2. AP Biology 2006-2007 Cellular Respiration Harvesting Chemical Energy ATP

3. AP Biology 2006-2007 What’s the point? The point is to make ATP ! ATP

4. AP Biology Harvesting stored energy  Energy is stored in organic molecules  carbohydrates, fats, proteins  Heterotrophs eat these organic molecules -> food  digest organic molecules to get…  raw materials for synthesis  fuels for energy  controlled release of energy  “burning” fuels in a series of step-by-step enzyme-controlled reactions

5. AP Biology Harvesting stored energy  Glucose is the model  catabolism of glucose to produce ATP C 6 H 12 O 6 6O 2 ATP6H 2 O6CO 2 -> + ++ CO 2 + H 2 O + heat fuel (carbohydrates) COMBUSTION = making a lot of heat energy by burning fuels in one step RESPIRATION = making ATP (& some heat) by burning fuels in many small steps CO 2 + H 2 O + ATP (+ heat) ATP glucose glucose + oxygen -> energy + water + carbon dioxide respiration O2O2 O2O2 + heat enzymes ATP

6. AP Biology How do we harvest energy from fuels?  Digest large molecules into smaller ones  break bonds & move electrons from one molecule to another  as electrons move they “carry energy” with them  that energy is stored in another bond, released as heat or harvested to make ATP e-e- ++ e-e- +– loses e-gains e-oxidizedreduced oxidationreduction redox e-e-

7. AP Biology How do we move electrons in biology?  Moving electrons in living systems  electrons cannot move alone in cells  electrons move as part of H atom  move H = move electrons p e + H + H +– loses e-gains e-oxidizedreduced oxidationreduction C 6 H 12 O 6 6O 2 6CO 2 6H 2 OATP  +++ oxidation reduction H e-e-

8. AP Biology Coupling oxidation & reduction  REDOX reactions in respiration  release energy as breakdown organic molecules  break C-C bonds  strip off electrons from C-H bonds by removing H atoms  C 6 H 12 O 6 -> CO 2 = the fuel has been oxidized  electrons attracted to more electronegative atoms  in biology, the most electronegative atom?  O 2 -> H 2 O = oxygen has been reduced  couple REDOX reactions & use the released energy to synthesize ATP C 6 H 12 O 6 6O 2 6CO 2 6H 2 OATP -> +++ oxidation reduction O2O2

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

10. AP Biology 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 niacin P O–O– O–O– O –O–O P O–O– O–O– O –O–O C C O NH 2 N+N+ H NADH carries electrons as a reduced molecule reducing power! How efficient! Build once, use many ways H like $$ in the bank

11. AP Biology 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. Krebs cycle 4. Electron transport chain C 6 H 12 O 6 6O 2 ATP6H 2 O6CO 2 -> +++ (+ heat )

12. AP Biology 2007-2008 Cellular Respiration Stage 1: Glycolysis

13. AP Biology Glycolysis glucose      pyruvate 2x2x 6C3C In the cytosol? Why does that make evolutionary sense? That’s not enough ATP for me!  Breaking down glucose  “glyco – lysis” (splitting sugar)  ancient pathway which harvests energy  where energy transfer first evolved  transfer energy from organic molecules to ATP  still is starting point for ALL cellular respiration  but it’s inefficient  generate only 2 ATP for every 1 glucose  occurs in cytosol

14. AP Biology Evolutionary perspective  Prokaryotes  first cells had no organelles  Anaerobic atmosphere  life on Earth first evolved without free oxygen (O 2 ) in atmosphere  energy had to be captured from organic molecules in absence of O 2  Prokaryotes that evolved glycolysis are ancestors of all modern life  ALL cells still utilize glycolysis You mean we’re related? Do I have to invite them over for the holidays? Enzymes of glycolysis are “well-conserved”

15. AP Biology 10 reactions  convert glucose (6C) to 2 pyruvate (3C)  produces: 4 ATP & 2 NADH  consumes: 2 ATP  net yield: 2 ATP & 2 NADH glucose C-C-C-C-C-C fructose-1,6bP P-C-C-C-C-C-C-P DHAP P-C-C-C G3P C-C-C-P pyruvate C-C-C Overview DHAP = dihydroxyacetone phosphate G3P = glyceraldehyde-3-phosphate ATP 2 ADP 2 ATP 4 ADP 4 NAD + 2 2Pi2Pi enzyme 2Pi2Pi 2H2H 2

