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AP Biology John D. O’Bryant School of Mathematics and Science

AP Biology John D. O’Bryant School of Mathematics and Science. October 24, 2012. Agenda. Do Now: HW Review Cellular Respiration: Lecture/Discussion, Lab Quiz. Cellular Respiration Stage 1: Glycolysis. What’s the point?. The point is to make ATP !. ATP. glucose      pyruvate. 6C.

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AP Biology John D. O’Bryant School of Mathematics and Science

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  1. AP BiologyJohn D. O’Bryant School of Mathematics and Science October 24, 2012

  2. Agenda • Do Now: HW Review • Cellular Respiration: Lecture/Discussion, Lab • Quiz

  3. Cellular RespirationStage 1:Glycolysis

  4. What’s thepoint? The pointis to makeATP! ATP

  5. glucose      pyruvate 6C 3C 2x Glycolysis • 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 only2 ATP for every 1 glucose • occurs in cytosol In thecytosol?Why doesthat makeevolutionarysense? That’s not enoughATP for me!

  6. Evolutionary perspective Enzymesof glycolysis are“well-conserved” • Prokaryotes • first cells had no organelles • Anaerobic atmosphere • life on Earth first evolved withoutfree oxygen (O2) in atmosphere • energy had to be captured from organic molecules in absence of O2 • Prokaryotes that evolved glycolysis are ancestors of all modern life • ALL cells still utilize glycolysis You meanwe’re related?Do I have to invitethem over for the holidays?

  7. enzyme enzyme enzyme enzyme enzyme enzyme enzyme enzyme ATP ATP 4 2 4 2 2 ADP NAD+ ADP 2Pi 2 2H 2Pi glucose C-C-C-C-C-C Overview 10 reactions • convert glucose (6C)to 2 pyruvate (3C) • produces:4 ATP & 2 NADH • consumes:2 ATP • net yield:2 ATP & 2 NADH 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 DHAP = dihydroxyacetone phosphate G3P = glyceraldehyde-3-phosphate

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

  9. 1st half of glycolysis (5 reactions) CH2OH Glucose “priming” O Glucose 1 ATP hexokinase • get glucose ready to split • phosphorylate glucose • molecular rearrangement • split destabilized glucose ADP CH2 O P O Glucose 6-phosphate 2 phosphoglucose isomerase CH2 P O CH2OH O Fructose 6-phosphate 3 ATP phosphofructokinase P O CH2 CH2 O P O ADP Fructose 1,6-bisphosphate aldolase 4,5 H O CH2 P isomerase C O C O Dihydroxyacetone phosphate Glyceraldehyde 3 -phosphate (G3P) CHOH CH2OH CH2 O P NAD+ Pi NAD+ Pi 6 glyceraldehyde 3-phosphate dehydrogenase NADH NADH P O O CHOH 1,3-Bisphosphoglycerate (BPG) 1,3-Bisphosphoglycerate (BPG) CH2 O P

  10. 2nd half of glycolysis (5 reactions) DHAP P-C-C-C G3P C-C-C-P Energy Harvest • 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 Pi Pi NAD+ NAD+ 6 NADH NADH 7 ADP ADP O- phosphoglycerate kinase C ATP ATP CHOH 3-Phosphoglycerate (3PG) 3-Phosphoglycerate (3PG) CH2 P O 8 O- phosphoglycero-mutase O C H C O P 2-Phosphoglycerate (2PG) 2-Phosphoglycerate (2PG) CH2OH O- 9 H2O H2O enolase C O O C P Phosphoenolpyruvate (PEP) Phosphoenolpyruvate (PEP) CH2 O- 10 ADP ADP C O pyruvate kinase Payola!Finally some ATP! ATP ATP C O CH3 Pyruvate Pyruvate

  11. O- 9 H2O H2O enolase C O O C P Phosphoenolpyruvate (PEP) Phosphoenolpyruvate (PEP) CH2 O- 10 ADP ADP C O pyruvate kinase ATP ATP C O CH3 Pyruvate Pyruvate Substrate-level Phosphorylation • In the last steps of glycolysis, where did the P come from to make ATP? • the sugar substrate (PEP) • P is transferred from PEP to ADP • kinase enzyme • ADP  ATP ATP I get it! The Pi camedirectly fromthe substrate!

