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CHAPTER 9 CELLULAR RESPIRATION: HARVESTING CHEMICAL ENERGY PowerPoint® Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece 1 Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings OVERVIEW: LIFE IS WORK • LIVING CELLS REQUIRE ENERGY FROM OUTSIDE SOURCES • SOME ANIMALS, SUCH AS THE GIANT PANDA, OBTAIN ENERGY BY EATING PLANTS, AND SOME ANIMALS FEED ON OTHER ORGANISMS THAT EAT PLANTS • THOSE THAT CAN MAKE THEIR OWN FOOD: AUTOTROPHS • THOSE THAT RECEIVE NUTRIENTS AND ENERGY FROM OTHER ORGANISMS: HETEROTROPHS 2 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • ENERGY FLOWS INTO AN ECOSYSTEM AS SUNLIGHT AND LEAVES AS HEAT • PHOTOSYNTHESIS GENERATES O2 AND ORGANIC MOLECULES, WHICH ARE USED IN CELLULAR RESPIRATION • CELLS USE CHEMICAL ENERGY STORED IN ORGANIC MOLECULES TO REGENERATE ATP, WHICH POWERS WORK 3 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings CONCEPT 9.1: CATABOLIC PATHWAYS YIELD ENERGY BY OXIDIZING ORGANIC FUELS 4 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings CATABOLIC PATHWAYS AND PRODUCTION OF ATP (THINK OF CATASTROPHES BREAKING THINGS DOWN) • FERMENTATION IS A PARTIAL DEGRADATION OF SUGARS THAT OCCURS WITHOUT O2 (YEAST, BACTERIA) • AEROBIC RESPIRATION CONSUMES ORGANIC MOLECULES AND O2 AND YIELDS ATP (VERY EFFICIENT AND IS THE PREFERRED FORM OF RESPIRATION) • ANAEROBIC RESPIRATION IS SIMILAR TO AEROBIC RESPIRATION BUT CONSUMES COMPOUNDS OTHER THAN O2 (LEAST PREFERRED METHOD BECAUSE NOT AS EFFICIENT, WILL ONLY OCCUR IF NO OTHER CHOICE) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 5 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 (ATP + HEAT) (GLUCOSE) (OXYGEN) > (CARBON DIOXIDE) (WATER) YES, YOU NEED TO KNOW THIS FORMULA! 6 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings THE BREAKDOWN OF GLUCOSE • IS EXERGONIC (GIVES OFF ENERGY) • ∆ G = -686 KCAL/MOL • CAN HAPPEN SPONTANEOUSLY 7 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) 9 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings THE ELECTRON DONOR IS CALLED THE REDUCING AGENT (THIS IS THE OIL PART) THE ELECTRON RECEPTOR IS CALLED THE OXIDIZING AGENT (THIS IS THE RIG PART) SOME REDOX REACTIONS DO NOT TRANSFER ELECTRONS BUT CHANGE THE ELECTRON SHARING IN COVALENT BONDS AN EXAMPLE IS THE REACTION BETWEEN Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 12 Fig. 9-UN3 OXIDATION OF ORGANIC FUEL MOLECULES DURING CELLULAR RESPIRATION During cellular respiration, the fuel (such as glucose) is oxidized, and O2 is reduced: becomes oxidized becomes reduced The electrons lose potential energy along the way and energy is released, allowing it to be used for ATP synthesis 15 BIG PICTURE FOR ELECTRONS • GLUCOSE -> NADH + FADH2 -> ELECTRON TRANSPORT TRAIN -> OXYGEN 23 THE STAGES OF CELLULAR RESPIRATION: A PREVIEW HOW OXYGEN IS KILLING YOU • CELLULAR RESPIRATION HAS THREE STAGES: • GLYCOLYSIS (BREAKS DOWN GLUCOSE (6 CARBONS) INTO TWO MOLECULES OF PYRUVATE (3 CARBONS APIECE) • THE CITRIC ACID CYCLE (COMPLETES THE BREAKDOWN OF GLUCOSE) • OXIDATIVE PHOSPHORYLATION (ACCOUNTS FOR MOST OF THE ATP SYNTHESIS) OXIDATIVE PHOSPHORYLATION ACCOUNTS FOR ALMOST 90% OF THE ATP GENERATED BY CELLULAR RESPIRATION • A SMALLER AMOUNT OF ATP IS FORMED IN GLYCOLYSIS AND THE CITRIC ACID CYCLE BY SUBSTRATE-LEVEL PHOSPHORYLATION 24 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 9-6-1 Electrons carried via NADH Glycolysis Pyruvate Glucose Cytosol ATP Substrate-level phosphorylation 25 Fig. 9-6-2 Electrons carried via NADH and FADH2 Electrons carried via NADH Citric acid cycle Glycolysis Pyruvate Glucose Mitochondrion Cytosol ATP ATP Substrate-level phosphorylation Substrate-level phosphorylation 26 Fig. 9-6-3 Electrons carried via NADH and FADH2 Electrons carried via NADH Citric acid cycle Glycolysis Pyruvate Glucose Oxidative phosphorylation: electron transport and chemiosmosis Mitochondrion Cytosol ATP ATP ATP Substrate-level phosphorylation Substrate-level phosphorylation Oxidative phosphorylation 27 Fig. 9-7 Substrate level phosphorylation Enzyme Enzyme ADP P Substrate + ATP Product 28 CONCEPT 9.2: GLYCOLYSIS HARVESTS CHEMICAL ENERGY BY OXIDIZING GLUCOSE TO PYRUVATE • GLYCOLYSIS (“SPLITTING OF SUGAR”) BREAKS DOWN GLUCOSE, A 6 CARBON SUGAR INTO TWO MOLECULES OF PYRUVATE EACH WITH 3 CARBONS, THIS IS AN ANAEROEBIC STEP IN CELL RESPIRATION • GLYCOLYSIS OCCURS IN THE CYTOPLASM AND HAS TWO MAJOR PHASES: • ENERGY INVESTMENT PHASE • ENERGY PAYOFF PHASE 29 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings WARNING: • PER COLLEGE BOARD: MEMORIZATION OF THE STEPS IN GLYCOLYSIS AND THE KREBS (CITRIC ACID) CYCLE, OR OF THE STRUCTURES OF THE MOLECULES AND THE NAMES OF THE ENZYMES INVOLVED, ARE BEYOND THE SCOPE OF THE COURSE AND THE AP EXAM • EXCEPT FOR ATP SYNTHASE 30 CONCENTRATE ON BIG PICTURE STUFF • WHAT SUBSTRATE AND ENERGY GOES IN • WHAT SUBSTRATE/PRODUCT AND ENERGY COMES OUT 31 GLYCOLYSIS (BREAKDOWN)- HAPPENS IN THE CYTOSOL Substrate level phosphorylation 32 • HTTP://WWW.YOUTUBE.COM/WATCH?V=CLXCQ0WFJKK&FEATURE= RELATED • CELLULAR RESPIRATION SONG TO “HEY THERE DELILAH” 33 Fig. 9-8 Energy investment phase Glucose 2 ADP + 2 P 2 ATP used 4 ATP formed Energy payoff phase 4 ADP + 4 P 2 NAD+ + 4 e– + 4 H+ 2 NADH + 2 H+ 2 Pyruvate + 2 H2O Net Glucose 4 ATP formed – 2 ATP used 2 Pyruvate + 2 H2O 2 ATP 34 2 NAD+ + 4 e– +4 H+ 2 NADH + 2 H+ BIG PICTURE: • WHAT GOES IN TO GLYCOLYSIS? • WHAT COMES OUT OF GLYCOLYSIS? • WHERE DOES GLYCOLYSIS OCCUR? • IS IT ANAEROBIC OR AEROBIC? • WHAT ENERGY GOES IN? • WHAT ENERGY COMES OUT? • WHAT IS THE NET ENERGY GAIN? 35 ANSWER: • GLUCOSE (6 CARBONS) GO IN • 2 PYRUVATES COME OUT (3 CARBONS EACH) • HAPPENS IN THE CYTOSOL OF THE CELL (NOT THE MITOCHONDRIA) • IT IS ANAEROBIC • INPUT OF 2 ATP • OUTPUT OF 2 NADH AND 4 ATP • OVERALL 2 NADH AND 2 ATP GAINED 36 CONCEPT 9.3: THE CITRIC ACID CYCLE COMPLETES THE ENERGY-YIELDING OXIDATION OF ORGANIC MOLECULES REMEMBER: GLYCOLYSIS IS AN ANAEROBIC PROCESS THAT YIELDS 2 PYRUVATE LESS THAN 25% OF THE CHEMICAL ENERGY IN GLUCOSE IS RELEASED FROM GLYCOLYSIS 37 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings IN THE PRESENCE OF O2 (MORE EFFICIENT), PYRUVATE ENTERS THE MITOCHONDRION THROUGH ACTIVE TRANSPORT BEFORE THE CITRIC ACID CYCLE CAN BEGIN, PYRUVATE MUST BE CONVERTED TO ACETYL COA, (WHICH IS ACETYL COENZYME) A BY THE CAPTURE OF ELECTRONS WHICH LINKS THE CYCLE TO GLYCOLYSIS 38 THE KREBS CYCLE IS ALSO CALLED: TRICARBOXYLIC ACID CYCLE (TCA) OR THE CITRIC ACID CYCLE 39 The net yield from the Krebs cycle per glucose: six CO2 molecules, two ATP, eight NADH, and two FADH2. INCREDIBLY IMPORTANT: There are 2 pyruvates that need to go through this cycle, so this wheel turns 2x per glucose 40 WHERE ARE WE SO FAR WITH ENERGY: • HOW MANY ATP DID WE NET FROM GLYCOLYSIS? • HOW MANY ATP DID WE NET FROM KREBS? • HOW MANY NADH DID WE NET FROM GLYCOLYSIS • HOW MANY NADH DID WE NET FROM KREBS? • HOW MANY FADH2 DID WE NET FROM KREBS? 41 ANSWER: • 10 NADH • 4 ATP • 2 FADH2 42 • THE CITRIC ACID CYCLE, ALSO CALLED THE KREBS CYCLE, TAKES PLACE WITHIN THE MITOCHONDRIAL MATRIX • THE CYCLE OXIDIZES ORGANIC FUEL DERIVED FROM PYRUVATE, GENERATING 1 ATP, 3 NADH, AND 1 FADH2 PER TURN • THERE ARE 2 TURNS PER GLUCOSE 43 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 9-11 Pyruvate CO2 NAD+ CoA NADH + H+ Acetyl CoA CoA CoA Citric acid cycle FADH2 2 CO2 3 NAD+ 3 NADH FAD + 3 H+ ADP + P i ATP 44 • THE CITRIC ACID 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 45 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 9-12-1 This molecule has 2 Carbon Acetyl CoA CoA—SH This molecule Has 4 carbons 1 They combine To make a 6 C molecule Oxaloacetate Citrate Citric acid cycle 46 Fig. 9-12-2 Acetyl CoA CoA—SH H2O 1 Oxaloacetate 2 Citrate Isocitrate Citric acid cycle Still 6 carbons, just rearranged 47 Fig. 9-12-3 Acetyl CoA CoA—SH 1 H2O Oxaloacetate 2 Citrate Isocitrate NAD+ Citric acid cycle NADH + H+ 3 CO2 -Ketoglutarate Lost a C as byproduct 48 Fig. 9-12-4 Acetyl CoA CoA—SH 1 H2O Oxaloacetate 2 Citrate Isocitrate NAD+ Citric acid cycle NADH + H+ 3 CO2 CoA—SH -Ketoglutarate 4 NAD+ Succinyl CoA CO2 NADH + H+ 49 Lost another C Fig. 9-12-5 Acetyl CoA CoA—SH 1 H2O Oxaloacetate 2 Citrate Isocitrate NAD+ Citric acid cycle NADH + H+ 3 CO2 CoA—SH -Ketoglutarate 4 CoA—SH Still 4 C but rearranged 5 NAD+ Succinate GTP GDP Pi Succinyl CoA CO2 NADH + H+ ADP 50 ATP Fig. 9-12-6 Acetyl CoA CoA—SH H2O 1 Oxaloacetate 2 Citrate Isocitrate NAD+ Still 4 C but rearranged Citric acid cycle NADH + H+ 3 CO2 Fumarate CoA—SH 6 -Ketoglutarate 4 CoA—SH 5 FADH2 NAD+ FAD Succinate GTP GDP Pi Succinyl CoA CO2 NADH + H+ ADP 51 ATP Fig. 9-12-7 Acetyl CoA CoA—SH Still 4 C but rearranged H2O 1 Oxaloacetate 2 Malate Citrate Isocitrate NAD+ Citric acid cycle 7 H2O NADH + H+ 3 CO2 Fumarate CoA—SH -Ketoglutarate 4 6 CoA—SH 5 FADH2 NAD+ FAD Succinate GTP GDP Pi Succinyl CoA CO2 NADH + H+ ADP 52 