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Read “How is a Marathoner Different from a Sprinter?” on page 90 Define the following in your notes as you read: “slow-twitch” fibers “fast-twitch” fibers ATP Aerobic Anaerobic Cellular respiration Answer the following questions: How do muscle types differ in energy production? Why do athletes experience cramping? Are muscle cells only cells to breakdown sugars? Chapter 6 How Cells Harvest Chemical Energy PowerPoint Lectures for Biology: Concepts & Connections, Sixth Edition Campbell, Reece, Taylor, Simon, and Dickey Lecture by Richard L. Myers Copyright © 2009 Pearson Education, Inc. Introduction: How Is a Marathoner Different from a Sprinter? Individuals inherit various percentages of the two main types of muscle fibers, slow and fast – The difference between the two is the process each uses to make ATP – Slow fibers make it aerobically using oxygen – Fast fibers work anaerobically without oxygen Copyright © 2009 Pearson Education, Inc. Introduction: How Is a Marathoner Different from a Sprinter? The percentage of slow and fast muscle fibers determines the difference between track athletes – Those with a large percentage of slow fibers make the best long-distance runners – Those with more fast fibers are good sprinters All of our cells harvest chemical energy (ATP) from our food Copyright © 2009 Pearson Education, Inc. INTRODUCTION TO CELLULAR RESPIRATION Copyright © 2009 Pearson Education, Inc. 6.1 Connections between photosynthesis and cellular respiration BOTH PROVIDE ENERGY! Energy is necessary for life processes – These include growth, transport, manufacture, movement, reproduction, and others – Energy that supports life on Earth is captured from sun rays reaching Earth through plant, algae, protist, and bacterial photosynthesis Copyright © 2009 Pearson Education, Inc. 6.1 Connections between photosynthesis and cellular respiration Where does all of Earth’s energy come from? How is this turned into glucose (sugar)? How do organisms get energy (ATP) from this glucose? Copyright © 2009 Pearson Education, Inc. Sunlight energy Now turn to the person next to you and explain the relationship between photosynthesis and cellular respiration in your own words ECOSYSTEM Photosynthesis in chloroplasts CO2 Glucose + + H2O O2 Cellular respiration in mitochondria ATP (for cellular work) Heat energy Why is this statement misleading? “Plants perform photosynthesis and animals perform cellular respiration” 6.2 Connection between cellular respiration and breathing Breathing and cellular respiration are closely related – Breathing: takes in _________ releases _______ – Cellular respiration (breathing at cellular level: takes in ______ to help __________________ releases _______ for energy and _____ as waste Copyright © 2009 Pearson Education, Inc. O2 Breathing CO2 Lungs CO2 Bloodstream Muscle cells carrying out Cellular Respiration Glucose + O2 CO2 + H2O + ATP O2 6.3 Making ATP from glucose Energy in bonds from glucose is transferred to ATP (like employer paying you in money) Cellular respiration produces 38 ATP molecules from each glucose molecule ENERGY RELEASING!! Like burning fuel in car or burning wood in fireplace – Other foods (organic molecules) can be used as a source of energy as well Copyright © 2009 Pearson Education, Inc. C6H12O6 Glucose + 6 O2 Oxygen 6 CO2 Carbon dioxide + 6 H2O Water + ATPs Energy 6.5 It’s all about ELECTRONS! Cellular respiration takes electrons from glucose and uses them to make ATP in a multi-step pathway When the carbon-hydrogen bonds of glucose are broken, electrons are transferred to oxygen (oxygen has a strong attraction for electrons) Only 40% of energy in glucose is transferred to ATP 60% released as ________ Copyright © 2009 Pearson Education, Inc. 6.5 It’s all about ELECTRONS! Cellular respiration is the controlled breakdown of glucose – Energy is released in small amounts that can be captured and stored in ATP – Why is controlled breakdown so important? Copyright © 2009 Pearson Education, Inc. 6.5 It’s all about ELECTRONS! Something has to carry electrons along pathway from _____________ to ___________ This molecule is _______ before it accepts electrons and called ________ after it has the electrons Copyright © 2009 Pearson Education, Inc. 6.5 It’s all about ELECTRONS! There are other electron “carrier” molecules that function like NAD+ – They form a staircase where the electrons pass from one to the next down the staircase – These electron carriers collectively are called the __________________________ – As electrons are transported down the chain, ATP is generated Copyright © 2009 Pearson Education, Inc. NADH NAD+ + ATP 2e– Controlled release of energy for synthesis of ATP H+ 2e– H+ H 2O 1 2 O2 STAGES OF CELLULAR RESPIRATION AND FERMENTATION Copyright © 2009 Pearson Education, Inc. 6.6 Three Main Stages of Cellular Respiration Stage 1: Glycolysis – Breaks down glucose (6C) into two pyruvates (3C) – Occurs in the cytoplasm Copyright © 2009 Pearson Education, Inc. 6.6 Three Main Stages Stage 2: The citric acid cycle – Breaks down pyruvate into carbon dioxide – supplies the third stage with electrons via NADH – One glucose – two turns of cycle – Occurs in the mitochondria Copyright © 2009 Pearson Education, Inc. 6.6 Three Main Stages Stage 3: Oxidative phosphorylation – Electrons are shuttled through the electron transport chain – ATP is generated through chemisosmosis – Occurs in the inner mitochondrion membrane Copyright © 2009 Pearson Education, Inc. NADH Mitochondrion High-energy electrons carried by NADH NADH FADH2 and OXIDATIVE GLYCOLYSIS Glucose PHOSPHORYLATION (Electron Transport and Chemiosmosis) CITRIC ACID CYCLE Pyruvate Cytoplasm Inner mitochondrial membrane CO2 CO2 ATP ATP Substrate-level phosphorylation Substrate-level phosphorylation ATP Oxidative phosphorylation 6.7 Glycolysis Glucose – 2 NAD+ 2 pyruvates 2 NADH (goes to ______) – 2 ATP made by substrate-level phosphorylation: – doesn’t use oxygen – Enzyme transfers phosphate from some substrate to ADP to make ATP Copyright © 2009 Pearson Education, Inc. Glucose 2 ADP 2 NAD+ + 2 P 2 NADH 2 ATP + 2 H+ 2 Pyruvate Enzyme Enzyme P ADP + P Substrate P Product ATP Glucose ATP Steps 1 – 3 A fuel molecule is energized, using ATP. ENERGY INVESTMENT PHASE Step 1 ADP P Glucose-6-phosphate P Fructose-6-phosphate P Fructose-1,6-bisphosphate 2 ATP 3 ADP P Glucose ATP Steps 1 – 3 A fuel molecule is energized, using ATP. ENERGY INVESTMENT PHASE Step 1 ADP P Glucose-6-phosphate P Fructose-6-phosphate P Fructose-1,6-bisphosphate 2 ATP 3 ADP P Step 4 A six-carbon intermediate splits Into two three-carbon intermediates. 4 P P Glyceraldehyde-3phosphate (G3P) Step 5 A redox reaction generates NADH. NAD+ NAD+ 5 P NADH Glyceraldehyde-3-phosphate (G3P) P P + H+ 5 ENERGY PAYOFF PHASE P NADH + H+ P P P P 1,3-Bisphosphoglycerate Step 5 A redox reaction generates NADH. Glyceraldehyde-3-phosphate (G3P) P P NAD+ NAD+ 5 P NADH 5 ENERGY PAYOFF PHASE P NADH + H+ + H+ P P P ADP P 1,3-Bisphosphoglycerate P 3-Phosphoglycerate ADP 6 6 ATP ATP P 7 Steps 6 – 9 ATP and pyruvate are produced. 7 P P 2-Phosphoglycerate 8 H2O 8 H2O P P ADP ADP 9 ATP Phosphoenolpyruvate (PEP) 9 ATP Pyruvate 6.8 Pyruvate enters CAC Pyruvate must undergo some changes before it enters mitochondria for CAC – The first step is removal of a carboxyl group that forms CO2 – The second is removal of 2 electrons from the twocarbon compound remaining – Finally, coenzyme A binds to the two-carbon fragment forming acetyl coenzyme A Copyright © 2009 Pearson Education, Inc. NADH + H+ NAD+ 2 CoA Pyruvate Acetyl coenzyme A 1 3 CO2 Coenzyme A 6.9 Citric Acid Cycle Acetyl (2C) enters CAC Products: 2 CO2 3 NADH 1 FADH2 (another electron carrier like NADH) 1 ATP (substrate-level phosphorylation) Copyright © 2009 Pearson Education, Inc. Acetyl CoA CoA CoA CITRIC ACID CYCLE 2 CO2 3 NAD+ FADH2 3 NADH FAD 3 H+ ATP ADP + P CoA Acetyl CoA CoA 2 carbons enter cycle Oxaloacetate 1 CITRIC ACID CYCLE Step 1 Acetyl CoA stokes the furnace. CoA Acetyl CoA CoA 2 carbons enter cycle Oxaloacetate 1 Citrate NAD+ 2 NADH + H+ CITRIC ACID CYCLE CO2 leaves cycle ADP + P ATP Alpha-ketoglutarate 3 CO2 leaves cycle NADH + H+ Step 1 Acetyl CoA stokes the furnace. NAD+ Steps 2 – 3 NADH, ATP, and CO2 are