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![Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 9.4
NAD+
2 e−
+ 2 H+
2[H]
(from food)
Nicotinamide
(oxidized form)
Reduction of NAD+
2 e−
+ H+
NADH
Nicotinamide
(reduced form)
Oxidation of NADH
H+
H+
Dehydrogenase](https://image.slidesharecdn.com/biochapter9respiration-151125144235-lva1-app6891/85/Chapter-9-Respiration-10-320.jpg)
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Chapter 9: Respiration
- 1. Chapter 9 Cellular Respiration:Harvesting Chemical Energy
- 2. Figure 9.2. TheCarbon Cycle Light energy Organic molecules O2 CO2 H2O+ Photosynthesis in chloroplasts Cellular respiration in mitochondria ECOSYSTEM ATP powers most cellular workATP Heat energy + Energy flows into an ecosystem as sunlight and leaves as heat
- 3. Catabolic Pathways andProduction of ATP • Electron transfer plays a major role • The breakdown of organic molecules is exergonic • Fermentation is a partial degradation of sugars that occurs without oxygen • Aerobic Cellular respiration consumes oxygen and organic molecules and yields ATP • Anaerobic respiration is similar to aerobic respiration but consumes compounds other than O2 • Although carbohydrates, fats, and proteins are consumed as fuel, it is helpful to trace cellular respiration with the sugar glucose: C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy (ATP + heat)
- 4. Redox Reactions: Oxidationand Reduction • The transfer of electrons during chemical reactions releases energy stored in organic molecules • This released energy is ultimately used to synthesize ATP • Chemical reactions that transfer electrons between reactants are called oxidation- reduction reactions, or redox reactions
- 5. The Principle ofRedox • 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) Xe- + Y X + Ye- becomes oxidized (loses electron) becomes reduced (gains electron) • Some redox reactions do not transfer electrons but change the electron sharing in covalent bonds. Remember our first lab!
- 6. Figure 9.3 Reactants Products Methane (reducing agent) Oxygen (oxidizing agent) Carbondioxide Water becomes oxidized becomes reduced
- 7. 1. Because ofdifferences in their initial oxidation state, the full oxidation of a single carbon molecule can result in different free energy changes, even though each forms just one CO2 molecule. Which choice correctly matches the reactions shown with the proper relative energy change in attojoules (1 aJ = 10-18 J)? 1.CH4 + 2 O2 → CO2 + 2 H2O 2.CH3OH + 3/2 O2 → CO2 + 2 H2O 3.H2CO + O2 → CO2 + H2O 4.HCOOH + 1/2 O2 → CO2 + H2O 1. 1: −0.32 aJ; 2 −0.57 aJ; 3 −0.89 aJ; 4 −1.14 aJ 2. 1: −0.32 aJ; 2 −1.14 aJ; 3 −0.89 aJ; 4 −0.57 aJ 3. 1: −0.57 aJ; 2 −0.32 aJ; 3 −1.14 aJ; 4 −0.89 aJ 4. 1: −0.89 aJ; 2 −0.32 aJ; 3 −0.57 aJ; 4 −1.14 aJ 5. 1: −1.14 aJ; 2 −0.89 aJ; 3 −0.57 aJ; 4 −0.32 aJ
- 8. 1. Because ofdifferences in their initial oxidation state, the full oxidation of a single carbon molecule can result in different free energy changes, even though each forms just one CO2 molecule. Which choice correctly matches the reactions shown with the proper relative energy change in attojoules (1 aJ = 10-18 J)? 1.CH4 + 2 O2 → CO2 + 2 H2O 2.CH3OH + 3/2 O2 → CO2 + 2 H2O 3.H2CO + O2 → CO2 + H2O 4.HCOOH + 1/2 O2 → CO2 + H2O 1. 1: −0.32 aJ; 2 −0.57 aJ; 3 −0.89 aJ; 4 −1.14 aJ 2. 1: −0.32 aJ; 2 −1.14 aJ; 3 −0.89 aJ; 4 −0.57 aJ 3. 1: −0.57 aJ; 2 −0.32 aJ; 3 −1.14 aJ; 4 −0.89 aJ 4. 1: −0.89 aJ; 2 −0.32 aJ; 3 −0.57 aJ; 4 −1.14 aJ 5. 1: −1.14 aJ; 2 −0.89 aJ; 3 −0.57 aJ; 4 −0.32 aJ
- 9. Copyright © 2005Pearson Education, Inc. publishing as Benjamin Cummings 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 C6H12O6 + 6O2 6CO2 + 6H2O + Energy becomes oxidized becomes reduced
- 10. Copyright © 2005Pearson Education, Inc. publishing as Benjamin Cummings Figure 9.4 NAD+ 2 e− + 2 H+ 2[H] (from food) Nicotinamide (oxidized form) Reduction of NAD+ 2 e− + H+ NADH Nicotinamide (reduced form) Oxidation of NADH H+ H+ Dehydrogenase
