BIOL 1441 1st Edition Lecture 14 Outline of Last Lecture I Metabolism a Metabolic pathways b Metabolic enzymes II Forms of energy III Laws of energy transformation IV 1st law of thermodynamics V 2nd law of thermodynamics VI Free energy Outline of Current Lecture I Exergonic Reactions II Endergonic Reactions III Equilibrium and Metabolism IV Energy Coupling a ATP V Enzymes Regulate Metabolism Current Lecture I Exergonic Reactions a Lose free energy G decreases b G is negative energy being removed These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute II III IV c Magnitude of G represents the maximum amount of work the reaction can perform d Greater the decrease in free energy greater amount of work can be done e Spontaneous catabolic f C6H12O6 6 O2 6 CO2 6 H2O i Breaking down glucose ii G 686 kcal mol iii For each mol of glucose 180 g broken down by respiration 686 kcal of energy are released that can be then used to do work Endergonic Reactions a Absorbs consumes free energy i storing free energy b G increases G is positive c Nonspontaneous anabolic d Magnitude of G is the quantity of energy required to drive the reaction e Plants use 686 kcal from sunlight to make a mol of glucose f Convert light energy into chemical energy Equilibrium and Metabolism a Reactions in a closed system eventually reach equilibrium and then do no work b Cells are not in equilibrium i Open systems experiencing a constant flow of materials c Catabolic pathway in a cell releases free energy in a series of reactions i Prevent reaching equilibrium product does not accumulate Energy Coupling a Mange energy resources to do cellular work b Use of an exergonic process to drive an endergonic one i Exergonic spontaneous release energy ii Endergonic nonspontaneous requires energy c Cellular Work i Three main kinds of work use energy 1 Mechanical beating of cilia muscle contraction 2 Transport pump substances across membrane against the concentration gradient 3 Chemical endergonic rxn s synthesis of polymers from monomers d Adenosine Triphosphate ATP i Provides energy for cellular functions ii Mediates energy coupling iii Break bonds between the phosphate groups by hydrolysis 1 Hydrolysis rxn s add water breaking apart polymers 2 Exergonic spontaneous rxn iv Terminal phosphate bond is broken energy is released from ATP v ATP High Energy Bonds V 1 Reactants ATP H2O have high energy relative to the energy of the products ADP Pi 2 Release of energy due to chemical change to a state of lower free energy a Complex structure high energy b Simple structures lower energy 3 Physical rearrangement of molecules to lower energy states vi ATP why so much energy 1 Phosphate groups negative charges 2 Crowded together repulsion B C NEGATIVE CHARGES 3 Contributes to instability more unstable higher energy vii How does ATP do work 1 Cells harness the energy released during ATP hydrolysis to perform cellular work 2 Energy released from ATP hydrolysis is used to drive endergonic rxn s nonspontaneous a Specific enzymes help 3 When endergonic rxn requires less energy than is released by ATP hydrolysis couple reactions a Coupled rxn becomes exergonic viii Coupled Rxn Exergonic 1 Transfer phosphate group from ATP to another molecule a Phosphorylation 2 Key is formation of phosphorylated intermediate more reactive less stable more energy ix Cellular Work 1 Transport mechanical ATP hydrolysis leads to a change in a protein s shape affects it ability to bind another molecule x Regeneration of ATP 1 ATP renewable resource 2 Regenerated by adding a phosphate group to ADP ATP synthase 3 Energy to phosphorylate ADP comes from catabolic reactions in the cell cellular respiration 4 ATP cycle couples exergonic processes to endergonic processes Enzymes regulate metabolism a Enzymes Rxn Rate i Spontaneous rxn s will move forward on their own exergonic rxn 1 Ex garbage in landfill 2 Takes lots of time ii Why Reactants or bond must become slightly more unstable higher energy before the rxn will proceed 1 Absorb heat from surroundings STRAINS BONDS HIGH ENERGY BREAKDOWN 2 Enzyme can catalyze the rxn iii Spontaneous rxn no outside energy requirement 1 Need input of energy to begin rxn absorb from surroundings 2 Occur very slowly iv Enzymes speed up chemical rxn s v Catalyst chemical agent that speeds up a reaction without being consumed by the reaction 1 Enzyme catalytic protein vi Every chemical reaction between molecules involves bond breaking bond forming vii Changing 1 molecule into another involves contorting the starting molecule into a highly unstable state before the rxn can occur viii To reach this unstable state absorb energy from surroundings 1 New bonds form energy is released return to stable shapeslower energy b Free Energy of Activation EA i Initial energy needed to start a chemical reaction ii Often supplied in the form of heat from the surroundings iii Activation energy determines the rate of the rxn 1 Reactants must absorb enough energy before rxn occur iv Most rxn s have a high activation energy would take a very long time to proceed v Enzymes catalyze rxn s by lowering activation energy 1 ENZYMES CANT CHANGE FREE ENERGY OF REACTANTS PRODUCTS c Heat Activation Energy i Complex molecules protein DNA rich in free energy ii Have potential to decompose spontaneously 1 Laws of thermodynamics favor their breakdown iii Persist b c at cellular temp molecules do not absorb enough energy to overcome activation energy iv Heat denature proteins kill cell speed up all rxn s d Enzymes Lower Activation Energy i Enable reactant molecules to absorb enough energy to reach the transition state even at mild temperatures ii Enzymes do NOT affect G 1 Cannot make endergonic rxn exergonic iii They hasten reactions that would occur eventually iv Very specific only certain pathways turned on at any one time 1 Shape determines function e Substrate Specificity of Enzymes i Substrate reactant that an enzyme acts on ii Active site region where substrate binds enzyme iii Forms enzyme substrate complex when substrate is in active site f Enzyme Active Site i Induced fit of a substrate brings chemical groups of the active site into positions that enhance their ability to catalyze the rxn ii Most enzymatic rxn s substrate is held in active site by weak interactionshydrogen bonds ionic bonds iii Convert substrate to product product departs iv Enzyme then takes up more