ATP Fig. 9-12-8 Acetyl CoA CoA—SH NADH +H+ H2O 1 NAD+ 8 Oxaloacetate 2 Malate Citrate Isocitrate NAD+ Citric acid cycle 7 H2O NADH + H+ 3 CO2 Fumarate CoA—SH 6 -Ketoglutarate 4 CoA—SH 5 FADH2 NAD+ FAD Succinate GTP GDP Pi Succinyl CoA CO2 NADH + H+ ADP 53 ATP 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 • REMEMBER THEY ACCEPTED ELECTRONS AND AT LEAST ONE PROTON • THESE TWO ELECTRON CARRIERS DONATE ELECTRONS TO THE ELECTRON TRANSPORT CHAIN, WHICH POWERS ATP SYNTHESIS VIA OXIDATIVE PHOSPHORYLATION • VIRTUAL CELL- ELECTRON TRANSPORT CHAIN 54 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 NUMBERED I THROUGH IV • THE CARRIERS ALTERNATE REDUCED AND OXIDIZED STATES AS THEY ACCEPT AND DONATE ELECTRONS • WHAT HAPPENS, A CARRIER ACCEPTS AN ELECTRON THEN HANDS IT DOWN TO THE NEXT CARRIER • ELECTRONS DROP IN FREE ENERGY AS THEY GO DOWN THE CHAIN AND ARE FINALLY PASSED TO O2, FORMING H2O 55 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 9-13 NADH You do not need to Know the electron Carrier proteins (called Cytochromes) 50 2 e– NAD+ FADH2 2 e– 40 FMN FAD Multiprotein complexes FAD Fe•S Fe•S Q You need to know that NADH And FADH2 Give their electrons that They just got from KREBS to the ETC No ATP is made Directly, it breaks the Fall from high free To smaller more Manageable steps ATP is made through chemiosmosis Cyt b 30 Fe•S Cyt c1 I V Cyt c Cyt a Cyt a3 20 10 2 e– (from NADH or FADH2) 0 2 H+ + 1/2 O2 56 H2O • ELECTRONS ARE TRANSFERRED FROM NADH OR FADH2 TO THE ELECTRON TRANSPORT CHAIN • ELECTRONS ARE PASSED THROUGH A NUMBER OF PROTEINS INCLUDING CYTOCHROMES (EACH WITH AN IRON ATOM) TO O2 • PROTONS ARE RELEASED INTO THE INNER MEMBRANE SPACE OF THE MITOCHONDRIA • 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 57 CHEMIOSMOSIS: THE ENERGY-COUPLING MECHANISM • ETC OCCURS IN THE INNER MEMBRANE OF THE MITOCHONDRIA • ELECTRON TRANSFER IN THE ELECTRON TRANSPORT CHAIN CAUSES PROTEINS TO PUMP H+ FROM THE MITOCHONDRIAL MATRIX TO THE INTERMEMBRANE SPACE CAUSING A PROTON GRADIENT THAT HAS POTENTIAL TO DO WORK 58 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • H+ THEN MOVES BACK ACROSS THE MEMBRANE, PASSING THROUGH CHANNELS IN ATP SYNTHASE (AN ENZYME) • ATP SYNTHASE USES THE EXERGONIC FLOW OF H+ TO DRIVE PHOSPHORYLATION OF ATP FROM ADP • THIS IS AN EXAMPLE OF CHEMIOSMOSIS, THE USE OF ENERGY IN A H+ GRADIENT TO DRIVE CELLULAR WORK 59 Fig. 9-14 INTERMEMBRANE SPACE H+ Stator Rotor Internal rod Catalytic knob ADP + P i ATP MITOCHONDRIAL MATRIX 60 • 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 • ATP SYNTHASE BIOLOGICAL GRADIENTS VIDEO 61 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 9-16 Inner membrane space 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 2 Chemiosmosis matrix Oxidative phosphorylation 62 AN ACCOUNTING OF ATP PRODUCTION BY CELLULAR RESPIRATION • DURING CELLULAR RESPIRATION, MOST ENERGY FLOWS IN THIS SEQUENCE: GLUCOSE NADH AND FADH2 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 