1 / 39

LE 9-2

LE 9-2. Light energy. ECOSYSTEM. Photosynthesis in chloroplasts. Organic molecules. CO 2 + H 2 O. + O 2. Cellular respiration in mitochondria. ATP. powers most cellular work. Heat energy. Redox Reactions: Oxidation and Reduction.

romney
Download Presentation

LE 9-2

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. LE 9-2 Light energy ECOSYSTEM Photosynthesis in chloroplasts Organic molecules CO2 + H2O + O2 Cellular respiration in mitochondria ATP powers most cellular work Heat energy

  2. Redox Reactions: Oxidation and Reduction • The transfer of electrons during chemical reactions releases energy stored in organic molecules • This released energy is ultimately used to synthesize ATP

  3. becomes oxidized(loses electron) Xe- + Y X + Ye- becomes reduced(gains electron) The Principle of Redox • Chemical reactions that transfer electrons between reactants are called oxidation-reduction reactions, or redox reactions • In oxidation, a substance loses electrons, or is oxidized • In reduction, a substance gains electrons, or is reduced (the amount of positive charge is reduced)

  4. The electron donor is called the reducing agent • The electron receptor is called the oxidizing agent

  5. becomes oxidized C6H12O6 + 6O2 6CO2 + 6H2O + Energy becomes reduced Oxidation of Organic Fuel Molecules During Cellular Respiration • During cellular respiration, the fuel (such as glucose) is oxidized and oxygen is reduced:

  6. Stepwise Energy Harvest via NAD+ and the Electron Transport Chain • In cellular respiration, glucose and other organic molecules are broken down in a series of steps • Electrons from organic compounds are usually first transferred to NAD+, a coenzyme • As an electron acceptor, NAD+ functions as an oxidizing agent during cellular respiration • Each NADH (the reduced form of NAD+) represents stored energy that is tapped to synthesize ATP

  7. LE 9-4 2e–+ 2H+ 2e–+ H+ H+ NADH NAD+ Dehydrogenase + 2[H] (from food) H+ + Nicotinamide (reduced form) Nicotinamide (oxidized form)

  8. LE 9-6_1 Glycolysis Pyruvate Glucose Cytosol Mitochondrion ATP Substrate-level phosphorylation

  9. LE 9-6_2 Glycolysis Citric acid cycle Pyruvate Glucose Cytosol Mitochondrion ATP ATP Substrate-level phosphorylation Substrate-level phosphorylation

  10. LE 9-6_3 Electrons carried via NADH and FADH2 Electrons carried via NADH Oxidative phosphorylation: electron transport and chemiosmosis Glycolysis Citric acid cycle Pyruvate Glucose Cytosol Mitochondrion ATP ATP ATP Substrate-level phosphorylation Oxidative phosphorylation Substrate-level phosphorylation

  11. LE 9-8 Energy investment phase Glucose 2 ATP 2 ADP + 2 P used Citric acid cycle Glycolysis Oxidative phosphorylation Energy payoff phase formed ATP ATP ATP 4 ADP + 4 P 4 ATP 2 NADH + 2 H+ 2 NAD+ + 4 e– + 4 H+ 2 Pyruvate + 2 H2O Net 2 Pyruvate + 2 H2O Glucose 4 ATP formed – 2 ATP used 2 ATP 2 NAD+ + 4 e– + 4 H+ 2 NADH + 2 H+

  12. Concept 9.2: Glycolysis harvests energy by oxidizing glucose to pyruvate • Glycolysis (“splitting of sugar”) breaks down glucose into two molecules of pyruvate • Glycolysis occurs in the cytoplasm and has two major phases: • Energy investment phase • Energy payoff phase

  13. LE 9-9a_1 Citric acid cycle Glycolysis Oxidation phosphorylation ATP ATP ATP Glucose ATP Hexokinase ADP Glucose-6-phosphate

