Harvesting stored energy

1. glucose + oxygen  energy + water + carbon dioxide respiration ATP + 6H2O + 6CO2 + heat  C6H12O6 + 6O2 COMBUSTION = making a lot of heat energy by burning fuels in one step ATP glucose O2 O2 fuel(carbohydrates) Harvesting stored energy • Glucose is the model • catabolism of glucose to produce ATP RESPIRATION = making ATP (& some heat)by burning fuels in many small steps ATP enzymes CO2 + H2O + heat CO2 + H2O + ATP (+ heat)

2. ATP= adenosine triphosphate -the energy “currency” of cells ATP stores energy in the bonds between phosphates

3. Energy Currency of Cells When the bond between phosphates is broken: ATP ADP + Pi energy is released ADP = adenosine diphosphate Pi = inorganic phosphate This reaction is reversible.

4. ATP Really high energy bond ADP + Pi

5. + + oxidation reduction e- 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 loses e- gains e- oxidized reduced + – e- e- redox

6. e p loses e- gains e- oxidized reduced + – + + H oxidation reduction H  C6H12O6 + 6O2 6CO2 + 6H2O + ATP H 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 oxidation reduction e-

7. O– O– O– O– P P P P –O –O –O –O O– O– O– O– O O O O NAD+ nicotinamide Vitamin B3 niacin O O H H C C NH2 C C NH2 How efficient! Build once,use many ways N+ N+ reduction + H oxidation phosphates adenine ribose sugar Moving electrons in respiration • Electron carriers move electrons by shuttling H atoms around • NAD+NADH (reduced) • FAD+2FADH2 (reduced) reducing power! NADH H carries electrons as a reduced molecule

8. Steps of Respiration The complete oxidation of glucose proceeds in stages: 1. glycolysis 2. pyruvate oxidation 3. Krebs cycle 4. electron transport chain & chemiosmosis

10. 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 That’s not enoughATP for me!

11. 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?

12. 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!

13. [ ] 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!

14. 3. Krebs Cycle -oxidizes the acetyl Co-A -occurs in the matrix of the mitochondria

15. Krebs Cycle After glycolysis, pyruvate oxidation, and the Krebs cycle, glucose has been oxidized to: - 6 CO2 - 4 ATP - 10 NADH - 2 FADH2 These electron carriers proceed to the electron transport chain.

16. O2 • Electron Transport Chain • series of proteins built into inner mitochondrial membrane • yields ~36 ATP from 1 glucose! • only in presence of O2 (aerobic respiration) Thatsounds morelike it!

17. H+ H+ H+ C e– Q e– 1 2 e– FADH2 FAD NADH 2H+ + O2 H2O NAD+ cytochromebc complex NADH dehydrogenase cytochrome coxidase complex • 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+

18. H+ H+ H+ H+ H+ H+ H+ H+ ADP + Pi H+ “proton-motive” force Chemiosmosis: • Set up a H+ gradient • Allow the protonsto flow through ATP synthase • Synthesizes ATP ADP + PiATP ATP

19. Intermembrane space Pyruvate from cytoplasm Inner mitochondrial membrane H+ H+ Electron transport system C Q NADH e- H+ 2. Electrons provide energy to pump protons across the membrane. 1. Electrons are harvested and carried to the transport system. e- Acetyl-CoA NADH e- H2O e- Krebs cycle 3. Oxygen joins with protons to form water. 1 FADH2 O2 2 O2 + 2H+ H+ CO2 ATP H+ ATP ATP 4. Protons diffuse back indown their concentrationgradient, driving the synthesis of ATP. ATP synthase Mitochondrial matrix

20. ~40 ATP Cellular respiration + + 2 ATP 2 ATP ~36 ATP

21. Oxidation Without O2 Respiration occurs without O2 via either: 1. anaerobic respiration -methanogens (CO2 CH4) -sulfur bacteria (SO4  H2S) 2. fermentation -ethanol (yeast) -lactic acid (animal cells)

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

23. 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)

24. Catabolism of Protein & Fat In the absence of carbohydrates, animals can break down other molecules: -proteins: amino acids converted to a molecule that enters glycolysis or the Krebs cycle -fats: fatty acids enter Krebs cycle (produces more energy than glucose)