63 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 9-17 Electron shuttles span membrane CYTOSOL 2 NADH Glycolysis Glucose 2 Pyruvate MITOCHONDRION 2 NADH or 2 FADH2 6 NADH 2 NADH 2 Acetyl CoA + 2 ATP Citric acid cycle + 2 ATP Maximum per glucose: 2 FADH2 Oxidative phosphorylation: electron transport and chemiosmosis + about 32 or 34 ATP About 36 or 38 ATP 64 CONCEPT 9.5: FERMENTATION AND ANAEROBIC RESPIRATION ENABLE CELLS TO PRODUCE ATP WITHOUT THE USE OF OXYGEN • 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 65 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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 66 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings TYPES OF FERMENTATION • FERMENTATION CONSISTS OF GLYCOLYSIS PLUS REACTIONS THAT REGENERATE NAD+, WHICH CAN BE REUSED BY GLYCOLYSIS • PYRUVIC ACID CAN GO THROUGH 3 DIFFERENT PATHWAYS KREB’S IF OXYGEN IS PRESENT LACTIC ACID FERMENTATION ALCOHOL FERMENTATION 67 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings AFTER GLYCOLYSIS IN ANAEROBES THERE ARE TWO KINDS OF FERMENTATION FERMENTATION IS BREAKING DOWN SUGAR WITHOUT OXYGEN IN ONE TYPE SUGAR BREAKS DOWN INTO LACTIC ACID C6H12O6 2 H+ + 2 C3H5O3- 68 LACTIC ACID FERMENTATION THIS IS DONE BY YOUR MUSCLES WHEN THE DEMAND FOR ATP IS HIGH, BUT YOU ARE LOW IN OXYGEN. (WHILE WORKING OUT) THIS CAN CAUSE SORENESS IN THE MUSCLES. KREBS AND THE ETC SLOW DOWN, DECREASING THE ATP PRODUCTION MUSCLE CELLS CAN STILL DO A BIT OF GLYCOLYSIS W/O OXYGEN GLUCOSE IS CONVERTED TO PYRUVIC ACID THEN AN ENZYME CONVERTS THAT TO LACTIC ACID THIS REACTION FREES UP THE NAD WHILE GIVING 2 ATP (ANOTHER NADH IS REOXIDIZED DURING FERMENTATION) THE LACTIC ACID BUILDS UP, CAUSING FATIGUE, AND THE MUSCLE 69 • 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 70 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 9-18b 2 ADP + 2 P i Glucose 2 ATP Glycolysis 2 NAD+ 2 NADH + 2 H+ 2 Pyruvate 2 Lactate 71 (b) Lactic acid fermentation ALCOHOL FERMENTATION • GLYCOLYSIS IS ANAEROBIC AND YIELDS 2 ATP, AND 2 NADH AND PYRUVATE (REALLY PYRUVIC ACID THAT GETS THE ACETYL COENZYME A ATTACHED) • YEASTS/BACTERIA CONVERT PYRUVIC ACID TO ETHYL ALCOHOL • DURING ALCOHOL FERMENTATION NADH LOSES ELECTRONS AND THE H+ • THE NAD IS FREED TO GO BACK THROUGH GLYCOLYSIS • THE OVERALL ENERGY FOR THE YEAST/BACTERIA WOULD ONLY BE THE 2 ORIGINAL ATP • JUST ENOUGH TO STAY ALIVE 72 ALCOHOLIC FERMENTATION SUGAR BREAKS DOWN INTO CARBON DIOXIDE AND ETHANOL C6H12O6 2 CO2 + 2 C2H5OH ETHANOL IS THE ACTIVE INGREDIENT IN WINE, BEER AND SPIRITS. THE CARBON DIOXIDE PRODUCED IN THIS MANNER CAN BE USED TO ALLOW BREAD TO RISE 73 • 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 74 Animation: Fermentation Overview Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 9-18a 2 ADP + 2 P i Glucose 2 ATP Glycolysis 2 Pyruvate 2 NAD+ 2 Ethanol 2 NADH + 2 H+ 2 CO2 2 Acetaldehyde 75 (a) Alcohol fermentation FERMENTATION AND AEROBIC RESPIRATION 