Enzymes work by lowering the activation energy. Which description best explains this mechanism?

Enzymes work by lowering the activation energy. Which description best explains this mechanism?

• A. Increasing activation energy
• B. Breaking bonds without energy change
• C. Storing energy in bonds
• D. Lowering activation energy

Answer: (D)

Activation energy is the energy barrier that reactants must overcome to reach the transition state and react. Enzymes speed reactions by providing an alternative path with a lower barrier. They do this mainly through the active site: binding substrates tightly and orienting them precisely, stabilizing the transition state with various interactions (like hydrogen bonds and ionic contacts), and sometimes forming temporary covalent bonds or creating a favorable microenvironment. All of these actions make it easier for the molecules to reach the transition state, so more molecules react in the same amount of time. Importantly, enzymes do not change the overall energy change of the reaction or the equilibrium; they only speed things up by lowering activation energy.

Activation energy is the energy barrier that reactants must overcome to reach the transition state and react. Enzymes speed reactions by providing an alternative path with a lower barrier. They do this mainly through the active site: binding substrates tightly and orienting them precisely, stabilizing the transition state with various interactions (like hydrogen bonds and ionic contacts), and sometimes forming temporary covalent bonds or creating a favorable microenvironment. All of these actions make it easier for the molecules to reach the transition state, so more molecules react in the same amount of time. Importantly, enzymes do not change the overall energy change of the reaction or the equilibrium; they only speed things up by lowering activation energy.