* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Chapter 9 - John A. Ferguson Senior High School
Biosynthesis wikipedia , lookup
Metalloprotein wikipedia , lookup
Amino acid synthesis wikipedia , lookup
Basal metabolic rate wikipedia , lookup
Lactate dehydrogenase wikipedia , lookup
Glyceroneogenesis wikipedia , lookup
Fatty acid synthesis wikipedia , lookup
Mitochondrion wikipedia , lookup
Butyric acid wikipedia , lookup
Photosynthesis wikipedia , lookup
Fatty acid metabolism wikipedia , lookup
Photosynthetic reaction centre wikipedia , lookup
Evolution of metal ions in biological systems wikipedia , lookup
NADH:ubiquinone oxidoreductase (H+-translocating) wikipedia , lookup
Phosphorylation wikipedia , lookup
Light-dependent reactions wikipedia , lookup
Nicotinamide adenine dinucleotide wikipedia , lookup
Microbial metabolism wikipedia , lookup
Electron transport chain wikipedia , lookup
Biochemistry wikipedia , lookup
Adenosine triphosphate wikipedia , lookup
Chapter 9 Cellular Respiration: Harvesting Chemical Energy PowerPoint® Lecture Presentations for Lectures prepared by Dr. Jorge L. Alonso Florida International University Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Photosynthesis and Respiration Theme 4: Organisms interact with their environments, exchanging matter and energy Sunlight Ecosystem Photosynthesis Cycling of chemical nutrients Heat Chemical energy Concept 9.1: Catabolic pathways yield energy by oxidizing organic fuels Respiration Heat Photosynthesis and Respiration Light energy ECOSYSTEM Photosynthesis Photosynthesis in chloroplasts CO2 + H2O C6H12O6 + O2 Cellular respiration in mitochondria Respiration ATP ATP powers most cellular work Heat energy Catabolic Pathways and Production of ATP • Fermentation is a partial degradation of sugars that occurs without O2 (anaerobic) to produce a little energy (ATP) and ethanol (or lactate). • Aerobic Respiration is a more complete degradation of sugars that occurs with O2 and yields much more energy (ATP) and CO2. Fermentation is a partial degradation of sugars that occurs without O2 (anaerobic) to produce a little energy (ATP) and ethanol (or lactate). Alcoholic Fermentation: in Yeast cells, enzymes facilitate production of ethanol. Lactic Acid Fermentation: in animal cells, in the absence of sufficient oxygen, enzymes facilitate production of lactic acid Other types of Fermentation Cellular Respiration • Cellular respiration includes both aerobic and anaerobic respiration but is often used to refer to aerobic respiration • Although carbohydrates, fats, and proteins are all consumed as fuel, it is helpful to trace cellular respiration with the sugar glucose: C6H12O6 + 6 O2 6 CO2 + 6 H2O + Energy (36 ATP + heat) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Cellular Respiration • It includes both aerobic and anaerobic components, but whole process is refered to as aerobic respiration C6H12O6 2 2 2 • C6H12O6 + 6 O2 6 CO2 + 6 H2O + Energy (ATP + heat) • The whole process is composed of three major stages 1. Glycolysis 2. Citric Acid (Krebs) Cycle 3. Oxidative Phosphorylation 4 2 Oxidative Phosphorylation 36 6 6 Redox Reactions: Oxidation and Reduction • Chemical reactions in which electrons are transferred between the reactants and release energy eEnergy Oxidation: substance loses electrons, or is oxidized Na Na+ + e- Reducing agent Reduction: substance gains electrons, or is reduced (the amount of positive charge is reduced) Cl + e- Cl- Oxidizing agent • In redox reactions involving covalent (organic) compounds the electrons are not transferred to produce ions, but a change occurs in