PowerPoint Presentation6.1 What Is Energy?Slide 3Author Animation: Types of EnergySlide 5Slide 6Energy Conversions Result in a Loss of Useful Energy6.2 How Does Energy Flow in Chemical Reactions?Author Animation: Exergonic and Endergonic ReactionsAn Exergonic ReactionAn Endergonic ReactionSlide 12Reactants and End Products of Burning GlucoseSlide 14Activation Energy in Exergonic ReactionsSlide 16Photosynthesis6.3 How Is Energy Transported Within Cells?Slide 19Slide 20Slide 21Slide 22Author Animation: Coupled ReactionsCoupled Reactions Within Living Cells6.4 How Do Enzymes Promote Biochemical Reactions?Slide 26Slide 27Author Animation: Activation EnergyCatalysts Such As Enzymes Lower Activation EnergySlide 30Slide 31Author Animation: Enzymes and SubstratesThe Cycle of Enzyme-Substrate Interactions6.5 How Do Cells Regulate Their Metabolic Reactions?Slide 35Slide 36Slide 37Competitive and Noncompetitive Enzyme InhibitionSlide 39Slide 40Slide 41Allosteric Regulation of an Enzyme by Feedback InhibitionSlide 43Slide 44Slide 45Human Enzymes Function Best Within Narrow Ranges of pH and TemperatureSlide 47Chapter 6Energy Flow in the Life of a Cell6.1 What Is Energy?Energy is the capacity to do work Work is a force acting on a object that causes the object to moveChemical energy is the energy that is contained in molecules and released by chemical reactions– Contained within sugar, glycogen, and fat– Cells use ATP to accept and transfer energy from one chemical reaction to the nextTwo fundamental types of energy–Potential energy is stored energy –i.e. chemical energy in bonds, electrical charge in a battery, rock at top of a hill –Kinetic energy is the energy of movement –i.e. light, heat, electricity, and the movement of objectsAuthor Animation: Types of EnergyThe laws of thermodynamics describe the quantity (total amount) and the quality (usefulness) of energy1. Energy can neither be created nor destroyed (the first law of thermodynamics), but can change form– often called the law of conservation of energy –total amount of energy within a closed system remains constant unless energy is added or removedThe laws of thermodynamics describe the basic properties of energy (continued)2. The amount of useful energy decreases when energy is converted from one form to another (the second law of thermodynamics)–Entropy (disorder) is a measure of disorder, or more precisely unpredictability –Energy Conversions Result in a Loss of Useful Energy Fig. 6-2100 units chemical energy(concentrated)25 units kinetic energy(motion)75 units heatenergyCombustion by engineWhen gasoline is burned, the orderly arrangement of eight carbons bound together in a gasoline molecule are converted to eight randomly moving molecules of carbon dioxide.6.2 How Does Energy Flow in Chemical Reactions?A chemical reaction is a process that forms or breaks chemical bonds holding atoms together– Chemical reactions convert reactants into products – All chemical reactions require a small input of energy – “you have to give a little to get a little bit of energy”–Exergonic reactions release energy –Endergonic reactions require an input of energyAuthor Animation: Exergonic and Endergonic ReactionsAn Exergonic Reaction Fig. 6-3Energy releasedreactantsproducts++An Endergonic Reaction Fig. 6-4reactantsproducts++Energy inputEXERGONIC reactions release energy– reactants contain more energy than products –Example: the burning of glucose–Overall: sugar combines with oxygen to produce carbon dioxide and water, releasing energy –Why? The molecules of sugar contain more energy than the molecules of carbon dioxide and water, the reaction releases energyReactants and End Products of Burning Glucose Fig. 6-5C6H12O6(glucose)6 O2(oxygen)6 CO2(carbondioxide)6 H2O(water)Energy releasedExergonic reactions release energy (continued)–All chemical reactions require an initial energy input (activation energy) to get started – The negatively charged electron shells of atoms repel one another and inhibit bond formation – Molecules need to be moving fast to overcome electronic repulsion and react– Increasing the temperature increases kinetic energy and thus, the rate of reactionActivation Energy in Exergonic Reactions Fig. 6-6highlowprogress of reactionenergycontentofmoleculesActivation energy neededto ignite glucoseenergy level of reactantsglucose + O2CO2 + H2OENDERGONIC reactions require a net input of energy– The reactants in endergonic reactions contain less energy than the products –Example: process of photosynthesis– plants add the energy of sunlight to the lower-energy reactants water and carbon dioxide to produce the higher-energy product sugarPhotosynthesis Fig. 6-7C6H12O6(glucose)6 O2(oxygen)6 CO2(carbondioxide)6 H2O(water)Energy input6.3 How Is Energy Transported Within Cells?Most organisms powered by breakdown of glucoseEnergy in glucose cannot be used directly to fuel endergonic reactionsEnergy released by glucose breakdown is first transferred to an energy-carrier molecule–high-energy, unstable molecules–present at the site of an exergonic reaction–capture some of the released energy from a reaction–transfer energy to an endergonic reaction elsewhere in a cellATP is the principal energy carrier in cellsATP is the principal energy carrier in cells (continued)–Energy is stored in the high-energy phosphate bonds of ATP– The formation of ATP is an endergonic reaction–At sites in the cell where energy is needed, ATP is broken down in ADP + P and its stored energy is released– Unlike glycogen and fat, ATP stores energy very briefly before being broken downElectron carriers also transport energy within cells–ATP is not the only energy-carrier molecule in cells–Energy can be transferred to electrons in glucose metabolism and photosynthesis–Electron carrier molecules such as NAD and FAD transport high-energy electrons–Electron carriers donate their high-energy electrons to other molecules, often leading to ATP synthesisCoupled reactions link exergonic with endergonic reactions– In a coupled reaction, an exergonic reaction provides the energy needed to drive an endergonic reaction – The two reactions may occur in different parts of the cell, so energy-carrier molecules carry the energy from one to the otherAuthor Animation: Coupled ReactionsCoupled Reactions Within Living Cells
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