Movement Across Membranes 。Osmosis Movement of water Glass tube- across a selectively Rubber permeable membrane stopper from an area of high Rubber band water concentration to Sucrose an area of lower water. molecule Cellophane 。Osmotic pressure sack Water- The pressure needed to molecule 00 stop the movement of (a)At beginning of osmotic water across the pressure experiment membrane. Figure 4.18a• Osmosis • Movement of water across a selectively permeable membrane from an area of high water concentration to an area of lower water. • Osmotic pressure • The pressure needed to stop the movement of water across the membrane. Movement Across Membranes Figure 4.18a