chapter4

chapter4 - Energy, Enzymes, and Biological Reactions...

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Energy, Enzymes, and Biological Reactions Chapter 4
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Why It Matters Decomposition by fungi Fig. 4-1, p. 72
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4.1 Energy, Life, and the Laws of Thermodynamics Energy exists in different forms and states The laws of thermodynamics describe energy flow in natural systems The first law of thermodynamics addresses energy content of systems and their surroundings
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4.1 (cont.) The second law of thermodynamics considers changes in degree of order Change in free energy indicates whether a reaction is spontaneous
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Energy Energy: the capacity to do work Kinetic energy: energy of motion Potential energy: stored energy Energy may be converted between potential and kinetic states
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Metabolism Metabolism Controlled acquisition and use of organic molecules and energy Catabolic reactions Breakdown complex molecules Release potential energy for cellular work Anabolic reactions Use energy to convert simple substances into more complex forms
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Thermodynamics Study of energy flow between a system and its surroundings during chemical and physical reactions Closed system exchanges energy but not matter with surroundings Open system exchanges energy and matter with surroundings
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Closed and Open Systems Fig. 4-2, p. 73
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Fig. 4-2a, p. 73
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Fig. 4-2a, p. 73 Energy exchange A closed system exchanges energy with its surroundings. a. Closed system Matter Energy Closed system Surroundings
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Fig. 4-2b, p. 73
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Fig. 4-2b, p. 73 Matter exchange An open system exchanges both energy and matter with its surroundings. b. Open system Open system Surroundings Energy exchange
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First Law of Thermodynamics Total amount of energy in a system and its surroundings remains constant Energy can be transferred or transformed but not created or destroyed Fig. 4-3, p. 73
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Fig. 4-3, p. 73 Heat energy lost from photosynthetic organisms Radiant energy lost from the sun Light energy absorbed by photosynthetic organisms and converted into potential chemical energy
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Second Law of Thermodynamics From initial to final state, the total disorder of the system and its surroundings always increases Total energy remains constant Entropy is a measure of disorder
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Spontaneous Reactions Chemical or physical reactions which occur without outside help Enzymes make spontaneous reactions go faster
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Free Energy ( Δ G) Energy available to do work Δ G = Δ H T Δ S Δ (delta) = change Δ G = change in free energy (Gibbs Free Energy) Δ H = change in total energy T = absolute temperature (degree Kelvin) Δ S = change in entropy
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Free Energy ( Δ G) Exergonic reactions release free energy (– Δ G) Endergonic reactions require free energy (+ Δ G) Fig. 4-4, p. 75
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Free energy (G) In an exergonic reaction, free energy is released. The products have less free energy than was present in the reactants, and the reaction proceeds spontaneously. a. Exergonic reaction
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chapter4 - Energy, Enzymes, and Biological Reactions...

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