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Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chapter 9 Cellular Respiration: Harvesting Chemical Energy 高醫 生物醫學暨環境生物學系 助理教授.

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Presentation on theme: "Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chapter 9 Cellular Respiration: Harvesting Chemical Energy 高醫 生物醫學暨環境生物學系 助理教授."— Presentation transcript:

1 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chapter 9 Cellular Respiration: Harvesting Chemical Energy 高醫 生物醫學暨環境生物學系 助理教授 張學偉 http://genomed.dlearn.kmu.edu.tw

2 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Energy – Flows into an ecosystem as sunlight and leaves as heat Light energy ECOSYSTEM CO 2 + H 2 O Photosynthesis in chloroplasts Cellular respiration in mitochondria Organic molecules + O 2 ATP powers most cellular work Heat energy Figure 9.2

3 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings To keep working, cells must regenerate ATP 本圖補充

4 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings An overview of cellular respiration Figure 9.6 Electrons carried via NADH Glycolysis Glucose Pyruvate ATP Substrate-level phosphorylation Electrons carried via NADH and FADH 2 Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis ATP Substrate-level phosphorylation Oxidative phosphorylation Mitochondrion Cytosol

5 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 1: Catabolic pathways yield energy by oxidizing organic fuels 2: Glycolysis harvests energy by oxidizing glucose to pyruvate 3: The citric acid cycle completes the energy-yielding oxidation of organic molecules 4: During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis 5: Fermentation enables some cells to produce ATP without the use of oxygen 6: Glycolysis and the citric acid cycle connect to many other metabolic pathways

6 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 9.1: Catabolic pathways yield energy by oxidizing organic fuels

7 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Catabolic pathways ( 異化 ) yield energy by oxidizing organic fuels 同化作用 exergonic ( 產能的 )endergonic 耗能的 Catabolic Pathways and Production of ATP 本圖為補充

8 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings One catabolic process, fermentation ( 發酵 ) – Is a partial degradation of sugars that occurs without oxygen Conecept 5: Fermentation enables some cells to produce ATP without the use of oxygen 稍後再講

9 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cellular respiration – Is the most prevalent and efficient catabolic pathway – Consumes oxygen (with O2 as the ultimate electron acceptor) and organic molecules such as glucose – Yields ATP It is called cellular respiration to distinguish it from the respiration of breathing.

10 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Redox Reactions: Oxidation and Reduction Catabolic pathways yield energy – Due to the transfer of electrons The Principle of Redox Redox reactions – Transfer electrons from one reactant to another by oxidation and reduction

11 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Definition of Oxidation & Reduction and its agent In oxidation – A substance loses electrons, or is oxidized In reduction – A substance gains electrons, or is reduced Reducting Agent Oxidating Agent Na + Cl Na + + Cl – becomes oxidized (loses electron) becomes reduced (gains electron)

12 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Some redox reactions – Do not completely exchange electrons – Change the degree of electron sharing in covalent bonds CH 4 H H H H C OO O O O C HH Methane (reducing agent) Oxygen (oxidizing agent) Carbon dioxideWater + 2O 2 CO 2 + Energy + 2 H 2 O becomes oxidized becomes reduced Reactants Products Figure 9.3 注意 : blue ball 位置

13 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Oxidation of Organic Fuel Molecules During Cellular Respiration During cellular respiration: - Glucose is oxidized in a series of steps and oxygen is reduced C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + Energy becomes oxidized becomes reduced △ G = - 686 Kcal △ G < 0 1.spontaneous reaction (without an input of energy) 2.Liberating energy

14 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings NAD + H O O OO–O– O O O–O– O O O P P CH 2 HO OH H H HOOH HO H H N+N+ C NH 2 H N H N N Nicotinamide (oxidized form) NH 2 + 2[H] (from food) Dehydrogenase Reduction of NAD + Oxidation of NADH 2 e – + 2 H + 2 e – + H + NADH O H H N C + Nicotinamide (reduced form) N Figure 9.4 H+ NAD + = Nicotinamide adenine dinucleotide Stepwise Energy Harvest via NAD + and the Electron Transport Chain adenine Nucleotide = Base + Sugar + Phosphate Nucleosides = Sugar + Base (no phosphate)

15 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Electrons from organic compounds – Are usually first transferred to NAD +, a coenzyme NAD + H O O OO–O– O O O–O– O O O P P CH 2 HO OH H H HOOH HO H H N+N+ C NH 2 H N H N N Nicotinamide (oxidized form) NH 2 + 2[H] (from food) Dehydrogenase Reduction of NAD + Oxidation of NADH 2 e – + 2 H + 2 e – + H + NADH O H H N C + Nicotinamide (reduced form) N Figure 9.4 H+ Hydrogen atom protonelectron 2 H  2H + +2e- (oxidation) NAD + + H + +2e-  NADH (reduction) = NAD + + 2H  NADH + H +

16 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A is the electron donor (so it is oxidized) FAD & NAD(P) is the electron acceptor (so it is reduced). The products of the reaction are B (oxidized state) FADH2 or NAD(P)H (reduced state). Ex. A  B + 2H + +2e- (oxidation) (+) FAD + 2H + +2e-  FADH2 (reduction) = A+ FAD B+ FADH2 A+ NAD(P) B+ NAD(P)H

17 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 圖形為補充 NADH passes the electrons to the electron transport chain

18 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings If electron transfer is not stepwise – A large release of energy occurs – As in the reaction of hydrogen and oxygen to form water (a) Uncontrolled reaction Free energy, G H2OH2O Explosive release of heat and light energy Figure 9.5 A H 2 + 1 / 2 O 2

19 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 比較 The electron transport chain Passes electrons in a series of steps instead of in one explosive reaction Uses the energy from the electron transfer to form ATP 2 H 1 / 2 O 2 (from food via NADH) 2 H + + 2 e – 2 H + 2 e – H2OH2O 1 / 2 O 2 Controlled release of energy for synthesis of ATP ATP Electron transport chain Free energy, G (b) Cellular respiration + Figure 9.5 B

20 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings An overview of cellular respiration Figure 9.6 Electrons carried via NADH Glycolsis Glucose Pyruvate ATP Substrate-level phosphorylation Electrons carried via NADH and FADH 2 Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis ATP Substrate-level phosphorylation Oxidative phosphorylation Mitochondrion Cytosol 1 2 3

21 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Glycolysis – Breaks down glucose into two molecules of pyruvate The citric acid cycle – Completes the breakdown of glucose Oxidative phosphorylation – Is driven by the electron transport chain – Generates ATP

22 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings substrate-level phosphorylation generate ATP from glycolysis and TCA cycle Figure 9.7 Enzyme ATP ADP Product Substrate P +

23 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 9.2: Glycolysis harvests energy by oxidizing glucose to pyruvate Glycolysis – Means “splitting of sugar” – Breaks down glucose into pyruvate – Occurs in the cytoplasm of the cell

24 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Glycolysis consists of two major phases – Energy investment phase – Energy payoff phase Glycolysis Citric acid cycle Oxidative phosphorylation ATP 2 ATP 4 ATP used formed Glucose 2 ATP + 2 P 4 ADP + 4 P 2 NAD + + 4 e - + 4 H + 2 NADH + 2 H + 2 Pyruvate + 2 H 2 O Energy investment phase Energy payoff phase Glucose 2 Pyruvate + 2 H 2 O 4 ATP formed – 2 ATP used 2 ATP 2 NAD + + 4 e – + 4 H + 2 NADH + 2 H + Net Rx Net Rx: Glucose + 2ADP+ 2Pi + NAD+  2 Pyruvate + 2ATP + 2NADH + 2 H+ Figure 9.8

25 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 9.9 A investment phase H H H H H OH HO OH CH 2 O H H H H O H OH HO OH P CH 2 O P H O H HO H OH CH 2 OH P O CH 2 O O P HO H H OH O P CH 2 C O CH 2 OH H C CHOH CH 2 O O P ATP ADP Hexokinase Glucose Glucose-6-phosphate Fructose-6-phosphate ATP ADP Phosphoglucoisomerase Phosphofructokinase Fructose- 1, 6-bisphosphate Aldolase Isomerase 1 2 3 4 5 O H OH Dihydroxyacetone phosphate Glyceraldehyde- 3-phosphate CH 2 OH Glycolysis Citric acid cycle Oxidative phosphorylation 2 NAD + NADH 2 + 2 H + Triose phosphate dehydrogenase 2 P i 2 P C CHOH O P O CH 2 O 2 O–O– 1, 3-Bisphosphoglycerate 2 ADP 2 ATP Phosphoglycerokinase CH 2 OP 2 C CHOH 3-Phosphoglycerate Phosphoglyceromutase O–O– C C CH 2 OH H O P 2-Phosphoglycerate 2 H 2 O 2 O–O– Enolase C C O P O CH 2 Phosphoenolpyruvate 2 ADP 2 ATP Pyruvate kinase O–O– C C O O CH 3 2 6 8 7 9 10 Pyruvate O Figure 9.8 payoff phase Kinase isomerase Mutase Aldolase enolase Dehydrogenase

26 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

27

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

29 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The citric acid cycle – Takes place in the matrix of the mitochondrion

30 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Before citric acid cycle can begin – Pyruvate must first be converted to acetyl CoA, which links the cycle to glycolysis CYTOSOLMITOCHONDRION NADH + H + NAD + 2 31 CO 2 Coenzyme A Pyruvate Acetyle CoA S CoA C CH 3 O Transport protein O–O– O O C C CH 3 Figure 9.10 From Vit B Pyruvate Oxidation

31 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings An overview of the citric acid cycle ATP 2 CO 2 3 NAD + 3 NADH + 3 H + ADP + P i FAD FADH 2 Citric acid cycle CoA Acetyle CoA NADH + 3 H + CoA CO 2 Pyruvate (from glycolysis, 2 molecules per glucose) ATP Glycolysis Citric acid cycle Oxidative phosphorylatio n Figure 9.11 = TCA (Tricarboxyl acid) = Krebs Cycle

32 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Acetyl CoA NADH Oxaloacetate Citrate Malate Fumarate Succinate Succinyl CoA  -Ketoglutarate Isocitrate Citric acid cycle SCoA SH NADH FADH 2 FAD GTP GDP NAD + ADP P i NAD + CO 2 CoA SH CoA SH CoA S H2OH2O + H + H2OH2O C CH 3 O OCCOO – CH 2 COO – CH 2 HO C COO – CH 2 COO – CH 2 HCCOO – HOCH COO – CH CH 2 COO – HO COO – CH HC COO – CH 2 COO – CH 2 CO COO – CH 2 CO COO – 1 2 3 4 5 6 7 8 Glycolysis Oxidative phosphorylation NAD + + H + ATP Citric acid cycle A closer look at the citric acid cycle Figure 9.12

33 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 9.12 Acetyl CoA NADH Oxaloacetate Citrate Malate Fumarate Succinate Succinyl CoA  -Ketoglutarate Isocitrate Citric acid cycle SCoA SH NADH FADH 2 FAD GTP GDP NAD + ADP P i NAD + CO 2 CoA SH CoA SH CoA S H2OH2O + H + H2OH2O C CH 3 O OCCOO – CH 2 COO – CH 2 HO C COO – CH 2 COO – CH 2 HCCOO – HOCH COO – CH CH 2 COO – HO COO – CH HC COO – CH 2 COO – CH 2 CO COO – CH 2 CO COO – 1 2 3 4 5 6 7 8 Glycolysis Oxidative phosphorylation NAD + + H + ATP Citric acid cycle Figure 9.12 A closer look at the citric acid cycle pyruvate NAD + CoANADH + CO2 3C 2C 6C 5C 4C ½ Glucose

34 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

35 Energetics DHase

36 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 9.4: During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis

37 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings An overview of cellular respiration Figure 9.6 Electrons carried via NADH Glycolsis Glucose Pyruvate ATP Substrate-level phosphorylation Electrons carried via NADH and FADH 2 Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis ATP Substrate-level phosphorylation Oxidative phosphorylation Mitochondrion Cytosol NADH and FADH2: Donate electrons to the electron transport chain (ETC), which powers ATP synthesis via oxidative phosphorylation

38 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Pathway of Electron Transport In the ETC – Electrons from NADH and FADH 2 lose energy in several steps H2OH2O O2O2 NADH FADH2 FMN FeS O FAD Cyt b Cyt c 1 Cyt c Cyt a Cyt a 3 2 H + + 1  2 I II III IV Multiprotein complexes 0 10 20 30 40 50 Free energy (G) relative to O 2 (kcl/mol) Figure 9.13 At the end of the chain – Electrons are passed to oxygen, forming water

39 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chemiosmosis: The Energy-Coupling Mechanism ATP synthase is the enzyme that actually makes ATP INTERMEMBRANE SPACE H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ P i + ADP ATP A rotor within the membrane spins clockwise when H + flows past it down the H + gradient. A stator anchored in the membrane holds the knob stationary. A rod (for “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. MITOCHONDRIAL MATRIX Figure 9.14 注意 : H+& ATP 的方向

40 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings At certain steps along the electron transport chain – Electron transfer causes protein complexes to pump H + from the mitochondrial matrix to the intermembrane space. [ 逆反應 ; 與產生 ATP 時 的 H+ 運送方向相反 ] 目的 : resulting H + gradient

41 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The resulting H + gradient – Stores energy – Is referred to as a proton-motive force – Drives chemiosmosis in ATP synthase Chemiosmosis – Is an energy-coupling mechanism that uses energy in the form of a H + gradient across a membrane to drive cellular work

42 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chemiosmosis & electron transport chain Oxidative phosphorylation. electron transport and chemiosmosis Glycolysis ATP Inner Mitochondrial membrane H+H+ H+H+ H+H+ H+H+ H+H+ ATP P i Protein complex of electron carners Cyt c I II III IV (Carrying electrons from, food) NADH + FADH 2 NAD + FAD + 2 H + + 1 / 2 O 2 H2OH2O ADP + 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 ATP synthase Q Oxidative phosphorylation Intermembrane space Inner mitochondrial membrane Mitochondrial matrix Figure 9.15 NADH  3 ATP; FADH2  2 ATP

43 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings An Accounting of ATP Production by Cellular Respiration Electron shuttles span membrane CYTOSOL 2 NADH 2 FADH 2 2 NADH 6 NADH 2 FADH 2 2 NADH Glycolysis Glucose 2 Pyruvate 2 Acetyl CoA Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis MITOCHONDRION by substrate-level phosphorylation by substrate-level phosphorylation by oxidative phosphorylation, depending on which shuttle transports electrons from NADH in cytosol Maximum per glucose: About 36 or 38 ATP + 2 ATP + about 32 or 34 ATP or Figure 9.16

44 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings DHAP/GA3P shuttle Malate/Asp shuttle Shuttles for transfer of reducing equivalents from cytosol into mitochondria 補充 不考

45 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 1 Pyruvate + NAD + + CoASH  1 Acetyl-CoA + 1 NADH + CO2 TCA Pyruvate Oxidation Glycolysis  Pyruvate Oxidation  TCA 2 ATP 2 NADH (2H) 2 (2x1) NADH 2 (2x1) GTP/ATP 6 (2x3) NADH 2 (2x1) FADH2 Glucose +2ADP + 2Pi+ 2NAD +  2 pyruvate +2ATP+2NADH+2H + +2H2O 2 Pyruvate + 2 NAD + + 2 CoASH  2 Acetyl-CoA + 2 NADH + 2 CO2 Glycolysis (aerobic) 2 Acetyl-CoA + 4 H2O + 6 NAD + + 2FAD + 2GDP + 2 Pi  2 CO2 + 6 NADH + 2 FADH2 + 2 CoA-SH + 2 GTP aerobic

46 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Glycolysis  Pyruvate Oxidation  TCA 2 ATP 2 NADH (2H) 2 (2x1) NADH 2 (2x1) GTP/ATP 6 (2x3) NADH 2 (2x1) FADH2 EST & chemiosmosis NADH  3 ATP; FADH2  2 ATP ATP 8 6 2 + 18 + 4 = 38 or (6) shuttle = 36 Glycolysis (aerobic) About 40% of the energy in a glucose molecule – Is transferred to ATP during cellular respiration, making approximately 38 ATP

47 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 9.5: Fermentation enables some cells to produce ATP without the use of oxygen

48 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cellular respiration – Relies on oxygen to produce ATP In the absence of oxygen [no cellular respiration] – Cells can still produce ATP through fermentation fermentation i s a partial degradation of sugars that occurs without oxygen

49 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Glycolysis – Can produce ATP with or without oxygen, in aerobic or anaerobic conditions Fermentation consists of – Glycolysis + reactions that regenerate NAD +, which can be reused by glyocolysis

50 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 2 ADP + 2 P1P1 2 ATP Glycolysis Glucose 2 NAD + 2 NADH 2 Pyruvate 2 Acetaldehyde 2 Ethanol (a) Alcohol fermentation 2 ADP + 2 P1P1 2 ATP Glycolysis Glucose 2 NAD + 2 NADH 2 Lactate (b) Lactic acid fermentation H H OH CH 3 C O – O C CO CH 3 H CO O–O– CO CO O CO C OHH CH 3 CO 2 2 Figure 9.17 3C 2C 3C alcohol fermentation – Pyruvate is converted to ethanol in two steps, one of which releases CO2 lactic acid fermentation – Pyruvate is reduced directly to NADH to form lactate as a waste product Types of Fermentation

51 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Anaerobic metabolism Figure 9.6 Electrons carried via NADH Glycolsis Glucose Pyruvate ATP Substrate-level phosphorylation Electrons carried via NADH and FADH 2 Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis ATP Substrate-level phosphorylation Oxidative phosphorylation Mitochondrion Cytosol lactate Or ethanol 2 1x232-34 2 3x2 2x2

52 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Pyruvate is a key juncture in catabolism Glucose CYTOSOL Pyruvate No O 2 present Fermentation O 2 present Cellular respiration Ethanol or lactate Acetyl CoA MITOCHONDRION Citric acid cycle Figure 9.18

53 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Summaries of Glycolysis 1. anaerobic Glucose -> 2 Lactate + 2 ATP (lactic acid fermentation) Glucose -> 2 Ethanol + 2 ATP (alcoholic fermentation) 2. aerobic Glucose -> 2 Pyruvate + 2ATP + 2NADH (aerobic subtotal) 註 : 2 NADH -> 6 ATP (aerobic conversion: 氧化磷酸化 )

54 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fermentation and Cellular Respiration Compared 相同點 Use glycolysis to oxidize glucose and other organic fuels to pyruvate 相異點 1.Differ in their final electron acceptor  Fermentation by acetylaldehyde (ethanol ferment.); by pyruvate (lactate ferment.)  Cellular Respiration by O 2 2.Cellular respiration produces more ATP

55 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Evolutionary Significance of Glycolysis Glycolysis – Occurs in nearly all organisms – Probably evolved in ancient prokaryotes before there was oxygen in the atmosphere

56 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 9.6: Glycolysis and the citric acid cycle connect to many other metabolic pathways The Versatility of Catabolism Catabolic pathways – Funnel electrons from many kinds of organic molecules into cellular respiration

57 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The catabolism of various molecules from food Amino acids Sugars Glycerol Fatty acids Glycolysis Glucose Glyceraldehyde-3- P Pyruvate Acetyl CoA NH 3 Citric acid cycle Oxidative phosphorylation Fats Proteins Carbohydrates Figure 9.19  -oxidation

58 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Biosynthesis (Anabolic Pathways) The body – Uses small molecules to build other substances These small molecules – May come directly from food or through glycolysis or the citric acid cycle

59 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Regulation of Cellular Respiration via Feedback Mechanisms Cellular respiration is controlled by allosteric enzymes (e.g., Phosphofructokinase) at key points in glycolysis and the citric acid cycle Allosteric regulation (see glossary) The binding of a molecule to a protein that affects the function of the protein at a different site. 補充圖

60 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The control of cellular respiration Glucose Glycolysis Fructose-6-phosphate Phosphofructokinase Fructose-1,6-bisphosphate Inhibits Pyruvate ATP Acetyl CoA Citric acid cycle Citrate Oxidative phosphorylation Stimulates AMP + – – Figure 9.20 ATP  AMP + pp i


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