We want to actually move those ATP molecules out of the matrix and into the cytoplasm of the cell so that the ATP can become readily available to actually power all the different types of biological processes that exist within the cytoplasm of the cell. Now, the problem with actually transporting ADP and ATP molecules across the inner mitochondrial membrane is the membrane is impermeable to these two molecules. Why? Well, because ADP contains the charge of negative three while ATP contained the charge of negative four. So both of these molecules are highly charged species. And what that means is they can't simply diffuse across the inner membrane of the mitochondria and their movement across the inner membrane of the mitochondria basically depends on the existence of a special type of antiporter transport system and exchange protein molecule known as ATP ATP translocase.