Overview: The Energy of Life ï‚‍ Living cell = miniature chemical factory where thousands of reactions occur ï‚‍ Cell extracts energy  applies it to perform

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  • Overview: The Energy of Life Living cell = miniature chemical factory where thousands of reactions occur Cell extracts energy applies it to perform work Some organisms convert energy light, bioluminescence
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  • Concept 8.1: An organisms metabolism transforms matter and energy, subject to the laws of thermodynamics Metabolism: totality of organism s chemical reactions an emergent property of life that arises from interactions between molecules within the cell Organization of the Chemistry of Life into Metabolic Pathways Metabolic pathway: begins with specific molecule and ends with a product Each step catalyzed by a specific enzyme
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  • Catabolic pathways: release energy by breaking down complex molecules into simpler compounds Ex: Cellular respiration= the breakdown of glucose in the presence of oxygen Anabolic pathways: consume energy to build complex molecules from simpler ones Ex: synthesis of protein from amino acids Bioenergetics: study of how organisms manage their energy resources Organization of the Chemistry of Life into Metabolic Pathways
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  • Forms of Energy Energy: the capacity to cause change exists in various forms, some can perform work Kinetic energy: energy associated with motion Heat (thermal energy): kinetic energy associated with random movement of atoms or molecules Potential energy: energy that matter possesses because of its location or structure Chemical energy: potential energy available for release in a chemical reaction Energy can be converted from one form to another
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  • Fig. 8-2 Climbing up converts the kinetic energy of muscle movement to potential energy. A diver has less potential energy in the water than on the platform. Diving converts potential energy to kinetic energy. A diver has more potential energy on the platform than in the water.
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  • The Laws of Energy Transformation Thermodynamics: study of energy transformations Closed system is isolated from its surroundings Ex: liquid in a thermos, In open system energy and matter can be transferred between the system and its surroundings Ex: Organisms! Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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  • The First Law of Thermodynamics First law of thermodynamics: energy of the universe is constant: Energy can be transferred and transformed, but it cannot be created or destroyed Also called the principle of conservation of energy
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  • The Second Law of Thermodynamics Second law of thermodynamics: during every energy transfer or transformation, some energy is unusable, and is often lost as heat Every energy transfer or transformation increases the entropy (disorder) of the universe Living cells unavoidably convert organized energy forms heat Spontaneous processes occur without energy input quickly or slowly For a process to occur without energy input, it must increase the entropy of universe
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  • Fig. 8-3 (a) First law of thermodynamics (b) Second law of thermodynamics Chemical energy Heat CO 2 H2OH2O +
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  • Biological Order and Disorder Cells create ordered structures from less ordered materials Organisms replace ordered forms of matter and energy with less ordered forms Energy: Flows into an ecosystem as light and Exits as heat Explain this. Evolution of more complex organisms does not violate the second law of thermodynamics Why not? Entropy (disorder) may decrease in an organism, but the universe s total entropy increases Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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  • Fig. 8-4 50 m Root of buttercup plant; As open system, plants can increase their order as long as order of surroundings decrease
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  • Concept 8.2: The free-energy change of a reaction tells us whether or not the reaction occurs spontaneously Biologists want to know which reactions occur spontaneously and which require input of energy THUS! they need to determine energy changes that occur in chemical reactions
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  • Free-Energy Change, G Free energy: energy that can do work when temperature and pressure are uniform like in a living cell Change in free energy (G) during a process is related to change in enthalpy/change in total energy (H), change in entropy (S), and temperature in Kelvin (T): G = H TS Only processes with a negative G are spontaneous Spontaneous processes can be harnessed to perform work Can you think of one? Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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  • Free Energy, Stability, and Equilibrium Free energy is a measure of a system s instability or its tendency to change to a more stable state During spontaneous change: free energy decreases stability of system increases Equilibrium: state of maximum stability A process is spontaneous and can perform work only when it is moving toward equilibrium
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  • Fig. 8-5 (a) Gravitational motion (b) Diffusion(c) Chemical reaction More free energy (higher G) Less stable Greater work capacity In a spontaneous change The free energy of the system decreases (G < 0) The system becomes more stable The released free energy can be harnessed to do work Less free energy (lower G) More stable Less work capacity
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  • Fig. 8-5a Less free energy (lower G) More stable Less work capacity More free energy (higher G) Less stable Greater work capacity In a spontaneous change The free energy of the system decreases (G < 0) The system becomes more stable The released free energy can be harnessed to do work
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  • Fig. 8-5b Spontaneous change Spontaneous change Spontaneous change (b) Diffusion(c) Chemical reaction(a) Gravitational motion
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  • Free Energy and Metabolism Concept of free energy can be applied to chemistry of lifes processes Exergonic reaction: net release of free energy; spontaneous Endergonic reaction: absorbs free energy from its surroundings; nonspontaneous
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  • Fig. 8-6a Energy (a) Exergonic reaction: energy released Progress of the reaction Free energy Products Amount of energy released (G < 0) Reactants
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  • Fig. 8-6b Energy (b) Endergonic reaction: energy required Progress of the reaction Free energy Products Amount of energy required (G > 0) Reactants
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  • Equilibrium and Metabolism Reactions in closed system eventually reach equilibrium and then do no work Cells not in equilibrium; they are open systems with constant flow of materials Defining feature of life = metabolism is never at equilibrium Catabolic pathway: releases free energy in a series of reactions Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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  • Fig. 8-7 (a) An isolated hydroelectric system G < 0G = 0 (b) An open hydroelectric system G < 0 (c) A multistep open hydroelectric system
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  • Fig. 8-7a (a) An isolated hydroelectric system G < 0G = 0
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  • Fig. 8-7b (b) An open hydroelectric system G < 0
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  • Fig. 8-7c (c) A multistep open hydroelectric system G < 0
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  • Concept 8.3: ATP powers cellular work by coupling exergonic reactions to endergonic reactions Cell does three main kinds of work: Chemical Transport Mechanical Cells manage energy resources by energy coupling the use of an exergonic process to drive an endergonic one Most energy coupling in cells mediated by ATP Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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  • The Structure and Hydrolysis of ATP ATP (adenosine triphosphate): cell s energy shuttle ATP is composed of : ribose (a sugar) adenine (a nitrogenous base) three phosphate groups Bonds between phosphate groups of ATP s tail can be broken by hydrolysis Energy released from ATP when terminal phosphate bond broken comes from chemical change to a state of lower free energy, not from the phosphate bonds themselves
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  • How ATP Performs Work Three types of cellular work (mechanical, transport, and chemical) powered by the hydrolysis of ATP In cell energy from exergonic reaction of ATP hydrolysis can be used to drive a endergonic reaction Overall: coupled reactions are exergonic ATP drives endergonic reactions by phosphorylation transferring a phosphate group to some other molecule, such as a reactant recipient molecule is now phosphorylated
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  • Fig. 8-10 (b) Coupled with ATP hydrolysis, an exergonic reaction Ammonia displaces the phosphate group, forming glutamine. (a) Endergonic reaction (c) Overall free-energy change P P Glu NH 3 NH 2 Glu i ADP + P ATP + + Glu ATP phosphorylates glutamic acid, making the amino acid less stable. Glu NH 3 NH 2 Glu + Glutamic acid Glutamine Ammonia G = +3.4 kcal/mol + 2 1
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  • The Regeneration of ATP ATP renewable resource that is regenerated by addition of phosphate group to adenosine diphosphate (ADP) Energy to phosphorylate ADP comes from catabolic reactions in the cell Chemical potential energy temporarily stored in ATP drives most

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