the way in which electron are shared in the covalent bonds (1) oxidation: epulled further away, (2) reduction: e- shared closer). becomes oxidized becomes reduced + + 4- + Carbon: has e- closer + 0 0 Oxygen: has efurther away 2- 4+ Carbon: has e- further away 2- + 2- Oxygen: has ecloser + How is the energy found in the bonding electrons of Glucose harvested to make ATP during Cellular Respiration? eHow are these electrons Energy transferred to oxygen? • Electrons from organic compounds are usually first transferred to NAD+, an electron-acceptor coenzyme found in cells • Electrons are carried in the form of high energy hydride ions: H- or H:- Carbohydrate (reduced) (oxidized) (oxidized) (reduced) • Each NADH (the reduced form of NAD+) represents stored energy that is tapped to synthesize ATP Nicotinamide Adenine Diphosphate (NAD+ NADH) H H 2 e– + 2 H+ Carbohydrate (reduced) 2 e– + H+ NADH H+ Dehydrogenase Reduction of NAD+ NAD+ + + H+ 2[H] Oxidation of NADH Nicotinamide (reduced form) Nicotinamide (oxidized form) • • • • How are electrons and their energy harvested from Glucose? NADH and FADH2 gather electrons (H-) at different stages of respiration and passes them to the electron transport chain. C6H12O6 2 2 2 The electron transport chain passes energetic electrons to O2 in a series of enzymatically controlled steps (instead of one explosive reaction) 4 (H-) O2 pulls electrons down the chain in an energy-yielding tumble and H2O is produced. The energy yielded is used to regenerate ATP (oxidative phosphorylation) 2 Oxidative Phosphorylation 36 6 6 • The electron transport chain passes energetic electrons to O2 in a series of enzymatically controlled steps (instead of one explosive reaction) H2 + 1/2 O2 2H (from glucose via NADH) Controlled release of 2 H+ + 2 e– energy for synthesis of ATP 1/ 2 O2 Explosive release of heat and light energy 1/ O 2 2 (a) Uncontrolled reaction (b) Cellular respiration The Stages of Cellular Respiration: 1. Glycolysis (breaks 2. down glucose into two molecules of pyruvate), some ATP and NADH produced Electrons carried via NADH Glycolysis Pyruvate Glucose Cytosol ATP Substrate-level phosphorylation The Citric Acid (Krebs) Cycle (breaks down pyruvate into CO2), producing some ATP, NADH and FADH2 The Stages of Cellular Respiration: 1. Glycolysis (breaks 2. down glucose into two molecules of pyruvate), some ATP and NADH produced The Citric Acid (Krebs) 3. Cycle (breaks down pyruvate into CO2), producing some ATP, NADH and FADH2 Electrons carried via NADH and FADH2 Electrons carried via NADH Citric acid cycle Glycolysis Pyruvate Glucose Oxidative Phosphorylation (uses H2O to oxidize the NADH & FADH2 produced in previous steps, producing O2 and lots of ATP) Mitochondrion Cytosol ATP ATP Substrate-level phosphorylation Substrate-level phosphorylation The Stages of Cellular Respiration: 1. Glycolysis (breaks 2. down glucose into two molecules of pyruvate), some ATP and NADH produced The Citric Acid (Krebs) 3. Cycle (breaks down pyruvate into CO2), producing some ATP, NADH and FADH2 Electrons carried via NADH and FADH2 Electrons carried via NADH Citric acid cycle Glycolysis Pyruvate Glucose Oxidative Phosphorylation (uses H2O to oxidize the NADH & FADH2 produced in previous steps, producing O2 and lots of ATP) Oxidative phosphorylation: (1) Electron transport and (2) chemiosmosis Mitochondrion Cytosol ATP ATP ATP Substrate-level phosphorylation Substrate-level phosphorylation Oxidative phosphorylation • About 10% of ATP is formed in glycolysis and the citric acid cycle by substrate-level phosphorylation Enzyme Substrate-Phosphorylated + ADP