- 11. • NADH passesthe electrons to the electron transport chain • Unlike an uncontrolled reaction, the electron transport chain passes electrons in a series of steps instead of one explosive reaction • Oxygen pulls electrons down the chain in an energy- yielding tumble • The energy yielded is used to regenerate ATP
- 12. H2 +½ O22 H + ½ O2 2 H+ 2 e− 2 e− 2 H+ + H2O ½ O2 Controlled release of energy Electrontransport chain ATP ATP ATP Explosive release Cellular respirationUncontrolled reaction(a) (b) Freeenergy,G Freeenergy,G H2O
- 13. The Stages ofCellular Respiration: A Preview • Cellular respiration has three stages: – Glycolysis (breaks down glucose into two molecules of pyruvate) – The citric acid cycle (completes the breakdown of glucose) – Oxidative phosphorylation (accounts for most of the ATP synthesis) • The process that generates most of the ATP is called oxidative phosphorylation because it is powered by redox reactions 1. 2. 3. GLYCOLYSIS (color-coded blue throughout the chapter) PYRUVATE OXIDATION and the CITRIC ACID CYCLE (color-coded orange) OXIDATIVE PHOSPHORYLATION: Electron transport and chemiosmosis (color-coded purple)
- 14.
- 15. Electrons via NADH Electrons via NADH andFADH2 ATP ATP CYTOSOL MITOCHONDRION Substrate-level Substrate-level GLYCOLYSIS PYRUVATE OXIDATION CITRIC ACID CYCLEAcetyl CoAGlucose Pyruvate Citric acid = Kreb’s = TCA = tri-carboxylic acid
- 16. Electrons via NADH Electrons via NADH andFADH2 ATP ATP ATP CYTOSOL MITOCHONDRION Substrate-level Substrate-level Oxidative GLYCOLYSIS PYRUVATE OXIDATION CITRIC ACID CYCLE OXIDATIVE PHOSPHORYLATION (Electron transport and chemiosmosis) Acetyl CoAGlucose Pyruvate
- 17. • Oxidative phosphorylationaccounts for almost 90% of the ATP generated by cellular respiration • A small amount of ATP is formed in glycolysis and the citric acid cycle by substrate-level phosphorylation VIDEO: Cellular Respiration For each molecule of glucose degraded to CO2and water by respiration, the cell makes up to 32 molecules of ATP
- 18. Glycolysis harvests energyby 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
- 19.
- 20. LE 9-8 Energy investmentphase Glucose 2 ATP used2 ADP + 2 P 4 ADP + 4 P 4 ATP formed 2 NAD+ + 4 e– + 4 H+ Energy payoff phase + 2 H+2 NADH 2 Pyruvate + 2 H2O 2 Pyruvate + 2 H2O 2 ATP 2 NADH + 2 H+ Glucose 4 ATP formed – 2 ATP used 2 NAD+ + 4 e– + 4 H+ Net Glycolysis Citric acid cycle Oxidative phosphorylation ATPATPATP
- 21. Figure 9.9a GLYCOLYSIS: EnergyInvestment Phase ADP Glucose 6-phosphate Fructose 6-phosphate ATP ATP ADP Glyceraldehyde 3-phosphate (G3P) Fructose 1,6-bisphosphate Dihydroxyacetone phosphate (DHAP) Glucose Hexokinase Phosphogluco- isomerase Phospho- fructokinase Aldolase Isomerase 1 2 5 4 3
- 22. Figure 9.9b GLYCOLYSIS: EnergyPayoff Phase Glycer- aldehyde 3-phosphate (G3P) Triose phosphate dehydrogenase 6 1,3-Bisphospho- glycerate 3-Phospho- glycerate 2-Phospho- glycerate Phosphoenol- pyruvate (PEP) Pyruvate Phospho- glycerokinase Phospho- glyceromutase Enolase Pyruvate kinase 2 NAD+ 7 8 9 10 2 NADH + 2 H+ 2 2 2 2 2 2 2 2 2 22 H2OATP ATP ADP ADP
- 23. The citric acidcycle 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
- 24. Figure 9.10 CYTOSOL Pyruvate Transport protein MITOCHONDRION AcetylCoANAD+ H+ NADH + CO2 Coenzyme A 1 2 3
- 25. • The citricacid 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
- 26. Figure 9.11 PYRUVATE OXIDATION Pyruvate(from glycolysis, 2 molecules per glucose) NADH NAD+ CO2 CoA CoA + H+ CoA CoA CO2 CITRIC ACID CYCLE FADH2 FAD ATP ADP + P i NAD+ + 3 H+ NADH3 3 2 Acetyl CoA
- 27. • The citricacid cycle has eight steps, each catalyzed by a specific enzyme • The acetyl group of acetyl CoA joins the cycle by combining with oxaloacetate, forming citrate • The next seven steps decompose the citrate back to oxaloacetate, making the process a cycle • The NADH and FADH2 produced by the cycle relay electrons extracted from food to the electron transport chain
- 28.
