2. AP Biology 2005-2006 Chapter 8. Cellular Respiration Harvesting Chemical Energy

3. AP Biology 2005-2006 The Point is to Make ATP! ATP What’s the point?

4. AP Biology 2005-2006 Harvesting stored energy  Energy is stored in organic molecules  heterotrophs eat food (organic molecules)  digest organic molecules  serve as raw materials for building & fuels for energy  controlled release of energy  series of step-by-step enzyme-controlled reactions  “burning” fuels  carbohydrates, lipids, proteins, nucleic acids

5. AP Biology 2005-2006 Harvesting energy stored in glucose  Glucose is the model  catabolism of glucose to produce ATP glucose + oxygen  carbon + water + energy dioxide C 6 H 12 O 6 6O 2 6CO 2 6H 2 OATP  + +++ heat CO 2 + H 2 O + heat fuel (carbohydrates) combustion = making heat energy by burning fuels in one step respiration = making ATP (& less heat) by burning fuels in many small steps ATP CO 2 + H 2 O + ATP (+ heat) respiration

6. AP Biology 2005-2006 Oxidation & reduction  Oxidation  adding O  removing H  loss of electrons  releases energy  exergonic  Reduction  removing O  adding H  gain of electrons  stores energy  endergonic C 6 H 12 O 6 6O 2 6CO 2 6H 2 OATP  +++ oxidation reduction

7. AP Biology 2005-2006 Moving electrons in respiration  Electron carriers move electrons by shuttling H atoms around  NAD +  NADH (reduced)  FAD +2  FADH 2 (reduced) + H reduction oxidation P O–O– O–O– O –O–O P O–O– O–O– O –O–O C C O NH 2 N+N+ H adenine ribose sugar phosphates NAD nicotinamide Vitamin B3 P O–O– O–O– O –O–O P O–O– O–O– O –O–O C C O NH 2 N+N+ H H NADH stores energy as a reduced molecule reducing power! How efficient! Build once, use many ways

8. AP Biology 2005-2006 Overview of cellular respiration  4 metabolic stages  Anaerobic respiration  1. Glycolysis  respiration without O 2  in cytosol  Aerobic respiration  respiration using O 2  in mitochondria  2. Pyruvate oxidation  3. Kreb’s cycle  4. Electron transport chain C 6 H 12 O 6 6O 2 6CO 2 6H 2 OATP  +++ (+ heat )

9. AP Biology 2005-2006 Chapter 8. Cellular Respiration STEP 1: Glycolysis

10. AP Biology 2005-2006 The Point is to Make ATP! ATP What’s the point?

11. AP Biology 2005-2006 Glycolysis  Breaking down glucose  “glyco – lysis” (splitting sugar)  most ancient form of energy capture  starting point for all cellular respiration  inefficient  generate only 2 ATP for every 1 glucose  in cytosol  why does that make evolutionary sense? glucose      pyruvate 2x2x 6C3C

12. AP Biology 2005-2006 Glycolysis summary endergonic invest some ATP exergonic harvest a little more ATP & a little NADH

13. AP Biology 2005-2006 Energy accounting of glycolysis  Net gain = 2 ATP  some energy investment (2 ATP)  small energy return (4 ATP)  1 6C sugar  2 3C sugars 2 ATP2 ADP 4 ADP4 ATP glucose      pyruvate 2x2x 6C3C All that work! And that’s all I get?

14. AP Biology 2005-2006 The Point is to Make ATP! ATP What’s the point?

15. AP Biology 2005-2006 Chapter 8. STEP 2 Cellular Respiration Oxidation of Pyruvate Krebs Cycle

16. AP Biology 2005-2006 Cellular respiration

17. AP Biology 2005-2006 Pyruvate oxidized to Acetyl CoA 1 pyruvate Yield = 2C sugar + CO 2 + 1 NADH reduction oxidation

18. AP Biology 2005-2006  Krebs cycle produces large quantities of electron carriers  NADH  FADH 2  stored energy!  go to ETC a.k.a. Citric Acid Cycle What’s so important about NADH?

