1. Chapter 8 Harvesting Energy

2. Chapter 8 2 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 C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + ATP The main stages of glucose metabolism are: Glycolysis Glycolysis Cellular respiration Cellular respiration

3. Chapter 8 3

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

5. Chapter 8 5 Overview of Glucose Breakdown If oxygen is absent fermentation occurs pyruvate is converted into either lactate, or into ethanol and CO 2 pyruvate is converted into either lactate, or into ethanol and CO 2 If oxygen is present cellular respiration occurs…

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

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

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

9. Chapter 8 9 Essentials of Glycolysis (a) CCCCCC GlucoseP P ATPADP CCCCCC Glucose-6- Phosphate P CCCCCC ATPADP P CCCCCC Fructose-1,6- Bisphosphate

10. Chapter 8 10Glycolysis Energy harvesting phase Fructose bisphosphate is split into two three-carbon molecules of glyceraldehyde 3-phosphate (G3P) 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 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 Because two ATPs were used to activate the glucose molecule there is a net gain of two ATPs per glucose molecule

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

12. Chapter 8 12Glycolysis 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 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 Because two G3P molecules are produced per glucose molecule, two NADH carrier molecules are formed

13. Chapter 8 13 Essentials of Glycolysis (c) PP P CCC P CCC P CCC P CCC CCCCCC PiPiPiPi PiPiPiPi NAD + NADHNADH ATPATPATPATP ADPADPADPADPPyruvates G3P

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

15. Chapter 8 15 Fermentation of Dough

16. Chapter 8 16Fermentation 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 17Fermentation 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 18Fermentation 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 19 Alcoholic Fermentation NAD + CCCCCC Glucoses CCC Glycolysis Alcoholic Fermentation NAD + NADH ADPATP ADPATP PyruvatesEthanols CCCCC CC NADH C O O C O O NADHNADH

20. Chapter 8 20Fermentation Some cells ferment pyruvate to form acids Human muscle cells can perform fermentation Anaerobic conditions produced when muscles use up O 2 faster than it can be delivered (e.g. while sprinting) Anaerobic conditions produced when muscles use up O 2 faster than it can be delivered (e.g. while sprinting) Lactate (lactic acid) produced from pyruvate Lactate (lactic acid) produced from pyruvate

21. Chapter 8 21 Lactate Fermentation NAD + CCCCCC Glucoses CCC CCC Glycolysis Lactate Fermentation NAD + NADH ADPATP ADPATP PyruvatesLactates CCC CCC NADH NADHNADH

22. Chapter 8 22 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 inner membrane encloses a central compartment containing the fluid matrix The outer membrane surrounds the organelle, producing an intermembrane space The outer membrane surrounds the organelle, producing an intermembrane space

23. Chapter 8 23 A Mitochondrion Matrix A Cell One of Its Mitochondria A Crista Outer & Inner Membranes Intermembrane Compartment a b c

24. Chapter 8 24 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 CO 2 and a 2 carbon acetyl group

25. Chapter 8 25 Cellular Respiration The acetyl group is further broken down into CO 2 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 26 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 27 Cellular Respiration

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

29. Chapter 8 29 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 CO 2

30. Chapter 8 30 Pyruvate Breakdown in Mitochondria Electron carriers NAD + and FAD are loaded with electrons to produce 3 NADH & 1 FADH 2 per Acetyl CoA 6. One ATP also made per Acetyl CoA in the Krebs Cycle

31. Chapter 8 31 Formation of Acetyl CoA CCCCCC CoACoA CCCCCC Pyruvates CoACoA CCCC NAD + NADHNADH C O O C O O Acetyl CoA CCCC

32. Chapter 8 32 Krebs Cycle: Summary CCCCC NADH CCCC CoA C CCCCC C O O C O O NAD + NADH NADH ADP ATP H2OH2OH2OH2O FADH 2 FAD H2OH2OH2OH2O CCCC C CCCCC CoA NAD + NADH C O O CCCCC H2OH2OH2OH2O NADH ADP ATP C O O CCCC NADH FADH 2 FAD H2OH2OH2OH2O 1 23 4 567 C CCCCC CCCCC CCCC CoACoA CCCC Acetyl CoA

33. Chapter 8 33 Electron Transport Chain Most of the energy in glucose is stored in electron carriers NADH and FADH 2 Only 4 total ATP produced per glucose after complete breakdown in the Krebs Cycle Only 4 total ATP produced per glucose after complete breakdown in the Krebs Cycle

34. Chapter 8 34 Electron Transport Chain NADH and FADH 2 deposit electrons into electron transport chains in the inner mitochondrial membrane Electrons join with oxygen gas and hydrogen ions to made H 2 O at the end of the ETCs

35. Chapter 8 35 Mitochondrial Electron Transport System

36. Chapter 8 36Chemiosmosis 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 Hydrogen ions accumulate in intermembrane space

37. Chapter 8 37Chemiosmosis 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 Process is called chemiosmosis

38. Chapter 8 38Chemiosmosis 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 39 Mitochondrial Chemiosmosis (1)

40. Chapter 8 40 Mitochondrial Chemiosmosis (2)

41. Chapter 8 41 Mitochondrial Chemiosmosis (3)

42. Chapter 8 42 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 O 2 availability

43. Chapter 8 43 Energy Harvested from Glucose

44. Chapter 8 44 Energy Harvested from Glucose (Cytoplasm) Glucose 2 NADH 6 NADH 2 FADH 2 2 Pyruvates 2 CO 2 4 CO 2 2 ATP 4 ATP (Mitochondrial Matrix) (Inner Membrane) 2 ATP 32 ATP Electron Transport System Glycolysis Krebs Cycle Water Oxygen

45. Chapter 8 The end