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Chapter 13 slides

Chapter 13 slides - Chapter 13 principles of bioenergetics...

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Chapter 13: principles of bioenergetics How to convert energy from environment into “work” by organisms….an early evolutionary event Processes follow the basic thermodynamic laws Free energy, enthalpy, and entropy ATP plays a central role
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Two fundamental laws: 1.Energy is conserved. Physical and chemical changes do not alter the amount of energy, simply its form, its location. 2. The universe tends to greater disorder. Entropy, a measure of disorder increases in all natural processes.
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Define the “system” Concept of controlled system vs living cells… Open vs closed, equilibrium vs non-equilibrium Gibbs free energy, G (J/mol, cal/mol ): energy available at constant T, P. Release of energy in process (exergonic, Δ G is negative); gain of energy ( Δ G, endergonic, positive). Enthalpy, H (J/mol, cal/mol ): heat content of system, determined by number/kinds of bonds in reactants/products; exothermic ( Δ H negative) and endothermic ( Δ H positive). Entropy, S (J/mol x K ): less complex, more disordered, “gain of entropy”. 1 cal = 4.184 J
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Constant T and P…. Δ G = Δ H - T Δ S Δ S…positive if entropy in the reacting system increases. Negative, if it decreases in system…coupled to an increase in their surrounding. Example: cells (isothermal) take in materials and energy, build “order” in the form of structures (e.g., macromolecules) and send out heat and increased entropy to the “environment”) Heterotrophs: nutrients; photosynthetic cells: solar radiation
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Equilibrium, equilibrium constants, and free energy Define K eq a A + b B c C + d D K eq = [C] c [D] d Standard conditions: 298 K= 25 o C [A] a [B] b 1 M for all reactants/products 1 ATM partial pressure Tendency to move towards equilibrium (driving force) is determined by Δ G However, 1M is nonphysiological….so pH 7 and 55.5 M water are “assumed”…. standard transformed constants Δ G ' o and K eq
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Similar relationships for kinetic constants … k forward and k reverse
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Actual vs standard free-energy changes….
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