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BU BIOL 118 - lecture 150211

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Pop quiz today Chapter 8 1 and 8 2 METABOLISM Two types of energy 1 Kinetic a energy of motion b Molecular level thermal energy heat or light c Ex Electrons falling to a lower energy shell 2 Potential energy a Energy of position or configuration b Molecular level chemical energy i Stored in the position of the electron ii If an electron is close to negative charges of other electrons and far from positive charges of nuclei potential energy is high because negative charges repel each other iii Outermost electron shell has highest potential energy iv Can move shells in fluorescence and release a photon energy Laws of Thermodynamics control reactions 1 Energy is conserved cannot be created or destroyed can only be transferred or transformed mass is technically energy a you cannot have more energy in the products than the reactants b energy will always be lost in a reaction so no reaction will be perfectly efficient theoretically perfect efficiency happens at absolute zero 0Kelvin but at that point everything is dead so do you really want perfect efficiency c everything takes energy even after you die your body will still be involved in chemical reactions 2 Chemical reactions involve such energy transformations 3 Entropy always increases in general physical and chemical processes proceed in the direction that results in lower potential energy enthalpy and increased disorder entropy which together are measured by free energy 4 Free energy G amount of energy available to do work a G is the change in free energy and it determines whether a reaction is spontaneous happens randomly or not requires energy to start b Combined contribution in heat content chemical potential energy and disorder of the system entropy as well as the overall temperature Formula g H T s c If the G of the products is lower than the G of the reactants then the reaction is spontaneous G 0 d If the G of the products is higher than the G of the reactants then the reaction is NOT spontaneous G 0 e Endergonic requires energy f Exergonic produces energy doesn t need any because it has extra Enthalpy measure of the total energy of a molecule involves Potential energy Pressure and volume H is the charge in enthalpy always do products reactants 1 Entropy S measure of disorder of a system S change in entropy S 0 then it s an endergonic reaction In the body energy can be released and then used to form ATP QUESTION EXPLAIN WHY THE SAME RXN CAN BE NON SPONTANEOUS AT ONE TEMPERATURE AND SPONTANEOUS AT ANOTHER high temperature molecules are moving around more and have more energy so the reactants will have more energy at a high temperature At a higher temperature there is more energy in the system so the system is more disorderly and the free energy changes At a low temperature molecules don t move much and have low energy so they need extra to start a reaction EXPLAIN WHY SOME EXOTHERMIC REACTIONS ARE NON SPONATEOUS some reactions require energy to get started and then release heat when they are done STATE WHEN THE OVERALL FREE ENERGY CHANGE IN A REATION IS MOST LIKELY TO BE NEGATIVE free energy change will be negative when a reaction is spontaneous the reactants had more energy than the products The reaction will probably be endothermic Non spontaneous reactions in cells are started in two ways transfer of high energy electrons Transfer of phosphate groups


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BU BIOL 118 - lecture 150211

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