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Chapter 3 Bioenergetics Objectives • Discuss the function of cell membrane, nucleus, & mitochondria • Define: endergonic, exergonic, coupled reactions & bioenergetics • Describe how enzymes work • Discuss nutrients used for energy • Identify high-energy phosphates Objectives • Discuss anaerobic & aerobic production of ATP • Describe how metabolic pathways are regulated • Discuss the interaction of anaerobic & aerobic ATP production during exercise • Identify the rate limiting enzymes 1 Metabolism • Total of all chemical reactions that occur in the body • Bioenergetics Cell Structure • Cell membrane • Nucleus • Cytoplasm Structure of a Typical Cell 2 Cellular Chemical Reactions • Endergonic reactions • Exergonic reactions • Coupled reactions The Breakdown of Glucose: An Exergonic Reaction Coupled Reactions 3 Enzymes • Catalysts that regulate the speed of reactions • Factors that regulate enzyme activity • Interact with specific substrates Enzyme-Substrate Interaction Fuels for Exercise • CHO • Fats • PRO 4 High-Energy Phosphates • Adenosine triphosphate (ATP) • Formation • Breakdown Structure of ATP Model of ATP as the Universal Energy Donor 5 Bioenergetics • Formation of ATP • Anaerobic pathways • Aerobic pathways Anaerobic ATP Production • ATP-PC system PC + ADP Creatine kinase ATP + C • Glycolysis – Energy investment phase – Energy generation phase The Two Phases of Glycolysis 6 Glycolysis: Energy Investment Phase Glycolysis: Energy Generation Phase Oxidation-Reduction Reactions • Oxidation • Reduction • Nicotinomide adenine dinucleotide (NAD) NAD + 2H+ → NADH + H+ • Flavin adenine dinucleotide (FAD) FAD + 2H+ → FADH2 7 Production of Lactic Acid • Normally, O2 is available in the mitochondria to accept H+ (and e-) from NADH produced in glycolysis • H+ & e- from NADH are accepted by pyruvic acid to form lactic acid Conversion of Pyruvic Acid to Lactic Acid Aerobic ATP Production • Krebs cycle (citric acid cycle) • Electron transport chain (ETC) 8 The Three Stages of Oxidative Phosphorylation The Krebs Cycle Relationship b/n the Metabolism of Proteins, Fats & Carbohydrates 9 Formation of ATP in the ETC The Chemiosmotic Hypothesis of ATP Formation • ETC chain results in pumping of H+ ions across inner mitochondrial membrane • Energy released to form ATP as H+ diffuse back across the mb The Chemiosmotic Hypothesis of ATP Formation 10 Aerobic ATP Tally Metabolic Process High-Energy Products ATP from Oxidative ATP Subtotal Phosphorylation Glycolysis 2 ATP 2 NADH — 6 2 (if anaerobic) 8 (if aerobic) Pyruvic acid to acetyl-CoA 2 NADH 6 14 Krebs cycle — 18 4 16 34 38 2 GTP 6 NADH 2 FADH Grand Total 38 Efficiency of Oxidative Phosphorylation • Aerobic metabolism of 1 molecule of glu • Aerobic metabolism of 1 molecule of glycogen • Overall efficiency of aerobic respiration is 40% Control of Bioenergetics • Rate-limiting enzymes • Levels of ATP and ADP+Pi • Calcium may stimulate aerobic ATP production 11 Action of Rate-Limiting Enzymes Control of Metabolic Pathways Pathway Rate-Limiting Enzyme Stimulators Inhibitors ATP-PC system Creatine kinase ADP ATP Glycolysis Phosphofructokinase AMP, ADP, Pi, ↑pH ATP, CP, citrate, ↓pH Krebs cycle Isocitrate dehydrogenase ADP, Ca++, NAD ATP, NADH ATP Electron transport Cytochrome Oxidase ADP, Pi chain Control of Bioenergetics Glycogen ATP-PC System PC + ADP C + ATP Glucose 1 Glucose 6-phosphate Glycerol Triglycerides 2 Phosphoglyceraldehyde Glycolysis Pyruvic Acid Lactic Acid β-ox Acetyl CoA Fatty acids Ketone bodies C4 Kreb’s Cycle 3 Amino Acids C6 C5 Proteins Urea NADH FADH ETS 4 12 Interaction b/n Aerobic & Anaerobic ATP Production • Energy to perform exercise comes from an interaction b/n aerobic & anaerobic pathways • Effect of duration & intensity – Short-term, high-intensity activities – Long-term, low to moderate-intensity exercise β-Oxidation A Closer Look - 3.4 13 β-Oxidation β-Oxidation • Long chain FA • Activated FA Î acetyl-CoA 4 Steps to β-Oxidation • Step 1: FA Î Activated FA • Step 2: Oxidization of activated FA Î fatty acetylCoA • Step 3: fatty acetyl-CoA Î β-hydroxyl acetyl-CoA • Step 4: β-hydroxyl acetyl-CoA Î Activated FA + Acetyl CoA 14 β-Oxidation • Example: Palmate (Palmitic acid) synthesis C16H32O2 C-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C 1 2 3 4 5 6 7 β-Oxidation • • • • • • • Total ATP Tally = Palmitic Acid 1 ATP investment (activation of FA) β-oxidization = 5 ATP (1 NADH + H+; 1FADH2) 1 Acetyl-CoA molecule enters Krebs Cycle 1ATP 3 NADH + H+ ………ETC = 9 ATP 1 FADH2…………….ETC = 2 ATP β-Oxidation • TOTAL ATP generation = Palmitic Acid 15 Play it again Sam… • How about Stearic Acid (C18H36O2) • β-Oxidization Î (18/2)-1 = 8 turns – ATP investment = 1 ATP – 1 NADH + H+; 1FADH2 • • • • x 8 turns = 40 ATP -1 = 39 ATP 9 Acetyl-CoA molecules enter into Krebs Cycle 9 ATP 3 NADH + H+ x 9 turns = 81 ATP in ETC 1 FADH2 x 9 turns = 18 ATP in ETC Total ATP Production = 147 ATP Bottom Line… But is it Efficient? 16 Hey Fatty, remember me? • Recall this term What about the glycerol backbone? • Converted to 3-phosphoglyceraldehyde (glycolysis) 17