Fungi are heterotropic—they cannot photosynthesize. In general, instead of taking food inside its body and then digesting it as an animal would, most fungi digest food outside their bodies by secreting special strong enzymes onto the food. In this way, complex organic compounds are broken down into simpler compounds that a fungus can absorb (which means fungi are osmotrophic) through their cell walls and cell membranes. In addition, fungi do not swim, walk, or run to get their nutritional needs—but move to the food by growing toward it.