Chapter 6 Energy Enzymes Metabolism I Metabolism A Organisms need a source of energy a source of carbon Fig 6 1 Sum of all chemical reactions in a cell organism II Energy A system s capacity to do work A Can be converted between forms ex potential kinetic 1 When energy changes forms it s conserved but less is available for work because of loss to entropy i e heat usually B Molecules contain potential energy 1 Electrons farther from the nucleus have more potential energy 2 Ex ATP contains potential energy because of clustering of 3 negative O charges III Chemical Reactions A Reactions have direction rate processes in which molecules are transformed B H G T S 1 Energy concentration of reactants drive direction rate 1 H G TS a H enthalpy total energy b G free energy FE usable energy for work c T Temperature d S entropy or unusable energy 2 G H TS 3 G H T S C Exergonic vs Endergonic Reactions 1 G H T S 2 G 0 exergonic reaction spontaneous free energy released a Spontaneous reaction that occur without an input of free energy i May occur very slowly at a given temperature ii Reaction rate kinetics is in depended of reaction spontaneity b ATP Hydrolysis ATP ADP P is exergonic i G 7kcal mol 3 G 0 endergonic reaction NOT spontaneous requires input of free energy 4 Cells couple exergonic endergonic reactions to push the endergonic reaction forward a Energy from the exergonic reaction is used to drive the endergonic one D Catabolism Anabolism 1 Catabolic reactions pathways break down molecules store energy in molecules ex ATP synthesis 2 Anabolic reactions use energy to build molecules IV Enzymes A Usually proteins B Big compared to reactant molecules C Catalyze reactions D Specific to substrates E Energy diagram Reaction process vs Free energy 1 Transition state highest energy state peak F How enzymes decrease activation energy 1 Reactants change shape when they bind with enzyme which strains bond energy a Easier to remove molecules needed for reaction ex ATP ADP P 2 Reactants are close together a Some enzymes bind to both reactants needed for a reaction increasing the likelihood that the reactants will contact each other V Metabolic Pathway A Each step is typically catalyzed by a single enzyme a coordinated series of chemical reactions
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