1. End Show Slide 1 of 37 Biology Mr. Karns Cell Respiration Krebs & Oxidative phosphorylation

2. End Show Slide 2 of 37 9-2 The Krebs Cycle and Electron Transport

3. End Show 9-2 The Krebs Cycle and Electron Transport Slide 3 of 37 9-2 The Krebs Cycle and Electron Transport Oxygen is required for the final steps of cellular respiration. Because the pathways of cellular respiration require oxygen, they are aerobic. Aerobic mean with oxygen !

4. End Show 9-2 The Krebs Cycle and Electron Transport Slide 4 of 37 The Krebs Cycle In the presence of oxygen, pyruvic acid produced in glycolysis passes to the second stage of cellular respiration, the Krebs cycle.

5. End Show Slide 5 of 37 9-2 The Krebs Cycle and Electron Transport The Krebs Cycle What happens during the Krebs cycle?

6. End Show Slide 6 of 37 9-2 The Krebs Cycle and Electron Transport The Krebs Cycle During the Krebs cycle, pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reactions.

7. End Show Slide 7 of 37 9-2 The Krebs Cycle and Electron Transport The Krebs Cycle The Krebs cycle begins when pyruvic acid produced by glycolysis enters the mitochondrion.

8. End Show Slide 8 of 37 9-2 The Krebs Cycle and Electron Transport The Krebs Cycle One carbon molecule is removed, forming CO 2, and electrons are removed, changing NAD + to NADH.

9. End Show Slide 9 of 37 9-2 The Krebs Cycle and Electron Transport The Krebs Cycle Coenzyme A joins the 2-carbon molecule, forming acetyl-CoA.

10. End Show Slide 10 of 37 9-2 The Krebs Cycle and Electron Transport The Krebs Cycle Citric acid Acetyl-CoA then adds the 2-carbon acetyl group to a 4- carbon compound, forming citric acid.

11. End Show Slide 11 of 37 9-2 The Krebs Cycle and Electron Transport The Krebs Cycle Citric acid is broken down into a 5-carbon compound, then into a 4-carbon compound.

12. End Show Slide 12 of 37 9-2 The Krebs Cycle and Electron Transport The Krebs Cycle Two more molecules of CO 2 are released and electrons join NAD + and FAD, forming NADH and FADH 2

13. End Show Slide 13 of 37 9-2 The Krebs Cycle and Electron Transport The Krebs Cycle In addition, one molecule of ATP is generated.

14. End Show 9-2 The Krebs Cycle and Electron Transport Slide 14 of 37 The Krebs Cycle The energy tally from 1 molecule of pyruvic acid is 4 NADH 1 FADH 2 1 ATP

15. End Show 9-2 The Krebs Cycle and Electron Transport Slide 15 of 37 The Krebs Cycle What does the cell do with all those high-energy electrons in carriers like NADH? In the presence of oxygen, those high-energy electrons can be used to generate huge amounts of ATP.

16. End Show Slide 16 of 37 9-2 The Krebs Cycle and Electron Transport Electron Transport How are high-energy electrons used by the electron transport chain?

17. End Show Slide 17 of 37 9-2 The Krebs Cycle and Electron Transport Electron Transport The electron transport chain uses the high- energy electrons from the Krebs cycle to convert ADP into ATP. The products from Krebs still contain lots of energy- the NADH and FADH 2

18. End Show Slide 18 of 37 9-2 The Krebs Cycle and Electron Transport Electron Transport High-energy electrons from NADH and FADH 2 are passed along the electron transport chain from one carrier protein to the next.

19. End Show Slide 19 of 37 9-2 The Krebs Cycle and Electron Transport Electron Transport At the end of the chain, an enzyme combines these electrons with hydrogen ions and oxygen to form water.

20. End Show Slide 20 of 37 9-2 The Krebs Cycle and Electron Transport Electron Transport As the final electron acceptor of the electron transport chain, oxygen gets rid of the low-energy electrons and hydrogen ions.

