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Biology Sylvia S. Mader Michael Windelspecht
Chapter 8 Cellular Respiration Lecture Outline See separate FlexArt PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes. 1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1
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Biology, 9th ed,Sylvia Mader
Chapter 08 8.1 Cellular Respiration Cellular Respiration Cellular respiration is a cellular process that breaks down nutrient molecules with the concomitant production of ATP Consumes oxygen and produces carbon dioxide (CO2) Cellular respiration is an aerobic process. Usually involves the breakdown of glucose to CO2 and H2O Energy is extracted from the glucose molecule: Released step-wise Allows ATP to be produced efficiently Oxidation-reduction enzymes include NAD+ and FAD as coenzymes
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Biology, 9th ed,Sylvia Mader
Chapter 08 Cellular Respiration Cellular Respiration Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Oxidation C6H12O6 + 6O2 6CO2 + 6H2O + energy glucose Reduction Electrons are removed from substrates and received by oxygen, which combines with H+ to become water. Glucose is oxidized and O2 is reduced
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Biology, 9th ed,Sylvia Mader
Cellular Respiration Chapter 08 Cellular Respiration Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. O2 and glucose enter cells, which release H2O and CO. CO2 H2O intermembrane space cristae Mitochondria use energy from glucose to form ATP from ADP + P . ATP ADP + P © E. & P. Bauer/zefa/Corbis
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Biology, 9th ed,Sylvia Mader
Chapter 08 Cellular Respiration Cellular Respiration NAD+ (nicotinamide adenine dinucleotide) A coenzyme of oxidation-reduction. It can: Oxidize a metabolite by accepting electrons Reduce a metabolite by giving up electrons Each NAD+ molecule is used over and over again FAD (flavin adenine dinucleotide) Also a coenzyme of oxidation-reduction Sometimes used instead of NAD+ Accepts two electrons and two hydrogen ions (H+) to become FADH2
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Biology, 9th ed,Sylvia Mader
Chapter 08 Cellular Respiration Cellular Respiration Cellular respiration includes four phases: Glycolysis is the breakdown of glucose into two molecules of pyruvate Occurs in the cytoplasm ATP is formed Does not utilize oxygen Preparatory (prep) reaction Both pyruvates are oxidized and enter the mitochondria Electron energy is stored in NADH Two carbons are released as CO2 (one from each pyruvate)
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Biology, 9th ed,Sylvia Mader
Chapter 08 Cellular Respiration Cellular Respiration Citric acid cycle Occurs in the matrix of the mitochondrion and produces NADH and FADH2 In series of reactions, it releases 4 carbons as CO2 Turns twice per glucose molecule (once for each pyruvate) Produces two immediate ATP molecules per glucose molecule Electron transport chain (ETC) Extracts energy from NADH & FADH2 Passes electrons from higher to lower energy states Produces 32 or 34 molecules of ATP
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The Four Phases of Complete Glucose Breakdown
Biology, 9th ed,Sylvia Mader Chapter 08 Slide #8 The Four Phases of Complete Glucose Breakdown Cellular Respiration Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. e– NADH NADH e– e– e– NADH and FADH2 Cytoplasm e– Mitochondrion e– e– Glycolysis Electron transport chain and chemiosmosis Preparatory reaction Citric acid cycle glucose pyruvate 2 ATP 2 ATP 4 ADP 4 ATP total 2 ATP net gain 2 ADP 2 ATP 32 ADP or 34 32 or 34 ATP 8
