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Bioenergetics

Bioenergetics. Oxidation and Reduction. Oxidation is the Loss of Electrons E.g., something that is oxidized in the course of a chemical reaction with Oxygen has had electrons stolen by Oxygen Reduction is the Gain of Elections

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Bioenergetics

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  1. Bioenergetics

  2. Oxidation and Reduction • Oxidation is the Loss of Electrons • E.g., something that is oxidized in the course of a chemical reaction with Oxygen has had electrons stolen by Oxygen • Reduction is the Gain of Elections • E.g., a gain of electrons results in a decrease (reduction) in electrical charge (since electrons carry a negative charge) • Metal ores are “Reduced” to metals (via the addition of electrons)—metals found in ores are in an oxidized form relative to metals found as metals

  3. Oxidation and Reduction • Note that oxidation and reduction are not necessarily complete: • E.g., movement of an electron from relatively close to an atom’s nucleus to farther away, but still bonded, is also oxidation • (and moving an electron closer is still reduction) • E.g., electrons in C-H bond are closer to C than those in C-O bond

  4. Increasing Oxidation Oxidation of Carbon (1/2)

  5. H H | | H-C-O | H O-H | H-C=O H | H-C=O H | H-C-H | H Oxidation of Carbon (2/2) O=C=O This is Carbon Dioxide

  6. X Y X Y X Y Complete Oxidation of a Hydrocarbon CXHY + (X+¼Y)O2 XCO2 + ½Y(H2O) + Energy • Note that each Carbon gives rise to one CO2 • Note that every 2 Hydrogens gives rise to one H2O • CO2 is the common highly Oxidized form of Carbon • H2O is the common highly Oxidized form of Hydrogen • (note also that H2O represents a reduced form of Oxygen) C3H8 + (3+2)O2 3CO2 + 4(H2O) + Energy

  7. Complete Oxidation of Glucose CXHY + (X+¼Y)O2 XCO2 + ½Y(H2O) + Energy C6H12O6 + (6+3-3)O2 6CO2 + 6(H2O) Glucose is a Hexose! C6H12O6 + 6O2 6CO2 + 6(H2O) + Energy

  8. Oxidizing Agents (e.g., NAD+)

  9. Oxidizing Agents (e.g., FAD)

  10. Oxidation and Reduction II • Recall that both FAD and NAD+ can oxidize other molecules • In doing so they remove two electrons and two protons • In the process FAD is reduced to FADH2 and NAD+ to NADH + H+ • Note that two electrons + two protons (I.e., 2H+) = two Hs • (that is, neutral Hydrogen atoms) • Note that FADH2 & NADH + H+ can be oxidized • In the course of this oxditation they are reduced

  11. Reducing Agents (e.g., NADH) • Oxidizing agents steal electrons • In the process they are reduced • Reducing agents donate electrons • In the process they are oxidized

  12. Pop Quiz! FADH2 So which is the Reducing agent, FAD or FADH2?

  13. Gravity (center Earth) Waste Heat (once reaches Bottom) Potential Energy Energy (another reminder) “Kinetic” Kinetic Energy

  14. C & H Oxidation Releases Energy Oxidation is the movement of electrons from near the nucleus of certain atoms (e.g., Carbon or Hydrogen) to even closer to the nucleus of another atom (e.g., Oxygen) The oxidation of atoms such as carbon or hydrogen therefore can liberate energy This liberated energy can be harnessed

  15. Dehydrogenases • Oxidation and Reduction in biological systems typically is catalyzed by enzymes • Oxidation mediated by the coenzyme NAD+ is catalyzed by enzymes know as Dehydrogenases • Note that these are de-Hydrogen-ases – these are enzymes that catalyze the removal of Hydrogen atoms • The general reaction in which NAD+ participates is: • NAD+ + 2H+ + 2e- NADH + H+ • which is equivalent to: • NAD+ + 2H  NADH + H+