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 OR ACETALDEHYDE) IN FERMENTATION AND O2 IN CELLULAR RESPIRATION • CELLULAR RESPIRATION PRODUCES 38 ATP PER GLUCOSE MOLECULE; FERMENTATION PRODUCES 2 ATP PER GLUCOSE MOLECULE • 3 ANIMALS THAT BREATH THROUGH THEIR BUTTS 76 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 77 • 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 (PREFERRED METHOD) Clostridium tetani an obligate anaerobe • IN A FACULTATIVE ANAEROBE, PYRUVATE IS A FORK IN THE METABOLIC ROAD THAT LEADS TO TWO ALTERNATIVE CATABOLIC ROUTES 78 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 79 THE EVOLUTIONARY SIGNIFICANCE OF GLYCOLYSIS GLYCOLYSIS OCCURS IN NEARLY ALL ORGANISMS GLYCOLYSIS PROBABLY EVOLVED IN ANCIENT PROKARYOTES BEFORE THERE WAS OXYGEN IN THE ATMOSPHERE IT IS BELIEVED SINCE THE CATABOLIC PATHWAY DOESN’T REQUIRE OTHER ORGANELLES THAT IT WAS EVOLVED VERY EARLY ON IN HISTORY 80 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings QUESTION: • CONSIDER THE NAD FORMED DURING GLYCOLYSIS. • WHAT IS THE FINAL ACCEPTOR FOR ITS ELECTRONS DURING FERMENTATION? • WHAT IS THE FINAL ACCEPTOR FOR ITS ELECTRONS DURING AEROBIC RESPIRATION 81 ANSWER: • A DERIVATIVE OF PYRUVATE LIKE ACETALDEHYDE DURING ALCOHOL FERMENTATION OR PYRUVATE ITSELF DURING LACTIC ACID FORMATION • OXYGEN 82 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 • WE DON’T EAT A LOT OF FREE GLUCOSE, BUT GET MOST OUR CALORIES FROM FATS, PROTEINS, SUCROSE, STARCH ETC • ALL THESE MOLECULES CAN BE USED IN CELLULAR RESPIRATION 83 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 • GLYCOLYSIS ACCEPTS A WIDE RANGE OF CARBOHYDRATES • PROTEINS MUST BE DIGESTED TO AMINO ACIDS; • AMINO ACIDS WILL GO TO CREATE MORE PROTEINS BUT AMINO GROUPS CAN FEED GLYCOLYSIS OR THE CITRIC ACID CYCLE (THE AMINO GROUP MUST BE REMOVED THROUGH DEAMINATION) 84 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • FATS ARE DIGESTED TO GLYCEROL (USED IN THE INTERMEDIATE GLYCERALDEHYE-3-PHOSPHATE IN A STEP IN GLYCOLYSIS) AND FATTY ACIDS (USED IN GENERATING ACETYL COA) • FATTY ACIDS ARE BROKEN DOWN BY BETA OXIDATION AND YIELD ACETYL COA (2 CARBON FRAGMENT) AND NADH AND FADH2 • AN OXIDIZED GRAM OF FAT PRODUCES MORE THAN TWICE AS MUCH ATP AS AN OXIDIZED GRAM OF CARBOHYDRATE 85 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 9-20 Proteins Carbohydrates Amino acids Sugars Fats Glycerol Fatty acids Glycolysis Glucose Glyceraldehyde-3- P NH3 Pyruvate Acetyl CoA Citric acid cycle 86 Oxidative phosphorylation BIOSYNTHESIS (ANABOLIC PATHWAYS) • REVIEW: NOT USUALLY SPONTANEOUS, REQUIRE ENERGY, • ∆ G IS POSITIVE • THE BODY USES SMALL MOLECULES TO BUILD OTHER SUBSTANCES (LIKE AMINO ACIDS USED TO MAKE PROTEINS) • THESE SMALL MOLECULES MAY COME DIRECTLY FROM FOOD, FROM GLYCOLYSIS, OR FROM THE CITRIC ACID CYCLE 87 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings ANABOLIC STEROIDS (BECAUSE I’M THINKING ABOUT IT) • MIMIC THE AFFECT OF TESTOSTERONE IN