A biochemist adds an enzyme to a reaction mixture that has already reached chemical equilibrium. What does the enzyme do?

Core Concept

At equilibrium the forward and reverse conversions occur at equal rates, so concentrations hold steady even though molecules react constantly. An enzyme lowers the activation energy barrier shared by both directions by stabilizing the transition state, raising the pace of both conversions identically. Because the endpoint energies are untouched, the ratio of products to reactants at equilibrium does not move. The mixture simply reaches that same equilibrium faster and maintains rapid exchange between the two directions.