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Cellular Respiration Harvesting Chemical Energy

Cellular Respiration Harvesting Chemical Energy. What is energy in biology?. ATP. Adenosine Tri Phosphate. ATP. food. ATP. +. 6CO 2. +. 6H 2 O. . C 6 H 12 O 6. +. 6O 2. glucose + oxygen  energy + carbon + water. dioxide. O 2. Harvesting energy stored in food.

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Cellular Respiration Harvesting Chemical Energy

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  1. Cellular RespirationHarvesting Chemical Energy

  2. What is energy in biology? ATP Adenosine TriPhosphate

  3. ATP food ATP + 6CO2 + 6H2O  C6H12O6 + 6O2 glucose+oxygenenergy+carbon+ water dioxide O2 Harvesting energy stored in food • Cellular respiration • breaking down food to produce ATP • in mitochondria • using oxygen • “aerobic” respiration • usually digesting glucose • but could be other sugars, fats, or proteins

  4. food O2 ATP CO2 H2O What do we need to make energy? • The “Furnace” for making energy • mitochondria • Fuel • food:carbohydrates, fats, proteins • Helpers • oxygen • enzymes • Product • ATP • Waste products • carbon dioxide • then used by plants • water enzymes

  5. Using ATP to do work? ATP • Can’t store ATP • too unstable • only used in cell that produces it • only short term energy storage • carbohydrates & fats are long term energy storage work Adenosine TriPhosphate Adenosine DiPhosphate ADP A working muscle recycles over 10 million ATPs per second

  6. 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

  7. Evolutionary perspective • 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

  8. enzyme enzyme enzyme enzyme enzyme enzyme ATP ATP 4 2 2 4 2 ADP ADP NAD+ 2 2e- 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 2 G3P C-C-C-P pyruvate C-C-C

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

  10. glucose      pyruvate 6C 3C 2x pyruvate       CO2 Glycolysis is only the start • Glycolysis • Pyruvate has more energy to yield • More e- to remove • if O2 is available, pyruvate enters mitochondria • enzymes of Krebs cycle complete the full breakdown of sugar to CO2 3C 1C

  11. Cellular respiration

  12. 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

  13. [ ] 2x pyruvate  acetyl CoA + CO2 NAD Production of Acetyl CoA • Pyruvate enters mitochondrial matrix • 3 step process • releases 2 CO2(count the carbons!) • reduces 2NAD  2 NADH (moves e-) • produces 2acetyl CoA • Acetyl CoA enters Krebs cycle 1C 3C 2C

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

  15. 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

  16. 2C 6C 5C 4C 3C 4C 4C 4C 4C 6C CO2 CO2 Count the carbons! pyruvate acetyl CoA citrate breakdownof sugars This happens twice for each glucose molecule x2

  17. 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 productionof electroncarriers This happens twice for each glucose molecule x2

  18. H+ H+ H+ H+ H+ H+ H+ H+ H+ Electron Carriers • Krebs cycle produces large quantities of electron carriers • NADH • FADH2 • go to Electron Transport Chain! ADP+ Pi ATP

  19. 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

  20. 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

  21. 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 ~38 ATP from 1 glucose! • only in presence of O2 (aerobic respiration)

  22. Mitochondria • Double membrane • outer membrane • inner membrane • highly folded cristae • enzymes & transport proteins • intermembrane space • fluid-filled space between membranes

  23. 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+ mitochondrialmatrix What powers the proton (H+) pumps?…

  24. H2O O2 But what “pulls” the electrons down the ETC?

  25. Electrons flow downhill • Electrons move in steps from carrier to carrier downhill to oxygen • each carrier more electronegative • controlled oxidation • controlled release of energy

  26. H+ H+ H+ H+ H+ H+ H+ H+ ADP + Pi H+ “proton-motive” force We did it! • Set up a H+ gradient • Allow the protonsto flow through ATP synthase • Synthesizes ATP ADP + PiATP ATP

  27. Chemiosmosis • The diffusion of ions across a membrane • build up of concentration gradient just so H+ could flow through ATP synthase enzyme to build ATP Chemiosmosis links the Electron Transport Chain to ATP synthesis

  28. ~38 ATP Cellular respiration + + ~34 ATP 2 ATP 2 ATP

  29. O2 What if oxygen is missing? • No oxygen available = can’t complete aerobic respiration • Fermentation • alcohol fermentation • lactic acid fermentation • no oxygen or no mitochondria (bacteria) • Anaerobic process • can only make very little ATP • large animals cannot survive yeast bacteria

  30. O2 Fermentation • alcohol fermentation • yeast • glucose  ATP + CO2+ alcohol • make beer, wine, bread • lactic acid fermentation • bacteria, animals • glucose  ATP + lactic acid • bacteria make yogurt • animals feel muscle fatigue

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