Biology · BIOMOLECULES

What is 'activation energy' in the context of an enzymatic reaction?

1. The difference in energy between the initial substrate (S) and the final product (P).
2. The difference between the average energy content of the substrate (S) and that of its transition state.
3. The net kinetic energy possessed by the free enzyme before substrate binding.
4. The thermal energy released when product molecules dissociate from the active site.