Enzyme Product-unPhosphorylated + ATP Enzyme ADP P Substrate + Product ATP The process that generates most of the ATP is called oxidative phosphorylation because it BioFlix: Cellular Respiration is powered by redox reactions H+ H+ H+ H+ Protein complex of electron carriers Cyt c V Q ATP synthase FADH2 NADH 2 H+ + 1/2O2 NAD+ ADP + P i (carrying electrons from food) ATP H+ 1 Electron transport chain • H2O FAD 2 Chemiosmosis This process accounts for almost 90% of the ATP generated by respiration Concept 9.2: Glycolysis harvests chemical energy by oxidizing glucose to pyruvate • Glycolysis (“splitting of sugar”) breaks down glucose into two molecules of pyruvate + Glucose • 2 Pyruvates Glycolysis has two major phases: (1)Energy investment phase (2)Energy payoff phase Glucose ATP 1 Hexokinase ADP Glucose Glucose-6-phosphate ATP 1 Hexokinase ADP Glucose-6-phosphate Glucose ATP 1 Hexokinase ADP Glucose-6-phosphate 2 Phosphoglucoisomerase Fructose-6-phosphate Glucose-6-phosphate 2 Phosphoglucoisomerase Fructose-6-phosphate Glucose ATP 1 Hexokinase ADP Fructose-6-phosphate Glucose-6-phosphate 2 Phosphoglucoisomerase ATP 3 Phosphofructokinase Fructose-6-phosphate ATP 3 Phosphofructokinase ADP ADP Fructose1, 6-bisphosphate Fructose1, 6-bisphosphate Glucose ATP 1 Hexokinase ADP Glucose-6-phosphate 2 Phosphoglucoisomerase Fructose1, 6-bisphosphate 4 Fructose-6-phosphate ATP Aldolase 3 Phosphofructokinase ADP 5 Isomerase Fructose1, 6-bisphosphate 4 Aldolase 5 Isomerase Dihydroxyacetone phosphate Dihydroxyacetone phosphate Glyceraldehyde3-phosphate Glyceraldehyde3-phosphate 2 NAD+ 2 NADH + 2 H+ 6 Triose phosphate dehydrogenase 2 Pi 2 1, 3-Bisphosphoglycerate Glyceraldehyde3-phosphate 2 NAD+ 2 NADH 6 Triose phosphate dehydrogenase 2 Pi + 2 H+ 2 1, 3-Bisphosphoglycerate 2 NAD+ 2 NADH + 2 H+ 6 Triose phosphate dehydrogenase 2 Pi 2 1, 3-Bisphosphoglycerate 2 ADP 7 Phosphoglycerokinase 2 ATP 2 1, 3-Bisphosphoglycerate 2 ADP 2 3-Phosphoglycerate 2 ATP 2 7 Phosphoglycerokinase 3-Phosphoglycerate 2 NAD+ 2 NADH + 2 H+ 6 Triose phosphate dehydrogenase 2 Pi 2 1, 3-Bisphosphoglycerate 2 ADP 7 Phosphoglycerokinase 2 ATP 2 3-Phosphoglycerate 8 2 3-Phosphoglycerate Phosphoglyceromutase 2 8 Phosphoglyceromutase 2-Phosphoglycerate 2 2-Phosphoglycerate 2 NAD+ 2 NADH + 2 H+ 6 Triose phosphate dehydrogenase 2 Pi 2 1, 3-Bisphosphoglycerate 2 ADP 7 Phosphoglycerokinase 2 ATP 2 3-Phosphoglycerate 2 2-Phosphoglycerate 8 Phosphoglyceromutase 9 2 2 H2O 2-Phosphoglycerate Enolase 9 Enolase 2 H2O 2 Phosphoenolpyruvate 2 Phosphoenolpyruvate 2 NAD+ 6 Triose phosphate dehydrogenase 2 Pi 2 NADH + 2 H+ 2 1, 3-Bisphosphoglycerate 2 ADP 7 Phosphoglycerokinase 2 ATP 2 Phosphoenolpyruvate 2 ADP 2 3-Phosphoglycerate 8 Phosphoglyceromutase 2 ATP 2 10 Pyruvate kinase 2-Phosphoglycerate 9 2 H2O Enolase 2 Phosphoenolpyruvate 2 ADP 10 Pyruvate kinase 2 ATP 2 2 Pyruvate Pyruvate Concept 9.3: The Citric Acid (Krebs) Cycle completes the energyyielding oxidation of organic molecules C6H12O6 2 2 2 • In the presence of O2, pyruvate enters the mitochondrion • Before the citric acid cycle can begin, pyruvate must be converted to acetyl CoA, which links the cycle to glycolysis 4 2 Oxidative Phosphorylation 36 6 6 The junction between glycolysis & the citric acid cycle: Conversion of pyruvate to acetyl CoA • In the presence of O2, pyruvate enters the mitochondrion, at the cost of an ATP for transport of each pyruvate molecule • Before the citric acid cycle can begin, pyruvate must be converted to acetyl CoA, which links the cycle to glycolysis CYTOSOL MITOCHONDRION NAD+ NADH + H+ 2 1 Pyruvate Transport protein 3 CO2 Coenzyme A