Each reaction has a transition state where the substrate is in an unstable, short-lived chemical/structural state. Free Energy of Activation is symbolized by ΔG‡. Enzymes act by lowering the free energy of the transition stateEach reaction has a transition state where the substrate is in an unstable, short-lived chemical/structural state. Free Energy of Activation is symbolized by ΔG‡. Enzymes act by lowering the free energy of the transition state