- 29.
- 30.
- 31.
- 32. Acetyl CoA H2O + H+ Oxaloacetate CoA-SH Citrate α-Ketoglutarate CoA-SH NAD+ CO2 NADH CO2 NAD+ NADH +H+ Succinyl CoA CITRIC ACID CYCLE Isocitrate 1 2 4 3
- 33. Acetyl CoA H2O + H+ Oxaloacetate CoA-SH Citrate α-Ketoglutarate CoA-SH NAD+ CO2 NADH CO2 NAD+ NADH +H+ Succinyl CoA ATP ADP GTP GDP Succinate CITRIC ACID CYCLE P i Isocitrate 1 2 5 4 3 CoA-SH
- 34. Acetyl CoA H2O + H+ Oxaloacetate CoA-SH Citrate α-Ketoglutarate CoA-SH NAD+ CO2 NADH CO2 NAD+ NADH +H+ Succinyl CoA ATP ADP GTP GDP Succinate FAD FADH2 Fumarate CITRIC ACID CYCLE P i Isocitrate 1 2 5 6 4 3 CoA-SH
- 35. Acetyl CoA H2O + H+ Oxaloacetate CoA-SH Citrate α-Ketoglutarate CoA-SH NAD+ CO2 NADH CO2 NAD+ NADH +H+ Succinyl CoA ATP ADP GTP GDP Succinate FAD FADH2 Fumarate H2O Malate CITRIC ACID CYCLE P i Isocitrate 1 2 5 6 4 3 7 CoA-SH
- 36. Acetyl CoA H2O + H+ Oxaloacetate CoA-SH Citrate α-Ketoglutarate CoA-SH NAD+ CO2 NADH CO2 NAD+ NADH +H+ Succinyl CoA ATP ADP GTP GDP Succinate FAD FADH2 Fumarate H2O Malate CITRIC ACID CYCLE + H+ NAD+ P i NADH Isocitrate 1 2 5 6 4 3 7 8 CoA-SH
- 37. During oxidative phosphorylation, chemiosmosiscouples 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
- 38. The Pathway ofElectron 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
- 39. ATP ATP ATP Glycolysis Oxidative phosphorylation: electrontransport and chemiosmosis Citric acid cycle NADH 50 FADH2 40 FMN Fe•S I FAD Fe•S II III Q Fe•S Cyt b 30 20 Cyt c Cyt c1 Cyt a Cyt a3 IV 10 0 Multiprotein complexes Freeenergy(G)relativetoO2(kcal/mol) H2O O22 H+ + 1 /2 •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
- 40. 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
- 41. Figure 9.14 INTERMEMBRANE SPACE Rotor H+Stator Internal rod Catalytic knob ADP + P i MITOCHONDRIAL MATRIX ATP A rotor within the membrane spins as shown when H+ flows past it down the H+ gradient. A stator anchored in the membrane holds the knob stationary. A rod (or “stalk”) extending into the knob also spins, activating catalytic sites in the knob. Three catalytic sites in the stationary knob join inorganic phosphate to ADP to make ATP.
- 42. ATP Synthase onmt cristae
- 43. • The energystored 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
- 44. Figure 9.15 Protein complex of electron carriers (carrying electrons from food) ATP synthase Electrontransport chain Chemiosmosis Oxidative phosphorylation 2 H+ + ½ O2 H2O ADP + Pi H+ ATP H+ H+ H+ H+ Cyt c Q I II III IV FADFADH2 NADH NAD+ 1 2
- 45. 2. The hydrogenstaken from glucose or a breakdown product of glucose are added to oxygen, releasing energy to a. actively transport H+ into the intermembrane space. b. actively transport NAD+ into the intermembrane space. c. actively transport Na+ into the matrix. d. power facilitated diffusion of H+ into the matrix. e. actively transport H+ into the matrix.
