General, Organic & Biological Chemistry 7th Edition Chapter 23 PDF

Section 23.1 Metabolism Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 1  Chapter 23 Chapter Outline 23.1 Metabolism 23.2 Metabolism and cell structure 23.3 Importan...

Section 23.1 Metabolism Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 1  Chapter 23 Chapter Outline 23.1 Metabolism 23.2 Metabolism and cell structure 23.3 Important nucleotide-containing compounds in metabolic pathways 23.4 Important carboxylate ions in metabolic pathways 23.5 High-energy phosphate compounds 23.6 An overview of biochemical energy production 23.7 The citric acid cycle 23.8 The electron transport chain 23.9 Oxidative phosphorylation 23.10 ATP production for the common metabolic pathway 23.11 Non-ETC oxygen-consuming reactions 23.12 B vitamins and the common metabolic pathway Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 2  Section 23.1 Metabolism Metabolism Sum total of all chemical reactions in a living organism Source of energy for the functioning of the human body Also needed for many of the cellular processes such as protein synthesis, DNA replication, RNA transcription, and membrane transport Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 3  Section 23.1 Metabolism Subtypes of Metabolic Reactions Catabolism: All metabolic reactions in which large biochemical molecules are broken down to smaller ones – Usually energy is released in these reactions – Example: Oxidation of glucose Anabolism: All metabolic reactions in which small biochemical molecules are joined to form larger ones – Usually require energy – Example: Synthesis of proteins Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 4  Section 23.1 Metabolism Figure 23.1 - The Processes of Catabolism and Anabolism Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 5  Section 23.1 Metabolism Metabolic Pathway Series of consecutive biochemical reactions used to convert a starting material into an end product There are two types of metabolic pathways: – Linear – Cyclic Major pathways for all forms of life are similar Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 6  Section 23.1 Metabolism Practice Exercise Classify each of the following chemical processes as anabolic or catabolic. a.Synthesis of a protein from amino acids b.Formation of a triacylglycerol from glycerol and fatty acids c.Hydrolysis of a polysaccharide to monosaccharides d.Formation of a nucleic acid from nucleotides Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 7  Section 23.1 Metabolism Practice Exercise Classify each of the following chemical processes as anabolic or catabolic. a.Synthesis of a protein from amino acids Anabolic b.Formation of a triacylglycerol from glycerol and fatty acids Anabolic c.Hydrolysis of a polysaccharide to monosaccharides Catabolic d.Formation of a nucleic acid from nucleotides Anabolic Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 8  Section 23.1 Metabolism What are the two types of metabolic reactions? a.Anabolism and catabolism b.Enzyme catalyzed and non-enzyme catalyzed c.Synthetic and non-synthetic d.Cofactor enhanced and coenzyme enhanced Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 9  Section 23.1 Metabolism What are the two types of metabolic reactions? a.Anabolism and catabolism b.Enzyme catalyzed and non-enzyme catalyzed c.Synthetic and non-synthetic d.Cofactor enhanced and coenzyme enhanced Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 10  Section 23.2 Metabolism and Cell Structure Knowledge of the cell structure is essential for understanding metabolism Prokaryotic cell: – No nucleus and found only in bacteria – Presence of a single circular DNA molecule near the center of the cell called nucleoid Eukaryotic cell: Cell where the DNA is found in a membrane-enclosed nucleus – About 1000 times larger than bacterial cells Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 11  Section 23.2 Metabolism and Cell Structure Figure 23.3 - Schematic Representation of a Eukaryotic Cell Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 12  Section 23.2 Metabolism and Cell Structure Eukaryotic Cell Organelles and Their Function Plasma membrane - Cellular boundary Cytoplasm: Water-based material of a eukaryotic cell Mitochondrion: Generates most of the energy needed for a cell Lysosome: Contains hydrolytic enzymes needed for cell rebuilding, repair, and degradation Ribosome - Site for protein synthesis Nucleus - Site where DNA is found Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 13  Section 23.2 Metabolism and Cell Structure Mitochondrion An organelle that is responsible for the generation of most of the energy for a cell – Outer membrane - Permeable to small molecules 50% lipid and 50% protein – Inner membrane - Highly impermeable to most substances 20% lipid and 80% protein Folded to increase surface area Synthesis of ATP occurs here Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 14  Section 23.2 Metabolism and Cell Structure What cellular organelle is responsible for the generation of most of the energy for the cell? a.Lysosome b.Mitochondrion c.Ribosomes