An enzyme increases the rate of the chemical reaction it catalyzes primarily by reducing the free energy of activation (EA) of the reaction.
Here's how this works:
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Free Energy of Activation (EA): Every chemical reaction requires a certain amount of energy to be overcome before the reaction can proceed. This is known as the activation energy (EA). Enzymes facilitate chemical reactions by lowering this activation energy barrier, allowing the reactants to convert to products more easily and rapidly.
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Active Site & Substrate Binding: Enzymes have a specific region called the active site where substrates (the reactants) bind. When substrates bind to the active site, it may induce changes in the enzyme's shape that help facilitate the transformation of substrates into products. This can stabilize the transition state, further lowering the activation energy required.
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Transition State Stabilization: By lowering the energy required to reach the transition state, enzymes make it more favorable for the reaction to occur at a given temperature and concentration of reactants.
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Equilibrium Considerations: While enzymes can speed up the rate of the reaction, they do not change the overall free energy change (ΔG) of the reaction or the position of equilibrium between reactants and products. Both the forward and reverse reaction rates are increased equally, maintaining the same equilibrium state.
Thus, the correct statement regarding how enzymes increase the rate of chemical reactions is that an enzyme reduces the free energy of activation (EA) of the reaction it catalyzes.