Week 2 Exb 110 2010 color

Week 2 Exb 110 2010 color - EXERCISE METABOLISM EXB 110...

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Unformatted text preview: EXERCISE METABOLISM EXB 110 Energy Systems and Bioenergetics Bioenergetics Refers to flow of energy in living systems 1 st law of thermodynamics states that energy can be transformed but not created or destroyed 2 nd law states that energy transformations increase entropy (=degree of disorganization of a system) Only free energy (energy in organized state) can be used to do work Systems tend to go from states of higher free energy to states of lower free energy Bioenergetics 2nd law dictates that all living organisms require continued input of energy Plants obtain this from sunlight Use it to make high free energy glucose mols from CO 2 and H 2 O mols that have less free energy (more entropy) we use energy in glucose to combat entropy and power our bodies Endergonic and Exergonic Reactions Endergonic reactions require input of energy to proceed Products contain more free energy than reactants Exergonic reactions release energy as they proceed Products contain less free energy than reactants Coupled Reactions: ATP Cells require constant inputs of free energy from environment to buck entropy and remain highly organized Do this by coupling endergonic reactions to exergonic reactions An exergonic reaction breaks down ATP- the universal energy carrier Most exergonic reactions in body make ATP ATP Oxidation-Reduction If a molecule gains electrons it is reduced If it loses electrons it is oxidized A reducing agent donates electrons An oxidizing agent accepts electrons Reduction and oxidation are always coupled reactions Coenzymes that play important roles as H carriers are NAD and FAD These are also vitamins Oxidation-Reduction Are contractile units of skeletal muscle consisting of components between 2 Z discs M l i n e s are structural proteins that anchor myosin during contraction Titin is elastic protein attaching myosin to Z disc that contributes to elastic recoil of muscle Sarcomeres Muscle Contraction Sliding Filament Theory of Contraction Muscle contracts because myofibrils get shorter Occurs because thin filaments slide over and between thick filaments towards center Shortening distance from Z disc to Z disc Sliding Filament Theory of Contraction During contraction: A bands (containing actin) move closer together, do not shorten I bands shorten because they define distance between A bands of successive sarcomeres H bands (containing myosin) shorten Cross Bridges Are formed by heads of myosin molecules that extend toward and interact with actin Sliding of filaments is produced by actions of cross bridges Each myosin head contains an ATP-binding site which functions as an ATPase Cross Bridges Myosin cant bind to actin unless it is cocked by ATP After binding, myosin undergoes conformational change (power stroke ) which exerts force on actin After power stroke myosin detaches Control of Contraction...
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Week 2 Exb 110 2010 color - EXERCISE METABOLISM EXB 110...

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