16. AP Biology Glycolysis summary endergonic invest some ATP exergonic harvest a little ATP & a little NADH net yield 2 ATP 2 NADH 4 ATP ENERGY INVESTMENT ENERGY PAYOFF G3P C-C-C-P NET YIELD like $$ in the bank -2 ATP

17. AP Biology PiPi 3 6 4,5 ADP NAD + Glucose hexokinase phosphoglucose isomerase phosphofructokinase Glyceraldehyde 3 -phosphate (G3P) Dihydroxyacetone phosphate Glucose 6-phosphate Fructose 6-phosphate Fructose 1,6-bisphosphate isomerase glyceraldehyde 3-phosphate dehydrogenase aldolase 1,3-Bisphosphoglycerate (BPG) 1,3-Bisphosphoglycerate (BPG) 1 2 ATP ADP ATP NADH NAD + NADH PiPi CH 2 CO CH 2 OH PO CH 2 OP O CHOH C CH 2 OP O CHOH CH 2 OP O OP O P O H CH 2 OH O CH 2 P O O CH 2 OH P O 1st half of glycolysis (5 reactions) Glucose “priming”  get glucose ready to split  phosphorylate glucose  molecular rearrangement  split destabilized glucose

18. AP Biology 2nd half of glycolysis (5 reactions) Payola! Finally some ATP! 7 8 H2OH2O 9 10 ADP ATP 3-Phosphoglycerate (3PG) 3-Phosphoglycerate (3PG) 2-Phosphoglycerate (2PG) 2-Phosphoglycerate (2PG) Phosphoenolpyruvate (PEP) Phosphoenolpyruvate (PEP) Pyruvate phosphoglycerate kinase phosphoglycero- mutase enolase pyruvate kinase ADP ATP ADP ATP ADP ATP H2OH2O CH 2 OH CH 3 CH 2 O-O- O C PH CHOH O-O- O-O- O-O- C C C C C C P P O O O O O O CH 2 NAD + NADH NAD + NADH Energy Harvest G3P C-C-C-P PiPi PiPi 6 DHAP P-C-C-C  NADH production  G3P donates H  oxidizes the sugar  reduces NAD +  NAD + -> NADH  ATP production  G3P -> pyruvate  PEP sugar donates P  “substrate level phosphorylation”  ADP -> ATP

19. AP Biology Substrate-level Phosphorylation P is transferred from PEP to ADP kinase enzyme ADP -> ATP I get it! The P i came directly from the substrate! H2OH2O 9 10 Phosphoenolpyruvate (PEP) Phosphoenolpyruvate (PEP) Pyruvate enolase pyruvate kinase ADP ATP ADP ATP H2OH2O CH 3 O-O- O C O-O- C C C P O O O CH 2  In the last steps of glycolysis, where did the P come from to make ATP?  the sugar substrate (PEP) ATP

20. AP Biology Energy accounting of glycolysis  Net gain = 2 ATP + 2 NADH  some energy investment (-2 ATP)  small energy return (4 ATP + 2 NADH)  1 6C sugar -> 2 3C sugars 2 ATP2 ADP 4 ADP glucose      pyruvate 2x2x 6C3C All that work! And that’s all I get? ATP 4 2 NAD + 2 But glucose has so much more to give!

21. AP Biology Is that all there is?  Not a lot of energy…  for 1 billon years + this is how life on Earth survived  no O 2 = slow growth, slow reproduction  only harvest 3.5% of energy stored in glucose  more carbons to strip off = more energy to harvest Hard way to make a living! O2O2 O2O2 O2O2 O2O2 O2O2

22. AP Biology 7 8 H2OH2O 9 10 ADP ATP 3-Phosphoglycerate (3PG) 3-Phosphoglycerate (3PG) 2-Phosphoglycerate (2PG) 2-Phosphoglycerate (2PG) Phosphoenolpyruvate (PEP) Phosphoenolpyruvate (PEP) Pyruvate ADP ATP ADP ATP ADP ATP H2OH2O NAD + NADH NAD + NADH PiPi PiPi 6 Glycolysis glucose + 2ADP + 2P i + 2 NAD + -> 2 pyruvate + 2ATP + 2NADH But can’t stop there!  Going to run out of NAD +  without regenerating NAD +, energy production would stop!  another molecule must accept H from NADH  so NAD + is freed up for another round PiPi NAD + G3P 1,3-BPG NADH NAD + NADH PiPi DHAP