  14. LE 9-9a_2 Citric acid cycle Glycolysis Oxidation phosphorylation ATP ATP ATP Glucose ATP Hexokinase ADP Glucose-6-phosphate Phosphoglucoisomerase Fructose-6-phosphate ATP Phosphofructokinase ADP Fructose- 1, 6-bisphosphate Aldolase Isomerase Dihydroxyacetone phosphate Glyceraldehyde- 3-phosphate

  15. LE 9-9b_1 2 NAD+ Triose phosphate dehydrogenase NADH 2 + 2 H+ 1, 3-Bisphosphoglycerate 2 ADP Phosphoglycerokinase 2 ATP 3-Phosphoglycerate Phosphoglyceromutase 2-Phosphoglycerate

  16. LE 9-9b_2 2 NAD+ Triose phosphate dehydrogenase NADH 2 + 2 H+ 1, 3-Bisphosphoglycerate 2 ADP Phosphoglycerokinase 2 ATP 3-Phosphoglycerate Phosphoglyceromutase 2-Phosphoglycerate Enolase 2 H2O Phosphoenolpyruvate 2 ADP Pyruvate kinase 2 ATP Pyruvate

  17. Concept 9.3: The citric acid cycle completes the energy-yielding oxidation of organic molecules • Before the citric acid cycle can begin, pyruvate must be converted to acetyl CoA, which links the cycle to glycolysis

  18. LE 9-10 MITOCHONDRION CYTOSOL NAD+ NADH + H+ Acetyl Co A CO2 Coenzyme A Pyruvate Transport protein

  19. The citric acid cycle, also called the Krebs cycle, takes place within the mitochondrial matrix • The cycle oxidizes organic fuel derived from pyruvate, generating one ATP, 3 NADH, and 1 FADH2 per turn

  20. LE 9-11 Pyruvate (from glycolysis, 2 molecules per glucose) Citric acid cycle Glycolysis Oxidation phosphorylation CO2 NAD+ CoA NADH ATP ATP ATP + H+ Acetyl CoA CoA CoA Citric acid cycle 2 CO2 FADH2 3 NAD+ 3 NADH FAD + 3 H+ ADP + P i ATP

  21. LE 9-12_1 Citric acid cycle Glycolysis Oxidation phosphorylation ATP ATP ATP Acetyl CoA H2O Oxaloacetate Citrate Isocitrate Citric acid cycle

  22. LE 9-12_2 Citric acid cycle Glycolysis Oxidation phosphorylation ATP ATP ATP Acetyl CoA H2O Oxaloacetate Citrate Isocitrate CO2 Citric acid cycle NAD+ NADH + H+ a-Ketoglutarate CO2 NAD+ NADH Succinyl CoA + H+

  23. LE 9-12_3 Citric acid cycle Glycolysis Oxidation phosphorylation ATP ATP ATP Acetyl CoA H2O Oxaloacetate Citrate Isocitrate CO2 Citric acid cycle NAD+ NADH + H+ Fumarate a-Ketoglutarate FADH2 CO2 NAD+ FAD Succinate NADH P i Succinyl CoA + H+ GDP GTP ADP ATP

  24. LE 9-12_4 Citric acid cycle Glycolysis Oxidation phosphorylation ATP ATP ATP Acetyl CoA NADH H2O + H+ NAD+ Oxaloacetate Malate Citrate Isocitrate CO2 Citric acid cycle NAD+ H2O NADH + H+ Fumarate a-Ketoglutarate FADH2 CO2 NAD+ FAD Succinate NADH P i Succinyl CoA + H+ GDP GTP ADP ATP

  25. Concept 9.4: During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis • Following glycolysis and the citric acid cycle, NADH and FADH2 account for most of the energy extracted from food • These two electron carriers donate electrons to the electron transport chain, which powers ATP synthesis via oxidative phosphorylation

  26. The Pathway of Electron Transport • The electron transport chain is in the cristae of the mitochondrion • Most of the chain’s components are proteins, which exist in multiprotein complexes • The carriers alternate reduced and oxidized states as they accept and donate electrons • Electrons drop in free energy as they go down the chain and are finally passed to O2, forming water

