is NADH • the major metabolic energy demand is for ATP • citric acid cycle enzymes are in the mitochondrial matrix • NADH reduces an enzymatic pathway on the inner mitochondrial membrane

  22. fate of electrons from glucoseFigure 7.10

  23. change in free energy during electron transportFigure 7.11

  24. electron transport proton pumpproton translocation during electron transportFigure 7.12

  25. retrieving energy from storage • NADH drives electron transport • electron transport drives proton pumping • proton pumping produces a transmembrane electrochemical gradient • the phospholipid bilayer blocks diffusion of protons into the matrix

  26. the ATP synthase proton channel relieves the transmembrane proton gradient, andthe proton gradient drives ATP synthesischemiosmosisFigure 7.12

  27. a proton gradient is sufficient to generate ATPFigure 7.13

  28. retrieving energy from storage • fermentation • occurs when O2 is insufficient to drive cellular (aerobic) respiration • IS NOT “anaerobic respiration” • regenerates NAD+

  29. lactic acid fermentation regenerates NAD+Figure 7.14

  30. ethanolic fermentation regenerates NAD+Figure 7.15

  31. energy balance sheetFigure 7.16

  32. interacting metabolic pathwaysFigure 7.17

  33. transamination forms an amino acidFigure 7.18

  34. positive & negative feedback coordinate the integrated metabolic pathwaysFigure 7.19

  35. positive & negative feedback control glycolysisFigure 7.20

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