d.Nucleus Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 15  Section 23.2 Metabolism and Cell Structure What cellular organelle is responsible for the generation of most of the energy for the cell? a.Lysosome b.Mitochondrion c.Ribosomes d.Nucleus Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 16  Section 23.3 Important Nucleotide-Containing Compounds in Metabolic Pathways Adenosine Phosphates (ATP, ADP, and AMP) Adenosine phosphates of interest: – Adenosine monophosphate (AMP) - One phosphate group Structural component of RNA – Adenosine diphosphate (ADP) - Two phosphate groups Key component of metabolic pathways – Adenosine triphosphate (ATP) - Three phosphate groups Key component of metabolic pathways Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 17  Section 23.3 Important Nucleotide-Containing Compounds in Metabolic Pathways A phosphoryl group is derived from a phosphate ion when it becomes part of another molecule The net energy produced in these reactions is used for cellular reactions Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 18  Section 23.3 Important Nucleotide-Containing Compounds in Metabolic Pathways In cellular reactions, ATP functions as both a source of a phosphate group and a source of energy – Example: Conversion of glucose to glucose-6-phosphate Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 19  Section 23.3 Important Nucleotide-Containing Compounds in Metabolic Pathways Role of Other Nucleotide Triphosphates in Metabolism Uridine triphosphate (UTP) - Involved in carbohydrate metabolism Guanosine triphosphate (GTP) - Involved in protein and carbohydrate metabolism Cytidine triphosphate (CTP) - Involved in lipid metabolism Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 20  Section 23.3 Important Nucleotide-Containing Compounds in Metabolic Pathways Flavin Adenine Dinucleotide (FAD) Coenzyme required in numerous metabolic redox reactions – Flavin subunit is the active form which gains H atoms when FAD is converted to FADH2 – Ribitol is a reduced form of the sugar ribose Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 21  Section 23.3 Important Nucleotide-Containing Compounds in Metabolic Pathways Figure 23.6 - Structural Formulas of FAD and NAD+ Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 22  Section 23.3 Important Nucleotide-Containing Compounds in Metabolic Pathways Flavin Adenine Dinucleotide (FAD) FAD is the oxidized form FADH2 is the reduced form In enzyme reactions, FAD goes back and forth from oxidized to reduced form Typical cellular reaction in which FAD serves as oxidizing agent involves conversion of an alkane to an alkene Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 23  Section 23.3 Important Nucleotide-Containing Compounds in Metabolic Pathways Nicotinamide Adenine Dinucleotide (NAD) Has coenzyme functions in metabolic redox pathways NAD+ is the oxidized form of NAD NADH is reduced form Typical cellular reaction in which NAD+ serves as the oxidizing agent is the oxidation of a secondary alcohol to give a ketone Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 24  Section 23.3 Important Nucleotide-Containing Compounds in Metabolic Pathways Subunit Structures of NAD 3-subunit structure: 6-subunit structure: Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 25  Section 23.3 Important Nucleotide-Containing Compounds in Metabolic Pathways Coenzyme A Derivative of vitamin B pantothenic acid Active form of coenzyme A is the sulfhydryl group (–SH group) in the ethanethiol subunit of the coenzyme Acetyl-CoA - Formed when acetyl group bonds to CoA–SH via a thioester bond Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 26  Section 23.3 Important Nucleotide-Containing Compounds in Metabolic Pathways Coenzyme A Subunit Structures 3-subunit structure: 6-subunit structure: Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 27  Section 23.3 Important Nucleotide-Containing Compounds in Metabolic Pathways Classification of Metabolic Intermediate Compounds Metabolic intermediate compounds can be classified into three groups based on their functions Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 28  Section 23.3 Important Nucleotide-Containing Compounds in Metabolic Pathways What intermediate molecule in metabolic reactions is responsible for producing energy in the human body? a.AMP b.ADP c.ATP d.NADH Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 29  Section 23.3 Important Nucleotide-Containing Compounds in Metabolic Pathways What intermediate molecule in metabolic reactions is responsible for producing energy in the human body? a.AMP b.ADP c.ATP d.NADH Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 30  Section 23.3 Important Nucleotide-Containing Compounds in Metabolic Pathways Why is ATP the best energy source for human beings? a.It makes better substrates for enzymes than any of the other energy molecule. b.It has an intermediate value in free energy, and it undergoes slow hydrolysis in an aqueous environment. c.The bonds in ATP are more easily broken during enzyme-catalyzed reactions. d.It has an intermediate value in free energy, and it undergoes rapid hydrolysis in an aqueous environment. Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 31  Section 23.3 Important Nucleotide-Containing Compounds in Metabolic Pathways Why is ATP the best energy source for human beings? a.It makes better substrates for enzymes than any of the other energy molecule. b.It has an intermediate value in free energy, and it undergoes slow hydrolysis in an aqueous environment. c.The bonds in ATP are more easily broken during enzyme-catalyzed reactions. d.It has an intermediate value in free energy, and it undergoes rapid hydrolysis in an aqueous environment. Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 32  Section 23.4 Important Carboxylate Ions in Metabolic Pathways Carboxylate Ions (Metabolic Acids) Polyfunctional acids formed as intermediates of metabolic reactions There are 5 such acids that serve as substrates for enzymes in metabolic reactions: − 3 succinic acid derivatives (C4 diacid) − Fumarate, oxaloacetate, and malate − 2 glutaric acid derivatives (C5 diacid) − α-ketoglutarate and citrate Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 33  Section 23.4 Important Carboxylate Ions in Metabolic Pathways Figure 23.9 - Structural Formulas for Polyfunctional Carboxylate Ions Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 34  Section 23.4 Important Carboxylate Ions in Metabolic Pathways Which of the following structural descriptions for metabolic carboxylate ions that are derivatives of succinic acid is incorrect? a.Malate contains a hydroxyl group and two carboxyl groups. b.Oxaloacetate contains a keto group and has a 22 charge. c.Fumarate contains a carbon–carbon double bond in a cis configuration. d.None of the above. Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 35  Section 23.4 Important Carboxylate Ions in Metabolic Pathways Which of the following structural descriptions for metabolic carboxylate ions that are derivatives of succinic acid is incorrect? a.Malate contains a hydroxyl group and two carboxyl groups. b.Oxaloacetate contains a keto group and has a 22 charge. c.Fumarate contains a carbon–carbon double bond in a cis configuration. d.None of the above. Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 36  Section 23.5 High-Energy Phosphate Compounds Several phosphate-containing compounds found in metabolic pathways are known as high-energy compounds High-energy compounds: Have greater free energy of hydrolysis than a typical compound – They contain at least one reactive bond called strained bond Energy to break these bonds is less than a normal bond More negative the free energy of hydrolysis, greater the bond strain Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 37  Section 23.5 High-Energy Phosphate Compounds Typically the free-energy release is greater than 6.0 kcal/mole (indicative of bond strain) Strained bonds are represented by the sign ~ (squiggle) Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 38  Section 23.5 High-Energy Phosphate Compounds Table 23.1 - Free Energies of Hydrolysis of Common Phosphate-Containing Metabolic Compounds Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 39  Section 23.5 High-Energy Phosphate Compounds Table 23.1 - Free Energies of Hydrolysis of Common Phosphate-Containing Metabolic Compounds Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 40  Section 23.5 High-Energy Phosphate Compounds How many “strained” bonds are present in an ATP molecule? a.One b.Two c.Three d.None of the above Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 41  Section 23.5 High-Energy Phosphate Compounds How many “strained” bonds are present in an ATP molecule? a.One b.Two c.Three d.None of the above Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 42  Section 23.6 An Overview of Biochemical Energy Production Energy needed to run the human body is obtained from food via a multistep process involving several different catabolic pathways There are four general stages in the biochemical energy production process: – Stage 1: Digestion – Stage 2: Acetyl group formation – Stage 3: Citric acid cycle – Stage 4: Electron transport chain and oxidative phosphorylation Each stage also involves numerous reactions Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 43  Section 23.6 An Overview of Biochemical Energy Production Stage 1: Digestion Begins in mouth (saliva contains starch-digesting enzymes), continues in the stomach (gastric juices), and is completed in small intestine – Results in small molecules that can cross intestinal membrane into the blood stream End products which are absorbed and transported to blood cells: – Glucose and monosaccharides from carbohydrates – Amino acids from proteins – Fatty acids and glycerol from fats and oils Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 44  Section 23.6 An Overview of Biochemical Energy Production Stage 2: Acetyl Group Formation The small molecules from Stage 1 are further oxidized End product of these oxidations is acetyl CoA and reduced coenzyme NADH This stage involves numerous reactions which occur both in the cytosol as well as the mitochondria of the cells Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 45  Section 23.6 An Overview of Biochemical Energy Production Stage 3: Citric Acid Cycle Takes place inside the mitochondria Acetyl group is oxidized to produce CO2 and energy Some energy produced in this stage is lost in the form of heat – Most energy is trapped in reduced coenzymes NADH and FADH2 The carbon dioxide we exhale comes primarily from this stage Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 46  Section 23.6 An Overview of Biochemical Energy Production Stage 4: Electron Transport Chain and Oxidative Phosphorylation Takes place in mitochondria NADH and FADH2 are oxidized to release H ions and electrons – Needed for the production of ATP, primary energy carrier in metabolic pathways O2 inhaled is converted into H2O in this stage Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 47  Section 23.6 An Overview of Biochemical Energy Production What are the stages of energy production in the order of occurrence? a.Digestion, the citric acid cycle, acetyl group formation, and electron transport chain and oxidative phosphorylation b.Digestion, acetyl group formation, electron transport chain and oxidative phosphorylation, and the citric acid cycle c.Digestion, acetyl group formation, the citric acid cycle, and electron transport and oxidative phosphorylation d.Digestion, the citric acid cycle, and electron transport and oxidative phosphorylation Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 48  Section 23.6 An Overview of Biochemical Energy Production What are the stages of energy production in the order of occurrence? a.Digestion, the citric acid cycle, acetyl group formation, and electron transport chain and oxidative phosphorylation b.Digestion, acetyl group formation, electron transport chain and oxidative phosphorylation, and the citric acid cycle c.Digestion, acetyl group formation, the citric acid cycle, and electron transport and oxidative phosphorylation d.Digestion, the citric acid cycle, and electron transport and oxidative phosphorylation Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 49  Section 23.7 The Citric Acid Cycle Citric Acid Cycle - An Introduction Is the series of biochemical reactions in which the acetyl portion of acetyl CoA is oxidized to carbon dioxide and the reduced coenzymes FADH2 and NADH are produced Also know as: – Tricarboxylic acid cycle (TCA) - Presence of three carboxylate groups in citric acid – Krebs cycle - Named after Hans Krebs who elucidated this pathway Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 50  Section 23.7 The Citric Acid Cycle Citric Acid Cycle - An Introduction Important reactions in the citric acid cycle include: – Reduction of NAD+ and FAD to produce NADH and FADH2 – Decarboxylation of citric acid to produce carbon dioxide Summary of citric acid cycle reactions: Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 51  Section 23.7 The Citric Acid Cycle Figure 23.11 - The Citric Acid Cycle Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 52  Section 23.7 The Citric Acid Cycle Reactions of the Citric Acid Cycle Step 1: Formation of citrate Step 2: Formation of isocitrate Step 3: Oxidation of isocitrate and formation of CO2 – Involves oxidation–reduction as well as decarboxylation Step 4: Oxidation of α-ketoglutarate and formation of CO2 Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 53  Section 23.7 The Citric Acid Cycle Reactions of the Citric Acid Cycle Step 5: Thioester bond cleavage in succinyl CoA and phosphorylation of GDP Step 6: Oxidation of succinate Step 7: Hydration of fumarate Step 8: Oxidation of L-Malate to regenerate oxaloacetate Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 54  Section 23.7 The Citric Acid Cycle Practice Exercise When one acetyl CoA is processed through the citric acid cycle, how many times does each of the following events occur? a. A FAD molecule is a reactant. b. A CoA-SH molecule is produced. c. A dehydrogenase enzyme is needed for the reaction to occur. d. A C5 molecule is produced. Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 55  Section 23.7 The Citric Acid Cycle Practice Exercise When one acetyl CoA is processed through the citric acid cycle, how many times does each of the following events occur? a. A FAD molecule is a reactant. One (Step 6) b. A CoA-SH molecule is produced. Two (Steps 1 and 5) c. A dehydrogenase enzyme is needed for the reaction to occur. Four (Steps 3,4,6, and 8) d. A C5 molecule is produced. One (Step 3) Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 56  Section 23.7 The Citric Acid Cycle Regulation of the Citric Acid Cycle The rate at which the citric acid cycle operates is controlled by the body’s need for ATP – When ATP supply is high, ATP inhibits citrate synthase (Step 1 of the cycle) – When ATP levels are low, ADP activates citrate synthase Similarly, ADP and NADH control isocitrate dehydrogenase – NADH acts as an inhibitor – ADP acts as an activator Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 57  Section 23.7 The Citric Acid Cycle How many high-energy molecules are formed in one turn of the citric acid cycle? a.2 NADH, 2 FADH2, and 1 GTP b.3 NADH and 2 FADH2 c.3 NADH, 2 FADH2, and 1 GTP d.3 NADH, 1 FADH2, and 1 GTP Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 58  Section 23.7 The Citric Acid Cycle How many high-energy molecules are formed in one turn of the citric acid cycle? a.2 NADH, 2 FADH2, and 1 GTP b.3 NADH and 2 FADH2 c.3 NADH, 2 FADH2, and 1 GTP d.3 NADH, 1 FADH2, and 1 GTP Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 59  Section 23.8 The Electron Transport Chain The Electron Transport Chain - An Introduction Series of biochemical reactions in which intermediate carriers aid the transfer of electrons and hydrogen ions from NADH and FADH2 – Ultimately react with molecular oxygen to give H2O Lost energy is used to synthesize ATP in oxidative phosphorylation Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 60  Section 23.8 The Electron Transport Chain Enzyme and Electron Carriers for ETC Located along inner mitochondrial membrane Organized into four distinct protein complexes and two mobile carriers – Protein complexes tightly bound to membrane: Complex I: NADH–coenzyme Q reductase Complex II: Succinate–coenzyme Q reductase Complex III: Coenzyme Q–cytochrome c reductase Complex IV: Cytochrome c oxidase – Two mobile electron carriers: Coenzyme Q and cytochrome c Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 61  Section 23.8 The Electron Transport Chain Complex I: NADH–Coenzyme Q Reductase NADH from citric acid cycle is the source of electrons processed via this complex It contains > 40 subunits including flavin mononucleotide (FMN) and several iron–sulfur protein clusters (FeSP) Net result is the transfer of electrons from NADH to coenzyme Q (CoQ) – Several intermediate carriers are involved in this electron transfer Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 62  Section 23.8 The Electron Transport Chain Complex II: Succinate–Coenzyme Q Reductase Smaller than complex I Contains only four subunits including two FeSPs Succinate is converted to fumarate via this complex This complex processes FADH2 – CoQ is the final recipient of the electrons from FADH2 Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 63  Section 23.8 The Electron Transport Chain Complex III: Coenzyme Q–Cytochrome c Reductase Contains 11 different subunits Several FeSP proteins and cytochromes are electron carriers in this complex – Cytochrome: Heme iron protein in which reversible oxidation of an iron atom occurs Various cytochromes, cyt a, cyt b, cyt c, and so on, differ from each other in: – Their protein constituents – The manner in which the heme is bonded to the protein – Attachments to the heme ring Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 64  Section 23.8 The Electron Transport Chain Complex IV: Cytochrome c Oxidase Contains 13 subunits including two cytochromes The electrons flow from cyt c to cyt a to cyt a3 In the final stage of electron transfer, the electrons from cyt a3 and hydrogen ions combine with oxygen (O2) to form water It is estimated that 95% of the oxygen used by cells serves as the final electron acceptor for the ETC Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 65  Section 23.8 The Electron Transport Chain Summary of the Flow of Electrons Through the Four Complexes of the Electron Transport Chain Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 66  Section 23.8 The Electron Transport Chain Practice Exercise With which of the four complexes in the electron transport chains is each of the following events associated? (There may be more than one correct answer in a given situation.) a.The metal iron is present in the form of Fe2+ and Fe3+ ions. b.FADH2 is needed as a reactant. c.The metal copper is present in the form of Cu+ and Cu2+ ions. d.Cytochromes are needed as reactants. Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 67  Section 23.8 The Electron Transport Chain Practice Exercise With which of the four complexes in the electron transport chains is each of the following events associated? (There may be more than one correct answer in a given situation.) a.The metal iron is present in the form of Fe2+ and Fe3+ ions. Complexes I, II, III, and IV b.FADH2 is needed as a reactant. Complex II c.The metal copper is present in the form of Cu+ and Cu2+ ions. Complex IV d.Cytochromes are needed as reactants. Complexes III and IV Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 68  Section 23.8 The Electron Transport Chain Which statement best describes the electron transport chain? a.It is a series of biochemical reactions in which electrons are passed to intermediate carriers to produce energy as the final product. b.It is a series of biochemical reactions in which electrons and hydrogen ions from NADH and FADH2 are passed to intermediate carriers that eventually react with molecular oxygen to produce water. c.It is a series of biochemical reactions in which hydrogen ions are passed to intermediates for the production of energy. d.It is a series of biochemical reactions in which electrons and hydrogen ions are used to produce energy. Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 69  Section 23.8 The Electron Transport Chain Which statement best describes the electron transport chain? a.It is a series of biochemical reactions in which electrons are passed to intermediate carriers to produce energy as the final product. b.It is a series of biochemical reactions in which electrons and hydrogen ions from NADH and FADH2 are passed to intermediate carriers that eventually react with molecular oxygen to produce water. c.It is a series of biochemical reactions in which hydrogen ions are passed to intermediates for the production of energy. d.It is a series of biochemical reactions in which electrons and hydrogen ions are used to produce energy. Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 70  Section 23.9 Oxidative Phosphorylation Oxidative Phosphorylation - An Introduction Oxidative phosphorylation: Process by which ATP is synthesized from ADP using the energy released in the electron transport chain – Can be coupled reactions Coupled reactions: Pairs of biochemical reactions that occur concurrently in which energy released by one reaction is used in the other reaction – Examples: Oxidative phosphorylation and the oxidation reactions of the electron transport chain Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 71  Section 23.9 Oxidative Phosphorylation Oxidative Phosphorylation - An Introduction Coupling of ATP synthesis with the reactions of the ETC is related to the movement of protons (H+ ions) across the inner mitochondrial membrane Complexes I, III, and IV of ETC chain have a second function – Serve as “proton pumps” transferring protons from the matrix side of the inner mitochondrial membrane to the intermembrane space Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 72  Section 23.9 Oxidative Phosphorylation For every two electrons passed through ETC, four protons cross the inner mitochondrial membrane through complex I, four through complex III, and two more though complex IV This proton flow causes a buildup of H+ in the intermembrane space This high concentration of protons passing through ATP synthase becomes the basis for the ATP synthesis Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 73  Section 23.9 Oxidative Phosphorylation Figure 23.18 - A Second Function for Protein Complexes I, III, and IV Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 74  Section 23.9 Oxidative Phosphorylation What main event in oxidative phosphorylation is responsible for ATP production? a.The movement of protons from a region of low to high concentration through a channel in membrane-bound ATP synthase, resulting in ATP formation b.The movement of protons from a region of high to low concentration through enzyme complexes called ATP synthase, resulting in ATP formation c.The movement of electrons from a region of high to low concentration through a channel in membrane-bound ATP synthase, resulting in ATP formation d.The difference in concentration, which constitutes an electrochemical gradient, resulting in ATP formation Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 75  Section 23.9 Oxidative Phosphorylation What main event in oxidative phosphorylation is responsible for ATP production? a.The movement of protons from a region of low to high concentration through a channel in membrane-bound ATP synthase, resulting in ATP formation b.The movement of protons from a region of high to low concentration through enzyme complexes called ATP synthase, resulting in ATP formation c.The movement of electrons from a region of high to low concentration through a channel in membrane-bound ATP synthase, resulting in ATP formation d.The difference in concentration, which constitutes an electrochemical gradient, resulting in ATP formation Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 76  Section 23.10 ATP Production for the Common Metabolic Pathway ATP Formation For each mole of NADH oxidized in the ETC, 2.5 moles of ATP are formed For each mole of FADH2 oxidized in the ETC, only 1.5 moles of ATP are formed For each mole of GTP hydrolyzed, one mole of ATP is formed Ten molecules of ATP are produced for each acetyl CoA catabolized Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 77  Section 23.10 ATP Production for the Common Metabolic Pathway How many moles of ATP are formed for each mole of NADH and FADH2? a.1.0 and 2.0 b.1.5 and 2.5 c.2.0 and 1.0 d.2.5 and 1.5 Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 78  Section 23.10 ATP Production for the Common Metabolic Pathway How many moles of ATP are formed for each mole of NADH and FADH2? a.1.0 and 2.0 b.1.5 and 2.5 c.2.0 and 1.0 d.2.5 and 1.5 Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 79  Section 23.10 ATP Production for the Common Metabolic Pathway How many moles of ATP are ultimately produced from the “processing” of one mole of acetyl CoA molecules through the common metabolic pathway? a.8 b.10 c.24 d.None of the above Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 80  Section 23.10 ATP Production for the Common Metabolic Pathway How many moles of ATP are ultimately produced from the “processing” of one mole of acetyl CoA molecules through the common metabolic pathway? a.8 b.10 c.24 d.None of the above Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 81  Section 23.11 Non-ETC Oxygen-Consuming Reactions Reactive Oxygen Species (ROS) >90% of inhaled oxygen via respiration is consumed during oxidative phosphorylation Remaining O2 is converted to several highly reactive oxygen species (ROS) within the body, which include: – Hydrogen peroxide (H2O2) – Superoxide ion (O2-) – Hydroxyl radical (OH) Superoxide ion and hydroxyl radicals have an unpaired electron Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 82  Section 23.11 Non-ETC Oxygen-Consuming Reactions Reactive Oxygen Species (ROS) Can also be formed due to external influences such as polluted air, cigarette smoke, and radiation exposure Are both beneficial as well as problematic within the body Example: White blood cells produce a significant amount of superoxide free radicals via the following reaction to destroy the invading bacteria and viruses Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 83  Section 23.11 Non-ETC Oxygen-Consuming Reactions Reactive Oxygen Species (ROS) ROS formed are quickly converted to non-toxic species About 5% of ROS escape destruction by superoxide dismutase and catalase enzymes Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 84  Section 23.11 Non-ETC Oxygen-Consuming Reactions Reactive Oxygen Species (ROS) Antioxidant molecules present in the body help trap ROS species – Vitamin E – Vitamin C – Glutathione (GSH) – Beta-carotene Major family of antioxidant phytochemicals are flavonoids Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 85  Section 23.11 Non-ETC Oxygen-Consuming Reactions What happens to unused oxygen from the electron transport chain? a.It is recycled in the body through the lungs. b.It provides oxygen-rich environments for other biochemical processes. c.It is converted to several highly reactive oxygen species (ROS). d.It is recycled through the electron transport chain to maintain an efficient environment. Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 86  Section 23.11 Non-ETC Oxygen-Consuming Reactions What happens to unused oxygen from the electron transport chain? a.It is recycled in the body through the lungs. b.It provides oxygen-rich environments for other biochemical processes. c.It is converted to several highly reactive oxygen species (ROS). d.It is recycled through the electron transport chain to maintain an efficient environment. Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 87  Section 23.12 B Vitamins and the Common Metabolic Pathway Structurally modified B vitamins function as coenzymes in metabolic pathways Four B vitamins participate in various reactions: – Niacin—as NAD+ and NADH – Riboflavin—as FAD, FADH2, and FMN – Thiamin—as TPP – Pantothenic acid—as CoA In the absence of these B vitamins, the body would be unable to utilize carbohydrates, proteins, and fats as energy sources Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 88  Section 23.12 B Vitamins and the Common Metabolic Pathway How many different B vitamins participate in the common metabolic pathway in the form of coenzymes? a.4 b.6 c.7 d.None of the above Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 89  Section 23.12 B Vitamins and the Common Metabolic Pathway How many different B vitamins participate in the common metabolic pathway in the form of coenzymes? a.4 b.6 c.7 d.None of the above Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 90  Chapter 23 Concept Question 1 White blood cells are necessary for the destruction of invading viruses and bacteria. A significantly concentrated species helps in this process. Identify the species. a.Hydrogen peroxide b.Superoxide free radicals c.Hydroxyl radicals d.Ozone Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 91  Chapter 23 Concept Question 1 White blood cells are necessary for the destruction of invading viruses and bacteria. A significantly concentrated species helps in this process. Identify the species. a.Hydrogen peroxide b.Superoxide free radicals c.Hydroxyl radicals d.Ozone Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 92  Chapter 23 Concept Question 2 Athletes have the ability to perform at high levels of activity because of their systems’ ability to produce large amounts of energy. How is this possible? a.They have an increased number of mitochondria which are able to produce large quantities of ATP. b.They metabolize glucose more efficiently. c.Their citric acid cycle functions at a higher rate than a non-athlete. d.They eat a lot of carbohydrates prior to a competition. Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 93  Chapter 23 Concept Question 2 Athletes have the ability to perform at high levels of activity because of their systems’ ability to produce large amounts of energy. How is this possible? a.They have an increased number of mitochondria which are able to produce large quantities of ATP. b.They metabolize glucose more efficiently. c.Their citric acid cycle functions at a higher rate than a non-athlete. d.They eat a lot of carbohydrates prior to a competition. Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 94