1 / 50

Understanding Cellular Respiration: Mitochondria, Energy Pathways, and Metabolic Disorders

This chapter explores how cells release stored energy through cellular respiration, focusing on the pivotal role of mitochondria. It details aerobic and anaerobic pathways, illustrating how glucose is transformed into energy via glycolysis and the Krebs cycle. With more than 100 mitochondrial disorders identified, including Friedreich’s ataxia, the implications of mitochondrial functions extend to human health and disease. Additionally, the chapter addresses energy roles in different organisms and the significance of ATP as a universal energy source.

kasi
Télécharger la présentation

Understanding Cellular Respiration: Mitochondria, Energy Pathways, and Metabolic Disorders

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CELLULAR RESPIRATIONChapter 8 How Cells Release Stored Energy

  2. Impacts, Issues: When Mitochondria Spin Their Wheels • More than 100 mitochondrial disorders are known • Friedreich’s ataxia, caused by a mutant gene, results in loss of cordination, weak muscles, and visual problems • Animal, plants, fungus, and most protists depend on structurally sound mitochondria • Defective mitochondria can result in life threatening disorders

  3. When Mitochondria Spin Their Wheels p.123

  4. “Killer” Bees • Descendents of African honeybees that were imported to Brazil in the 1950s • More aggressive, wider-ranging than other honeybees • Africanized bee’s muscle cells have large mitochondria

  5. ATP Is Universal Energy Source • Photosynthesizers get energy from the sun • Animals get energy second- or third-hand from plants or other organisms • Regardless, the energy is converted to the chemical bond energy of ATP

  6. Main Types of Energy-Releasing Pathways Aerobic pathways • Evolved later • Require oxygen • Start with glycolysis in cytoplasm • Completed in mitochondria Anaerobic pathways • Evolved first • Don’t require oxygen • Start with glycolysis in cytoplasm • Completed in cytoplasm

  7. Main Types of Energy-Releasing Pathways start (glycolysis) in cytoplasm start (glycolysis) in cytoplasm completed in cytoplasm completed in mitochondrion Anaerobic Energy-Releasing Pathways Aerobic Respiration Fig. 8-2, p.124

  8. Summary Equation for Aerobic Respiration C6H1206 + 6O2 6CO2 + 6H20 glucose oxygen carbon water dioxide

  9. CYTOPLASM glucose Overview of Aerobic Respiration ATP 4 2 ATP Glycolysis e- + H+ (2 ATP net) 2 pyruvate 2 NADH e- + H+ 2 CO2 2 NADH e- + H+ 4 CO2 8 NADH Krebs CYCLE e- + H+ 2 ATP 2 FADH2 e- Electron Transfer Phosphorylation 32 ATP H+ water e- +oxygen Typical Energy Yield: 36 ATP Fig. 8-3, p. 135

  10. The Role of Coenzymes • NAD+ and FAD accept electrons and hydrogen • Become NADH and FADH2 • Deliver electrons and hydrogen to the electron transfer chain

  11. Glucose • A simple sugar (C6H12O6) • Atoms held together by covalent bonds In-text figurePage 126

  12. Glycolysis Occurs in Two Stages • Energy-requiring steps • ATP energy activates glucose and its six-carbon derivatives • Energy-releasing steps • The products of the first part are split into three-carbon pyruvate molecules • ATP and NADH form

  13. glucose Glycolysis GYCOLYSIS pyruvate to second stage of aerobic respiration or to a different energy-releasing pathway GLUCOSE Fig. 8-4a, p.126

  14. Glycolysis ENERGY-REQUIRING STEPS OF GLYCOLYSIS glucose ATP 2 ATP invested ADP P glucose–6–phosphate P fructose–6–phosphate ATP ADP P P fructose–1,6–bisphosphate DHAP Fig. 8-4b, p.127

  15. Glycolysis ENERGY-RELEASING STEPS OF GLYCOLYSIS P P PGAL PGAL NAD+ NAD+ NADH NADH Pi Pi P P P P 1,3–bisphosphoglycerate 1,3–bisphosphoglycerate substrate-level phsphorylation ADP ADP ATP ATP 2 ATP invested P P 3–phosphoglycerate 3–phosphoglycerate Fig. 8-4c, p.127