Acetyl CoA The junction between glycolysis & the citric acid cycle: Conversion of pyruvate to acetyl CoA Enzymes of Glycolysis juction to CAC: 1. Citrate synthase 2. Pyruvate carboxylase The Citric Acid (Krebs) Cycle Pyruvate CO2 NAD+ CoA • The CAC takes place within the mitochondrial matrix NADH + H+ Acetyl CoA CoA CoA • The cycle oxidizes organic fuel derived from pyruvate, generating 1 ATP, 3 NADH, and 1 FADH2 per turn Citric acid cycle FADH2 2 CO2 3 NAD+ 3 NADH FAD + 3 H+ ADP + P i ATP The Citric Acid (Krebs) Cycle • In the first of eight steps in the CAC, the acetyl group of acetyl CoA joins the cycle by combining with oxaloacetate, forming citrate. Each step is catalyzed by a specific enzyme Enzymes of CAC: 1. • Citrate synthase The next seven steps decompose the citrate back to oxaloacetate, making the process a cycle Acetyl CoA CoA—SH 1 Oxaloacetate Citrate Citric Acid Cycle The Citric Acid (Krebs) Cycle Acetyl CoA CoA—SH H2O 1 Oxaloacetate 2 Citrate Isocitrate Enzymes of CAC: 1. Citrate synthase 2. Aconitase Citric Acid Cycle The Citric Acid (Krebs) Cycle • Acetyl CoA CoA—SH 1 The NADH and FADH2 produced by the cycle relay electrons extracted from food to the electron transport chain Enzymes of CAC: 1. Citrate synthase 2. Aconitase 3. Isocirate dehydrogenase H2O Oxaloacetate 2 Citrate Isocitrate NAD+ Citric Acid Cycle 3 NADH + H+ CO2 -Ketoglutarate The Citric Acid (Krebs) Cycle Acetyl CoA CoA—SH 1 H2O Oxaloacetate 2 Citrate Isocitrate NAD+ Enzymes of CAC: Citric Acid Cycle NADH + H+ 3 CO2 CoA—SH 1. Citrate synthase 2. Aconitase 3. Isocirate dehydrogenase 4. -Ketoglutarate 4 NAD+ ά-ketoglutarate dehydrogenase Succinyl CoA NADH + H+ CO2 The Citric Acid (Krebs) Cycle Acetyl CoA CoA—SH 1 H2O Oxaloacetate 2 Citrate Isocitrate NAD+ Citric Acid Cycle Enzymes of CAC: NADH + H+ 3 CO2 CoA—SH 1. Citrate synthase 2. Aconitase 3. Isocirate dehydrogenase 4. ά-ketoglutarate dehydrogenase 5. Succinyl-CoA synthetase -Ketoglutarate 4 CoA—SH 5 NAD+ Succinate GTP GDP ADP ATP Pi Succinyl CoA NADH + H+ CO2 The Citric Acid (Krebs) Cycle Acetyl CoA CoA—SH H2O 1 Oxaloacetate 2 Citrate Isocitrate NAD+ Citric Acid Cycle Enzymes of CAC: 1. Citrate synthase 2. Aconitase 3. Isocirate dehydrogenase 4. ά-ketoglutarate dehydrogenase 5. Succinyl-CoA synthetase 6. Succinate dehydrogenase Fumarate NADH + H+ 3 CO2 CoA—SH 6 -Ketoglutarate 4 CoA—SH 5 FADH2 NAD+ FAD Succinate GTP GDP ADP ATP Pi Succinyl CoA NADH + H+ CO2 The Citric Acid (Krebs) Cycle Acetyl CoA CoA—SH H2O 1 Oxaloacetate 2 Malate Citrate Isocitrate NAD+ Citric Acid Cycle 7 H2O Enzymes of CAC: 1. Citrate synthase 2. Aconitase 3. Isocirate dehydrogenase 4. ά-ketoglutarate dehydrogenase 5. Succinyl-CoA synthetase 6. Succinate dehydrogenase 7. Fumarase Fumarate NADH + H+ 3 CO2 CoA—SH -Ketoglutarate 4 6 CoA—SH 5 FADH2 NAD+ FAD Succinate GTP GDP ADP ATP Pi Succinyl CoA NADH + H+ CO2 The Citric Acid (Krebs) Cycle Acetyl CoA CoA—SH NADH +H+ H2O 1 NAD+ 8 Oxaloacetate 2 Malate Citrate Isocitrate NAD+ Citric Acid Cycle 7 H2O Enzymes of CAC: 1. Citrate synthase 2. Aconitase 3. Isocirate dehydrogenase 4. ά-ketoglutarate dehydrogenase 5. Succinyl-CoA synthetase 6. Succinate dehydrogenase 7. Fumarase 8. Malate dehydrogenase Fumarate NADH + H+ 3 CO2 CoA—SH 6 -Ketoglutarate 4 CoA—SH 5 FADH2 NAD+ FAD Succinate GTP GDP ADP ATP Pi Succinyl CoA NADH + H+ CO2 PowerPoint® Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Concept 9.4: During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis C6H12O6 2 2 2 • • 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 4 2 Oxidative Phosphorylation 36 6 6 Oxidative Phosphorylation • The Enzymes for