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Overview

ATP. ATP. 2. 4. 2. 2. 4. NAD +. ADP. ADP. 2 P i. 2. 2 P i. 2 H. 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

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Overview

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  1. 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

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

  3. 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

  4. Cellular respiration

  5. 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?

  6. 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!

  7. [ ] 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!

  8. 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

  9. 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

  10. 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

  11. 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

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

  13. 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?

  14. 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

  15. 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

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

  17. 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?

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

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