Chapter 8 - Chapter 8 An Introduction to Metabolism Some...

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Chapter 8 An Introduction to Metabolism
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Some organisms Convert energy to light, as in bioluminescence Figure 8.1
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Concept 8.1: An organism’s metabolism transforms matter and energy, subject to the laws of thermodynamics
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Organization of the Chemistry of Life into Metabolic Pathways Metabolic pathway has many steps Each catalyzed by a specific enzyme Enzyme 1 Enzyme 2 Enzyme 3 A B C D Reaction 1 Reaction 2 Reaction 3 Starting molecule Product
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Catabolic (cata = down) pathways (cell respiration) Break down complex molecules into simpler compounds Release energy
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Anabolic (ana = up) pathways (photosynthesis) Build complicated molecules from simpler ones Consume energy
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Forms of Energy Energy - Capacity to cause change, exists in various forms Kinetic – energy in motion Potential – stored, location or structure
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The First Law of Thermodynamics Energy can be transferred and transformed Energy cannot be created or destroyed
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The Second Law of Thermodynamics Spontaneous changes that do not require outside energy increase entropy (disorder) of universe Figure 8.3 Second law of thermodynamics: Every energy transfer or transformation increases the disorder (entropy) of the universe. For example, disorder is added to the cheetah’s surroundings in the form of heat and the small molecules that are the by-products of metabolism. (b) Heat co 2 H 2 O +
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Biological Order and Disorder Living systems Increase entropy of universe Use energy to maintain order
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Concept 8.2: The free-energy change of a reaction tells us whether the reaction occurs spontaneously Free-Energy Change, G: energy that can do work under cellular conditions Change in free energy (∆ G) during biological process related directly to: enthalpy change (total energy, ∆ H ) and: change in entropy (disorder, ∆S) G = ∆ H T S Use in studies of metabolism
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Free Energy, Stability, and Equilibrium Organisms live at expense of free energy During spontaneous change Free energy decreases & stability of system increases
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At maximum stability system is at equilibrium Chemical reaction. In a cell, a sugar molecule is broken down into simpler molecules. . Diffusion. Molecules in a drop of dye diffuse until they are randomly dispersed. Gravitational motion. Objects move spontaneously from a higher altitude to a lower one. • More free energy (higher G ) • Less stable • Greater work capacity • Less free energy (lower G ) • More stable • Less work capacity In a spontaneously 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 (a) (b) (c) Figure 8.5
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Reactions in Metabolism Exergonic reaction net release of free energy, spontaneous Figure 8.6 Reactants Products Energy
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Chapter 8 - Chapter 8 An Introduction to Metabolism Some...

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