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8.2 Outside the Mitochondria: Glycolysis
Biology, 9th ed,Sylvia Mader Chapter 08 8.2 Outside the Mitochondria: Glycolysis Cellular Respiration Glycolysis occurs in cytoplasm outside mitochondria Energy Investment Step: Two ATP are used to activate glucose Glucose splits into two G3P molecules Energy Harvesting Step: Oxidation of G3P occurs by removal of electrons and hydrogen ions Two electrons and one hydrogen ion are accepted by NAD+ resulting in two NADH Four ATP are produced by substrate-level phosphorylation Net gain of two ATP (4 ATP produced - 2 ATP consumed) Both G3Ps converted to pyruvates
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Outside the Mitochondria: Glycolysis
Biology, 9th ed,Sylvia Mader Chapter 08 Outside the Mitochondria: Glycolysis Cellular Respiration Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Glycolysis inputs outputs 6C glucose 2 (3C) pyruvate 2 NAD+ 2 NADH ATP 2 ADP 2 4 ADP P ATP total 4 2 ATP net gain
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Glycolysis Cellular Respiration Biology, 9th ed,Sylvia Mader
Chapter 08 Slide #11 Glycolysis Cellular Respiration Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Glycolysis Energy-investment Step C C C C C C G3P glyceraldehyde-3-phosphate glucose BPG 1,3-bisphosphoglycerate –2 ATP ATP ATP 3PG phosphoglycerate ADP ADP P C C C C C C P Two ATP are used to get started. Splitting produces two 3-carbon molecules. P C C C C C C P G3P G3P Energy-harvesting Steps NAD+ NAD+ E1 NADH NADH Oxidation of G3P occurs as NAD+ receives high-energy electrons. P P P C C C P P C C C P BPG BPG A D P E2 ADP Substrate-level ATP synthesis. +2 ATP ATP ATP P C C C C C C P 3PG 3PG E3 Oxidation of 3PG occurs by removal of water. H2O H2O P C C C C C C P PEP PEP ADP E4 ADP Substrate-level ATP synthesis. +2 ATP ATP ATP C C C C C C Two molecules of pyruvate are the end products of glycolysis. 2 ATP (net gain) pyruvate pyruvate
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Substrate-level ATP Synthesis
Biology, 9th ed,Sylvia Mader Substrate-level ATP Synthesis Chapter 08 Cellular Respiration Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. enzyme P ADP P BPG ATP P 3PG
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8.3 Outside the Mitochondria: Fermentation
Biology, 9th ed,Sylvia Mader Chapter 08 8.3 Outside the Mitochondria: Fermentation Cellular Respiration Pyruvate is a pivotal metabolite in cellular respiration If O2 is not available to the cell, fermentation, an anaerobic process, occurs in the cytoplasm. During fermentation, glucose is incompletely metabolized to lactate, or to CO2 and alcohol (depending on the organism). If O2 is available to the cell, pyruvate enters the mitochondria for aerobic respiration.
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Outside the Mitochondria: Fermentation
Biology, 9th ed,Sylvia Mader Chapter 08 Outside the Mitochondria: Fermentation Cellular Respiration Fermentation is an anaerobic process that reduces pyruvate to either lactate or alcohol and CO2 NADH transfers its electrons to pyruvate Alcoholic fermentation, carried out by yeasts, produces carbon dioxide and ethyl alcohol Used in the production of alcoholic spirits and breads. Lactic acid fermentation, carried out by certain bacteria and fungi, produces lactic acid (lactate) Used commercially in the production of cheese, yogurt, and sauerkraut. Other bacteria produce chemicals anaerobically, including isopropanol, butyric acid, proprionic acid, and acetic acid.
