Flowing water keeps driving the generator because

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Unformatted text preview: actions in a closed system • Eventually reach equilibrium ∆G < 0 Figure 8.7 A ∆G = 0 (a) A closed hydroelectric system. Water flowing downhill turns a turbine that drives a generator providing electricity to a light bulb, but only until the system reaches equilibrium. • Cells in our body • Experience a constant flow of materials in and out, preventing metabolic pathways from reaching equilibrium (b) An open hydroelectric system. Flowing water keeps driving the generator because intake and outflow of water keep the system from reaching equlibrium. Figure 8.7 ∆G < 0 • Metabolism • Is the totality of an organism’s chemical reactions • Arises from interactions between molecules • Catabolic pathways • Break down complex molecules into simpler compounds • Release energy • Anabolic pathways • Build complicated molecules from simpler ones • Consume energy • Energy coupling • Is a key feature in the way cells manage their energy resources to do this work The Structure and Hydrolysis of ATP of • ATP (adenosine triphosphate) • Is the cell’s energy shuttle • Provides energy for cellular functions Adenine N O O -O O - - O Phosphate groups Figure 8.8 O O C C N HC O O O NH2 N CH2 - O H N H H H OH CH C OH Ribose • Energy is released from ATP • When the terminal phosphate bond is broken P P P Adenosine triphosphate (ATP) H2O P i + Figure 8.9 Inorganic phosphate P P Adenosine diphosphate (ADP) Energy • ATP hydrolysis • Can be coupled to other reactions Endergonic reaction: ∆G is positive, reaction is not spontaneous NH2 Glu + Glutamic acid NH3 Ammonia ∆G = +3.4 kcal/mol Glu Glutamine Exergonic reaction: ∆ G is negative, reaction is spontaneous ATP Figure 8.10 + H2O ADP + Coupled reactions: Overall ∆G is negative; together, reactions are spontaneous P ∆G = - 7.3 kcal/mol ∆G = –3.9 kcal/mol How ATP Performs Work How • ATP drives endergonic reactions • By phosphorylation, transferring a phosphate to other molecules • The three types of cellular work • Are powered by the hydrolysis of ATP P i P Motor protein Protein moved (a) Mechanical work: ATP phosphorylates motor proteins Me...
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This note was uploaded on 11/09/2011 for the course BIO 181 taught by Professor Staff during the Summer '10 term at Chandler-Gilbert Community College.

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