23. AP Biology NADH pyruvate acetyl-CoA lactate ethanol NAD + NADH NAD + NADH CO 2 acetaldehyde H2OH2O Krebs cycle O2O2 lactic acid fermentation with oxygen aerobic respiration without oxygen anaerobic respiration “fermentation” How is NADH recycled to NAD + ? Another molecule must accept H from NADH recycle NADH which path you use depends on who you are… alcohol fermentation

24. AP Biology Pyruvate is a branching point Pyruvate O2O2 O2O2 mitochondria Krebs cycle aerobic respiration fermentation anaerobic respiration

25. AP Biology 10 reactions  convert glucose (6C) to 2 pyruvate (3C)  produces: 4 ATP & 2 NADH  consumes: 2 ATP  net: 2 ATP & 2 NADH glucose C-C-C-C-C-C fructose-1,6bP P-C-C-C-C-C-C-P DHAP P-C-C-C G3P C-C-C-P pyruvate C-C-C Overview ATP 2 ADP 2 ATP 4 ADP 4 NAD + 2 2 2Pi2Pi 2Pi2Pi 2H2H

26. AP Biology 2006-2007 Cellular Respiration Stage 2 & 3: Oxidation of Pyruvate Krebs Cycle

27. AP Biology pyruvate -> CO 2 Glycolysis is only the start  Glycolysis  Pyruvate has more energy to yield  3 more C to strip off (to oxidize)  if O 2 is available, pyruvate enters mitochondria  enzymes of Krebs cycle complete the full oxidation of sugar to CO 2 2x2x 6C3C Glucose -> pyruvate 3C1C

28. AP Biology Cellular respiration

29. AP Biology intermembrane space inner membrane outer membrane matrix cristae Mitochondria — Structure  Double membrane energy harvesting organelle  smooth outer membrane  highly folded inner membrane  cristae  intermembrane space  fluid-filled space between membranes  matrix  inner fluid-filled space  DNA, ribosomes  enzymes  free in matrix & membrane-bound mitochondrial DNA What cells would have a lot of mitochondria?

30. AP Biology Mitochondria – Function What does this tell us about the evolution of eukaryotes? Endosymbiosis! Dividing mitochondria Who else divides like that? Advantage of highly folded inner membrane? More surface area for membrane- bound enzymes & permeases Membrane-bound proteins Enzymes & permeases Oooooh! Form fits function! bacteria!

31. AP Biology pyruvate    acetyl CoA + CO 2 Oxidation of pyruvate NAD 3C2C 1C [ 2x ]  Pyruvate enters mitochondrial matrix  3 step oxidation process  releases 2 CO 2 (count the carbons!)  reduces 2 NAD -> 2 NADH (moves e - )  produces 2 acetyl CoA  Acetyl CoA enters Krebs cycle Where does the CO 2 go? Exhale!

32. AP Biology Pyruvate oxidized to Acetyl CoA Yield = 2C sugar + NADH + CO 2 reduction oxidation Coenzyme A Pyruvate Acetyl CoA C-C-C C-C CO 2 NAD + 2 x []

33. AP Biology Krebs cycle  aka Citric Acid Cycle  in mitochondrial matrix  8 step pathway  each catalyzed by specific enzyme  step-wise catabolism of 6C citrate molecule  Evolved later than glycolysis  does that make evolutionary sense?  Bacteria 3.5 billion years ago (glycolysis)  free O 2 2.7 billion years ago (photosynthesis)  Eukaryotes 1.5 billion years ago (aerobic respiration = organelles and mitochondria) 1937 | 1953 Hans Krebs 1900-1981

34. AP Biology 4C6C4C 2C6C5C4C CO 2 citrate acetyl CoA Count the carbons! 3C pyruvate x2x2 oxidation of sugars This happens twice for each glucose molecule

35. AP Biology 4C6C4C 2C6C5C4C CO 2 citrate acetyl CoA Count the electron carriers! 3C pyruvate reduction of electron carriers This happens twice for each glucose molecule x2x2 CO 2 NADH FADH 2 ATP

36. AP Biology So we fully oxidized glucose C 6 H 12 O 6 to CO 2 & ended up with 4 ATP! Whassup? What’s the point?

37. AP Biology  Krebs cycle produces large quantities of electron carriers  NADH  FADH 2  go to Electron Transport Chain! Electron Carriers = Hydrogen Carriers What’s so important about electron carriers? H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ ATP ADP + P i