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Biology, 9th ed,Sylvia Mader
Fermentation Chapter 08 Cellular Respiration Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. glucose – 2 ATP 2 ATP E1 2ADP 2 C C C P G3P 2NAD; 2 P E2 2 NADH 2 P C C C P BPG 4ADP E3 + 4 ATP 4 ATP 2 C C C pyruvate E4 or C C 2CO 2 2 ATP (net gain) C C C C 2 lactate or 2 alcohol Animals Plants
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Fermentation Helps Produce Numerous Food Products
Biology, 9th ed,Sylvia Mader Chapter 08 Cellular Respiration Fermentation Helps Produce Numerous Food Products Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. © The McGraw Hill Companies, Inc./Bruce M. Johnson, photographer
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Fermentation Helps Produce Numerous Food Products
Biology, 9th ed,Sylvia Mader Chapter 08 Fermentation Helps Produce Numerous Food Products Cellular Respiration
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Fermentation Helps Produce Numerous Food Products
Biology, 9th ed,Sylvia Mader Chapter 08 Fermentation Helps Produce Numerous Food Products Cellular Respiration
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Outside the Mitochondria: Fermentation
Biology, 9th ed,Sylvia Mader Chapter 08 Outside the Mitochondria: Fermentation Cellular Respiration Advantages Provides a quick burst of ATP energy for muscular activity. Disadvantages Lactate and alcohol are toxic to cells. Lactate changes pH and causes muscles to fatigue. Oxygen debt Yeast die from the alcohol they produce by fermentation Efficiency of Fermentation Two ATP produced per glucose of molecule during fermentation is equivalent to 14.6 kcal. Complete oxidation of glucose can yield 686 kcal. Only 2 ATP per glucose are produced, compared to 36 or 38 ATP molecules per glucose produced by cellular respiration.
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Outside the Mitochondria: Fermentation
Biology, 9th ed,Sylvia Mader Chapter 08 Outside the Mitochondria: Fermentation Cellular Respiration Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fermentation inputs outputs glucose 2 lactate or 2 alcohol and 2 CO2 ATP 2 ADP + 2 P 2 net gain
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8.4 Inside the Mitochondria
Biology, 9th ed,Sylvia Mader Chapter 08 8.4 Inside the Mitochondria Cellular Respiration The Preparatory (prep) Reaction Connects glycolysis to the citric acid cycle End product of glycolysis, pyruvate, enters the mitochondrial matrix Pyruvate is converted to a 2-carbon acetyl group Attached to Coenzyme A to form acetyl-CoA Electrons are picked up (as hydrogen atom) by NAD+ CO2 is released and transported out of mitochondria into the cytoplasm
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Inside the Mitochondria
Biology, 9th ed,Sylvia Mader Chapter 08 Inside the Mitochondria Cellular Respiration Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 2 NAD+ 2 NADH O OH CoA C 2 C O + 2 CoA 2 C O + 2 CO2 CH3 CH carbon 3 pyruvate acetyl CoA dioxide 2 pyruvate + 2 CoA 2 acetyl CoA + 2 carbon dioxide
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Mitochondrion Structure and Function
Biology, 9th ed,Sylvia Mader Mitochondrion Structure and Function Chapter 08 Cellular Respiration Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cristae: location of the electron transportchain (ETC) Matrix: location of the prep reaction and the citric acid cycle outer membrane inner membrane cristae intermembrane space matrix 45,0003X © Dr. Donald Fawcett and Dr. Porter/Visuals Unlimited
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Inside the Mitochondria
Biology, 9th ed,Sylvia Mader Chapter 08 Inside the Mitochondria Cellular Respiration Citric Acid Cycle Also called the Krebs cycle Occurs in the matrix of mitochondria Begins with the addition of a two-carbon acetyl group (from acetyl-CoA) to a four-carbon molecule (oxaloacetate), forming a six-carbon molecule (citric acid) NADH and FADH2 capture energy rich electrons ATP is formed by substrate-level phosphorylation Turns twice for one glucose molecule (once for each pyruvate) Produces 4 CO2, 2 ATP, 6 NADH and 2 FADH2 per glucose molecule
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Citric Acid Cycle Cellular Respiration Biology, 9th ed,Sylvia Mader
Chapter 08 Slide #25 Cellular Respiration Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. NADH e– NADH e– e– NADHand FADH2 e– e– e– e– Glycolysis Preparatory reaction Citric acid cycle Electron transport chain and chemiosmosis glucose pyruvate Matrix 2 ATP 2 ADP 4 ADP 4 ATP total 2 ATP 1. The cycle begins when a C2 acetyl group carried by CoA combines with a C4 molecule to form citrate. net 2ADP 2 ATP 32ADP or 34 32 or 34 ATP CoA acetyl CoA C2 citrate C6 NAD oxaloacetate C2 NADH NADH 2. Twice over, substrates are oxidized as NAD+ is Reduced to NADH, and CO2 is released. 5. Once again a substrate is oxidized, and NAD+ is reduced to NADH. Citric acid cycle NAD+ CO2 fumarate C4 ketoglutarate C5 NAD+ succinate C4 4. Again a substrate is oxidized, but this time FAD is reduced to FADH2 FAD CO2 NADH FADH ATP 3. ATP is produced as an energized phosphate is transferred from a substrate to ADP.