  16. Glycolysis P P 2–phosphoglycerate 2–phosphoglycerate H2O H2O P P PEP PEP substrate-level phsphorylation ADP ADP ATP ATP 2 ATP produced pyruvate pyruvate Fig. 8-4d, p.127

  17. Energy-Requiring Steps of Glycolysis 2 ATP invested glucose ADP ATP ATP P P P P P P glucose-6-phosphate fructose-6-phosphate ADP fructose1,6-bisphosphate PGAL PGAL Energy-Requiring Steps Figure 8-4(2)Page 127

  18. ATP ATP ATP ATP P P P P P P P P P P P P Energy-Releasing Steps PGAL PGAL NAD+ NAD+ NADH NADH Pi Pi 1,3-bisphosphoglycerate 1,3-bisphosphoglycerate ADP ADP 3-phosphoglycerate 3-phosphoglycerate 2-phosphoglycerate 2-phosphoglycerate H2O H2O PEP PEP ADP ADP pyruvate pyruvate Figure 8-4 Page 127

  19. Glycolysis: Net Energy Yield Energy requiring steps: 2 ATP invested Energy releasing steps: 2 NADH formed 4 ATP formed Net yield is 2 ATP and 2 NADH

  20. Second Stage Reactions • Preparatory reactions • Pyruvate is oxidized into two-carbon acetyl units and carbon dioxide • NAD+ is reduced • Krebs cycle • The acetyl units are oxidized to carbon dioxide • NAD+and FAD are reduced

  21. Second Stage Reactions mitochondrion mitochondrion Fig. 8-5a, p.128

  22. Second Stage Reactions inner mitochondrial membrane outer mitochondrial membrane inner compartment outer compartment Fig. 8-6a, p.128

  23. Two pyruvates cross the inner mitochondrial membrane. outer mitochondrial compartment inner mitochondrial compartment NADH 2 NADH 6 Krebs Cycle Eight NADH, two FADH 2, and two ATP are the payoff from the complete break-down of two pyruvates in the second-stage reactions. FADH2 2 ATP 2 The six carbon atoms from two pyruvates diffuse out of the mitochondrion, then out of the cell, in six CO 6 CO2 Fig. 8-6b, p.128

  24. O O Preparatory Reactions pyruvate coenzyme A (CoA) NAD+ carbon dioxide NADH CoA acetyl-CoA

  25. Acetyl-CoA Formation pyruvate Preparatory Reactions coenzyme A NAD+ (CO2) NADH CoA acetyl-CoA Krebs Cycle CoA oxaloacetate citrate NAD+ NADH NADH NAD+ NAD+ FADH2 FAD NADH ADP + phosphate group ATP Fig. 8-7a, p.129

  26. glucose Preparatory Reactions GLYCOLYSIS pyruvate KREBS CYCLE ELECTRON TRANSFER PHOSPHORYLATION Fig. 8-7b, p.129

  27. The Krebs Cycle Overall Products • Coenzyme A • 2 CO2 • 3 NADH • FADH2 • ATP Overall Reactants • Acetyl-CoA • 3 NAD+ • FAD • ADP and Pi

  28. ATP O O =CoA Krebs Cycle acetyl-CoA CoA oxaloacetate citrate H2O NADH NAD+ H2O malate isocitrate NAD+ H2O O O NADH fumarate FADH2 a-ketoglutarate FAD NAD+ CoA NADH succinate succinyl-CoA ADP + phosphate group Figure 8-6Page 129

  29. Results of the Second Stage • All of the carbon molecules in pyruvate end up in carbon dioxide • Coenzymes are reduced (they pick up electrons and hydrogen) • One molecule of ATP forms • Four-carbon oxaloacetate regenerates

  30. Coenzyme Reductions during First Two Stages • Glycolysis 2 NADH • Preparatory reactions 2 NADH • Krebs cycle 2 FADH2 + 6 NADH • Total 2 FADH2 + 10 NADH

  31. Electron Transfer Phosphorylation • Occurs in the mitochondria • Coenzymes deliver electrons to electron transfer chains • Electron transfer sets up H+ ion gradients • Flow of H+ down gradients powers ATP formation

  32. glucose Phosphorylation GLYCOLYSIS pyruvate KREBS CYCLE ELECTRON TRANSFER PHOSPHORYLATION Fig. 8-8a, p.130