- 46. 2. The hydrogenstaken from glucose or a breakdown product of glucose are added to oxygen, releasing energy to a. actively transport H+ into the intermembrane space. b. actively transport NAD+ into the intermembrane space. c. actively transport Na+ into the matrix. d. power facilitated diffusion of H+ into the matrix. e. actively transport H+ into the matrix.
- 47. Copyright © 2005Pearson Education, Inc. publishing as Benjamin Cummings An Accounting of ATP Production by Cellular Respiration • During cellular respiration, most energy flows in this sequence: glucose → NADH → electron transport chain → proton-motive force → ATP • About 34% of the energy in a glucose molecule is transferred to ATP during cellular respiration, making about 32 ATP • There are several reasons why the number of ATP is not known exactly
- 48. Copyright © 2005Pearson Education, Inc. publishing as Benjamin Cummings Figure 9.16 Electron shuttles span membrane CYTOSOL 2 NADH or 2 FADH2 2 NADH 2 FADH26 NADH MITOCHONDRION OXIDATIVE PHOSPHORYLATION (Electron transport and chemiosmosis) CITRIC ACID CYCLE PYRUVATE OXIDATION 2 Acetyl CoA GLYCOLYSIS Glucose 2 Pyruvate + 2 ATP + 2 ATP Maximum per glucose: About 30 or 32 ATP + about 26 or 28 ATP 2 NADH
- 49. Fermentation enables somecells 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 • 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
- 50. Figure 9.17 2 ADP+ 2 P i 2 ATP Glucose 2 NAD+ NADH2 + 2 H+ 2 Pyruvate CO22 2 Ethanol (a) Alcohol fermentation 2 Acetaldehyde 2 Lactate Lactic acid fermentation 2 ADP + 2 P i 2 ATP GLYCOLYSIS NAD+ + 2 H+ NADH22 2 Pyruvate (b) GLYCOLYSIS Glucose
- 51. Fermentation and CellularRespiration Compared • Both processes use glycolysis to oxidize glucose and other organic fuels to pyruvate • The processes have different final electron acceptors: an organic molecule (such as pyruvate) in fermentation and O2 in cellular respiration • Cellular respiration produces much more ATP
- 52. • Yeast andmany bacteria are facultative anaerobes, meaning that they can survive using either fermentation or cellular respiration • In a facultative anaerobe, pyruvate is a fork in the metabolic road that leads to two alternative catabolic routes
- 53. LE 9-18 Pyruvate Glucose CYTOSOL No O2present Fermentation Ethanol or lactate Acetyl CoA MITOCHONDRION O2 present Cellular respiration Citric acid cycle
- 54. The Evolutionary Significanceof Glycolysis • Glycolysis occurs in nearly all organisms • Glycolysis probably evolved in ancient prokaryotes before there was oxygen in the atmosphere • Very little O2 was available in the atmosphere until about 2.7 billion years ago, so early prokaryotes likely used only glycolysis to generate ATP • Gycolysis and the citric acid cycle are major intersections to various catabolic and anabolic pathways
- 55. The Versatility ofCatabolism • Catabolic pathways funnel electrons from many kinds of organic molecules into cellular respiration • Glycolysis accepts a wide range of carbohydrates • Proteins must be digested to amino acids; amino groups can feed glycolysis or the citric acid cycle • Fats are digested to glycerol (used in glycolysis) and fatty acids (used in generating acetyl CoA) • An oxidized gram of fat produces more than twice as much ATP as an oxidized gram of carbohydrate (has more reducing power because less oxidized)
- 56. Proteins Carbohydrates Fats Amino acids SugarsGlycerol Fatty acids GLYCOLYSIS Glucose Glyceraldehyde 3- P Pyruvate Acetyl CoA CITRIC ACID CYCLE OXIDATIVE PHOSPHORYLATION NH3
- 57. Copyright © 2005Pearson Education, Inc. publishing as Benjamin Cummings Regulation of Cellular Respiration via Feedback Mechanisms • Feedback inhibition is the most common mechanism for control • If ATP concentration begins to drop, respiration speeds up; when there is plenty of ATP, respiration slows down • Control of catabolism is based mainly on regulating the activity of enzymes at strategic points in the catabolic pathway
