12 energy for cellular work endergonic

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Unformatted text preview: mbrane protein ADP + ATP P P P Solute i Solute transported (b) Transport work: ATP phosphorylates transport proteins P Glu + NH3 Reactants: Glutamic acid and ammonia Figure 8.11 NH2 Glu + P i Product (glutamine) made (c) Chemical work: ATP phosphorylates key reactants i The Regeneration of ATP The • Catabolic pathways • Drive the regeneration of ATP from ADP and phosphate ATP hydrolysis to ADP + P i yields energy ATP synthesis from ADP + P i requires energy ATP Energy from catabolism (exergonic, energy yielding processes) Figure 8.12 Energy for cellular work (endergonic, energyconsuming processes) ADP + P i • It is estimated that a 150 lb person needs 17 lbs of ATP per hour but has only about 2 oz. available. This means that one’s entire ATP supply is being cycled at least once a minute! • The activation energy, EA • Is the initial amount of energy needed to start a chemical reaction Is often supplied in the form of heat from the surroundings in a system • The energy profile for an exergonic reaction A B C D Free energy Transition state A B C EA D Reactants A B C D ∆G < O Products Progress of the reaction Figure 8.14 • Every chemical reaction between molecules • Involves both bond breaking and bond forming • Hydrolysis • Is an example of a chemical reaction CH2OH CH2OH O O HH H H OH H HO O + CH2OH H OH H OH Sucrase H2O CH2OH OH H H OH H OH HO H OH Sucrose Glucose C12H22O11 C6H12O6 Figure 8.13 CH2OH O HO H HO H CH2OH OH H Fructose C6H12O6 Remember the enzyme lab? Why is hydrogen peroxide stored in a dark container? Enzymes Enzymes • Concept 8.4: Enzymes speed up metabolic reactions by lowering energy barriers • A catalyst • Is a chemical agent that speeds up a reaction without being consumed by the reaction • An enzyme • Is a catalytic protein • The effect of enzymes on reaction rate Free energy Course of reaction without enzyme EA without enzyme EA with enzyme is lower Reactants ∆G is unaffected by enzyme Course of reaction with enzyme Products Progress of the reaction Figure 8.15 Substrate Specificity of Enzymes Enzymes • The substrate • Is the reactant an enzyme acts on • The enzyme • Binds to its substrate, forming an enzyme­ substra...
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