  33. Phosphorylation H+ H+ OUTER COMPARTMENT H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ e- e- e- H+ H+ ATP H+ ADP + Pi NADH + H+ NAD+ + 2H+ FADH2 FAD + 2H+ 2H+ + 1/2 02 H2O Electron Transfer Chain ATP Synthase H+ INNER COMPARTMENT Fig. 8-8b, p.130

  34. Phosphorylation glucose ATP 2 PGAL ATP 2 NADH 2 pyruvate glycolysis 2 FADH2 2 CO2 e– 2 acetyl-CoA 2 NADH H+ H+ 6 NADH KREBS CYCLE 2 ATP Krebs Cycle ATP H+ 2 FADH2 ATP H+ 4 CO2 36 ATP H+ H+ ADP + Pi electron transfer phosphorylation H+ H+ H+ Fig. 8-9, p.131

  35. Creating an H+ Gradient OUTER COMPARTMENT NADH INNER COMPARTMENT

  36. Making ATP: Chemiosmotic Model ATP INNER COMPARTMENT ADP+Pi

  37. Importance of Oxygen • Electron transport phosphorylation requires the presence of oxygen • Oxygen withdraws spent electrons from the electron transfer chain, then combines with H+ to form water

  38. Summary of Energy Harvest(per molecule of glucose) • Glycolysis • 2 ATP formed by substrate-level phosphorylation • Krebs cycle and preparatory reactions • 2 ATP formed by substrate-level phosphorylation • Electron transport phosphorylation • 32 ATP formed

  39. Energy Harvest Varies • NADH formed in cytoplasm cannot enter mitochondrion • It delivers electrons to mitochondrial membrane • Membrane proteins shuttle electrons to NAD+ or FAD inside mitochondrion • Electrons given to FAD yield less ATP than those given to NAD+

  40. Efficiency of Aerobic Respiration • 686 kcal of energy are released • 7.5 kcal are conserved in each ATP • When 36 ATP form, 270 kcal (36 X 7.5) are captured in ATP • Efficiency is 270 / 686 X 100 = 39 percent • Most energy is lost as heat

  41. Anaerobic Pathways • Do not use oxygen • Produce less ATP than aerobic pathways • Two types • Fermentation pathways • Anaerobic electron transport

  42. Fermentation Pathways • Begin with glycolysis • Do not break glucose down completely to carbon dioxide and water • Yield only the 2 ATP from glycolysis • Steps that follow glycolysis serve only to regenerate NAD+

  43. glycolysis Alcoholic Fermentation C6H12O6 ATP 2 energy input 2 ADP 2 NAD+ NADH 2 4 ATP 2 pyruvate energy output 2 ATP net ethanol formation 2 H2O 2 CO2 2 acetaldehyde electrons, hydrogen from NADH 2 ethanol Fig. 8-10d, p.132

  44. Lactate Fermentation glycolysis C6H12O6 ATP 2 energy input 2 ADP 2 NAD+ 2 NADH 4 ATP 2 pyruvate energy output 2 ATP net lactate fermentation electrons, hydrogen from NADH 2 lactate Fig. 8-11, p.133

  45. Lactate Fermentation Fig. 8-12, p.133

  46. Anaerobic Electron Transport • Carried out by certain bacteria • Electron transfer chain is in bacterial plasma membrane • Final electron acceptor is compound from environment (such as nitrate), not oxygen • ATP yield is low

  47. FOOD proteins fats glycogen complex carbohydrates simple sugars glycerol fatty acids amino acids glucose-6-phosphate NH3 carbon backbones GLYCOLYSIS urea PGAL pyruvate acetyl-CoA KREBS CYCLE

  48. Alternative Energy Sources FOOD complex carbohydrates fats glycogen proteins simple sugars (e.g., glucose) fatty acids amino acids glycerol NH3 carbon backbones glucose-6-phosphate urea PGAL glycolysis 4 2 ATP ATP (2 ATP net) NADH pyruvate acetyl-CoA NADH CO2 Krebs Cycle NADH, FADH2 2 ATP CO2 e– ATP ATP electron transfer phosphorylation ATP many ATP water H+ e– + oxygen Fig. 8-13b, p.135

  49. Evolution of Metabolic Pathways • When life originated, atmosphere had little oxygen • Earliest organisms used anaerobic pathways • Later, noncyclic pathway of photosynthesis increased atmospheric oxygen • Cells arose that used oxygen as final acceptor in electron transport

  50. Processes Are Linked p.136b

More Related