1. which mechanism requires energy to move materials? a. exocytosis b. osmosis c. diffusion of ions through potassium channel 2. facilitated diffusion is a process that involves a. the expenditure of energy as atp b. the selective movement of substances based on molecule size c. the use of special proteins to channels materials through the cell membrane 3. which of the following processes does not require a concentration gradient? a. osmosis b. facilitated diffusion c. active transport 4. a hypotonic solution is one whose concentration is a. equal to that inside a cell b. less than that inside a cell