38. AP Biology Value of Krebs cycle?  If the yield is only 2 ATP then how was the Krebs cycle an adaptation?  value of NADH & FADH 2  electron carriers & H carriers  reduced molecules move electrons  reduced molecules move H + ions  to be used in the Electron Transport Chain like $$ in the bank

39. AP Biology H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ And how do we do that? ATP But… Have we done that yet? ADP P +  ATP synthase  set up a H + gradient  allow H + to flow through ATP synthase  powers bonding of P i to ADP ADP + P i -> ATP

40. AP Biology 2006-2007 Cellular Respiration Stage 4: Electron Transport Chain

41. AP Biology Cellular respiration

42. AP Biology 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! A working muscle recycles over 10 million ATPs per second There’s got to be a better way! I need a lot more ATP!

43. AP Biology There is a better way!  Electron Transport Chain  series of proteins built into inner mitochondrial membrane  along cristae  transport proteins & enzymes  transport of electrons down ETC linked to pumping of H + to create H + gradient  yields ~36 ATP from 1 glucose!  only in presence of O 2 (aerobic respiration) O2O2 That sounds more like it!

44. AP Biology Mitochondria  Double membrane  outer membrane  inner membrane  highly folded cristae  enzymes & transport proteins  intermembrane space  fluid-filled space between membranes Oooooh! Form fits function!

45. AP Biology Electron Transport Chain Intermembrane space Mitochondrial matrix Q C NADH dehydrogenase cytochrome bc complex cytochrome c oxidase complex Inner mitochondrial membrane

46. AP Biology G3P Glycolysis Krebs cycle 8 NADH 2 FADH 2 Remember the Electron Carriers? 2 NADH Time to break open the piggybank! glucose

47. AP Biology Electron Transport Chain intermembrane space mitochondrial matrix inner mitochondrial membrane NAD + Q C NADH H 2 O H+H+ e–e– 2H + +O2O2 H+H+ H+H+ e–e– FADH 2 1212 NADH dehydrogenase cytochrome bc complex cytochrome c oxidase complex FAD e–e– H H = e- + H + NADH -> NAD + + H H p e Building proton gradient! What powers the proton (H + ) pumps?…

48. AP Biology H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ ATP NAD + Q C NADH H 2 O H+H+ e–e– 2H + +O2O2 H+H+ H+H+ e–e– FADH 2 1212 NADH dehydrogenase cytochrome bc complex cytochrome c oxidase complex FAD e–e– Stripping H from Electron Carriers  Electron carriers pass electrons & H + to ETC  H cleaved off NADH & FADH 2  electrons stripped from H atoms and H + (protons)  electrons passed from one electron carrier to next in mitochondrial membrane (ETC)  flowing electrons = energy to do work  transport proteins in membrane pump H + (protons) across inner membrane to intermembrane space ADP + P i TA-DA!! Moving electrons do the work! H+H+ H+H+ H+H+

49. AP Biology But what “pulls” the electrons down the ETC? electrons flow downhill to O 2 oxidative phosphorylation O2O2 H2OH2O

50. AP Biology Electrons flow downhill  Electrons move in steps from carrier to carrier downhill to oxygen  each carrier more electronegative  controlled oxidation  controlled release of energy make ATP instead of fire!

51. AP Biology H+H+ ADP + P i H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ We did it! ATP  Set up a H + gradient  Allow the protons to flow through ATP synthase  Synthesizes ATP ADP + P i -> ATP Are we there yet? “proton-motive” force

52. AP Biology  The diffusion of ions across a membrane  build up of proton gradient just so H+ could flow through ATP synthase enzyme to build ATP Chemiosmosis Chemiosmosis links the Electron Transport Chain to ATP synthesis So that’s the point!

53. AP Biology Cellular respiration 2 ATP ~36 ATP ++ ~40 ATP

54. AP Biology 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 CO 2 go?  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~40 ATP  +++

55. AP Biology  ETC backs up  nothing to pull electrons down chain  NADH & FADH 2 can’t unload H  ATP production ceases  cells run out of energy  and you die! Taking it beyond…  What is the final electron acceptor in Electron Transport Chain? O2O2  So what happens if O 2 unavailable? NAD + Q C NADH H 2 O H+H+ e–e– 2H + +O2O2 H+H+ H+H+ e–e– FADH 2 1212 NADH dehydrogenase cytochrome bc complex cytochrome c oxidase complex FAD e–e–