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Harvesting Energy

Harvesting Energy. Overview of Glucose Breakdown. The overall equation for the complete breakdown of glucose is: C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + ATP The main stages of glucose metabolism are: Glycolysis Cellular respiration. Overview of Glucose Breakdown. Glycolysis

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Harvesting Energy

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  1. Chapter 8 Harvesting Energy

  2. Chapter 8 Overview of Glucose Breakdown • The overall equation for the complete breakdown of glucose is: • C6H12O6 + 6O2 6CO2 + 6H2O + ATP • The main stages of glucose metabolism are: • Glycolysis • Cellular respiration

  3. Chapter 8

  4. Chapter 8 Overview of Glucose Breakdown • Glycolysis • Occurs in the cytosol • Does not require oxygen • Breaks glucose into pyruvate • Yields two molecules of ATP per molecule of glucose

  5. Chapter 8 Overview of Glucose Breakdown • If oxygen is absent fermentation occurs • pyruvate is converted into either lactate, or into ethanol and CO2 • If oxygen is present cellular respiration occurs…

  6. Chapter 8 Overview of Glucose Breakdown • Cellular respiration • Occurs in mitochondria (in eukaryotes) • Requires oxygen • Breaks down pyruvate into carbon dioxide and water • Produces an additional 32 or 34 ATP molecules, depending on the cell type

  7. Chapter 8 Glycolysis • Overview of the two major phases of glycolysis • Glucose activation phase • Energy harvesting phase

  8. Chapter 8 Glycolysis • Glucose activation phase • Glucose molecule converted to highly reactive fructose bisphosphate by two enzyme-catalyzed reactions, using 2 ATPs

  9. Chapter 8 Essentials of Glycolysis (a) ATP ADP P P P C C C C C C C C C C C C C C C C C C C C C C C C P ATP ADP Glucose-6-Phosphate Glucose Glucose-6-Phosphate Fructose-1,6-Bisphosphate

  10. Chapter 8 Glycolysis • Energy harvesting phase • Fructose bisphosphate is split into two three-carbon molecules of glyceraldehyde 3-phosphate (G3P) • In a series of reactions, each G3P molecule is converted into a pyruvate, generating two ATPs per conversion, for a total of four ATPs • Because two ATPs were used to activate the glucose molecule there is a net gain of two ATPs per glucose molecule

  11. Chapter 8 Essentials of Glycolysis (b) Fructose-1,6-Bisphosphate P P P C C C C C C P P C C C C C C C C C C C C P G3P

  12. Chapter 8 Glycolysis • Energy harvesting phase (continued) • As each G3P is converted to pyruvate, two high-energy electrons and a hydrogen ion are added to an “empty” electron-carrier NAD+ to make the high-energy electron-carrier molecule NADH • Because two G3P molecules are produced per glucose molecule, two NADH carrier molecules are formed

  13. Chapter 8 Essentials of Glycolysis (c) Pi Pi NAD+ NAD+ NADH NADH P P ADP ADP ADP ADP C C C C C C C C C C C C C C C C C C P P ATP ATP P P ATP ATP G3P Pyruvates

  14. Chapter 8 Glycolysis • Summary of glycolysis: • Each molecule of glucose is broken down to two molecules of pyruvate • A net of two ATP molecules and two NADH (high-energy electron carriers) are formed

  15. Chapter 8 Fermentation of Dough

  16. Chapter 8 Fermentation • Pyruvate is processed differently under aerobic and anaerobic conditions • Under aerobic conditions, the high energy electrons in NADH produced in glycolysis are ferried to ATP-generating reactions in the mitochondria, making NAD+ available to recycle in glycolysis

  17. Chapter 8 Fermentation • Under anaerobic conditions, pyruvate is converted into lactate or ethanol, a process called fermentation • Fermentation does not produce more ATP, but is necessary to regenerate the high-energy electron carrier molecule NAD+, which must be available for glycolysis to continue

  18. Chapter 8 Fermentation • Some microbes ferment pyruvate to other acids (as seen in making of cheese, yogurt, sour cream) • Some microbes perform fermentation exclusively (instead of aerobic respiration) • Yeast cells perform alcoholic fermentation

  19. Chapter 8 Alcoholic Fermentation O O NADH C C O O NADH C C C C C C C C C C C C C C C C NAD+ NAD+ NADH NAD+ NAD+ NADH AlcoholicFermentation Glycolysis Glucoses Pyruvates Ethanols ADP ATP ADP ATP

  20. Chapter 8 Fermentation • Some cells ferment pyruvate to form acids • Human muscle cells can perform fermentation • Anaerobic conditions produced when muscles use up O2 faster than it can be delivered (e.g. while sprinting) • Lactate (lactic acid) produced from pyruvate

  21. Chapter 8 Lactate Fermentation NADH NADH C C C C C C C C C C C C C C C C C C NAD+ NADH NAD+ NAD+ NADH NAD+ LactateFermentation Glycolysis Glucoses Pyruvates Lactates ADP ATP ADP ATP

