What it does, this arachidonic acid basically is found within the hydrophobic region of the membrane. It moves into the active side of this enzyme, and it moves into the active side without actually having to interact with the aqueous environment of the Er lumen. Why? Well, because it moves from inside the core of that membrane and directly into the active side. And that's important because this substrate is predominantly not polar. It will not want to dissolve or interact with the water molecules in the aqueous environment.