Unit III Ch6 Energy_1 - Chapter 6 Energy Flow in Cells...

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Unformatted text preview: Chapter 6 Energy Flow in Cells Chapter 6 1 Energy Capacity to do work Kinetic Heat, light, electricity Potential Movement Stored Chemical, battery, positional Chapter 6 2 Laws of Thermodynamics 1st Law 2nd Law In a closed system, Energy cannot be created or destroyed Can be changed in form When changed in form Useful energy decreases Entropy increases Chapter 6 3 Chapter 6 4 gas 75 units heat Energy 100 units Chemical potential energy (concentrated) 25 units kinetic energy (motion) The rest is lost as HEAT Entropy Increase in randomness, disorder, stability Less potential energy Sunlight is source of energy for Earth Chapter 6 5 Chemical Reaction To make or break chemical bonds Reactants / Substrates Products Endergonic Energy required Exergonic Energy released Metabolism: sum of all chemical reactions in cells Chapter 6 6 Endergonic Reaction Photosynthesis ADP + Pi ATP energy input 6OO 6OCO carbon dioxide 6H O glucose H Products: higher energy water Substrates / Reactants: lower energy oxygen Chapter 6 7 Exergonic Reaction Burning Glucose = Aerobic Respiration ATP ADP + Pi energy released as heat 6O O Glucose + 36 – 38 ATP oxygen 6OCO 6 H OH carbon water dioxide Products More organized Higher potential energy Less stable Lower entropy Substrates Chapter 6 Less organized Lower potential energy 8 More stable Higher entropy ADP cannot be used for work Energy of ATP between 2nd & 3rd Pi bond = = Chapter 6 9 Coupled Reactions Chapter 6 10 Coupled Reactions within Living Cells Chapter 6 11 Electron Carriers (NADH, NADPH, FADH ) 2 Chapter 6 12 Burning glucose (sugar): an EXERGONIC reaction Photosynthesis: an ENDERGONIC reaction high high activation energy needed to ignite glucose energy content of molecules glucose + O2 energy released by burning glucose activation energy from light captured by photosynthesis energy content of molecules CO2 + H2O glucose net energy captured by synthesizing glucose CO2 + H2O low low progress of reaction progress of reaction Activation energy controls rate of reaction high Energy content of molecules low Activation energy without catalyst Activation energy with catalyst Chapter 6 Progress of reaction 13 Catalyst Enzymes Speeds up rate of reaction by lowering activation energy Protein catalysts Complex 3­D shapes Denatured w/high temperature Highly specific Not consumed by reaction Highly regulated Coenzymes help some enzymes Chapter 6 14 Enzymes have ACTIVE SITE where SUBSTRATES temporarily bind PRODUCTS Could be synthesis of ATP or disaccharide 1 Substrate Substrate s enter enter active site active Substrate Substrate Active Site Enzyme 1 Product Product released; released; enzyme ready enzyme again again 2 Shape change Shape promotes reaction reaction Many reactions linked by Metabolic Pathways One enzyme catalyzes one reaction Initial eactants/ ubstrates A Intermediates B C Final Products E D Enzyme 1 Enzyme 2 Enzyme 3 Enzyme 4 athway 1 Pathway 2 F Enzyme 5 Enzyme 6 G Enzyme Regulation Sensitive to environment Can be synthesized in inactive forms Inhibitor = molecule that binds enzyme & blocks activity Competitive inhibition Allosteric inhibition / activation Feedback inhibition Irreversible inhibitors Competitive inhibition Competitive inhibitor occupies active site Competitive Inhibition: inhibitor binds to active site Allosteric Inhibition: inhibitor binds to different site, changes shape of enzyme & inhibits it Allosteric Activator: activator binds to different site, changes shape of enzyme & turns it on substrate active site enzyme Allosteric Inhibition Shape of active site changed regulatory site inhibitor CH3 CH3 H H C C A OH NH3 Enz. 1 B C CH2 D Enz. 3 Enz. 4 Enz. 5 Enz. COOH Threonine (substrate) H C CH3 H Enz. 2 C NH3 COOH Feedback Inhibition A Isoleucine inhibits enzyme 1 a Isoleucine (end product) Feedback inhibition Too much end product from a metabolic pathway shuts down the pathway Speed of Enzyme affected by Temperature pH Increase [Substrate] will increase reaction rate until saturated ...
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