  22. Chapter 8 Cellular Respiration • In eukaryotic cells, cellular respiration occurs within mitochondria, organelles with two membranes that produce two compartments • The inner membrane encloses a central compartment containing the fluid matrix • The outer membrane surrounds the organelle, producing an intermembrane space

  23. Chapter 8 A Mitochondrion One of ItsMitochondria a b A Cell A Crista Outer& InnerMembranes c Matrix IntermembraneCompartment

  24. Chapter 8 Cellular Respiration • Overview of Aerobic Cellular Respiration: • Glucose is first broken down into pyruvate, through glycolysis, in the cell cytoplasm • Pyruvate is transported into the mitochondrion (eukaryotes) and split into CO2 and a 2 carbon acetyl group

  25. Chapter 8 Cellular Respiration • The acetyl group is further broken down into CO2 in the Krebs Cycle (matrix space) as electron carriers are loaded • Electron carriers loaded up in glycolysis and the Krebs Cycle give up electrons to the electron transport chain (ETC) along the inner mitochondrial membrane

  26. Chapter 8 Cellular Respiration • A hydrogen ion gradient produced by the ETC is used to make ATP (chemiosmosis) • ATP is transported out of the mitochondrion to provide energy for cellular activities

  27. Chapter 8 Cellular Respiration

  28. Chapter 8 Pyruvate Breakdown in Mitochondria • After glycolysis, pyruvate diffuses into the mitochondrion into the matrix space • Pyruvate is split into CO2 and a 2-carbon acetyl group, generating 1 NADH per pyruvate

  29. Chapter 8 Pyruvate Breakdown in Mitochondria • Acetyl group is carried by a helper molecule called Coenzyme A, now called Acetyl CoA • Acetyl CoA enters the Krebs Cycle and is broken down into CO2

  30. Chapter 8 Pyruvate Breakdown in Mitochondria • Electron carriers NAD+ and FAD are loaded with electrons to produce 3 NADH & 1 FADH2 per Acetyl CoA • 6. One ATP also made per Acetyl CoA in the Krebs Cycle

  31. Chapter 8 Formation of Acetyl CoA O C O O C NAD+ NAD+ O C C C C C C C C CoA CoA NADH NADH CoA CoA C C C C C C C C C C C C Pyruvates Acetyl CoA

  32. Chapter 8 Krebs Cycle: Summary CoA O O O O C C C C O O O O C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C NAD+ NADH NADH NAD+ H2O CoA CoA NAD+ C C C C C C C C FADH2 NADH FAD ADP ATP H2O CoA Acetyl CoA 1 NAD+ NADH 2 3 NADH NAD+ H2O 5 6 7 NAD+ FADH2 NADH FAD ADP ATP 4 H2O

  33. Chapter 8 Electron Transport Chain • Most of the energy in glucose is stored in electron carriers NADH and FADH2 • Only 4 total ATP produced per glucose after complete breakdown in the Krebs Cycle

  34. Chapter 8 Electron Transport Chain • NADH and FADH2 deposit electrons into electron transport chains in the inner mitochondrial membrane • Electrons join with oxygen gas and hydrogen ions to made H2O at the end of the ETCs

  35. Chapter 8 MitochondrialElectron Transport System

  36. Chapter 8 Chemiosmosis • Energy is released from electrons as they are passed down the electron transport chain • Released energy used to pump hydrogen ions across the inner membrane • Hydrogen ions accumulate in intermembrane space

  37. Chapter 8 Chemiosmosis • Hydrogen ions form a concentration gradient across the membrane, a form of stored energy • Hydrogen ions flow back into the matrix through an ATP synthesizing enzyme • Process is called chemiosmosis

  38. Chapter 8 Chemiosmosis • Flow of hydrogen ions provides energy to link 32-34 molecules of ADP with phosphate, forming 32-34 ATP • ATP then diffuses out of mitochondrion and used for energy-requiring activities in the cell

  39. Chapter 8 MitochondrialChemiosmosis (1)

  40. Chapter 8 MitochondrialChemiosmosis (2)

  41. Chapter 8 MitochondrialChemiosmosis (3)

  42. Chapter 8 Influence on How Organisms Function • Metabolic processes in cells are heavily dependent on ATP generation (cyanide kills by preventing this) • Muscle cells switch between fermentation and aerobic cell respiration depending on O2 availability

  43. Chapter 8 Energy Harvested from Glucose

  44. Chapter 8 Energy Harvested from Glucose Glucose (Cytoplasm) 4 ATP Glycolysis 2 ATP 2 Pyruvates 2 NADH (MitochondrialMatrix) 2 CO2 2 NADH KrebsCycle 6 NADH 4 CO2 2 FADH2 2 ATP (InnerMembrane) Water Electron TransportSystem 32 ATP Oxygen

  45. Chapter 8 The end

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