generated during redox reactions. CoA Acetyl CoA CoA 2 carbons enter cycle Oxaloacetate 1 Citrate NADH + H+ NAD+ 5 NAD+ 2 NADH + H+ CITRIC ACID CYCLE CO2 leaves cycle Malate ADP + P FADH2 4 ATP FAD Alpha-ketoglutarate 3 CO2 leaves cycle Succinate NADH + H+ Step 1 Acetyl CoA stokes the furnace. NAD+ Steps 2 – 3 NADH, ATP, and CO2 are generated during redox reactions. Steps 4 – 5 Redox reactions generate FADH2 and NADH. 6.10 Most ATP production occurs by oxidative phosphorylation Oxidative phosphorylation involves electron transport and chemiosmosis and requires an adequate supply of oxygen – NADH and FADH2 and the inner membrane of the mitochondria are also involved – A H+ ion gradient formed from all of the redox reactions of glycolysis and the citric acid cycle provide energy for the synthesis of ATP Copyright © 2009 Pearson Education, Inc. 6.6 Chemiosmosis Electron Transport Chain creates a concentration gradient of H+ ions – The potential energy of this concentration gradient is used to make ATP by a process called chemiosmosis – The concentration gradient drives H+ through ATP synthases and enzymes found in the membrane, and ATP is produced Copyright © 2009 Pearson Education, Inc. Intermembrane space Protein complex of electron carriers H+ H+ H+ H+ H+ H+ H+ Electron carrier H+ H+ ATP synthase Inner mitochondrial membrane FADH2 Electron flow NADH Mitochondrial matrix FAD NAD+ H+ 1 2 O2 + 2 H+ H+ H+ H2O Electron Transport Chain OXIDATIVE PHOSPHORYLATION ADP + P ATP H+ Chemiosmosis 6.11 CONNECTION: Certain poisons interrupt critical events in cellular respiration There are three different categories of cellular poisons that affect cellular respiration – The first category blocks the electron transport chain (for example, rotenone, cyanide, and carbon monoxide) – The second inhibits ATP synthase (for example, oligomycin) – Finally, the third makes the membrane leaky to hydrogen ions (for example, dinitrophenol) Copyright © 2009 Pearson Education, Inc. Cyanide, carbon monoxide Rotenone Oligomycin H+ H+ H+ ATP synthase H+ H+ H+ H+ DNP FADH2 FAD 1 2 NAD+ NADH O2 + 2 H+ H+ H+ H2O ADP + P ATP H+ Electron Transport Chain Chemiosmosis 6.12 Review: Each molecule of glucose yields many molecules of ATP Recall that the energy payoff of cellular respiration involves (1) glycolysis, (2) alteration of pyruvate, (3) the citric acid cycle, and (4) oxidative phosphorylation – The total yield of ATP molecules per glucose molecule has a theoretical maximum of about 38 – This is about 40% of a glucose molecule potential energy – Additionally, water and CO2 are produced Copyright © 2009 Pearson Education, Inc. Electron shuttle across membrane Cytoplasm 2 NADH Mitochondrion 2 NADH (or 2 FADH2) 6 NADH 2 NADH GLYCOLYSIS Glucose 2 Pyruvate 2 Acetyl CoA + 2 ATP by substrate-level phosphorylation Maximum per glucose: CITRIC ACID CYCLE + 2 ATP by substrate-level phosphorylation About 38 ATP 2 FADH2 OXIDATIVE PHOSPHORYLATION (Electron Transport and Chemiosmosis) + about 34 ATP by oxidative phosphorylation 6.13 Fermentation enables cells to produce ATP without oxygen Fermentation is an anaerobic (without oxygen) energy-generating process – It takes advantage of glycolysis, producing two ATP molecules and reducing NAD+ to NADH – The trick is to oxidize the NADH without passing its electrons through the electron transport chain to oxygen Copyright © 2009 Pearson Education, Inc. 6.13 Fermentation enables cells to produce ATP without oxygen Your muscle cells and certain bacteria can oxidize NADH through lactic acid fermentation – NADH is oxidized to NAD+ when pyruvate is reduced to lactate – In a sense, pyruvate is serving as an “electron sink,” a place to dispose of the electrons generated by oxidation reactions in glycolysis Animation: Fermentation Overview Copyright © 2009 Pearson Education, Inc. 2 ADP +2 P 2 ATP GLYCOLYSIS Glucose 2 NAD+ 2 NADH 2 Pyruvate 2 NADH 2 NAD+ 2 Lactate Lactic acid fermentation 6.13 Fermentation enables cells to produce ATP without oxygen The baking and winemaking industry have used alcohol fermentation for thousands of years – Yeasts are single-celled fungi that not only can use