Unformatted text preview: needed to start a chemical reacEon is called the free energy of ac1va1on, or ac1va1on energy (EA) • AcEvaEon energy is oQen supplied in the form of heat from the surroundings Fig. 8-14 A
Old bonds are starting to break B D
New bond formed C Transition state Free energy A C B D EA Reactants A C B ∆G < O D Products Progress of the reaction How Enzymes Lower the EA Barrier • Enzymes catalyze reacEons by lowering the EA barrier • Enzymes do not aﬀect the change in free energy (∆G); instead, they hasten reacEons that would occur eventually Fig. 8-15 Course of reaction without enzyme EA without enzyme EA with enzyme is lower Free energy Reactants Course of reaction with enzyme ∆G is unaffected by enzyme Products Progress of the reaction Where substrate binds and where the chemistry occurs Substrate Speciﬁcity of Enzymes • The reactant that an enzyme acts on is called the enzyme’s substrate • The enzyme binds to its substrate, forming an enzyme‐substra...
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