  12. 2 ATP 2 ADP 2 NAD+ 4 ADP ATP 4 2 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 glucose      pyruvate 6C 3C 2x All that work! And that’s all I get? Butglucose hasso much moreto give!

  13. O2 O2 O2 O2 O2 3C 2x Is that all there is? • Not a lot of energy… • for 1 billon years+ this is how life on Earth survived • no O2 = slow growth, slow reproduction • only harvest 3.5% of energy stored in glucose • more carbons to strip off = more energy to harvest glucose     pyruvate 6C Hard wayto makea living!

  14. DHAP G3P NAD+ Pi NAD+ Pi NADH NADH 1,3-BPG 1,3-BPG Pi Pi NAD+ NAD+ 6 NADH NADH 7 ADP ADP ATP ATP 3-Phosphoglycerate (3PG) 3-Phosphoglycerate (3PG) 8 2-Phosphoglycerate (2PG) 2-Phosphoglycerate (2PG) 9 H2O H2O Phosphoenolpyruvate (PEP) Phosphoenolpyruvate (PEP) 10 ADP ADP ATP ATP Pyruvate Pyruvate 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 raw materialsproducts Glycolysis glucose + 2ADP + 2Pi + 2 NAD+2pyruvate+2ATP+2NADH

  15. recycleNADH How is NADH recycled to NAD+? without oxygen anaerobic respiration “fermentation” with oxygen aerobic respiration Another molecule must accept H from NADH pyruvate NAD+ H2O CO2 NADH NADH O2 acetaldehyde NADH acetyl-CoA NAD+ NAD+ lactate lactic acidfermentation which path you use depends on who you are… Krebs cycle ethanol alcoholfermentation

  16. pyruvate  ethanol + CO2 3C 2C 1C pyruvate  lactic acid NADH NADH NAD+ NAD+ 3C 3C Fermentation (anaerobic) • Bacteria, yeast back to glycolysis • beer, wine, bread • Animals, some fungi back to glycolysis • cheese, anaerobic exercise (no O2)

  17. pyruvate  ethanol + CO2 3C 2C 1C NADH NAD+ recycleNADH bacteria yeast Alcohol Fermentation back to glycolysis • Dead end process • at ~12% ethanol, kills yeast • can’t reverse the reaction Count thecarbons!

  18. O2 pyruvate  lactic acid NADH NAD+ 3C 3C recycleNADH animalssome fungi Lactic Acid Fermentation  back to glycolysis • Reversible process • once O2 is available, lactate is converted back to pyruvate by the liver Count thecarbons!

  19. O2 O2 Pyruvate is a branching point Pyruvate fermentation anaerobicrespiration mitochondria Krebs cycle aerobic respiration

  20. What’s thepoint? The pointis to makeATP! ATP

  21. H+ H+ H+ H+ H+ H+ H+ H+ + P H+ And how do we do that? • ATP synthase • set up a H+ gradient • allow H+ to flow through ATP synthase • powers bonding of Pi to ADP ADP + PiATP ADP ATP But… Have we done that yet?

  22. NO!There’s still more to my story! Any Questions?

  23. ATP ATP 2 4 2 2 4 NAD+ ADP ADP 2Pi 2 2Pi 2H glucose C-C-C-C-C-C Overview 10 reactions • convert glucose (6C)to 2 pyruvate (3C) • produces:4 ATP & 2 NADH • consumes:2 ATP • net:2 ATP & 2 NADH 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

  24. Cellular RespirationStage 2 & 3: Oxidation of Pyruvate Krebs Cycle

  25. glucose      pyruvate 6C 3C 2x pyruvate       CO2 Glycolysis is only the start • Glycolysis • Pyruvate has more energy to yield • 3 more C to strip off (to oxidize) • if O2 is available, pyruvate enters mitochondria • enzymes of Krebs cycle complete the full oxidation of sugar to CO2 3C 1C

  26. Cellular respiration

  27. outer membrane intermembrane space inner membrane cristae matrix mitochondrialDNA 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 What cells would have a lot of mitochondria?

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

  29. [ ] 2x pyruvate  acetyl CoA + CO2 NAD Oxidation of pyruvate • Pyruvate enters mitochondrial matrix • 3 step oxidation process • releases 2 CO2(count the carbons!) • reduces 2NAD  2 NADH (moves e-) • produces 2acetyl CoA • Acetyl CoA enters Krebs cycle 1C 3C 2C Wheredoes theCO2 go? Exhale!