THE BODY • INCREASE PROTEIN SYNTHESIS WITH BUILD UP IN BODY TISSUE RESULTING • INCREASE IN MALE CHARACTERISTICS • PROBLEMS: LIVER DAMAGE, HEART DAMAGE, HIGH CHOLESTEROL, HIGH BLOOD PRESSURE 88 REGULATION OF CELLULAR RESPIRATION VIA FEEDBACK MECHANISMS • FEEDBACK INHIBITION IS THE MOST COMMON MECHANISM FOR CONTROL • A LOT OF “END PRODUCT” SENDS A MESSAGE TO THE STARTING POINT OR AN EARLIER INTERMEDIATE STEP TO SLOW DOWN PRODUCTION • IF ATP CONCENTRATION BEGINS TO DROP, RESPIRATION SPEEDS UP; WHEN THERE IS PLENTY OF ATP, RESPIRATION SLOWS DOWN (YOUR BODY IS EFFICIENT AND DOESN’T WANT TO WASTE THIS ENERGY) • CONTROL OF CATABOLISM IS BASED MAINLY ON REGULATING THE ACTIVITY 89 OF ENZYMES AT STRATEGIC POINTS IN THE CATABOLIC PATHWAY Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings DIABETES- INSULIN RESISTANT TYPE • INSULIN SIGNALS THE BODY TO REMOVE GLUCOSE FROM THE BLOOD STREAM AND DELIVER IT TO CELLS • INSULIN ALSO SPEEDS UP THE CONVERSION OF GLUCOSE TO GLYCOGEN (THE STORAGE FORM OF CARBS WE USE); INCREASES THE UPTAKE OF AMINO ACIDS AND THE SYNTHESIS OF PROTEINS • IF SOMEONE IS INSULIN RESISTANT OR DOESN’T PRODUCE ENOUGH INSULIN THEN THESE THINGS ACCUMULATE IN THE BLOOD • AT FIRST THE BETA CELLS WILL INCREASE INSULIN PRODUCTION BUT EVENTUALLY THE BETA CELLS THAT SECRETE INSULIN CAN’T KEEP UP • HIGH GLUCOSE CAUSES EXCESSIVE THIRST AND FATIGUE 90 INSULIN DEPENDENT DIABETES • GLUCOSE ACCUMULATES IN THE BLOOD BECAUSE THE PANCREAS ISN’T PRODUCING ENOUGH INSULIN TO GET THE GLUCOSE INTO THE CELLS (SO, THIRST AND FATIGUE BECAUSE YOUR BODY DOESN’T DO CELLULAR RESPIRATION AS EFFICIENTLY) • THESE PATIENTS INJECT THEMSELVES WITH INSULIN SO THAT THE GLUCOSE DOES GO INTO THE CELLS AND THE BODY USES IT TO BREAK DOWN FOR ENERGY 91 • HTTP://WWW.YOUTUBE.COM/WATCH?V=GH2P5CMCC0M • BOZEMAN ON CELL RESPIRATION 92 EVOLUTION CONNECTION • ATP SYNTHASES ARE FOUND IN THE PROKARYOTIC PLASMA MEMBRANE AND IN MITOCHONDRIA AND CHLOROPLASTS. WHAT DOES THIS SUGGEST ABOUT THE EVOLUTIONARY RELATIONSHIP OF THESE EUKARYOTIC ORGANELLES TO PROKARYOTES? • HOW MIGHT THE AMINO ACID SEQUENCES OF THE ATP SYNTHASES FROM THE DIFFERENT SOURCES SUPPORT OR REFUTE YOUR HYPOTHESIS? 93 • HAD EVOLUTIONARY ORIGIN IN MITOCHONDRIA AND PLASTIDS WHEN THEY WERE ORIGINALLY THEIR OWN INDEPENDENT PROKARYOTE • THESE ANCESTORS WERE CAPABLE OF SYNTHESIZING ATP • WE CAN SEQUENCE THE AMINO ACIDS FOR SIMILARITIES BETWEEN THE MITOCHONDRIA, CHLOROPLASTS AND PROKARYOTES IF THEY ARE HIGHLY CONSERVED IT WOULD SUGGEST COMMON ANCESTRY • IF THE ENZYMES ARE SIMILAR THIS WOULD SUGGEST COMMON ANCESTRY TOO 94 Fig. 9-21 Glucose AMP Glycolysis Fructose-6-phosphate – Stimulates + Phosphofructokinase – Fructose-1,6-bisphosphate Inhibits Inhibits Pyruvate ATP Citrate Acetyl CoA Citric acid cycle 95 Oxidative phosphorylation 96 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 97 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 98 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings