Fundamentals of general organic and biological chemistry 8th global edtion by mcmurry 1

Fundamentals of general organic and biological chemistry 8th global edtion by mcmurry 1 Fundamentals of general organic and biological chemistry 8th global edtion by mcmurry 1 Fundamentals of general organic and biological chemistry 8th global edtion by mcmurry 1 Fundamentals of general organic and biological chemistry 8th global edtion by mcmurry 1 Fundamentals of general organic and biological chemistry 8th global edtion by mcmurry 1

Periodic Table of the Elements Main groups Main groups 1A Period 1 8A H 18 2A 1.00794 7A 13 14 15 16 17 4.00260 10 C N O F Ne Be B 9.01218 12 10.81 13 Na Mg K Ca Rb Sr 85.4678 55 87.62 56 Cs Ba Fr (223) 3B 4B 5B 6B 7B 8B Ra 10 2B 11 12 12.011 14.0067 15.9994 18.9984 20.1797 16 17 18 14 15 Al Si P S Cl Ar 26.98154 28.0855 30.9738 32.066 35.4527 39.948 31 32 33 34 35 36 21 22 23 24 25 26 27 28 29 30 Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr 58.69 46 63.546 47 65.39 48 69.72 49 72.61 50 74.9216 51 78.96 52 79.904 53 83.80 54 Pd Ag Cd In Sn Sb Te I Xe Y 47.88 40 50.9415 51.996 54.9380 55.847 58.9332 42 43 44 41 45 Zr *La Hf Mo Tc 95.94 74 (98) 75 W Re Nb 88.9059 91.224 92.9064 72 57 73 Ac 226.0254 227.0278 Ta Ru Rh 101.07 102.9055 106.42 107.8682 112.41 76 77 78 80 79 Os Ir 190.2 108 192.22 109 Pt Au Hg Tl Rf Db Sg Bh Hs Mt Ds Rg Cn (262) (266) (264) (269) (268) (271) (272) (285) Nonmetals 114.82 118.710 121.757 127.60 126.9045 131.29 81 82 85 86 84 83 Pb 195.08 196.9665 200.59 204.383 110 112 113 111 (261) Actinides Metalloids 1B He Sc Lanthanides Metals 6A Li 132.9054 137.33 138.9055 178.49 180.9479 183.85 186.207 87 104 105 106 107 89 88 5A Transition metal groups 39.0983 40.078 44.9559 37 38 39 4A 6.941 11 22.98977 24.305 19 20 3A (284) Po At Rn 207.2 208.9804 114 115 Bi (209) 116 (210) 117 (222) 118 (289) (292) (293) (294) (288) 58 59 60 61 62 63 64 65 66 67 68 69 70 71 Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu 140.12 140.9077 144.24 90 91 92 Th Pa U (145) 93 Np 232.0381 231.0399 238.0289 237.048 150.36 151.965 157.25 158.9254 162.50 164.9304 167.26 168.9342 173.04 174.967 103 94 95 96 97 98 99 100 101 102 Pu Am Cm Bk Cf Es Fm Md No Lr (244) (243) (247) (247) (251) (252) (257) (258) (259) (262) This page intentionally left blank Fundamentals of General, Organic, and Biological Chemistry This page intentionally left blank Fundamentals of General, Organic, and Biological Chemistry Eighth Edition in SI Units John McMurry Cornell University David S Ballantine Northern Illinois University Carl A Hoeger University of California, San Diego Virginia E Peterson University of Missouri, Columbia with contributions by Sara Madsen and SI conversions by Christel Meert Hogeschool Gent Andrew Pearson Griffith University Boston Columbus Indianapolis New York San Francisco Amsterdam Cape Town Dubai London Madrid Milan Munich Paris Montréal Toronto Delhi Mexico City São Paulo Sydney Hong Kong Seoul Singapore Taipei Tokyo Editor-in-Chief: Jeanne Zalesky Senior Acquisitions Editor: Chris Hess / Scott Dustan Assistant Acquisitions Editor, Global Editions: Aditee Agarwal Director of Development: Jennifer Hart Product Marketing Manager: Elizabeth Ellsworth Development Editor: Coleen Morrison Program Manager: Sarah Shefveland Project Manager: Beth Sweeten Assistant Project Editor, Global Editions: Aurko Mitra Senior Media Producer: Jackie Jacob Media Production Manager, Global Editions: Vikram Kumar Permissions Project Manager: William Opaluch Permissions Specialist: Christina Simpson, QBS Learning Program Management Team Lead: Kristen Flatham Project Management Team Lead: David Zielonka Senior Manufacturing Controller, Global Editions: Trudy Kimber Production Management: Andrea Stefanowicz, Lumina Datamatics, Inc Design Manager: Mark Ong Interior Designer: Tamara Newnam Cover Designer: Lumina Datamatics, Inc Illustrators: Lachina Photo Researcher: Eric Shrader Operations Specialist: Maura Zaldivar-Garcia Cover Photo Credit: Triff/Shutterstock Acknowledgements of third-party content appear on page 957, which constitutes an extension of this copyright page PEARSON, ALWAYS LEARNING and Pearson Mastering Chemistry are exclusive trademarks in the U.S and/or other countries owned by Pearson Education, Inc or its affiliates Pearson Education Limited Edinburgh Gate Harlow Essex CM20 2JE England and Associated Companies throughout the world Visit us on the World Wide Web at: www.pearsonglobaleditions.com © Pearson Education Limited 2018 The rights of John E McMurry, David S Ballantine, Carl A Hoeger, and Virginia E Peterson to be identified as the authors of this work have been asserted by them in accordance with the Copyright, Designs and Patents Act 1988 Authorized adaptation from the United States edition, entitled Fundamentals of General, Organic, and Biological Chemistry, 8th Edition, ISBN 978-0-13-401518-7, by John E McMurry, David S Ballantine, Carl A Hoeger, and Virginia E Peterson published by Pearson Education © 2018 All rights reserved No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without either the prior written permission of the publisher or a license permitting restricted copying in the United Kingdom issued by the Copyright Licensing Agency Ltd, Saffron House, 6–10 Kirby Street, London EC1N 8TS All trademarks used herein are the property of their respective owners The use of any trademark in this text does not vest in the author or publisher any trademark ownership rights in such trademarks, nor does the use of such trademarks imply any affiliation with or endorsement of this book by such owners British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library 10 ISBN 10: 1-292-12346-X ISBN 13: 978-1-292-12346-2 Typeset by Lumina Datamatics, Inc Printed and bound in Malaysia About the Authors John McMurry, educated at Harvard and Columbia, has taught approximately 17,000 students in general and organic chemistry over a 30-year period A professor of chemistry at Cornell University since 1980, Dr McMurry previously spent 13 years on the faculty at the University of California at Santa Cruz He has received numerous awards, including the Alfred P Sloan Fellowship (1969–1971), the National Institute of Health Career Development Award (1975–1980), the Alexander von Humboldt Senior Scientist Award (1986–1987), and the Max Planck Research Award (1991) David S Ballantine received his B.S in Chemistry in 1977 from the College of William and Mary in Williamsburg, VA, and his Ph.D in Chemistry in 1983 from the University of Maryland at College Park After several years as a researcher at the Naval Research Labs in Washington, DC, he joined the faculty in the Department of Chemistry and Biochemistry of Northern Illinois University, where he has been a professor since 1989 He was awarded the Excellence in Undergraduate Teaching Award in 1998 Since then, he has served as the coordinator for the Introductory and General Chemistry programs, with responsibilities for supervision of supervising the laboratory teaching assistants He served as the departmental director of undergraduate studies from 2008 to 2014 and is currently the associate dean for undergraduate affairs in the College of Liberal Arts and Sciences He continues to teach in the Department of Chemistry and Biochemistry Carl A Hoeger received his B.S in Chemistry from San Diego State University and his Ph.D in Organic Chemistry from the University of Wisconsin–Madison in 1983 After a postdoctoral stint at the University of California–Riverside, he joined the Peptide Biology Laboratory at the Salk Institute in 1985, where he supervised the NIH Peptide Facility while doing basic research in the development of peptide agonists and antagonists During this time, he also taught general, organic, and biochemistry at San Diego City College, Palomar College, and Miramar College He joined the teaching faculty at University of California–San Diego (UCSD) in 1998 Dr Hoeger has been teaching chemistry to undergraduates for 30 years, where he continues to explore the use of technology in the classroom; his current project involves the use of video podcasts as adjuncts to live lectures, along with the use of tablets to deliver real-time lectures with slide annotations In 2004, he won the Barbara and Paul Saltman Distinguished Teaching Award from UCSD He is deeply involved with both the general and organic chemistry programs at UCSD and has shared partial responsibility for the training and guidance of teaching assistants and new instructors in the Chemistry and Biochemistry department About the Authors Virginia E Peterson received her B.S in Chemistry in 1967 from the University of Washington in Seattle and her Ph.D in Biochemistry in 1980 from the University of Maryland at College Park Between her undergraduate and graduate years, she worked in lipid, diabetes, and heart disease research at Stanford University Following her Ph.D., she took a position in the Biochemistry Department at the University of Missouri in Columbia and is now professor emerita When she retired in 2011, she had been the director of undergraduate advising for the department for years and had taught both senior capstone classes and biochemistry classes for nonscience majors Although retired, Dr Peterson continues to advise undergraduates and teach classes Awards include both the college-level and the university-wide Excellence in Teaching Award and, in 2006, the University’s Outstanding Advisor Award and the State of Missouri Outstanding University Advisor Award Dr Peterson believes in public service and in 2003 received the Silver Beaver Award for service from the Boy Scouts of America In retirement, she continues her public service activities by participating in a first-year medical student mentoring program and her more than 25-year commitment to the Boy Scouts of America as an active adult volunteer Sara K Madsen received her B.S in Chemistry at Central Washington University in Ellensburg, Washington, in 1988 and her Ph.D in Inorganic Chemistry at the University of Wyoming in 1998 She has been teaching since 2001 The beginning of her teaching career started with a one-semester survey course and moved from there to courses in general, organic, and biochemistry, general chemistry, organic and inorganic chemistry for undergraduates, and inorganic chemistry for graduate students She loves helping students develop the connections between ideas and concepts and, above all, exposing their realization about how chemistry is involved in their program of study or professional path Brief Contents Features 16 Preface 18 Matter and Measurements 34 Atoms and the Periodic Table 76 Ionic Compounds 106 17 Carboxylic Acids and Their Derivatives 556 18 Amino Acids and Proteins 588 19 Enzymes and Vitamins 624 Molecular Compounds 134 20 Carbohydrates 660 Classification and Balancing of Chemical Reactions 170 21 The Generation of Biochemical Energy 692 Chemical Reactions: Mole and Mass Relationships 196 22 Carbohydrate Metabolism 724 23 Lipids 748 24 Lipid Metabolism 774 25 Protein and Amino Acid Metabolism 796 26 Nucleic Acids and Protein Synthesis 814 27 Genomics 840 28 Chemical Messengers: Hormones, Neurotransmitters, and Drugs 858 29 Body Fluids 882 10 11 Chemical Reactions: Energy, Rates, and Equilibrium 218 Gases, Liquids, and Solids 250 Solutions 288 Acids And Bases 324 Nuclear Chemistry 362 12 Introduction to Organic Chemistry: Alkanes 390 13 Alkenes, Alkynes, and Aromatic Compounds 436 14 Some Compounds with Oxygen, Sulfur, or a Halogen 474 15 Aldehydes and Ketones 508 16 Amines 536 Appendices 905 Answers to Selected Problems 911 Glossary 949 Credits 957 Index 959 www.downloadslide.net Additional Problems (c) H (d) O CH2OH C C O 689 20.43 What generalization can you make about the direction and degree of rotation of light by enantiomers? REACTIONS OF CARBOHYDRATES (SECTIONS 20.3, 20.4, AND 20.5) H C OH HO C H HO C H HO C H 20.44 What does the term reducing sugar mean? H C OH OH 20.45 What structural property makes a sugar a reducing sugar? C H CH2OH Xylose CH2OH Tagatose 20.32 How many chiral carbon atoms are present in each of the molecules shown in Problem 20.31? 20.33 How many chiral carbon atoms are there in each of the two parts of the repeating unit in heparin (p 684)? What is the total number of chiral carbon atoms in the repeating unit? 20.46 What is mutarotation? Do all chiral molecules this? 20.47 What are anomers, and how the anomers of a given sugar differ from each other? 20.48 What is the structural difference between the a hemiacetal form of a carbohydrate and the b form? 20.49 d-Gulose, an aldohexose isomer of glucose, has the cyclic structure shown here Which is shown, the a form or the b form? CH2OH 20.34 Draw the open-chain structure of a ketoheptose 20.35 Draw the open-chain structure of a 4-carbon deoxy sugar O OH 20.36 Name four important monosaccharides and tell where each occurs in nature OH 20.37 Name a common use for each monosaccharide listed in Problem 20.36 OH OH D-Gulose HANDEDNESS IN CARBOHYDRATES (SECTION 20.2) 20.38 How are enantiomers related to each other? 20.39 What is the structural relationship between L-glucose and d-glucose? 20.40 Only three stereoisomers are possible for 2,3-dibromo-2, 3-dichlorobutane Draw them, indicating which pair are enantiomers (optical isomers) Why does the other isomer not have an enantiomer? 20.41 In Section 15.6, you saw that aldehydes react with reducing agents to yield primary alcohols 1RCH “ O ¡ RCH2OH2 The structures of two d-aldotetroses are shown One of them can be reduced to yield a chiral product, but the other yields an achiral product Explain H O H C O C H C OH HO C H H C OH H C OH CH2OH D-Erythrose CH2OH D-Threose 20.42 Sucrose and d-glucose rotate plane-polarized light to the right; d-fructose rotates light to the left When sucrose is hydrolyzed, the glucose–fructose mixture rotates light to the left (a) What does this indicate about the relative degrees of rotation of light of glucose and fructose? (b) Why you think the mixture is called “invert sugar”? 20.50 In its open-chain form, d-mannose, an aldohexose found in orange peels, has the structure shown here Coil mannose around and draw it in the cyclic hemiacetal a and b forms HO H H H OH OH O C C C C C H OH OH H H C H D-Mannose 20.51 In its open-chain form, d-altrose has the structure shown here Coil altrose around and draw it in the cyclic hemiacetal a and b forms HO H H H H OH O C C C C C H OH OH OH H C H D-Altrose 20.52 Treatment of d-glucose with a reducing agent yields sorbitol, a substance used as a sugar substitute by people with diabetes Draw the structure of sorbitol 20.53 Reduction of d-fructose with a reducing agent yields a mixture of d-sorbitol along with a second, isomeric product What is the structure of the second product? 20.54 Treatment of an aldose with an oxidizing agent such as Tollens’ reagent (Section 15.5) yields a carboxylic acid Gluconic acid, the product of glucose oxidation, is used as its magnesium salt for the treatment of magnesium deficiency Draw the structure of gluconic acid www.downloadslide.net 690 CHAPTER 20 Carbohydrates 20.55 Oxidation of the aldehyde group of ribose yields a carboxylic acid Draw the structure of ribonic acid 20.56 What is the structural difference between a hemiacetal and an acetal? 20.57 What are glycosides, and how can they be formed? 20.58 Look at the open-chain form of d-mannose (Problem 20.50) and draw the two glycosidic products that you expect to obtain by reacting d-mannose with methanol 20.67 Does gentiobiose (Problem 20.66) have an acetal grouping? A hemiacetal grouping? Do you expect gentiobiose to be a reducing or nonreducing sugar? How would you classify the linkage (a or b and carbon numbers) between the two monosaccharides? 20.68 Trehalose, a disaccharide found in the blood of insects, has the following structure What simple sugars would you obtain on hydrolysis of trehalose? (Hint: Rotate one of the rings in your head or redraw it rotated.) 20.59 Draw a disaccharide of two cyclic mannose molecules attached by an a-1,4 glycosidic linkage Explain why the glycosidic products in Problem 20.58 are not reducing sugars, but the product in this problem is a reducing sugar CH2OH O CH2OH OH O OH DISACCHARIDES AND POLYSACCHARIDES (SECTIONS 20.6 AND 20.7) 20.61 Lactose and maltose are reducing disaccharides, but sucrose is a nonreducing disaccharide Explain 20.62 Amylose (a form of starch) and cellulose are both polymers of glucose What is the main structural difference between them? What roles these two polymers have in nature? 20.63 How are amylose and amylopectin similar to each other, and how are they different from each other? 20.64 Which of the following is not a use for cellulose? lumber for building fodder for cattle raw material for computer chips fabric for t-shirts (a) ice cream (b) french fries (c) a chocolate milkshake CH2 O O OH OH OH OH OH Gentiobiose OH Trehalose 20.69 Does trehalose (Problem 20.68) have an acetal grouping? A hemiacetal grouping? Do you expect trehalose to be a reducing or nonreducing sugar? Classify the linkage between the two monosaccharides 20.70 Amylopectin (a form of starch) and glycogen are both a-linked polymers of glucose What is the structural difference between them? 20.71 What is the physiological purpose of starch in a seed or other plant tissue? What is the physiological purpose of glycogen in a mammal? 20.73 What is the function of heparin, hyaluronate, and chondroitin-6-sulfate? ConCEPtuAl ProBlEMS 20.66 Gentiobiose, a rare disaccharide found in saffron, has the following structure What simple sugars you obtain on hydrolysis of gentiobiose? O OH 20.72 What modified sugars makeup heparin, hyaluronate, and chondroitin-6-sulfate? 20.65 Which of the following foods can someone who has lactose intolerance eat? CH2OH OH OH 20.60 Give the names of three important disaccharides Tell where each occurs in nature From which two monosaccharides is each made? (a) (b) (c) (d) O OH OH 20.74 Are the a and b forms of monosaccharides enantiomers of each other? Why or why not? 20.75 Are the a and b forms of the disaccharide lactose enantiomers of each other? Why or why not? 20.76 d-Fructose can form a six-membered cyclic hemiacetal as well as the more prevalent five-membered cyclic form Draw the a isomer of d-fructose in the six-membered ring 20.77 Raffinose, found in sugar beets, is the most prevalent trisaccharide It is formed by an a-1,6 linkage of d-galactose to the glucose portion of sucrose Draw the structure of raffinose www.downloadslide.net Group Problems 20.78 Write the open-chain structure of the only ketotriose Name this compound and explain why it has no optical isomers 20.79 Write the open-chain structure of the only ketotetrose Name this compound Does it have an optical isomer? 20.80 What is lactose intolerance, and what are its symptoms? 20.81 What is the group of disorders that result when the body lacks an enzyme necessary to digest galactose? What are the symptoms? 20.82 When a person cannot digest galactose, its reduced form, called dulcitol, often accumulates in the blood and tissues Write the structure of the open-chain form of dulcitol Does dulcitol have an enantiomer? Why or why not? 20.83 Describe the differences between mono-, di-, and polysaccharides 20.84 Name a naturally occurring carbohydrate and its source for each type of carbohydrate listed in Problem 20.83 20.85 Compare and contrast lactose intolerance with galactosemia (Hint: Make a table.) 691 grouP ProBlEMS 20.86 Many people who are lactose intolerant can eat yogurt, which is prepared from milk curdled by bacteria, without any digestive problems Give a reason why this is possible (Hint: Read the label on each of several yogurt containers Do the ingredients make a difference?) 20.87 Carbohydrates provide 16.7 kJ per gram If a person eats 200 g per day of digestible carbohydrates, what percentage of an 8350 kJ daily diet would be digestible carbohydrate? 20.88 A 33 cL can of cherry-flavored cola contains 42 grams of sugar If sugar provides 16.7 kJ per gram, how many kilojoules are in one can of cola? 20.89 Explain why cotton fibers, which are nearly pure cellulose, are insoluble in water, while glycogen, another polymer of glucose, will dissolve in water www.downloadslide.net 21 The Generation of Biochemical Energy CONTENTS 21.1 Energy, Life, and Biochemical Reactions 21.2 Cells and Their Structure 21.3 An Overview of Metabolism and Energy Production 21.4 Strategies of Metabolism: ATP and Energy Transfer 21.5 Strategies of Metabolism: Metabolic Pathways and Coupled Reactions 21.6 Strategies of Metabolism: Oxidized and Reduced Coenzymes 21.7 The Citric Acid Cycle 21.8 The Electron-Transport Chain and ATP Production CONCEPTS TO REVIEW A Oxidation-Reduction Reactions (Sections 5.5 and 5.6) B Energy in Chemical Reactions (Sections 7.2 and 7.4) C Enzymes (Sections 19.1 and 19.4) ▲ Exercise routines like this require the constant generation of large amounts of biological energy, the topic of this chapter J asmine, 22, was enthusiastic about bodybuilding and how it improved her self-confidence After a year of training and following advice on dietary supplements from older bodybuilders, Jasmine prepared for competition by sculpting Sculpting involves losing fat to emphasize muscles and requires dieting After several weeks of dieting, Jasmine turned to diet pills recommended by others at the training gym to try to speed up her results Unsatisfied with her slow fat loss, Jasmine doubled the daily dose of the diet pills 692 www.downloadslide.net Several hours later she collapsed and was unresponsive When she arrived at the emergency room (ER), Jasmine’s body temperature was 41 °C (314 K) and rising In her possession were diet pills containing dinitrophenol, a known toxic substance with dangerous side effects We’ll learn more about dinitrophenol (or DNP) later in the chapter in the Chemistry in Action “Metabolic Poisons” on page 717 All organisms obtain energy from their surroundings to stay alive In animals, the energy comes from food and is released through the exquisitely interconnected reaction pathways of metabolism We are powered by the oxidation of biomolecules made mainly of carbon, hydrogen, and oxygen The end products are carbon dioxide, water, and energy C, H, O 1food molecules2 + O2 ¡ CO2 + H2O + Energy The principal food molecules—lipids, proteins, and carbohydrates—differ in structure and are broken down by individual pathways that are examined in later chapters The product of these individual pathways, usually acetyl coenzyme A, enters the central final pathways that yield usable energy In this chapter, we are going to concentrate on these final common pathways that release energy from all types of food molecules 21.1 Energy, Life, and Biochemical Reactions Learning Objectives: • Identify energy sources and our specific requirements for energy regulation • Explain the significance of exergonic and endergonic reactions in metabolism Living things must mechanical work—microorganisms engulf food, plants bend toward the sun, and humans walk about Organisms must the chemical work of synthesizing the biomolecules needed for energy storage, growth, repair, and replacement In addition, cells need energy for the work of moving molecules and ions across cell membranes In humans, it is the energy released from food that allows this work to be done Energy can be converted from one form to another but can be neither created nor destroyed (see Section 7.2) Ultimately, the energy used by all but a few living things comes from the sun (Figure 21.1) Plants convert sunlight to potential energy stored mainly in the chemical bonds of carbohydrates Plant-eating animals utilize this energy, some of it for immediate needs and the rest to be stored for future needs, mainly in the chemical bonds of fats Other animals, including humans, are able to eat plants or animals and use the chemical energy these organisms have stored Sun Chemical synthesis A + B + energy Solar energy Work Transport across membrane AB Mechanical work Chemical energy Plants — photosynthesis ▲ Animals— release of chemical energy in catabolism Heat Lost to Maintain + body temperature surroundings Figure 21.1 The flow of energy through the biosphere Energy from the sun is ultimately stored in chemical bonds, used for cellular or mechanical work, used to maintain body temperature, or lost as heat 693 www.downloadslide.net 694 CHAPTER 21 The Generation of Biochemical Energy Our bodies not produce energy by burning up a meal all at once because the release of a large quantity of energy (primarily as heat) would be harmful to us Furthermore, it is difficult to capture energy for storage once it has been converted to heat We need energy that can be stored and then released in the right amounts when and where it is needed, whether we are jogging, studying, or sleeping We, therefore, have some specific requirements for energy • • • • • Energy must be released from food gradually Energy must be stored in readily accessible forms as glycogen and fat (triacylglycerides) Release of energy from storage must be finely controlled so that it is available exactly when and where it is needed Just enough energy must be released as heat to maintain constant body temperature Energy in a form other than heat must be available to drive chemical reactions that are not favorable at body temperatures This chapter looks at some of the ways these requirements for energy regulation are met We begin by reviewing basic concepts about energy and then learn about metabolism Next, we look at the citric acid cycle and oxidative phosphorylation, which together form the common pathway for the production of energy Biochemical reactions ConCEPtS to rEViEW Review entropy, enthalpy, endergonic, exergonic, and free-energy change in Sections 7.2–7.4 Chemical reactions either release or absorb energy Whether a reaction is favorable or not depends on either the release or absorption of energy as heat (the change in enthalpy, ∆H), together with the increase or decrease in disorder (∆S, the entropy change) caused by the reaction The net effect of these changes is given by the free-energy change of a reaction: ∆G = ∆H - T∆S Reactions in living organisms are no different from reactions in a chemistry laboratory Both follow the same laws, and both have the same energy requirements Spontaneous reactions—that is, those that are favorable in the forward direction—release free energy, and the energy released is available to work Such reactions, described as exergonic, are the source of our biochemical energy As shown by the energy diagram in Figure 7.3 the products of a favorable, exergonic reaction are farther downhill on the energy scale than the reactants That is, the products are more stable than the reactants, and as a result the free-energy change ∆G2 has a negative value Oxidation reactions, for example, are usually downhill reactions that release energy Oxidation of glucose, the principal source of energy for animals, produces 2870 kJ of free energy per mole of glucose C6H12O6 + O2 ¡ CO2 + H2O ∆G = - 2870 kJ>mol The greater the amount of free energy released, the farther a reaction proceeds toward product formation before reaching equilibrium Reactions in which the products are higher in energy than the reactants can also take place, but such unfavorable reactions cannot occur without the input of energy from an external source; such reactions are endergonic The free-energy change switches sign for the reverse of a reaction, but the value does not change Photosynthesis, the process whereby plants convert CO2 and H2O to glucose and O2, is the reverse of the oxidation of glucose Its ∆G is therefore positive and equal to the value for the oxidation of glucose (see the Chemistry in Action “Plants and Photosynthesis” on p 696) The sun provides the necessary external energy for photosynthesis (2870 kJ>mol of glucose formed) www.downloadslide.net SECTION 21.1 Photosynthesis 6CO2 + 6H2O Energy, Life, and Biochemical Reactions 695 ∆G = + 2870 kJ/mol (endergonic, energy required) C6H12O6 + 6O2 Oxidation ∆G = −2870 kJ/mol (exergonic, energy released) Living systems make constant use of this principle in the series of chemical reactions we know as the biochemical pathways Energy is stored in the products of an overall endergonic reaction pathway This stored energy is released as needed in an overall exergonic reaction pathway that regenerates the original reactants It is not necessary that every reaction in the pathways between the reactants and products be the same, so long as the pathways connect the same reactants and products Pathway A series of enzymecatalyzed chemical reactions that are connected by their intermediates, that is, the product of the first reaction is the reactant for the second reaction, and so on Worked Example 21.1 Determining Reaction Energy Are the following reactions exergonic or endergonic? (a) Glucose 6@phosphate S Fructose 6@phosphate ∆G = + 2.09 kJ>mol (b) Fructose 6@phosphate + ATP S Fructose 1,6@bisphosphate + ADP ∆G = - 14.2 kJ>mol AnAlySiS Exergonic reactions release free energy, and ∆G is negative Endergonic reactions gain free energy, and so ∆G is positive Solution Reaction (a), the conversion of glucose 6-phosphate to fructose 6-phosphate has a positive ∆G; therefore, it is endergonic Reaction (b), the conversion of fructose 6-phosphate to fructose 1,6-bisphosphate has a negative ∆G; therefore it is exergonic KEy ConCEPt ProBlEM 21.1 In a cell, glucose can be oxidized via metabolic pathways Alternatively, you could burn glucose in the laboratory Which of these methods consumes or produces more energy? (Hint: All of the energy comes from converting the energy stored in the reduced bonds in glucose into the most oxidized form, carbon dioxide.) KEy ConCEPt ProBlEM 21.2 The overall equation in this section, 6CO2 + 6H2O photosynthesis oxidation C6H12O6 + 6O2, shows the cycle between photosynthesis and oxidation Pathways operating in opposite directions cannot be exergonic in both directions (a) Which of the two pathways in this cycle is exergonic and which is endergonic? (b) Where does the energy for the endergonic pathway come from? www.downloadslide.net 696 CHAPTER 21 The Generation of Biochemical Energy CHEMiStry in ACtion Plants and Photosynthesis The principal biochemical difference between humans and plants is that plants derive energy directly from sunlight and we cannot In the process of photosynthesis, plants use solar energy to synthesize oxygen and energy-rich carbohydrates from energy-poor reactants: CO2 and water Our metabolism breaks down energy-rich reactants to extract the useful energy and produce energy-poor products: CO2 and water Is it surprising to discover that despite this difference in the direction of their reactions, plants rely on biochemical pathways very much like our own? The energy-capturing phase of photosynthesis takes place mainly in green leaves Plant cells contain chloroplasts, which, though larger and more complex in structure, resemble mitochondria Embedded in membranes within the chloroplasts are large groups of chlorophyll molecules and the enzymes of an electron-transport chain Chlorophyll is similar in structure to heme but contains magnesium ions 1Mg2+ instead of iron ions 1Fe2+ As solar energy is absorbed, chlorophyll molecules pass it along to specialized reaction centers, where it is used to boost the energy of electrons The excited electrons then give up their extra energy as they pass down a pair of electron-transport chains Some of this energy is used to oxidize water, splitting it into oxygen, hydrogen ions, and electrons (which replace those entering the electron-transport chain) At the end of the chain, the hydrogen ions, together with the electrons, are used to reduce NADP+ to NADPH Along the way, part of the energy of the electrons is used to pump hydrogen ions across a membrane to create a concentration gradient As in mitochondria, the hydrogen ions can only return across the membrane at enzyme complexes that convert ADP to ATP Water needed for these light-dependent reactions enters the plant through the roots and leaves, and the oxygen that is formed is released through openings in the leaves The energy-carrying ATP and NADPH enter the fluid interior of the chloroplasts Here their energy is used to drive the synthesis of carbohydrate molecules So long as ATP and NADPH are available, this part of photosynthesis is light-independent—it can proceed in the absence of sunlight Plants have mitochondria as well as chloroplasts, so they can also carry out the release of energy from stored carbohydrates Because the breakdown of carbohydrates continues in many harvested fruits and vegetables, the goal in storage is to slow it down Refrigeration is one measure that is taken, since (like most chemical reactions) the rate of respiration decreases at lower temperatures Another is replacement of air over stored fruits and vegetables with carbon dioxide or nitrogen These flowers are converting the potential energy of the sun into chemical potential energy stored in the bonds of carbohydrates ▲ H2O LIGHT-DEPENDENT REACTIONS Depleted carriers (ADP, NADP+) Glucose ▲ O2 Energized carriers (ATP, NADPH) LIGHT-INDEPENDENT REACTIONS CO2 + H2O The coupled reactions of photosynthesis CiA Problem 21.1 Chlorophyll is similar in structure to heme in red blood cells but does not have an iron atom What metal ion is present in chlorophyll? CiA Problem 21.2 Photosynthesis consists of both light-dependent and light-independent reactions What is the purpose of each type of reaction? CiA Problem 21.3 One step of the cycle that incorporates CO2 into glyceraldehyde in plants is the production of two 3-phosphoglycerates ∆G = - 3.5 kJ>mol for this reaction Is this process endergonic or exergonic? CiA Problem 21.4 What general process does refrigeration of harvested fruits and vegetables slow? What cellular processes are slowed by refrigeration? www.downloadslide.net SECTION 21.2 Cells and Their Structure 697 21.2 Cells and Their Structure Learning Objective: • Describe the eukaryotic cell and explain the function of each structure Before learning about metabolism, it is important to see where the energy-generating reactions take place within the cells of living organisms There are two main categories of cells: prokaryotic cells, found in single-celled organisms (e.g., bacteria and bluegreen algae), and eukaryotic cells, found in some single-celled organisms, such as yeast, and all plants and animals Eukaryotic cells are about 1000 times larger than bacterial cells, have a membraneenclosed nucleus that contains their deoxyribonucleic acid (DNA), and include several other kinds of internal structures known as organelles—small, functional units that perform specialized tasks A generalized eukaryotic cell is shown in Figure 21.2 with short descriptions of the functions of some of its major parts Everything between the cell membrane and the nuclear membrane in a eukaryotic cell, including the various organelles, is the cytoplasm The organelles are surrounded by the fluid part of the cytoplasm, the cytosol, which contains electrolytes, nutrients, and many enzymes, all in aqueous solution Cytoplasm The region between the cell membrane and the nuclear membrane in a eukaryotic cell Cytosol The fluid part of the cytoplasm surrounding the organelles within a cell, contains dissolved proteins and nutrients Cilia (movement of materials) Microvilli (absorption of extracellular substances) Cytosol (intracellular fluid) Mitochondrion (synthesis of ATP) Nucleus (replication of DNA) Golgi apparatus (synthesis of macromolecules) Smooth endoplasmic reticulum (synthesis of lipids and carbohydrates) Rough endoplasmic reticulum (protein synthesis and transport) Lysosome (breakdown of unwanted molecules and cellular components) Ribosomes (protein synthesis) Cell membrane (separates cell contents from exterior; permits exchange of molecules with exterior fluid and delivers signals to interior) ▲ Figure 21.2 A generalized eukaryotic cell Major cell components are labeled with a description of their primary function The mitochondria (singular, mitochondrion), often called the cell’s “power plants,” are the most important of the organelles for energy production and produce about 90% of the body’s energy-carrying molecule, ATP A mitochondrion is a roughly egg-shaped structure composed of a smooth outer membrane and a folded inner membrane (Figure 21.3) The space enclosed by the inner membrane is the mitochondrial matrix Within the matrix, the citric acid cycle (Section 21.7) and production of most of the body’s adenosine triphosphate (ATP) take place The coenzymes and proteins that manage the transfer of energy to the chemical bonds of ATP (Section 21.8) are embedded in the inner membrane of the mitochondrion Mitochondrion (plural, mitochondria) An egg-shaped organelle where small molecules are broken down to provide the energy for an organism Mitochondrial matrix The space surrounded by the inner membrane of a mitochondrion Adenosine triphosphate (ATP) The principal energy-carrying molecule, removal of a phosphoryl group to give ADP releases free energy www.downloadslide.net 698 CHAPTER 21 The Generation of Biochemical Energy Intermembrane space Outer membrane ATP Inner membrane O2 CO2 Glucose, O2, ADP, HOPO32− Matrix CO2 Citric acid cycle ATP Mitochondrion ATP synthase enzymes— sites of ATP production Matrix Enzymes ADP+ and phosphate coenzymes of cristae H Cristae ▲ Figure 21.3 The mitochondrion Cells have many mitochondria The citric acid cycle takes place in the matrix Electron transport and ATP production, the final stage in biochemical energy generation (described in Section 21.8), take place at the inner surface of the inner membrane The numerous folds in the inner membrane—known as cristae—increase the surface area over which these pathways can take place Mitochondria contain their own DNA, synthesize some of their own proteins, and multiply using chemicals moved from the cell cytosol into the mitochondrial matrix The number of mitochondria is greatest in eye, brain, heart, and muscle cells, where the need for energy is greatest The ability of mitochondria to reproduce is seen in athletes who put heavy energy demands on their bodies—they develop an increased number of mitochondria to aid in energy production 21.3 An Overview of Metabolism and Energy Production Learning Objective: • List the stages in catabolism of food and describe the role of each stage Metabolism The sum of all of the chemical reactions that take place in an organism Together, all of the chemical reactions that take place in an organism constitute its metabolism Most of these reactions occur in the reaction sequences of metabolic pathways, a sequence of reactions where the product of one reaction serves as the starting material for the next Such pathways may be linear (a series of reactions that convert a reactant into a specific product through a series of intermediate molecules and reactions), cyclic (a series of reactions that regenerates one of the first reactants), or spiral (the same set of enzymes progressively builds up or breaks down a molecule) A linear sequence A Enzyme Enzyme C Enzyme A Enzyme A cyclic sequence B A D Enzyme Enzyme B C Enzyme A spiral sequence Enzymes Enzymes Enzymes B C Final product Catabolism Metabolic reaction pathways that break down food molecules and release biochemical energy As we study metabolism we will encounter each of these types of pathways Those pathways that break molecules apart are known collectively as catabolism, whereas those that put building blocks back together to assemble larger molecules are known www.downloadslide.net SECTION 21.3 An Overview of Metabolism and Energy Production collectively as anabolism The purpose of catabolism is to release energy from food, and the purpose of anabolism is to synthesize new biomolecules, including those that store energy 699 Anabolism Metabolic reactions that build larger biological molecules from smaller pieces CATABOLISM + Energy Smaller molecules Larger molecules A N A B O L IS M The overall picture of digestion, catabolism, and energy production is simple: eating provides fuel, breathing provides oxygen, and our bodies oxidize the fuel to extract energy The process can be roughly divided into the four stages described here and shown in Figure 21.4 StAgE 1: Digestion Enzymes in saliva, the stomach, and the small intestine convert the large molecules of carbohydrates, proteins, and lipids to smaller molecules Carbohydrates are broken down to glucose and other sugars; proteins are broken down to amino acids; and triacylglycerols, the lipids commonly known as fats and oils, are broken down to glycerol plus long-chain carboxylic acids, termed fatty acids These smaller molecules are transferred into the blood for transport to cells throughout the body StAgE 2: Acetyl-coenzyme A production The small molecules from digestion follow separate pathways that separate their carbon atoms into two-carbon acetyl groups The acetyl groups are attached to coenzyme A by a high-energy bond between the sulfur atom of the thiol ¬ SH2 group at the end of the coenzyme A molecule and the carbonyl carbon atom of the acetyl group See the chemical structure of coenzyme A in Figure 19.10 Acetyl-coenzyme A (acetyl-CoA) Acetyl-substituted coenzyme A—the common intermediate that carries acetyl groups into the citric acid cycle Acetyl group Attachment of acetyl group to coenzyme A Acetyl group CH3 O C S [Coenzyme A] The resultant compound, acetyl-coenzyme A, which is abbreviated acetyl-CoA, is an intermediate in the breakdown of all classes of food molecules It carries the acetyl groups into the common pathways of catabolism—Stage 3, the citric acid cycle and Stage 4, electron transport and ATP production StAgE 3: Citric acid cycle Within mitochondria, the acetyl-group carbon atoms are oxidized to the carbon dioxide that we exhale Most of the energy released in the oxidation leaves the citric acid cycle in the chemical bonds of reduced coenzymes (NADH, FADH2) Some energy also leaves the cycle stored in the chemical bonds of ATP or a related triphosphate StAgE 4: ATP production Electrons from the reduced coenzymes are passed from molecule to molecule down an electron-transport chain Along the way, their energy is harnessed to produce more ATP At the end of the process, these electrons—along with hydrogen ions from the reduced coenzymes—combine with oxygen we breathe in to produce water Thus, the reduced coenzymes are in effect oxidized by atmospheric oxygen, and the energy that they carried is stored in the chemical bonds of ATP molecules Acetyl-coenzyme A looKing AHEAD Digestion and conversion of food molecules to acetylCoA, Stages and in Figure 21.4, occur by different metabolic pathways for carbohydrates, lipids, and proteins Each of these pathways is discussed separately in later chapters: carbohydrate metabolism in Chapter 22, lipid metabolism in Chapter 24, and protein metabolism in Chapter 25 www.downloadslide.net 700 CHAPTER 21 The Generation of Biochemical Energy ▶ Figure 21.4 Pathways for the digestion of food and the production of biochemical energy This diagram summarizes pathways covered in this chapter (the citric acid cycle and electron transport) and also the pathways discussed in Chapter 22 for carbohydrate metabolism, in Chapter 24 for lipid metabolism, and in Chapter 25 for protein metabolism FOOD LIPIDS Stage Digestion Bulk food is digested in the mouth, stomach, and small intestine to yield Fatty acids small molecules and glycerol CARBOHYDRATES PROTEINS Glucose and other sugars Amino acids Glycolysis Amino acid catabolism Fatty acid oxidation ATP Stage Acetyl-CoA Production Sugar and amino acid molecules are degraded in the cytoplasm of cells to yield acetyl-CoA Fatty acid molecules are degraded in the mitochondria of cells to yield acetyl-CoA Stage Citric Acid Cycle Acetyl-CoA is oxidized inside mitochondria by the citric acid cycle to yield CO2 and reduced coenzymes Pyruvate Acetyl-CoA Citric acid cycle CO2 ATP REDUCED COENZYMES Stage ATP Production The energy transferred to the reduced coenzymes in stage is used to make ATP by the coupled pathways of electron transport and oxidative phosphorylation Electron transport chain ATP O2 H2O Worked Example 21.2 Identifying Metabolic Pathways That Convert Basic Molecules to Energy (a) In Figure 21.4, identify the stages in the catabolic pathway in which lipids ultimately yield ATP (b) In Figure 21.4, identify the place at which the products of lipid catabolism can join the common metabolism pathway AnAlySiS Look at Figure 21.4 and find the pathway for lipids Follow the arrows to trace the flow of energy Note that Stage is the point at which the products of lipid, carbohydrate, and protein catabolism all feed into a central, common metabolic pathway, the citric acid cycle The lipid molecules that feed into Stage so via acetyl-CoA (Stage 2) Note also that most products of Stage catabolism feed into Stage catabolism to produce ATP Solution The lipids in food are broken down in Stage (digestion) to fatty acids and glycerol Stage (acetyl-CoA production) results in fatty acid oxidation to acetyl-CoA In Stage (citric acid cycle), acetyl-CoA enters the citric acid cycle (the common metabolism pathway), which produces ATP, reduced coenzymes, and CO2 In Stage (ATP production), the energy stored in the reduced coenzymes (from the citric acid cycle) is converted to ATP energy www.downloadslide.net SECTION 21.4 Strategies of Metabolism: ATP and Energy Transfer ProBlEM 21.3 (a) In Figure 21.4, identify the stages in the pathway for the conversion of the energy from carbohydrates to energy stored in ATP molecules (b) In Figure 21.4, identify the three places at which the products of amino acid catabolism can join the central metabolism pathway 21.4 Strategies of Metabolism: ATP and Energy Transfer Learning Objective: • Describe the role of ATP in energy transfer ATP is the body’s energy-transporting molecule What exactly does that mean? Consider that the molecule has three ¬ PO3- groups Adenosine NH2 Triphosphate group O − O P O − P O − O O Bond broken in hydrolysis to ADP N O O P O CH2 − O N O OH N N OH Adenosine triphosphate (ATP) Removal of the terminal ¬ PO3 - group from ATP by hydrolysis gives adenosine diphosphate (ADP) The ATP S ADP reaction is exergonic; it releases chemical energy that was held in the bond to the ¬ PO32- group ATP + H2O ¡ ADP + HOPO32- + H + ∆G = - 30.5 kJ>mol The reverse of ATP hydrolysis—a phosphorylation reaction—is endergonic ADP + HOPO32- + H + ¡ ATP + H2O ∆G = + 30.5 kJ>mol (In equations for biochemical reactions, we represent ATP and other energycarrying molecules in red and their lower-energy equivalent molecules in blue.) ATP is an energy transporter because its production from ADP requires an input of energy that is released when the reverse reaction occurs Biochemical energy is gathered from exergonic reactions and stored in the bonds of the ATP molecule ATP hydrolysis releases energy for energy-requiring work Biochemical energy production, transport, and use, all depend upon the ATP ÷ ADP interconversion P P P O Adenosine ATP Energy from food Energy for work ADP Phosphate P P O Adenosine Phosphate The hydrolysis of ATP to give ADP and its reverse, the phosphorylation of ADP, are reactions perfectly suited to their role in metabolism for two major reasons Firstly, ATP hydrolysis occurs slowly in the absence of a catalyst, so the stored energy is released only in the presence of the appropriate enzymes 701 www.downloadslide.net 702 CHAPTER 21 The Generation of Biochemical Energy Secondly, the free energy of hydrolysis of ATP is an intermediate value for energy carriers (Table 21.1) Since the primary metabolic function of