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How Cells Harvest Energy

How Cells Harvest Energy. Lecture #6. Autotrophs. “producers” of the world Can convert radiant energy (sun) to chemical energy Plants, algae and some bacteria (cyanobacteria) Photosynthesis. Heterotrophs. “eaters” of the world Lack the ability to directly absorb radiant energy

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How Cells Harvest Energy

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  1. How Cells Harvest Energy Lecture #6

  2. Autotrophs • “producers” of the world • Can convert radiant energy (sun) to chemical energy • Plants, algae and some bacteria (cyanobacteria) • Photosynthesis

  3. Heterotrophs • “eaters” of the world • Lack the ability to directly absorb radiant energy • Must rely on autotrophs for their energy input • 95% of all living species are heterotrophs.

  4. Energy Transfer Autotrophs Heterotrophs

  5. Autotrophs • Capture radiant energy into: • Sugars carbohydrates (CHO) • Amino acids proteins (PRO) • Fatty acids lipids (FAT) • So, what happens when a heterotroph eats an autotroph?

  6. Heterotroph • Break down complex molecules into subunits….digestion • Then break down subunits to release energy….catabolism • CHO sugars energy • PRO amino acids energy • FAT fatty acids energy

  7. Catabolism • Hydrogen – 1 proton (H+) & 1 electron (e-) • Energy……follow the electron • Electrons are passed on to electron acceptors such as NAD+ • The H+ (proton) is passed on to one of two recipients: • Oxygen….oxidative respiration(aerobic) • Organic molecules….fermentation (anaerobic)

  8. Oxidative Respiration

  9. Oxidative Respiration • Catabolism of glucose into CO2 and H2O with the release of energy C6H12O6 + 6O2 6CO2 + 6H2O + energy ATP HEAT

  10. So….how is the energy released from glucose? • Gas tank….quick or in smaller events? • Catabolism of glucose (and harvesting of energy)….four stage process

  11. CATabolism

  12. Four Stages • Glycolysis • Pyruvate oxidation • The Krebs cycle • Electron transport chain C6H12O6 + 6O2 6CO2 + 6H2O + energy

  13. Mitochondrion

  14. Cell Location of Each Stage Stage #1 – in cytoplasm Stages #2 – 3 – 4 – within mitochondria

  15. Overview of Aerobic Respiration

  16. Stage #1 -- Glycolysis • Glucose (6 C) 2 Pyruvate (3C) • 10 reaction process • Occurs in the cytoplasm of the cell

  17. Glycolysis (Rx 1 – 6)

  18. Glycolysis (Rx 7 – 10)

  19. Three Steps • Glucose priming • Requires 2 ATP • 6 C 6C – PP (glucose) (fructose 1,6-bisphosphate)

  20. Overview of Glycolysis

  21. Three Steps • Cleavage • 6 C – PP 2 X 3C – P (glyceraldehyde-3-phosphate)

  22. Overview of Glycolysis

  23. Three Steps • Generation of Energy Molecules • 2 X 3C – P 3C (pyruvate) • Production of 2 NADH and 4 ATP (-2ATP for priming of glucose)

  24. Overview of Glycolysis

  25. Summary of Glycolysis • Glucose (6C) 2 X Pyruvate (3C) • 10 step process (in cytoplasm) • Yields 2 NADH and 2 ATP • Takes place in the absence of O2 • All cells use glycolysis (prokaryote and eukaryote). • Probably one of the earliest biochemical reactions to evolve.

  26. Stage #2-Oxidation of Pyruvate • Takes place in the mitochondria • Oxygen is used • Pyruvate was generated in cytoplasm, then transported into mitochondria.

  27. Stage #2–Oxidation of Pyruvate • Pyruvate + O2 Acetyl + CoA + CO2 (3C) (2C) (1C) • Acetyl + CoA Acetyl-CoA (2C) + NADH • Pyruvate + O2 Acetyl-CoA + CO2 + NADH

  28. Acetyl-CoA

  29. Review • Stage #1 – glycolysis • glucose pyruvate • 6C 2 X 3C + 2NADH + 2ATP 2. Stage #2 – oxidation of pyruvate • pyruvate acetyl CoA • 3C 2C + CO2 + NADH

  30. Stage #3 – The Krebs Cycle • 9 sequential reactions • Extracts electrons into electron acceptors • 3 steps

  31. Oxidation vs Reduction • Oxidation is the loss of electrons. • Reduction is the gain of electrons. • NAD+ is reduced to NADH because it gains 2 e- . • FAD is reduced to FADH2 because it gains 2 e- . • NADH and FADH2 are high energy molecules ATP

  32. Krebs Cycle– 3 Steps • Step #1 Acetyl-CoA + oxaloacetate citrate (2C) + (4C) (6C)

  33. Step #2 Citrate a-ketoglutarate + CO2 + NADH (6C) (5C) + (1C) a-ketoglutaratesuccinyl-CoA +CO2 + NADH (5C) (4C) (1C)

  34. Step #3 Succinyl-CoA oxaloacetate + ATP (4C) (4C) FADH2 NADH

  35. Yield from 1 6C Citrate • 3 NADH (NAD+ NADH) • 1 FADH2 (FAD FADH2) NAD+ and FAD are electron acceptors. NADH and FADH2 are energy (electron) transporters. 3. 1 ATP and 2 CO2 + oxaloacetate (4C)

  36. Stage #4The Electron Transport Chain • Takes place on the inner membranes of the mitochondria

  37. Overview of Aerobic Respiration

  38. Stage #4The Electron Transport Chain • A series of oxidation-reduction reactions

  39. Stage #4The Electron Transport Chain • Ripping off electrons and protons from NADH and FADH2…..to form ATP

  40. Electron Transport • e- are transferred down a series of enzymes • Enzymes located within inner membrane

  41. Structure of hydrogen • 1 proton (+) and one electron (e-)

  42. Electron Transport

  43. Electrons are passed onto a series of enzymes

  44. This produces protons also which are pumped across inner membrane

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