Question

how enzymes act upon energy of activation

Answer 1

All chemical reactions require some energy input to begin. The amount of energy needed before a reaction will proceed on its own is called activation energy. Energy is needed to break existing bonds before new bonds can be formed. The formation of new bonds may release more energy than was needed to break the original bonds. Even though there may be a net (overall) release of energy, the need for activation energy can act as a barrier to the chemical reaction occurring.