- 58. Copyright © 2005Pearson Education, Inc. publishing as Benjamin Cummings Figure 9.20 Glucose AMP Stimulates GLYCOLYSIS Fructose 6-phosphate Phosphofructokinase Fructose 1,6-bisphosphate Inhibits Inhibits Citrate Pyruvate Acetyl CoA ATP CITRIC ACID CYCLE Oxidative phosphorylation Video Review of catabolism
- 59. Copyright © 2005Pearson Education, Inc. publishing as Benjamin Cummings 3. Which choice correctly orders the following four reactions from that with the highest free energy change to that with the lowest free energy change? 1. NADH + H+ → NAD+ + 2 H 2. C6H12O6 + 6 O2 → 6 CO2 + 6 H2O 3. ATP + H2O → ADP + H3PO4 4. pyruvate + CoA → acetyl-CoA + CO2 + 2 H a) 3 > 1 > 4 > 2 d) 3 > 2 > 1 > 4 b) 2 > 4 > 1 > 3 e) 2 > 1 > 4 > 3 c) 1 > 3 > 4 > 2
- 60. Copyright © 2005Pearson Education, Inc. publishing as Benjamin Cummings 3. Which choice correctly orders the following four reactions from that with the highest free energy change to that with the lowest free energy change? 1. NADH + H+ → NAD+ + 2 H (enough energy to produce 3 ATP bonds) 2. C6H12O6 + 6 O2 → 6 CO2 + 6 H2O 3. ATP + H2O → ADP + H3PO4 4. pyruvate + CoA → acetyl-CoA + CO2 + 2 H (decarboxylation and oxidation.) a) 3 > 1 > 4 > 2 d) 3 > 2 > 1 > 4 b) 2 > 4 > 1 > 3 e) 2 > 1 > 4 > 3 c) 1 > 3 > 4 > 2
Editor's Notes
- #3 Figure 9.2 Energy flow and chemical recycling in ecosystems
- #7 Figure 9.3 Methane combustion as an energy-yielding redox reaction
- #8 Answer: E Energy calculations based on: Cotterill R- 2002-Biophysics. An Introduction. Pgs. 34-35. John Wiley & Sons. West Sussex, England.
- #9 Answer: E Energy calculations based on: Cotterill R- 2002-Biophysics. An Introduction. Pgs. 34-35. John Wiley & Sons. West Sussex, England.
- #11 Figure 9.4 NAD+ as an electron shuttle
- #13 Figure 9.5 An introduction to electron transport chains
- #15 Figure 9.6-1 An overview of cellular respiration (step 1)
- #16 Figure 9.6-2 An overview of cellular respiration (step 2)
- #17 Figure 9.6-3 An overview of cellular respiration (step 3)
- #20 Figure 9.UN06 In-text figure, mini-map, glycolysis, p. 168
- #22 Figure 9.9a A closer look at glycolysis (part 1: investment phase)
- #23 Figure 9.9b A closer look at glycolysis (part 2: payoff phase)
- #25 Figure 9.10 Oxidation of pyruvate to acetyl CoA, the step before the citric acid cycle
- #27 Figure 9.11 An overview of pyruvate oxidation and the citric acid cycle
- #29 Figure 9.UN08 In-text figure, mini-map, citric acid cycle, p. 171
- #30 Figure 9.12-1 A closer look at the citric acid cycle (step 1)
- #31 Figure 9.12-2 A closer look at the citric acid cycle (step 2)
- #32 Figure 9.12-3 A closer look at the citric acid cycle (step 3)
- #33 Figure 9.12-4 A closer look at the citric acid cycle (step 4)
- #34 Figure 9.12-5 A closer look at the citric acid cycle (step 5)
- #35 Figure 9.12-6 A closer look at the citric acid cycle (step 6)
- #36 Figure 9.12-7 A closer look at the citric acid cycle (step 7)
- #37 Figure 9.12-8 A closer look at the citric acid cycle (step 8)
- #42 Figure 9.14 ATP synthase, a molecular mill
- #45 Figure 9.15 Chemiosmosis couples the electron transport chain to ATP synthesis
- #46 Answer: A Respiration will occur only through alternative substrates such as FADH2 that are oxidized downstream of complex I.
- #47 Answer: A Respiration will occur only through alternative substrates such as FADH2 that are oxidized downstream of complex I.
- #49 Figure 9.16 ATP yield per molecule of glucose at each stage of cellular respiration
- #51 Figure 9.17 Fermentation
- #57 Figure 9.19-5 The catabolism of various molecules from food (step 5)
- #59 Figure 9.20 The control of cellular respiration
- #60 Answer: B
- #61 Answer: B