Energy Metabolism PDF

Energy Metabolism Fundamentals of Sport and Exercise Science PSA020 Dr Laura A. Barrett Objectives 1. Discuss the biochemical pathways involved in anaerobic ATP production 2. Discuss the aerobic production of ATP 3. Discuss the interaction between aerobic and anaerobic ATP produc...

Energy Metabolism Fundamentals of Sport and Exercise Science PSA020 Dr Laura A. Barrett Objectives 1. Discuss the biochemical pathways involved in anaerobic ATP production 2. Discuss the aerobic production of ATP 3. Discuss the interaction between aerobic and anaerobic ATP production during exercise 6. Identify the enzymes that are considered rate limiting in glycolysis and the Krebs cycle Energy release from food food sources are broken down to be used by our cells Energy is transferred from food sources to ATP via phosphorylation ATP is a high-energy compound for storing and conserving energy ATP stores in the muscle are limited and therefore must be continuously re-synthesised to maintain physical activity  High-Energy Phosphates High-Energy Phosphates Adenosine triphosphate (ATP) – Consists of adenine, ribose, and three linked phosphates Synthesis ADP + Pi ATP Breakdown ATP ATPase ADP + Pi + Energy  Bioenergetics Bioenergetics Formation of ATP – Phosphocreatine (PC) breakdown – Degradation of glucose and glycogen  Glycolysis – Oxidative formation of ATP Anaerobic pathways – Do not involve O2 – PC breakdown and glycolysis Aerobic pathways – Require O2 – Oxidative phosphorylation  Bioenergetics Anaerobic ATP Production Phosphocreatine system (ATP-PC system) – Immediate source of ATP PC + ADP ATP + C Creatine kinase Glycolysis – Glucose 2 pyruvic acid or 2 lactic acid – Energy investment phase  Requires 2 ATP – Energy generation phase  Produces 4 ATP, 2 NADH, and 2 pyruvate or 2 lactate Regulates rate whole pathway proceeds Substrate Level Phosphorylation Net Gain of 2 ATP Molecules Efficiency of Glycolysis – 30%  Glycolysis only yields 5% of ATP from glucose breakdown – so why bother? RAPID transfer of energy Net gain of 3 ATP  Aerobic Anaerobic Glycolysis? Glycolysis?  Bioenergetics Hydrogen and Electron Carrier Molecules Transport hydrogens and associated electrons – To mitochondria for ATP generation (aerobic) – To convert pyruvic acid to lactic acid (anaerobic) Nicotinamide adenine dinucleotide (NAD) NAD + 2H+ NADH + H+ Flavin adenine dinucleotide (FAD) FAD + 2H+ FADH2  Bioenergetics NADH is “Shuttled” into Mitochondria NADH produced in glycolysis must be converted back to NAD – By converting pyruvic acid to lactic acid – By “shuttling” H+ into the mitochondria A specific transport system shuttles H+ across the mitochondrial membrane – Located in the mitochondrial membrane The Krebs Cycle  2 molecules of pyruvate from one glucose molecule Substrate Level Phosphorylation  Electron transport chain http://highered.mheducation.com/sites/0072507470/student_view0/chapter25/animation__electron_transp ort_system_and_atp_synthesis__quiz_1_.html  Bioenergetics Aerobic ATP Production Electron transport chain – Oxidative phosphorylation occurs in the mitochondria – Electrons removed from NADH and FADH are passed along a series of carriers (cytochromes) to produce ATP  Each NADH produces 2.5 ATP  Each FADH produces 1.5 ATP – H+ from NADH and FADH are accepted by O2 to form water  02 02 0 Simplified ETC 02 0 2 2 02 02 NAD+ C1 C2 C3 C4 NADH E E E E H2 O  Stops 02 02 0 being oxidised Simplified ETC 0 02 2 02 02 2 NAD+ C1 C2 C3 C4 NADH E E E E NADH NADH NADH NADH NADH Backs up H2 O C4 cannot be oxidised Accumulate  The Krebs Cycle - Summary Anaerobic reactions of glycolysis release only about 5% of energy in glucose molecule – need another means of extracting remaining potential energy Also known as “critic acid” or “tricarboxylic acid (TCA) cycle” Occurs in the mitochondrion matrix Pyruvate is irreversibly converted to a form of acetic acid called acetyl-CoA  The Krebs Cycle - Summary Main function to degrade acetyl-CoA substrate to CO2 and hydrogen atoms Hydrogen atoms then oxidized in electron transport- oxidative phosphorylation - ATP subsequently regenerated The most important function of the Krebs cycle is the generation of electrons (hydrogens) for transfer to the electron transport chain by means of NAD+ and in one instance FAD  Bioenergetics Relationship Between the Metabolism of Proteins, Carbohydrates, and Fats Figure 3.19  Control of Bioenergetics Control of Bioenergetics Rate-limiting enzymes – An enzyme that regulates the rate of a metabolic pathway Modulators of rate-limiting enzymes – Levels of ATP and ADP+Pi  High levels of ATP inhibit ATP production  Low levels of ATP and high levels of ADP+Pi stimulate ATP production – Calcium may stimulate aerobic ATP production  Control of Bioenergetics Factors Known to Affect Rate-Limiting Enzymes  Interaction Between Aerobic/Anaerobic ATP Production Interaction Between Aerobic/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 Contribution of Aerobic /Anaerobic ATP Production During Sporting Events  Aerobic exercise? Anaerobic exercise? Example Exam Questions 1. Where do glycolysis, the Krebs cycle, and oxidative phosphorylation take place in the cell? 2. Define the terms glycogen, glycogenolysis, and glycolysis. 3. What are the high-energy phosphates? 4. Define the terms aerobic and anaerobic. 5. Briefly discuss the function of glycolysis in energy production. What role does NAD play in glycolysis? Example Exam Questions 6. Discuss the operation of the Krebs cycle and the electron transport chain in the aerobic production of ATP. What is the function of NAD and FAD in these pathways? 7. What is the efficiency of the aerobic degradation of glucose? 8. What is the role of oxygen in aerobic metabolism? 9. What are the rate-limiting enzymes for the following metabolic pathways: ATP-PC system, glycolysis, Krebs cycle, and electron transport chain? 10. Briefly discuss the interaction of anaerobic versus aerobic ATP production during exercise.