The arrow representing the activation energy will decrease in magnitude.
This arrow will be beginning at the x-axis and going up to the maximum of the graph. The reason that its magnitude decreases is because enzymes provide alternate pathways to reactions; the new pathway has a lower activation energy, so the reaction occurs faster when an enzyme is added. This is why enzymes are referred to as biological catalysts and are a vital part of an organism's body
The energy represented in the graph is the energy required as activation energy for initiating any chemical reaction. Thus, higher is the peak of energy absorbed, higher is the activation energy and hence lower are the chances of chemical reaction catalyzed by an enzyme. With this understanding, the reaction with lowest peak requires the least energy for initiating the chemical reaction and hence it is facilitated by the presence of an enzyme.