  16. Dehydrogenases • H-C-O-H + NAD+ + dehydrogenase  • C=O + NADH + H+ + dehydrogenase • Note that the dehydrogenase is found on both sides of the equation: it is a catalyst so is not used up • 2H-C-C-H2 + FAD + dehydrogenase  • H-C=C-H + FADH2 + dehydrogenase • Note in both reactions the loss of two hydrogen atoms

  17. products substrates Glyceraldehyde-3-Phosphate Dehydrogenase enzyme

  18. ATP – Energy Currency of Cells - - - -

  19. Cellular Respiration, Overview

  20. Glycolysis ATP-Producing Pathways Cellular Respiration Photosynthesis

  21. Oxidative vs. Substrate-Level Phosphorylation • These are concepts whose distinction may not make sense to you until we’ve covered the entire chapter • Substrate-Level Phosphorylation is donation of phosphate to ADP that is directly powered by making & breaking bonds • Substrate  Product (Energy) + ADP + Pi  ATP • Oxidative Phosphorylation: powered by a Proton-Motive Force • There are a variety of ways to produce a Proton-Motive Force, all more complicated than Substrate-Level Phosphorylation • These ways typically involving Electron Transport

  22. Glycolyis in Detail

  23. Glycolyis in Detail

  24. Glycolyis in Detail

  25. Glycolyis in Detail

  26. Glycolyis in Detail

  27. Glucose ATP ATP 6-Carbon Compounds Sugar-Splitting Glyco-lysis! 3-Carbon Compounds NAD+ NAD+ NADH NADH ATP ATP ATP ATP Pyruvate Pyruvate Outline of Glycolysis An Enzyme- and Coenzyme-mediated catabolic pathway

  28. Synopsis of Glycolysis • C6 (a.k.a., glucose) + ATP  C6-P + ADP • C6-P + ATP  P-C6-P + ADP • P-C6-P  2C3-P (this is the sugar-splitting step) • (note: the stoichiometry of all of the following are 2 for every one glucose) • C3-P + NAD+ + Pi  P-C3-P + NADH + H+ • P-C3-P + ADP  C3-P + ATP • C3-P + ADP  C3 (a.k.a., pyruvate) + ATP This is the minimal level at which you must learn the steps of glycolysis

  29. Substrate-Level Phosphorylation

  30. Substrate-Level Phosphorylation

  31. Bioenergetics

  32. Mitochondrial Reactions

  33. That’s a fairly well oxidized carbon… …and there it goes …and there go its electrons… Pyruvate Oxidation

  34. Acetyl CoA Coenzyme A acetyl

  35. What’s this? Oxaloacetate  Citrate a.k.a., Citric Acid a.k.a., Tricarboxylic Acid

  36. Krebs Citric Acid Cycle

  37. Krebs Citric Acid Cycle Do you see the error in this figure? • Note that these are per Acetyl-CoA • That means two turns of Krebs cycle per Glucose

  38. citric acid oxaloacetate Krebs Citric Acid Cycle citrate

  39. Bioenergetics

  40. Electron Transport Chain

  41. Electron Transport Chain

  42. Electron Transport Chain H+ H+ H+ H+ Note generation of Proton Motive Force

  43. Proton Motive Force Oxidative vs. Substrate-Level Phosphorylation

  44. Reverse-Running H+ Pump

  45. electron transport electron transport ATP Bookkeeping glycolysis pyruvate oxidation Krebs cycle

  46. ATP Bookkeeping • One glucose yields: • 2 ATP in glycolysis • 2 NADH in glycolysis • 2 NADH as pyruvate enters citric acid cycle • 2 ATP in citric acid cycle • 6 NADH in citric acid cycle • 2 FADH2 in citric acid cycle

  47. ATP Bookkeeping

  48. Anaerobic Respiration

  49. Anaerobic Respiration …employs an inorganic molecule other than O2 as a terminal electron acceptor.

  50. Glucose NAD+ NADH ATP ATP Pyruvate Glycolysis NAD+ Requirement     

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