The rectangular active side changes in shape slightly and the trapezoid, we can imagine the trapezoid also changing in shape. For example, it is basically lengthened. So we see that the substrate as well as our enzyme are not really perfect fits but when they interact within the active side, the enzyme as well as the substrate, they change in shape to basically create that perfect fit. And this model is known as the induced fit model where the lock and key model basically states that the active size shape and our substrate shape does not actually change in shape in any way because they are essentially a perfect fit. So this fits perfectly into the active side of the enzyme. So this theory doesn't really hold very much when you think about it from a physics perspective because we know from physics when our molecules interact because of the electrostatic forces, electromagnetic forces, whenever molecules are essentially approach one another there has to be some change in shape of those molecules as a result of those electric forces.