respiration for energy but can ferment under anaerobic conditions – They convert pyruvate to CO2 and ethanol while oxidizing NADH back to NAD+ Copyright © 2009 Pearson Education, Inc. 2 ADP +2 P 2 ATP GLYCOLYSIS Glucose 2 NAD+ 2 NADH 2 Pyruvate 2 NADH 2 CO2 released 2 NAD+ 2 Ethanol Alcohol fermentation 6.14 EVOLUTION CONNECTION: Glycolysis evolved early in the history of life on Earth Glycolysis is the universal energy-harvesting process of living organisms – So, all cells can use glycolysis for the energy necessary for viability – The fact that glycolysis has such a widespread distribution is good evidence for evolution Copyright © 2009 Pearson Education, Inc. INTERCONNECTIONS BETWEEN MOLECULAR BREAKDOWN AND SYNTHESIS Copyright © 2009 Pearson Education, Inc. 6.15 Cells use many kinds of organic molecules as fuel for cellular respiration Although glucose is considered to be the primary source of sugar for respiration and fermentation, there are actually three sources of molecules for generation of ATP – Carbohydrates (disaccharides) – Proteins (after conversion to amino acids) – Fats Copyright © 2009 Pearson Education, Inc. Food, such as peanuts Carbohydrates Fats Glycerol Sugars Proteins Fatty acids Amino acids Amino groups Glucose G3P Pyruvate GLYCOLYSIS Acetyl CoA ATP CITRIC ACID CYCLE OXIDATIVE PHOSPHORYLATION (Electron Transport and Chemiosmosis) 6.16 Food molecules provide raw materials for biosynthesis Many metabolic pathways are involved in biosynthesis of biological molecules – To survive, cells must be able to biosynthesize molecules that are not present in its foods – Often the cell will convert the intermediate compounds of glycolysis and the citric acid cycle to molecules not found in food Copyright © 2009 Pearson Education, Inc. ATP needed to drive biosynthesis ATP CITRIC ACID CYCLE GLUCOSE SYNTHESIS Acetyl CoA Pyruvate G3P Glucose Amino groups Amino acids Proteins Fatty acids Glycerol Fats Cells, tissues, organisms Sugars Carbohydrates Cytoplasm NADH Mitochondrion NADH and FADH2 Glycolysis Glucose Pyruvate CO2 ATP Oxidative phosphorylation (Electron Transport and Chemiosmosis) Citric acid cycle CO2 ATP ATP Cellular respiration generates has three stages oxidizes uses ATP produce some glucose and organic fuels (a) C6H12O6 energy for produces many (b) (d) to pull to electrons down (c) cellular work by process called chemiosmosis uses H+ diffuse through ATP synthase uses (e) pumps H+ to create H+ gradient (f) 0.3 0.3 Color intensity 0.2 0.1 0.2 0.1 a. Time 0.2 0.1 b. 0.3 Time c. Time You should now be able to 1. Explain how photosynthesis and cellular respiration are necessary to provide energy that is required to sustain your life 2. Explain why breathing is necessary to support cellular respiration 3. Describe how cellular respiration produces energy that can be stored in ATP 4. Explain why ATP is required for human activities Copyright © 2009 Pearson Education, Inc. You should now be able to 5. Describe the process of energy production from movement of electrons 6. List and describe the three main stages of cellular respiration 7. Describe the major steps of glycolysis and explain why glycolysis is considered to be a metabolic pathway 8. Explain how pyruvate is altered to enter the citric acid cycle and why coenzymes are important to the process Copyright © 2009 Pearson Education, Inc. You should now be able to 9. Describe the citric acid cycle as a metabolic pathway designed for generating additional energy from glucose 10. Discuss the importance of oxidative phosphorylation in producing ATP 11. Describe useful applications of poisons that interrupt critical steps in cellular respiration 12. Review the steps in oxidation of a glucose molecule aerobically Copyright © 2009 Pearson Education, Inc. You should now be able to 13. Compare respiration and fermentation 14. Provide evidence that glycolysis evolved early in the history of life on Earth 15. Provide criteria that a molecule must possess to be considered a fuel for cellular respiration 16. Discuss the mechanisms that cells use to biosynthesize cell components from food Copyright © 2009 Pearson Education, Inc.