Oxidative Phosphorylation are located in the inner membrane of the cristae in the mitochondrion. • Most of the chain’s components are proteins, which exist in multiprotein complexes • Oxidative Phosphorylation is composed of two separate processes: 1. Electron Transport Chain, which uses the energy in electrons to pump H+ ions from the matrix to the intermembrane space. {ETC 1} 2. Chemosmosis, which uses the osmotic pressure from now concentrated H+ ions to energize ATP {ChmOsmo} INTER- Glycolysis MEMBRANE SPACE Krebs Cycle MITOCHONDIRAL MATRIX The Pathway of Electron Transport NADH • Electrons are transferred from NADH or FADH2 to the electron transport chain 50 2 e– Electrons are passed through a number of proteins including cytochromes (each with an iron atom) to O2 FMN FAD Multiprotein complexes FAD Fe•S Fe•S Q Cyt b 30 Fe•S Cyt c1 IV Cyt c Cyt a • 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 H2O • FADH2 2 e– 40 • NAD+ The electron transport chain generates no ATP Cyt a3 20 10 2 e– (from NADH or FADH2) 0 2 H+ + 1/2 O2 H 2O The Pathway of Electron Transport • 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 INTERMEMBRANE SPACE MITOCHONDIRAL MATRIX ATP synthase, a molecular mill INTERMEMBRANE SPACE • The energy stored in a H+ gradient across a membrane couples the redox reactions of the electron transport chain to ATP synthesis • The gradient is referred to as a proton-motive force, emphasizing its capacity to do work H+ H+ Stator Rotor Internal rod Catalytic knob ADP + P i ATP MITOCHONDRIAL MATRIX Fig. 9-15 EXPERIMENT Magnetic bead Electromagnet Sample Internal rod Catalytic knob Nickel plate RESULTS Rotation in one direction Number of photons detected (103) Rotation in opposite direction No rotation 30 25 20 0 Sequential trials Fig. 9-15a EXPERIMENT Magnetic bead Electromagnet Sample Internal rod Catalytic knob Nickel plate Fig. 9-15b RESULTS Rotation in one direction Rotation in opposite direction No rotation 30 25 20 0 Sequential trials Fig. 9-16 H+ H+ H+ H+ Protein complex of electron carriers Cyt c V Q ATP synthase FADH2 NADH 2 H+ + 1/2O2 H2O FAD NAD+ ADP + P i (carrying electrons from food) ATP H+ 1 Electron transport chain Oxidative phosphorylation 2 Chemiosmosis ATP Production by Cellular Respiration • During cellular respiration, most energy flows in this sequence: glucose NADH electron transport chain proton-motive force ATP • About 40% of the energy in a glucose molecule is transferred to ATP during cellular respiration, making about 38 ATP Concept 9.5: Fermentation and anaerobic respiration enable cells to produce ATP without the use of oxygen C6H12O6 2 2 2 • Most 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 or anaerobic respiration to produce ATP 4 2 Oxidative Phosphorylation 36 6 6 • Anaerobic respiration uses an electron transport chain with an electron acceptor other than O2, for example sulfate • Fermentation uses phosphorylation instead of an electron transport chain to generate ATP Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Types of Fermentation Animation: Fermentation Overview 2 ADP + 2 Pi • Fermentation consists of glycolysis plus reactions that regenerate NAD+, which can be reused by glycolysis Glucose Two common types are alcohol fermentation and lactic acid fermentation • 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 • 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 Glycolysis 2 Pyruvate • • 2 ATP 2 NAD+ 2 NADH + 2 H+ 2 CO2 2 Acetaldehyde 2 Ethanol (a) Alcohol fermentation 2 ADP + 2 Pi Glucose 2 ATP Glycolysis 2 NAD+ 2 NADH + 2 H+ 2 Pyruvate 2 Lactate (b) Lactic acid fermentation C6H12O6 