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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 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 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 mitochondria • 3 step oxidation process • releases 1 CO2(count the carbons!) • reduces 2NAD  2 NADH (moves e-) • produces acetyl CoA • Acetyl CoA enters Krebs cycle 1C 3C 2C Wheredoes theCO2 go? Exhale!

  8. Oxidation of Pyruvate to Acetyl CoA (pyruvate)+ (NAD) + (CoA)===(acetyl CoA) +(NADH) +(CO2) + (H)

  9. 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

  10. 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

  11. The Krebs cycle has FIVE Main Steps • STEP 1 - A Two-Carbon Molecule of Acetyl CoA Combines with a Four-Carbon Compound, OXALOACETIC ACID (AHKS-uh-loh-SEET-ik), to Produce a Six-Carbon Compound CITRIC ACID. • STEP 2 -  Citric Acid Releases a CO2 Molecule and a Hydrogen Atom to Form a Five-Carbon Compound.  By LOSING a Hydrogen Atom with its Electron, Citric Acid is OXIDIZED.  The Hydrogen atom is transferred to NAD+, REDUCING it to NADH.

  12. Kreb Cycle cont • STEP 3 - The Five-Carbon Compound Releases a CO2 Molecule and a Hydrogen Atom, forming a Four-Carbon Compound.  NAD+ is reduced to NADH.  A Molecule of ATP is also Synthesized from ADP. • STEP 4 -  The Four-Carbon Compound Releases a Hydrogen Atom to form another Four-Carbon Compound.  The Hydrogen is used to Reduce FAD (Flavin Adenine Dinucleotide) to FADH2, a Molecule similar to NAD+ that Accepts Electron during Redox Reactions. • STEP 5 - The Four-Carbon Compound Releases a Hydrogen Atom to REGENERATE OXALOACETIC ACID, which keeps the Krebs cycle operating.  The Hydrogen Atom Reduces NAD+ to NADH.

  13. KREbs • In Glycolysis one Glucose Molecule produces TWO Pyruvic Acid Molecules, which can then form TWO Molecules of Acetyl CoA. • One Glucose Molecule causes TWO Turns of the Krebs cycle. • The Two Turns produce SIX NADH, TWO FADH2, TWO ATP, and FOUR CO2 Molecules. • The CO2 is a WASTE PRODUCT that Diffuses out of the cells and is given off by the organism. • The BULK of the Energy released by the Oxidation of Glucose still has NOT been transferred to ATP.  Only FOUR Molecules of ATP - TWO from Glycolysis and TWO From the Krebs cycle

  14. 2C 6C 5C 4C 3C 4C 4C 4C 4C 6C CO2 CO2 Count the carbons! pyruvate acetyl CoA citrate x 2 This happens twice for each glucose molecule oxidationof sugars

  15. 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 x2 This happens twice for each glucose molecule reductionof electroncarriers

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

  17. 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?

  18. 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

  19. 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

  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? • 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!The final chapter to my story is next! Any Questions?

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