EXSS 376 1nd Edition Exam 1 Bioenergetics Importance Identifying the predominant SOURCES required for a particular sport or activity provides the basis for an effective and INDIVUDALIZED exercise training program Energy Food is necessary to provide ENERGY that is essential for all cellular activity Energy is the capacity to do WORK Movement of the human body work represents MECHANICAL energy that is supported by the CHEMICAL energy derived from food fuels First law of thermodynamics o Energy cannot be created nor destroyed rather it is TRANSFERRED from one form to another without being depleted Bioenergetics FLOW of energy in a living system Energy transfer occurs as a result of a series of chemical reactions o Exergonic ENERGY RELEASING reactions generally catabolic reactions breakdown o Endergonic ENERGY CONSUMING reactions generally anabolic reactions formation Metabolism total of all chemical reactions that occur in the cells of the body Coupled Reactions The energy given off by the exergonic reaction POWERS the endergonic reaction Factors Affecting Bioenergetics Exercise INTESITY ultimately depends on the RATE that cells extract conserve and transfer the chemical energy in food nutrients to contractile elements of skeletal muscle Enzymes CATALYSTS affect the RATE of energy release during chemical reactions o Substrate reactant enzyme product Enzymes Chemical reactions occur when substrates reactants have sufficient energy to initiate chemical reactions ACTIVATION ENERGY Enzymes work as catalysts by LOWERING activation energy Decrease activation energy increase speed of chemical reactions increase rate of product formation Lock and Key Model of Enzyme Action Substrate sucrose approaches active site on enzyme Substrate fits into active site forming enzyme substrate COMPLEX SPECIFIC to that substrate Enzyme releases products glucose and fructose Enzyme does NOT cause reaction to occur just regulates rate Enzymes does NOT change nature of the reaction or its final result PRODUCTS w few exceptions i e pepsin all enzyme names end with suffix ASE Factors that alter Enzymes temperature individual enzymes have optimum temperature at which they are most active o normal body temp enzyme activity is LESS than max o exercise body temp enzyme activity OPTIMAL o bioenergetics is ENHANCED INCREASED rate of reactions during exercise pH levels individual enzymes have optimum pH at which they are most active o average pH levels in arterial blood 7 45 o during intense exercise skeletal muscles produce large amounts of H ions ATP ADENOSINE TRIPHOSPHATE cells energy CURRENCY Special carrier for free energy and provides required energy for all cellular functions HIGH ENERGY BONDS stored energy ATP hydrolysis o Catabolism of 1 molecule of ATP o ATP H2O ATPase ADP P H energy o This reaction generates considerable energy rapidly which is why we refer to ATP as a high energy phosphate compound However o Body only has LIMITED STORED quantity of ATP 80 100g 3 5 oz of ATP o because cells need constant supply of ATP must be RESYNTHESIZED continually BIOLOGICAL ENERGY SYSTEMS three energy systems used to replenish ATP o phosphagen occurs in SARCOPLASM anaerobic energy system o glycolysis occurs in SARCOPLASM anaerobic energy system o oxidative occurs in MITOCHONDRIA aerobic energy system all energy systems active at any given time extent of their contribution depends on o primary INTENSITY power output work rate o secondary DURATION Phosphagen System RAPIDLY replenishes ATP stores Provides ATP primarily for short term high intensity activities 5 sec Active at start of EXERCISE regardless of intensity ADP CP H creatine kinase ATP creatine Skeletal muscle concentrations of CP are 4 6 times greater than ATP concentrations Still limited amounts Another important SINGLE enzyme reaction that rapidly replenishes ATP is myokinase reaction AMP a product of myokinase reaction is a powerful STIMULANT of glycolysis o 2ADP ATP AMP Glycolysis anaerobic glycolysis is a second metabolic pathway capable of producing ATP RAPIDLY WITHOUT involvement of O2 substrates glycolysis involves breakdown of glucose or GLYCOGEN resynthesis glycolysis involves series of enzymatically CATALYZED or COUPLED reactions that transfer bond energy from glucose to rejoin P to ADP glucose glycogen storage o muscle glycogen 300 400 g o blood glucose 3 5 g o liver glycogen 75 100 g Big Picture phase 1 energy investment phase o 5 enzymatically controlled reactions o ATP are USED Phase 2 energy generation phase o 5 enzymatically controlled reactions o ATP and NADH H are PRODUCED o PYRUVATE or LACTATE is formed Reduction reactions Oxidation and reduction always coupled together Oxidation loss of electrons Reduction gain of electrons Oxidation and reduction reactions often transfer hydrogen atoms rather than just FREE electrons WHY o Hydrogen contains 1 electron and 1 proton in nucleus o Molecule that loses H atom also loses an ELECTRON Coenzymes derivatives of vitamins o Transport electrons CARRIER MOLECULES o Nicotinamide adenine dinucleotide NAD Derived from vitamin B3 NAD NADH H o Flavin adenine dinucleotide FAD Derived from vitamin B2 FAD FADH2 When NAD reacts w 2 H it binds to one of them and ACCEPTS the electron from the other to form NADH H When FAD reacts with 2 H it binds to BOTH of them to form FADH2 Glycolysis Phase 1 energy investment phase ATP priming o 2 ATP USED for PHOSPHORYLATION addition of phosphate groups glucose PHOSPHORYLATED via ATP glucose G6P REARRANGEMENT G6P fructose 6 phosphate Fructose 6 phosphate is PHOSPHORYLATED via ATP fructose 1 6 biphosphate 6 carbon molecule is SPLIT into 2 3 carbon molecules what happens if glycolysis begins with glycogen o If glycolysis begins with glycogen only ONE ATP required Uses Pi WITHIN THE CELL o Blood glucose needs 2 ATP to trap it in the muscle cell via phosphorylation Phase 2 energy generation phase o 4 total ATP are produced 2 for each separate reaction o G3P is OXIDIZED NAD REDUCED BPG 1 3 biphosphoglycerate NADH and H o ADP removes PHOSPHATE group from BPG 3PG o ATP PRODUCED o 3PG h2o PEP o ADP removes PHOSPHATE group from PEP o ATP PRODUCED o Pyruvate is end product o If oxygen is available pyruvate enters KREBS CYCLE for further breakdown Big Picture Anaerobic glycolysis yields o 2 NET ATP starting w glucose o 3 NET ATP starting w glycogen Glycolysis NAD NADH must be converted back to NAD o If sufficient O2 available HYDROGENS from NADH H are shuttled into mitochondria from