Fermentation and Aerobic Respiration Compared • • • Both processes use glycolysis to oxidize glucose and other organic fuels to pyruvate 2 2 2 The processes have different final electron acceptors: an organic molecule (such as pyruvate or acetaldehyde) in fermentation and O2 in cellular respiration Cellular respiration produces 38 ATP per glucose molecule; fermentation produces 2 ATP per glucose molecule 4 2 Oxidative Phosphorylation 36 6 6 • Obligate anaerobes carry out fermentation or anaerobic respiration and cannot survive in the presence of O2 • Yeast and many 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 9-19 Glucose CYTOSOL Glycolysis Pyruvate No O2 present: Fermentation O2 present: Aerobic cellular respiration MITOCHONDRION Ethanol or lactate Acetyl CoA Citric acid cycle The Evolutionary Significance of Glycolysis • Glycolysis occurs in nearly all organisms • Glycolysis probably evolved in ancient prokaryotes before there was oxygen in the atmosphere Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Concept 9.6: Glycolysis and the citric acid cycle connect to many other metabolic pathways • Gycolysis and the citric acid cycle are major intersections to various catabolic and anabolic pathways • Although carbohydrates, fats, and proteins are all consumed as fuel, it is helpful to trace cellular respiration with the sugar glucose: Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The Versatility of Catabolism • • • • Catabolic pathways funnel electrons from many kinds of organic molecules into cellular respiration Fats are digested to glycerol (used in glycolysis) and fatty acids (used in generating acetyl CoA) • Fatty acids are broken down by beta oxidation and yield acetyl CoA • An oxidized gram of fat produces more than twice as much ATP as an oxidized gram of carbohydrate Carbohydrates Amino acids Sugars Glycolysis Glycolysis accepts a wide range of carbohydrates Proteins must be digested to amino acids; amino groups can feed glycolysis or the citric acid cycle Proteins Glucose Glyceraldehyde-3- P NH3 Pyruvate Acetyl CoA Citric acid cycle Oxidative phosphorylation Fats Glycerol Fatty acids Biosynthesis (Anabolic Pathways) • The body uses small molecules to build other substances • These small molecules may come directly from food, from glycolysis, or from the citric acid cycle Copyright © 2008 Pearson Education, Inc., publishing as Pearson 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 Glucose AMP Glycolysis Fructose-6-phosphate – Stimulates + Phosphofructokinase – Fructose-1,6-bisphosphate Inhibits Inhibits Pyruvate ATP Citrate Acetyl CoA Citric acid cycle Oxidative phosphorylation Fig. 9-UN5 Outputs Inputs 2 ATP Glycolysis + 2 NADH Glucose 2 Pyruvate Fig. 9-UN6 Inputs Outputs S—CoA C 2 ATP 6 NADH O CH3 2 Acetyl CoA O C COO CH2 COO 2 Oxaloacetate Citric acid cycle 2 FADH2 Fig. 9-UN7 INTERMEMBRANE SPACE H+ ATP synthase ADP + P i MITOCHONDRIAL MATRIX ATP H+ Fig. 9-UN8 Time Fig. 9-UN9 You should now be able to: 1. Explain in general terms how redox reactions are involved in energy exchanges 2. Name the three stages of cellular respiration; for each, state the region of the eukaryotic cell where it occurs and the products that result 3. In general terms, explain the role of the electron transport chain in cellular respiration Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 4. Explain where and how the respiratory electron transport chain creates a proton gradient 5. Distinguish between fermentation and anaerobic respiration 6. Distinguish between obligate and facultative anaerobes Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings