© 2007 McGraw-Hill Higher Education. All rights reserved. Chapter 3 Bioenergetics EXERCISE PHYSIOLOGY Theory and Application to Fitness and Performance, 6 th edition Scott K. Powers & Edward T. Howley

© 2007 McGraw-Hill Higher Education. All rights reserved. Introduction Metabolism: total of all chemical reactions that occur in the body –Anabolic reactions Synthesis of molecules –Catabolic reactions Breakdown of molecules Bioenergetics –Converting foodstuffs (fats, proteins, carbohydrates) into energy

© 2007 McGraw-Hill Higher Education. All rights reserved. Objectives Discuss the function of cell membrane, nucleus, and mitochondria Define: endergonic, exergonic, coupled reactions, and bioenergetics Describe how enzymes work Discuss nutrients used for energy Identify high-energy phosphates

© 2007 McGraw-Hill Higher Education. All rights reserved. Objectives Discuss anaerobic and aerobic production of ATP Describe how metabolic pathways are regulated Discuss the interaction of anaerobic and aerobic ATP production during exercise Identify the rate limiting enzymes

© 2007 McGraw-Hill Higher Education. All rights reserved. Cell Structure Cell membrane –Protective barrier between interior of cell and extracellular fluid Nucleus –Contains genes that regulate protein synthesis Cytoplasm –Fluid portion of cell –Contains organelles (mitochondria)

© 2007 McGraw-Hill Higher Education. All rights reserved. Structure of a Typical Cell Fig 3.1

© 2007 McGraw-Hill Higher Education. All rights reserved. Cellular Chemical Reactions Endergonic reactions –Require energy to be added Exergonic reactions –Release energy Coupled reactions –Liberation of energy in an exergonic reaction drives an endergonic reaction

© 2007 McGraw-Hill Higher Education. All rights reserved. The Breakdown of Glucose: An Exergonic Reaction Fig 3.3

© 2007 McGraw-Hill Higher Education. All rights reserved. Coupled Reactions Fig 3.4

© 2007 McGraw-Hill Higher Education. All rights reserved. Oxidation-Reduction Reactions Oxidation: removing an electron Reduction: addition of an electron Oxidation and reduction are always coupled reactions In cells, often involve the transfer of hydrogen atoms rather than free electrons –Hydrogen atom contains one electron –A molecule that loses a hydrogen also loses an electron and, therefore, is oxidized

© 2007 McGraw-Hill Higher Education. All rights reserved. Enzymes Catalysts that regulate the speed of reactions –Lower the energy of activation Factors that regulate enzyme activity –Temperature –pH Interact with specific substrates –Lock and key model

© 2007 McGraw-Hill Higher Education. All rights reserved. Enzymes Lower the Energy of Activation Fig 3.6

© 2007 McGraw-Hill Higher Education. All rights reserved. Enzyme- Substrate Interaction Fig 3.7

© 2007 McGraw-Hill Higher Education. All rights reserved. Fuels for Exercise Carbohydrates –Glucose Stored as glycogen Fats –Primarily fatty acids Stored as triglycerides Proteins –Not a primary energy source during exercise

© 2007 McGraw-Hill Higher Education. All rights reserved. High-Energy Phosphates Adenosine triphosphate (ATP) –Consists of adenine, ribose, and three linked phosphates Formation Breakdown ADP + P i  ATP ADP + P i + EnergyATP ATPase

© 2007 McGraw-Hill Higher Education. All rights reserved. Structure of ATP Fig 3.8

© 2007 McGraw-Hill Higher Education. All rights reserved. Model of ATP as the Universal Energy Donor Fig 3.9

© 2007 McGraw-Hill Higher Education. All rights reserved. Bioenergetics Formation of ATP –Phosphocreatine (PC) breakdown –Degradation of glucose and glycogen (glycolysis) –Oxidative formation of ATP Anaerobic pathways –Do not involve O 2 –PC breakdown and glycolysis Aerobic pathways –Require O 2 –Oxidative phosphorylation

© 2007 McGraw-Hill Higher Education. All rights reserved. Anaerobic ATP Production ATP-PC system –Immediate source of ATP Glycolysis –Energy investment phase Requires 2 ATP –Energy generation phase Produces ATP, NADH (carrier molecule), and pyruvate or lactate PC + ADPATP + C Creatine kinase

© 2007 McGraw-Hill Higher Education. All rights reserved. The Two Phases of Glycolysis Fig 3.10

© 2007 McGraw-Hill Higher Education. All rights reserved. Glycolysis Energy Investment Phase Fig 3.11

© 2007 McGraw-Hill Higher Education. All rights reserved. Glycolysis Energy Generation Phase Fig 3.11

© 2007 McGraw-Hill Higher Education. All rights reserved. Oxidation-Reduction Reactions Oxidation –Molecule accepts electrons (along with H + ) Reduction –Molecule donates electrons Nicotinomide adenine dinucleotide (NAD) Flavin adenine dinucleotide (FAD) FAD + 2H +  FADH 2 NAD + 2H +  NADH + H +

© 2007 McGraw-Hill Higher Education. All rights reserved. Production of Lactic Acid Normally, O 2 is available in the mitochondria to accept H + (and electrons) from NADH produced in glycolysis –In anaerobic pathways, O 2 is not available H + and electrons from NADH are accepted by pyruvic acid to form lactic acid

© 2007 McGraw-Hill Higher Education. All rights reserved. Conversion of Pyruvic Acid to Lactic Acid Fig 3.12

© 2007 McGraw-Hill Higher Education. All rights reserved. Aerobic ATP Production Krebs cycle (citric acid cycle) –Completes the oxidation of substrates and produces NADH and FADH to enter the electron transport chain Electron transport chain –Oxidative phosphorylation –Electrons removed from NADH and FADH are passed along a series of carriers to produce ATP –H + from NADH and FADH are accepted by O 2 to form water

© 2007 McGraw-Hill Higher Education. All rights reserved. The Three Stages of Oxidative Phosphorylation Fig 3.13

© 2007 McGraw-Hill Higher Education. All rights reserved. The Krebs Cycle Fig 3.14

© 2007 McGraw-Hill Higher Education. All rights reserved. Relationship Between the Metabolism of Proteins, Fats, and Carbohydrates Fig 3.15

© 2007 McGraw-Hill Higher Education. All rights reserved. Electron Transport Chain Fig 3.17

© 2007 McGraw-Hill Higher Education. All rights reserved. The Chemiosmotic Hypothesis of ATP Formation Electron transport chain results in pumping of H + ions across inner mitochondrial membrane –Results in H + gradient across membrane Energy released to form ATP as H + diffuse back across the membrane

© 2007 McGraw-Hill Higher Education. All rights reserved. The Chemiosmotic Hypothesis of ATP Formation Fig 3.16

© 2007 McGraw-Hill Higher Education. All rights reserved. Aerobic ATP Tally Table ATP per NADH 1.5 APT per FADH

© 2007 McGraw-Hill Higher Education. All rights reserved. Efficiency of Oxidative Phosphorylation Aerobic metabolism of one molecule of glucose –Yields 32 ATP Aerobic metabolism of one molecule of glycogen –Yields 33 ATP Overall efficiency of aerobic respiration is 34% –66% of energy released as heat

© 2007 McGraw-Hill Higher Education. All rights reserved. Control of Bioenergetics Rate-limiting enzymes –An enzyme that regulates the rate of a metabolic pathway Levels of ATP and ADP+P i –High levels of ATP inhibit ATP production –Low levels of ATP and high levels of ADP+P i stimulate ATP production Calcium may stimulate aerobic ATP production

© 2007 McGraw-Hill Higher Education. All rights reserved. Action of Rate-Limiting Enzymes Fig 3.19

© 2007 McGraw-Hill Higher Education. All rights reserved. Control of Metabolic Pathways Table 3.2

© 2007 McGraw-Hill Higher Education. All rights reserved. Control of Bioenergetics Glycogen Glucose 6-phosphate Phosphoglyceraldehyde Pyruvic Acid Acetyl CoA Amino Acids Proteins Ketone bodies Fatty acids Triglycerides Glycerol Lactic Acid Krebs Cycle C6C6 C5C5 C4C4 Urea Glucose 2 Rate Limiting Enzymes 1. Creatine kinase 2. Phosphofructokinase 3. Iscitrate dehydrogenase 4. Cytochrome oxidase  -ox 3 ETS NADH FADH 4 Glycolysis 1 PC + ADP C + ATP ATP-PC System Table 3.2

© 2007 McGraw-Hill Higher Education. All rights reserved. Interaction Between Aerobic and Anaerobic ATP Production Energy to perform exercise comes from an interaction between aerobic and anaerobic pathways Effect of duration and intensity –Short-term, high-intensity activities Greater contribution of anaerobic energy systems –Long-term, low to moderate-intensity exercise Majority of ATP produced from aerobic sources

© 2007 McGraw-Hill Higher Education. All rights reserved. Chapter 3 Bioenergetics