So this is our lock and key model. Now the more accepted model, what we think actually takes place on the molecular level between the substrate is the enzyme and the enzyme is described by the induced fit model or the induced fit theory. So this is the much more accepted model. It states that the active side is not exactly a perfect fit. However, as the substrate basically goes into the active side what happens is the active side, the actual enzymes active side as well as the substrate itself actually change in shape ever so slightly to basically create that perfect fit. And that makes sense because if we examine the subatomic level, if we examine the molecular level and we discuss the electric forces involved whenever we have the interaction between different molecules these electric attractive and repulsive forces will basically change the shape of the molecule just a little bit.