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Oxidation to Release…

Cellular Respiration. Oxidation to Release…. Energy. Matter is recycled Energy is not (Entropy). Cells use energy for work and growth Chemical products (CO 2 , H 2 O) are recycled. Concept 9.1: Catabolic pathways yield energy by oxidizing organic fuels.

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Oxidation to Release…

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  1. Cellular Respiration Oxidation to Release… Energy

  2. Matter is recycled Energy is not (Entropy) Cells use energy for work and growth Chemical products (CO2, H2O) are recycled

  3. Concept 9.1: Catabolic pathways yield energy by oxidizing organic fuels

  4. Catabolic Pathways and Production of ATP • The breakdown of organic molecules is exergonic • Two methods: • Cellular respiration • Fermentation

  5. Catabolic Pathways and ATP • Cellular respiration • Aerobic • Most prevalent and efficient catabolic pathway • Consumes oxygen and organic molecules • Yields ATP (coupled reaction) • Fermentation - partial degradation of sugars • Anaerobic

  6. ATP and Cellular Work • Lots of energy in C-H bonds • Carbos are primary source of C-H, but lipids, proteins can be used • Alternative metabolic pathways

  7. Redox Reactions: Oxidation and Reduction • Catabolic pathways yield energy due to the transfer of electrons • Redox reactions transfer electrons from one reactant to another • Oxidation - substance loses electrons, (oxidized), gains oxygen • Reduction - substance gains electrons, (reduced), gains hydrogen

  8. Methane combustion is a redox reaction

  9. Electrons ‘Fall’ During Respiration • From high potential energy to low potential energy

  10. Electrons ‘Fall’ Via Steps • Electrons passed to COENZYME first • Nicotinamide adenine dinucleotide (NAD+) • Dehydrogenase removes a pair of hydrogen atoms (2 protons; 2 electrons) from the substrate (sugar)

  11. NAD+ • NAD+ keeps the two electrons and 1 hydrogen proton • NADH becomes a ‘taxi’ carrying H and electrons to the ETC

  12. Coupled reaction

  13. Steps of Respiration 1.Glycolysis 2. Kreb’s Citric Acid Cycle 3. Electron Transport Chain (ETC)

  14. Steps of Respiration • Mitochondria = site of Kreb’s and ETC • Formation of acetyl CoA ?

  15. Cellular Respiration • What you need to know: • Where does each step take place? • What are the reactants and products? • How is ATP produced? • How does the structure of the mitochondria enable respiration to take place?

  16. Acetyl CoA

  17. Where Do the Reactions Take Place? • Glycolysis = cytosol • Formation of Acetyl CoA = cytosol/mitochondria • Kreb’s = mitochondrial matrix • ETC = mitochondrial inner membrane (cristae)

  18. Glycolysis: ‘Split Sugar’ • In the cytosol • Anaerobic • ATP produced by Substrate-level phosphorylation • Exergonic; captured by ATP and NAD (coupling) • Two major phases • Energy investment phase • Energy payoff phase

  19. Substrate-level phosphorylation: Phosphate group is enzymatically transferred to ATP

  20. 2 ATP are USED to initiate the reaction (activation energy) 4 ATP are FORMED near the end of glycolysis (coupled reaction)

  21. Glucose is phosphorylated

  22. Substrate-level phosphorylation

  23. S-L phosphorylation

  24. Reactants: Glucose; C6H12O6 2ATP 4 ADP + P 2 NAD + H Products: (2) pyruvate 3C Pyruvic acid 4 ATP 2 NADH 2 H2O Glycolysis:

  25. Glycolysis

  26. Glycolysis • ATP used for work • NADH goes to ETC • H2O = metabolic water (?) • (2) Pyruvate go into mitochondria and formation of Acetyl CoA

  27. Concept 9.3: The citric acid cycle completes the energy-yielding oxidation of organic molecules

  28. Formation of Acetyl Coenzyme A • Transition between glycolysis (anaerobic) and Kreb’s (aerobic) • Pyruvate enters mitochondrion: • Oxidized to form acetate (2C); 3 enzymes • Multienzyme complex

  29. Acetyl CoA • CO2 removed; (1st) • 6C to 4C • NAD reduced to NADH (2x) • Coenzyme A is added to acetate group • Acetyl Coenzyme A

  30. Reactants 2 Pyruvate 2 NAD + H Products 2 Acetyl CoA (2C) 2 NADH 2 CO2 Acetyl CoA

  31. Acetyl CoA • CO2 is waste • (out of cell) • NADH is transferred to ETC • Acetyl CoA goes into Kreb’s

  32. Krebs • Cyclical • Citric acid cycle • Hans Krebs; 1930’s • 2 turns of Krebs for each glucose to be oxidized • Enzymes are in the mitochondrial matrix

  33. Acetyl CoA transfers acetate (2C) to OAA (4C) CoA remains present and reusable Water removed and re-added: rearranges the citric acid

  34. Isocitrate loses CO2 2H are picked up by NAD

  35. aKetoglutarate loses the last CO2 molecule 2 H (electrons and proton) picked up by NAD

  36. ATP generated by s-l phosphorylation

  37. 2 H picked up by FAD

  38. 1 more H picked up by NAD Water added

  39. Krebs • Exergonic; 8 steps • Energy used to reduce coenzymes • NAD to NADH • FAD to FADH • 2 ATP produced (substrate-level phosphorylation) • Oxaloacetate is regenerated

  40. Reactants: 2 Acetyl (2C) 2 ADP + P 6 NAD + H 2 FAD + H2 Products: 4 CO2 2 ATP; substrate-level phosphorylation 6 NADH 2 FADH2 Krebs

  41. Krebs • H is ‘carried’ by NADH/FADH to ETC to generate ATP by… • OXIDATIVE PHOSPHORYLATION • CHEMIOSMOSIS

  42. Kreb’s ETC

  43. Concept 9.4: During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis • NADH and FADH2 donate electrons to the electron transport chain, which powers ATP synthesis via oxidative phosphorylation

  44. ETC • Most ATP created during ETC; • Oxidative phosphorylation • Energy from Krebs is stored in NADH and FADH2 • Exergonic transfer of electrons to ETC generates 32 ATP

  45. ETC • Electron carrier molecules (proteins) are embedded within the inner membrane • Each successive carrier has a higher electronegativity than the previous one • Electrons are ‘pulled’ downhill toOxygen • Strongest electronegativity • Final acceptor (inorganic)

  46. Coupled reaction

  47. ETC • Ubiquinone = lipid • Prosthetic groups = nonprotein cofactors on the carrier molecules that accept and donate electrons as they are passed down the ETC - FMN, iron/sulfur, hemes • Cytochrome= protein carrier in the ETC with a heme group • Iron transfers electrons • Several different cytochromes (similarity suggests evolution)

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