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Inside the Mitochondria
Biology, 9th ed,Sylvia Mader Chapter 08 Inside the Mitochondria Cellular Respiration Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Citric acid cycle inputs outputs 4 CO2 2 (2c) acetyl groups 6 NADH 6 NAD+ 2 FADH2 2 FAD 2 ADP +2 P 2 ATP
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Inside the Mitochondria
Biology, 9th ed,Sylvia Mader Chapter 08 Inside the Mitochondria Cellular Respiration Electron Transport Chain (ETC) Location: Eukaryotes: cristae of the mitochondria Aerobic prokaryotes: plasma membrane Series of carrier molecules: Pass energy-rich electrons successively from one to another Complex arrays of protein and cytochrome Cytochromes are proteins with heme groups with central iron atoms The electron transport chain Receives electrons from NADH & FADH2 Produces ATP by oxidative phosphorylation Oxygen serves as the final electron acceptor Oxygen combines with hydrogen ions to form water
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Inside the Mitochondria
Biology, 9th ed,Sylvia Mader Chapter 08 Inside the Mitochondria Cellular Respiration The fate of the hydrogens: Hydrogens from NADH deliver enough energy to make 3 ATPs Those from FADH2 have only enough for 2 ATPs “Spent” hydrogens combine with oxygen Recycling of coenzymes increases efficiency Once NADH delivers hydrogens, it returns (as NAD+) to pick up more hydrogens However, hydrogens must be combined with oxygen to make water If O2 is not present, NADH cannot release H+ No longer recycled back to NAD+
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Inside the Mitochondria
Biology, 9th ed,Sylvia Mader Chapter 08 Inside the Mitochondria Cellular Respiration The electron transport chain complexes pump H+ from the matrix into the intermembrane space of the mitochondrion H+ therefore becomes more concentrated in the intermembrane space, creating an electrochemical gradient. ATP synthase allows H+ to flow down its gradient. Flow of H+ drives the synthesis of ATP from ADP and inorganic phosphate by ATP synthase. This process is called chemiosmosis ATP production is linked to the establishment of the H+ gradient ATP moves out of mitochondria and is used for cellular work It can be broken down to ADP and inorganic phosphate These molecules are returned to the mitochondria for more ATP production 29
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Organization and Function of the Electron Transport Chain
Biology, 9th ed,Sylvia Mader Chapter 08 Organization and Function of the Electron Transport Chain Cellular Respiration Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. NADH e- NADH e- e- NADH and FADH2 e- e- e- e- Glycolysis Preparatory reaction Citric acid cycle Electron transport chemiosmosis chain and glucose pyruvate 2ATP 2ADP 4 ADP 4 ATP total 2 ATP net ADP or 34 32 ADP 32 or 34 ATP H+ Electron transport chain NADH-Q reductase H+ H+ H+ H+ H+ cytochrome reductase H+ H+ H+ cytochrome c coenzyme Q H+ cytochrome oxidase H+ e : H+ H+ low energy electron FADH2 : high energy electron FAD + e H+ 2 H+ H+ NAD+ H+ 2 H+ NADH H+ H+ H+ H2O 1 O2 ATP ADP H+ + P 2 H+ H+ Matrix H+ Intermembrane space H+ H+ H+ ATP synthase complex H+ H+ H+ H+ ATP channel protein H+ H+ Chemiosmosis ATP H+ H+
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Inside the Mitochondria
Biology, 9th ed,Sylvia Mader Chapter 08 Inside the Mitochondria Cellular Respiration Energy yield from glucose metabolism: Net yield per glucose: From glycolysis – 2 ATP From citric acid cycle – 2 ATP From electron transport chain – 32 or 34 ATP Energy content: Reactant (glucose) 686 kcal Energy yield (36 ATP) 263 kcal Efficiency is 39% The rest of the energy from glucose is lost as heat
