So in the lock and key model, the substrate fits precisely and perfectly into the active side due to their complementary shape. So even before they actually bind, what this model tells us is the active side of the enzyme. So the green structure is the enzyme, this is the active side and this is a substrate. And notice that before the binding actually takes place, this is complementary in structure to this active side. And so when they fit, this simply moves into the active side and then they form those non covalent interactions. Now, according to our induced fit model, the active side of that enzyme is not exactly complementary to our substrate.