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UNC-Chapel Hill EXSS 376 - Exam 1 Study Guide

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EXSS 376 1nd EditionExam #1BioenergeticsImportance- Identifying the predominant SOURCES required for a particular sport or activity provides the basis for an effective and INDIVUDALIZED exercise training programEnergy- 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 thermodynamicso 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 reactionso 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 bodyCoupled Reactions- The energy given off by the exergonic reaction POWERS the endergonic reactionFactors 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 reactionso Substrate (reactant) + enzyme => productEnzymes- 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 formationLock-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 ASEFactors that alter Enzymes- temperature: individual enzymes have optimum temperature at which they are most activeo normal body temp: enzyme activity is LESS than maxo exercise body temp: enzyme activity OPTIMALo bioenergetics is ENHANCED (INCREASED rate of reactions) during exercise- pH levels: individual enzymes have optimum pH at which they are most activeo average pH levels in arterial blood ~7.45o during intense exercise, skeletal muscles produce large amounts of H+ ionsATP- ADENOSINE TRIPHOSPHATE: cells energy CURRENCY- Special carrier for free energy and provides required energy for all cellular functions- HIGH ENERGY BONDS – stored energy- ATP hydrolysiso Catabolism of 1 molecule of ATPo ATP + H2O <= ATPase => ADP + P + H+ + energyo This reaction generates considerable energy rapidly, which is why we refer to ATPas a high-energy phosphate compound- However…o Body only has LIMITED STORED quantity of ATP 80-100g (3.5 oz.) of ATPo because cells need constant supply of ATP, must be RESYNTHESIZED continuallyBIOLOGICAL ENERGY SYSTEMS- three energy systems used to replenish ATPo phosphagen occurs in SARCOPLASM anaerobic energy systemo glycolysis occurs in SARCOPLASM anaerobic energy systemo 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 rateo secondary: DURATIONPhosphagen 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 glycolysiso 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 go blood glucose: 3-5 go liver glycogen: 75-100 gBig Picture- phase 1: energy investment phaseo 5 enzymatically controlled reactionso ATP are USED- Phase 2: energy generation phaseo 5 enzymatically controlled reactionso ATP and NADH + H are PRODUCEDo PYRUVATE or LACTATE is formedReduction 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 nucleuso Molecule that loses H atom also loses an ELECTRON- Coenzymes: derivatives of vitaminso Transport electrons => CARRIER MOLECULESo 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 FADH2Glycolysis- Phase 1: energy investment phase- ATP primingo 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 CELLo Blood glucose needs 2 ATP to trap it in the muscle cell via phosphorylation- Phase 2: energy generation phaseo 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 PRODUCEDo 3PG – h2o = PEPo ADP removes PHOSPHATE group from PEPo ATP PRODUCEDo Pyruvate is end producto If oxygen is available, pyruvate enters KREBS CYCLE for further


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