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Accounting of Energy Yield per Glucose Molecule Breakdown
Biology, 9th ed,Sylvia Mader Chapter 08 Accounting of Energy Yield per Glucose Molecule Breakdown Cellular Respiration Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. glucose
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Accounting of Energy Yield per Glucose Molecule Breakdown
Biology, 9th ed,Sylvia Mader Chapter 08 Slide #33 Accounting of Energy Yield per Glucose Molecule Breakdown Cellular Respiration Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. glucose Cytoplasm glycolysis 2 ATP net 2 NADH 4 or 6 ATP 2 pyruvate 2 NADH 6 ATP 2 acetyl CoA Electron transport chain 2 CO2 6 NADH 18 ATP Mitochondrion Citric acid cycle 2 ATP 2 FADH2 4 ATP 4 CO2 6 O2 6 H2O subtotal subtotal 4 ATP 32 ATP or 34 33 36 or 38 total ATP
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Biology, 9th ed,Sylvia Mader
Chapter 08 8.5 Metabolic Pool Cellular Respiration Foods: Sources of energy rich molecules Carbohydrates, fats, and proteins Degradative reactions (Catabolism) break down molecules Tend to be exergonic (release energy) Synthetic reactions (anabolism) build molecules Tend to be endergonic (consume energy)
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The Metabolic Pool Concept
Biology, 9th ed,Sylvia Mader The Metabolic Pool Concept Chapter 08 Cellular Respiration Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. proteins carbohydrates fats amino acids glucose glycerol fatty acids Glycolysis ATP pyruvate acetyl CoA Citric acid cycle ATP Electron transport chain ATP © C Squared Studios/Getty Images.
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Biology, 9th ed,Sylvia Mader
Chapter 08 Metabolic Pool Cellular Respiration Glucose is broken down in cellular respiration. Fat breaks down into glycerol and three fatty acids. Amino acids break down into carbon chains and amino groups Deamination (NH2 removed) occurs in the liver Results in poisonous ammonia (NH3) Quickly converted to urea Different R-groups from amino acids are processed differently Fragments enter respiratory pathways at many different points
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Biology, 9th ed,Sylvia Mader
Chapter 08 Metabolic Pool Cellular Respiration All metabolic compounds are part of the metabolic pool Intermediates from respiratory pathways can be used for anabolism Anabolism (synthetic reactions of metabolism): Carbohydrates Start with acetyl-CoA Basically reverses glycolysis (but different pathway) Fats G3P converted to glycerol Acetyl groups are connected in pairs to form fatty acids
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Biology, 9th ed,Sylvia Mader
Chapter 08 Metabolic Pool Cellular Respiration Anabolism (cont.): Proteins: Made up of combinations of 20 different amino acids Some amino acids (11) can be synthesized by adult humans However, other amino acids (9) cannot be synthesized by humans Essential amino acids Must be present in the diet
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Photosynthesis vs. Cellular Respiration
Biology, 9th ed,Sylvia Mader Chapter 08 Photosynthesis vs. Cellular Respiration Cellular Respiration Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Photosynthesis grana enzymes membrane NADPH NADP+ H2O O2 CO2 CH2O ATP production via chemiosmosis enzyme-catalyzed reactions ADP ATP NAD+ NADH O2 H2O Cellular Respiration CH2O CO2 membrane cristae enzymes
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