Membrane Practice Test AP Biology Choose the response which best completes the following statements or answers the following questions. 1. If a solution outside a cell is more concentrated so that the cell loses water to its environment,??the external solution is said to be __________ to the cell contents.??(1.) hypertonic (2.) in equilibrium (3.) isotonic (4.) hypotonic 2. Which mechanism requires energy? (1.) facilitated diffusion (2.) osmosis (3.) diffusion (4.) active transport 3. Pinching in of fluids by a unicellular organism is the process of (1.) phagocytosis (2.) osmosis (3.) pinocytosis??(4.) exocytosis (5.) facilitated diffusion