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Chapter 6 - Respiration

CHAPTER 6 - RESPIRATION. Chapter 6 - Respiration. O 2. CO 2 + H 2 O. HEAT + ENERGY. Glucose. The only reason humans need to breathe oxygen is to accept electrons in the final stage of ATP synthesis in the mitochondria. CHAPTER OUTLINE. Outline. I. OVERVIEW II. GLYCOLYSIS

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Chapter 6 - Respiration

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  1. CHAPTER 6 - RESPIRATION Chapter 6 - Respiration O2 CO2 + H2O HEAT + ENERGY Glucose

  2. The only reason humans need to breathe oxygen is to accept electrons in the final stage of ATP synthesis in the mitochondria.

  3. CHAPTER OUTLINE Outline • I. OVERVIEW • II. GLYCOLYSIS • Getting to glucose • Mechanisms by which ATP is synthesized • Glycolysis – steps in the process • Glycolysis - summary • III. THE AEROBIC PATHWAY • Mitochondrion structure • A preliminary step • The Krebs cycle • Oxidative phosphorylation • IV. ANAEROBIC PATHWAYS • V. OTHER TYPES OF RESPIRATION

  4. Outline OVERVIEW

  5. I. OVERVIEW All organisms harvest energy from stored chemicals (starch, sugars, lipids) in the same way The metabolic pathways by which organisms liberate stored energy are referred to as cellular respiration

  6. THE OVERALL EQUATION FOR RESPIRATION OF GLUCOSE C6H12O6 + O2CO2 + H2O + ENERGY Respiration of glucose - equation Carbon Dioxide

  7. Cellular Respiration

  8. Cellular Respiration Glucose → CO2 + H2O + energy (ATP)

  9. Overview This is the same equation for starting a fire using glucose as a fuel. The difference is that the reaction in living systems is tightly controlled and energy normally lost as heat is captured for other uses.

  10. Glucose is used as a source of energy for two kinds of respiration: • Aerobic • Anaerobic

  11. Overview - aerobic respiration • Aerobic Respiration - requires oxygen as the terminal electron acceptor • 1) Stages involved • a) Krebs cycle • b) Oxidative phosphorylation (synthesis of ATP) • 2) Disposition of Energy • a) Some energy is stored in ATP and in other compounds • b) Other energy dissipates as heat

  12. Overview - anaerobic respiration • Anaerobic Respiration: (without oxygen) • Fermentation: Metabolic pathways by which energy is liberated from pyruvic acid, the end product of glycolysis, in the absence of oxygen.

  13. Outline GLYCOLYSIS Getting to Glycolysis

  14. Glycolysis is the breakdown of glucose to pyruvic acid (pyruvate).

  15. Retrieving glucose from other molecules • GLUCOSE IS NOT ABUNDANT IN CELLS • CELLS OBTAIN GLUCOSE BY BREAKING DOWN GLUCOSE-CONTAINING STORAGE MOLECULES, OFTEN SUCROSE OR STARCH

  16. Sucrose, Starch, Fructose, etc Fig 6-2

  17. COMMON GLUCOSE STORAGE COMPOUNDS Retrieving glucose from other molecules • SUCROSE (TABLE SUGAR), FRUCTOSE (FRUIT SUGAR) AND OTHER SUGARS • STARCH • POLYMERS OF FRUCTOSE

  18. GLUCOSE IS RETREIVED FROM SUCROSE BY BY HYDROLYSIS Requires the enzyme “sucrase”

  19. Retrieving glucose from other molecules STARCH IS A BRANCHED POLYMER MADE UP OF GLUCOSE MOLECULES • SEVERAL DIFFERENT KINDS OF ENZYMES ARE REQUIRED TO BREAKDOWN STARCH • Amylases • Starch phosphorylase • Debranching enzymes

  20. Amylases hydrolyze alpha 1-4 glucose linkages Starch phosphorylase cleaves glucose at the end of a chain end by adding a phosphate to it starch + H2PO4 → glucose 1-phosphate Retrieving glucose from other molecules Debranching enzymes hydrolize starch at branch points

  21. Outline GLYCOLYSIS Mechanisms by which ATP is synthesized

  22. Synthesis of ATP ATP is synthesized during respiration by - 1. Substrate-level phosphorylation 2. ATP synthase complexes in mitochondrial and chloroplast membranes (Oxidative Phosphorylation)

  23. Substrate-level phosphorylation PHOSPHOENOLPYRUVIC ACID =Transfer of a phosphate directly from an organic molecule to ADP to make ATP

  24. ATP synthase complex Oxidative Phosphorylation = Coupling energy from an electron donor with an electrochemical gradient that spans a membrane to phosphorylate ADP Fig 6-15

  25. Outline GLYCOLYSIS Steps in the process

  26. This is glycolysis Fig 6-2

  27. Glycolysis occurs in the cytoplasm!!!!

  28. Uses 1 ATP Fig 6-4

  29. Uses 2nd ATP

  30. We will follow what happens to glyceraldehyde 3-phosphate only. Note-all products are from this point on are doubled

  31. 2 molecules Generates 2 NADH

  32. Generates 2 ATP

  33. 2 molecules

  34. 2 molecules

  35. Generates 2 ATP

  36. Total yield of energy-transport molecules from glycolysis Fig 6-17

  37. Outline AEROBIC RESPIRATION Mitochondrion structure

  38. Pyruvic acid is imported into mitochondria

  39. The Krebs cycle occurs in the matrix of the mitochondria

  40. AEROBIC RESPIRATION Oxidative decarboxylation of pyruvate Outline

  41. Pyruvate is transported into the mitochondria Fig 6-7

  42. Fig 6-17

  43. AEROBIC RESPIRATION Krebs Cycle Outline

  44. Fig 6-2

  45. Krebs cycle = TCA cycle The Krebs cycle is also called the TCA cycle (tricarbocylic acid cycle) because citric acid has three carboxyl groups) or The citric acid cycle

  46. Krebs cycles X 2 The chemical reaction repeatedly recycles, taking in two carbons and producing two CO2 molecules

  47. Two carbons enter Fig 6-8

  48. Two CO2 molecules are produced (4/molecule of glucose) Fig 6-8

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