21. End Show Slide 21 of 37 9-2 The Krebs Cycle and Electron Transport Electron Transport When 2 high-energy electrons move down the electron transport chain, their energy is used to move hydrogen ions (H + ) across the membrane.

22. End Show Slide 22 of 37 9-2 The Krebs Cycle and Electron Transport Electron Transport During electron transport, H + ions build up in the intermembrane space, so it is positively charged.

23. End Show Slide 23 of 37 9-2 The Krebs Cycle and Electron Transport Electron Transport The other side of the membrane, from which those H + ions are taken, is now negatively charged.

24. End Show Slide 24 of 37 9-2 The Krebs Cycle and Electron Transport Electron Transport ATP synthase The inner membranes of the mitochondria contain protein spheres called ATP synthases.

25. End Show Slide 25 of 37 9-2 The Krebs Cycle and Electron Transport Electron Transport As H + ions escape through channels into these proteins, the ATP synthase spins. ATP synthase Channel

26. End Show Slide 26 of 37 9-2 The Krebs Cycle and Electron Transport Electron Transport As it rotates, the enzyme grabs a low-energy ADP, attaching a phosphate, forming high-energy ATP. ATP ATP synthase Channel

27. End Show 9-2 The Krebs Cycle and Electron Transport Slide 27 of 37 Electron Transport FADH 2 makes two ATP as it enters the ETS at a lower level. NADH 2 makes 3 ATP molecules.

28. End Show 9-2 The Krebs Cycle and Electron Transport Slide 28 of 37 The Totals Glycolysis produces just 2 ATP molecules per molecule of glucose. The complete breakdown of glucose through cellular respiration, including glycolysis, results in the net production of 36 molecules of ATP. So an investment of 2 ATP in glycolysis, results in about 36 net ATP produced. This is an average, could be as high as 38 !

29. End Show 9-2 The Krebs Cycle and Electron Transport Slide 29 of 37 The Totals

30. End Show 9-2 The Krebs Cycle and Electron Transport Slide 30 of 37 Comparing Photosynthesis and Cellular Respiration The energy flows in photosynthesis and cellular respiration take place in opposite directions.

31. End Show 9-2 The Krebs Cycle and Electron Transport Slide 31 of 37 Comparing Photosynthesis and Cellular Respiration On a global level, photosynthesis and cellular respiration are also opposites. Photosynthesis removes carbon dioxide from the atmosphere and cellular respiration puts it back. Photosynthesis releases oxygen into the atmosphere and cellular respiration uses that oxygen to release energy from food. Plants do both Cell respiration and Photosynthesis. We only do cell respiration! So we need plants, they don’t need us.

32. End Show - or - Continue to: Click to Launch: Slide 32 of 37 9-2

33. End Show Slide 33 of 37 9-2 The Krebs cycle breaks pyruvic acid down into a.oxygen. b.NADH. c.carbon dioxide. d.alcohol.

34. End Show Slide 34 of 37 9-2 What role does the Krebs cycle play in the cell? a.It breaks down glucose and releases its stored energy. b.It releases energy from molecules formed during glycolysis. c.It combines carbon dioxide and water into high-energy molecules. d.It breaks down ATP and NADH, releasing stored energy.

35. End Show Slide 35 of 37 9-2 In eukaryotes, the electron transport chain is located in the a.cell membrane. b.inner mitochondrial membrane. c.cytoplasm. d.outer mitochondrial membrane.

36. End Show Slide 36 of 37 9-2 To generate energy over long periods, the body must use a.stored ATP. b.lactic acid fermentation. c.cellular respiration. d.glycolysis.

37. End Show Slide 37 of 37 9-2 Which statement correctly describes photosynthesis and cellular respiration? a.Photosynthesis releases energy, while cellular respiration stores energy. b.Photosynthesis and cellular respiration use the same raw materials. c.Cellular respiration releases energy, while photosynthesis stores energy. d.Cellular respiration and photosynthesis produce the same products.

38. END OF SECTION