So this is basically the diagram that describes the locking key. So we can basically imagine that the enzyme has this active side that is a perfect fit for this substrate in the same way that our lock is a perfect fit for our key. And when we place that key into our lock the key nor the lock actually changes in shape. They do not change in shape. And so this is our lock and key model. So the substrate shown in red fits perfectly into the active side of the enzyme and no change in structure actually takes place.