  27. LE 9-13 NADH 50 FADH2 Multiprotein complexes I FAD 40 FMN II Fe•S Fe•S Q III Cyt b Oxidative phosphorylation: electron transport and chemiosmosis Citric acid cycle Glycolysis Fe•S 30 Cyt c1 IV Free energy (G) relative to O2 (kcal/mol) Cyt c ATP ATP ATP Cyt a Cyt a3 20 10 2 H+ + 1/2 O2 0 H2O

  28. The electron transport chain generates no ATP • The chain’s function is to break the large free-energy drop from food to O2 into smaller steps that release energy in manageable amounts

  29. Chemiosmosis: The Energy-Coupling Mechanism • Electron transfer in the electron transport chain causes proteins to pump H+ from the mitochondrial matrix to the intermembrane space • H+ then moves back across the membrane, passing through channels in ATP synthase • ATP synthase uses the exergonic flow of H+ to drive phosphorylation of ATP • This is an example of chemiosmosis, the use of energy in a H+ gradient to drive cellular work

  30. The energy stored in a H+ gradient across a membrane couples the redox reactions of the electron transport chain to ATP synthesis • The H+ gradient is referred to as a proton-motive force, emphasizing its capacity to do work

  31. LE 9-15 Inner mitochondrial membrane Oxidative phosphorylation: electron transport and chemiosmosis Citric acid cycle Glycolysis ATP ATP ATP H+ H+ H+ H+ Cyt c Protein complex of electron carriers Intermembrane space Q IV III I ATP synthase II Inner mitochondrial membrane H2O 2H+ + 1/2 O2 FADH2 FAD NAD+ NADH + H+ ATP ADP + P i (carrying electrons from food) H+ Mitochondrial matrix Electron transport chain Electron transport and pumping of protons (H+), Which create an H+ gradient across the membrane Chemiosmosis ATP synthesis powered by the flow of H+ back across the membrane Oxidative phosphorylation

  32. LE 9-16 Electron shuttles span membrane MITOCHONDRION CYTOSOL 2 NADH or 2 FADH2 2 NADH 2 NADH 6 NADH 2 FADH2 Oxidative phosphorylation: electron transport and chemiosmosis Glycolysis 2 Acetyl CoA Citric acid cycle 2 Pyruvate Glucose + 2 ATP + 2 ATP + about 32 or 34 ATP by substrate-level phosphorylation by substrate-level phosphorylation by oxidation phosphorylation, depending on which shuttle transports electrons form NADH in cytosol About 36 or 38 ATP Maximum per glucose:

  33. Concept 9.5: Fermentation enables some cells to produce ATP without the use of oxygen • Cellular respiration requires O2 to produce ATP • Glycolysis can produce ATP with or without O2 (in aerobic or anaerobic conditions) • In the absence of O2, glycolysis couples with fermentation to produce ATP

  34. Types of Fermentation • Fermentation consists of glycolysis plus reactions that regenerate NAD+, which can be reused by glycolysis • Two common types are alcohol fermentation and lactic acid fermentation

  35. In alcohol fermentation, pyruvate is converted to ethanol in two steps, with the first releasing CO2 • Alcohol fermentation by yeast is used in brewing, winemaking, and baking

  36. LE 9-17a P 2 ADP + 2 2 ATP i Glycolysis Glucose 2 Pyruvate 2 NAD+ 2 NADH CO2 2 + 2 H+ 2 Acetaldehyde 2 Ethanol Alcohol fermentation

  37. In lactic acid fermentation, pyruvate is reduced to NADH, forming lactate as an end product, with no release of CO2 • Lactic acid fermentation by some fungi and bacteria is used to make cheese and yogurt • Human muscle cells use lactic acid fermentation to generate ATP when O2 is scarce

  38. LE 9-17b P 2 ADP + 2 2 ATP i Glycolysis Glucose 2 NAD+ 2 NADH CO2 2 + 2 H+ 2 Pyruvate 2 Lactate Lactic acid fermentation

  39. The Evolutionary Significance of Glycolysis • Glycolysis occurs in nearly all organisms • Glycolysis probably evolved in ancient prokaryotes before there was oxygen in the atmosphere

More Related