ATP is to transport energy, it is often referred to as a “high-energy” molecule or as containing “high-energy” phosphorus–oxygen bonds These terms are misleading because they promote the idea that ATP is somehow different from other compounds The terms mean only that ATP is reactive and that a useful amount of energy is released when a phosphoryl group is removed from it by hydrolysis table 21.1  Free Energies of Hydrolysis of Some Phosphates O R O P O O2 H2O ROH HO O2 O2 P ∆G 1kJ>mol2 O2 Compound Name Function Phosphoenol pyruvate Final intermediate in conversion of glucose to pyruvate (glycolysis)— Stage 2, Figure 21.5 1, 3-Bisphosphoglycerate Another intermediate in glycolysis - 49.4 Energy storage in muscle cells - 43.1 Principal energy carrier - 30.5 Glucose 1-phosphate First intermediate in breakdown of carbohydrates stored as starch or glycogen - 20.9 Glucose 6-phosphate First intermediate in glycolysis - 13.8 Fructose 6-phosphate Second intermediate in glycolysis - 13.8 ATP ¡ ADP2 Creatine phosphate - 61.9 In fact, if removal of a phosphoryl group from ATP released unusually large amounts of energy, other reactions would not be able to provide enough energy to convert ADP back to ATP ATP is a convenient energy carrier in metabolism because its free energy of hydrolysis has an intermediate value among high energy carriers For this reason, the phosphorylation of ADP can be driven by coupling this reaction with a more exergonic reaction ProBlEM 21.4 Acetyl phosphate, whose structure is given here, is another compound with a relatively high free energy of hydrolysis O O CH3 C O P O− O− Using structural formulas, write the equation for the hydrolysis of this phosphate ProBlEM 21.5 A common metabolic strategy is the lack of reactivity—that is, the slowness to react— of compounds whose breakdown is exergonic For example, hydrolysis of ATP to ADP or adenosine monophosphate (AMP) is exergonic but does not take place without an appropriate enzyme present Why would the cell use this metabolic strategy? www.downloadslide.net Strategies of Metabolism: Metabolic Pathways and Coupled Reactions SECTION 21.5 703 CHEMiStry in ACtion Harmful Oxygen Species and Antioxidant Vitamins Inflammation Radiation High pO2 Smog (O3 , NO2) More than 90% of the oxygen we breathe is used in electron-transport– Reactive Normal Injured oxygen species O2 ATP synthesis reactions In these and metabolism cell (⋅O2−, H2O2, ⋅OH−) other O consuming reactions, the product can be water or one of these Chemicals Aging oxygen-containing free radicals: the and superoxide ion 1# O2 - 2, the hydroxyl Reperfusion drugs injury free radical 1# OH- 2, and hydrogen peroxide, H2O2, a relatively strong oxiOur protection against ROS is provided by superoxide disdizer These three species are dangerous to cells; the superoxmutase (converts the superoxide ion to hydrogen peroxide) ide ion is beneficial in destroying infectious microorganisms and catalase (converts hydrogen peroxide to water), which are In what is known as a “respiratory burst,” phagocytes (cells among the fastest-acting enzymes (see Section 19.1) Other that engulf bacteria) produce superoxide ions that react deenzymes in cells also provide some protection; however, cerstructively with bacteria tain vitamins, such as vitamins E, C, and A (or its precursor + + # b@carotene), function as antioxidants as well These molecules O2 + NADPH ¡ O2 + NADP + H disarm free radicals by bonding with them (see Section 19.9) Reactive oxygen species (ROS) are dangerous to our own Vitamin E is fat-soluble, and its major function is to protect cells, especially since most ROS are produced in mitochoncell membranes from potential damage initiated when a cell dria where they can disrupt energy production ROS can break membrane lipid (RH) is converted to an oxygen-containing free covalent bonds in enzymes and other proteins, DNA, and the radical ROO # Because Vitamin C is water-soluble, it is a freelipids in cell membranes causing cell injury or death Among radical scavenger in the blood There are also many other natuthe possible outcomes of such destruction are cancer, liver ral antioxidants among the chemical compounds distributed in damage, rheumatoid arthritis, heart disease, immune system fruits and vegetables damage, and possibly the changes regarded as normal aging CiA Problem 21.5 Which of the following are ROS? Internal processes such as inflammation and drug ingestion (a) H2O (b) H2O2 (c) ROO # (d) # OHand external influences like radiation and smog, including CiA Problem 21.6 How does a cell disarm each of the ROS in CIA second-hand cigarette smoke, all produce these ROS in our Problem 21.5? What enzymes and vitamins are involved? bodies 21.5 Strategies of Metabolism: Metabolic Pathways and Coupled Reactions Learning Objective: • Explain why some reactions are coupled and give an example of a coupled reaction How is stored chemical energy gradually released and how is it used to drive endergonic (uphill) reactions? Remember that your body cannot burn up the energy obtained from consuming a meal all at once As shown in Figure 7.3, however, the energy difference between a reactant (the meal) and the ultimate products of its catabolism (mainly carbon dioxide and water) is a fixed quantity The same amount of energy is released no matter what pathway is taken between reactants and products The metabolic pathways of catabolism take advantage of this fact by releasing energy bit by bit in a series of reactions, somewhat like the stepwise release of potential energy as water flows down an elaborate waterfall The overall reaction and the overall free-energy change for any series of reactions can be found by summing up the equations and the free-energy changes for the individual steps For example, glucose is converted to pyruvate via the 10 reactions of the glycolysis pathway (part of Stage 2, Figure 21.4, and Section 22.3) The overall free-energy change for glycolysis is about - 33.5 kJ>mol, showing This waterfall illustrates a stepwise release of potential energy No matter what the pathway from the top to the bottom, the amount of potential energy released as the water falls from the top to the very bottom is the same ▲ ... 16 Preface 18 1. 1 1. 2 1. 3 1. 4 1. 5 1. 6 1. 7 1. 8 1. 9 1. 10 1. 11 1 .12 2 .1 2.2 2.3 2.4 2.5 2.6 2.7 10 Matter and Measurements 34 Chemistry: The Central Science 35 HANDS-ON CHEMISTRY 1. 1 37 States of. .. Body: Acidosis and Alkalosis 355 11 Nuclear Chemistry 362 11 .1 11. 2 11 .3 11 .4 11 .5 11 .6 11 .7 11 .8 11 .9 Nuclear Reactions 363 The Discovery and Nature of Radioactivity 364 Stable and Unstable Isotopes... 11 8. 710 12 1.757 12 7.60 12 6.9045 13 1.29 81 82 85 86 84 83 Pb 19 5.08 19 6.9665 200.59 204.383 11 0 11 2 11 3 11 1 (2 61) Actinides Metalloids 1B He Sc Lanthanides Metals 6A Li 13 2.9054 13 7.33 13 8.9055 17 8.49