  30. NAD+ 2 x [ ] Pyruvate oxidized to Acetyl CoA reduction Acetyl CoA Coenzyme A CO2 Pyruvate C-C C-C-C oxidation Yield = 2C sugar + NADH + CO2

  31. 1937 | 1953 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 O22.7 billion years ago (photosynthesis) • eukaryotes 1.5 billion years ago (aerobic respiration = organelles  mitochondria) Hans Krebs 1900-1981

  32. 2C 6C 5C 4C 3C 4C 4C 4C 4C 6C CO2 CO2 Count the carbons! pyruvate acetyl CoA citrate oxidationof sugars This happens twice for each glucose molecule x2

  33. 2C 6C 5C 4C 3C 4C 6C 4C 4C 4C NADH ATP CO2 CO2 CO2 NADH NADH FADH2 NADH Count the electron carriers! pyruvate acetyl CoA citrate reductionof electroncarriers This happens twice for each glucose molecule x2

  34. Whassup? So we fully oxidized glucose C6H12O6  CO2 & ended up with 4 ATP! What’s the point?

  35. H+ H+ H+ H+ H+ H+ H+ H+ H+ Electron Carriers = Hydrogen Carriers • Krebs cycle produces large quantities of electron carriers • NADH • FADH2 • go to Electron Transport Chain! ADP+ Pi ATP What’s so important about electron carriers?

  36. 4 NAD+1 FAD 4 NADH+1FADH2 2x 1C 3x 1 ADP 1 ATP Energy accounting of Krebs cycle Net gain = 2 ATP = 8 NADH + 2 FADH2 pyruvate          CO2 3C ATP

  37. Value of Krebs cycle? • If the yield is only 2 ATP then how was the Krebs cycle an adaptation? • value of NADH & FADH2 • 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

  38. What’s thepoint? The pointis to makeATP! ATP

  39. H+ H+ H+ H+ H+ H+ H+ H+ + P H+ And how do we do that? • ATP synthase • set up a H+ gradient • allow H+ to flow through ATP synthase • powers bonding of Pi to ADP ADP + PiATP ADP ATP But… Have we done that yet?

  40. NO!The final chapter to my story is next! Any Questions?

  41. Cellular RespirationStage 4: Electron Transport Chain

  42. Cellular respiration

  43. What’s thepoint? The pointis to makeATP! ATP

  44. ATP accounting so far… • Glycolysis 2ATP • Kreb’s cycle 2ATP • Life takes a lot of energy to run, need to extract more energy than 4 ATP! There’s got to be a better way! I need a lotmore ATP! A working muscle recycles over 10 million ATPs per second

  45. O2 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 O2 (aerobic respiration) Thatsounds morelike it!

  46. Mitochondria • Double membrane • outer membrane • inner membrane • highly folded cristae • enzymes & transport proteins • intermembrane space • fluid-filled space between membranes Oooooh!Form fits function!

  47. Innermitochondrialmembrane Electron Transport Chain Intermembrane space C Q cytochromebc complex cytochrome coxidase complex NADH dehydrogenase Mitochondrial matrix

  48. Remember the Electron Carriers? glucose Krebs cycle Glycolysis G3P 8 NADH 2 FADH2 2 NADH Time tobreak openthe piggybank!

  49. e p 1 2 Electron Transport Chain Building proton gradient! NADH  NAD+ + H intermembranespace H+ H+ H+ innermitochondrialmembrane H  e- + H+ C e– Q e– H e– FADH2 FAD H NADH 2H+ + O2 H2O NAD+ cytochromebc complex cytochrome coxidase complex NADH dehydrogenase mitochondrialmatrix What powers the proton (H+) pumps?…

  50. H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ C e– Q e– 1 2 e– FADH2 FAD NADH 2H+ + O2 H2O NAD+ cytochromebc complex NADH dehydrogenase cytochrome coxidase complex Stripping H from Electron Carriers • Electron carriers pass electrons & H+ to ETC • H cleaved off NADH & FADH2 • electrons stripped from H atoms  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 H+ H+ H+ TA-DA!! Moving electronsdo the work! ADP+ Pi ATP

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