19. AP Biology 2005-2006 Energy accounting of Krebs cycle  Net gain=2 ATP = 8 NADH + 2 FADH 2 4 NAD + 1 FAD 4 NADH + 1 FADH 2 1 ADP1 ATP 3x3x pyruvate          CO 2 ][ 2x 3C 1C

20. AP Biology 2005-2006 So why the Krebs cycle?  If the yield is only 2 ATP, then why?  value of NADH & FADH 2  electron carriers  reduced molecules store energy!  to be used in the Electron Transport Chain

21. AP Biology 2005-2006 The Point is to Make ATP! ATP What’s the point?

22. AP Biology 2005-2006 Chapter 8. STEP 3: Cellular Respiration Electron Transport Chain

23. AP Biology 2005-2006 Cellular respiration

24. AP Biology 2005-2006 The Point is to Make ATP! ATP What’s the point?

25. AP Biology 2005-2006 ATP accounting so far…  Glycolysis  2 ATP  Kreb’s cycle  2 ATP  Life takes a lot of energy to run, need to extract more energy than 4 ATP! There’s got to be a better way! What’s the Point?

26. AP Biology 2005-2006 There is a better way!  Electron Transport Chain  series of molecules built into inner mitochondrial membrane  mostly transport proteins  transport of electrons down ETC linked to ATP synthesis  yields ~34 ATP from 1 glucose!  only in presence of O 2 (aerobic) That sounds more like it!

27. AP Biology 2005-2006 Mitochondria  Double membrane  outer membrane  inner membrane  highly folded cristae*  fluid-filled space between membranes = intermembrane space  matrix  central fluid-filled space * form fits function!

28. AP Biology 2005-2006 Electron Transport Chain

29. AP Biology 2005-2006 PGAL Glycolysis Kreb’s cycle 2 NADH 8 NADH 2 FADH 2 Remember the NADH?

30. AP Biology 2005-2006 Electron Transport Chain  NADH passes electrons to ETC  H cleaved off NADH & FADH 2  electrons stripped from H atoms  H + (H ions)  electrons passed from one electron carrier to next in mitochondrial membrane (ETC)  transport proteins in membrane pump H + across inner membrane to intermembrane space

31. AP Biology 2005-2006 But what “pulls” the electrons down the ETC? electrons flow downhill to O 2

32. AP Biology 2005-2006 Cellular respiration

33. AP Biology 2005-2006 Summary of cellular respiration  Where did the glucose come from?  Where did the O 2 come from?  Where did the CO 2 come from?  Where did the H 2 O come from?  Where did the ATP come from?  What else is produced that is not listed in this equation?  Why do we breathe? C 6 H 12 O 6 6O 2 6CO 2 6H 2 O~36 ATP  +++

34. AP Biology 2005-2006 Taking it beyond…  What is the final electron acceptor in electron transport chain? O2O2  So what happens if O 2 unavailable for organisms that REQUIRE oxygen?  ETC backs up  ATP production ceases  cells run out of energy  and you die!

35. AP Biology THERE IS ANOTHER WAY  ANAEROBIC RESPIRATION 1. Alcoholic Fermentation 2. Lactic Acid Fermentation Less efficient Original pathway in evolutionary history 2005-2006

36. AP Biology 2005-2006 Anaerobic ethanol fermentation  Bacteria, yeast 1C 3C2C pyruvate  ethanol + CO 2  Animals, some fungi pyruvate  lactic acid 3C  beer, wine, bread  at ~12% ethanol, kills yeast  cheese, yogurt, anaerobic exercise (no O 2 ) NADHNAD + NADHNAD +

37. AP Biology 2005-2006 Pyruvate is a branching point Pyruvate O2O2 O2O2 Kreb’s cycle mitochondria fermentation

38. AP Biology 2005-2006 The Point is to Make ATP! ATP What’s the point?