The cell membrane regulates what enters and leaves the cell, providing protection and support. Diffusion is the passive movement of substances from high to low concentration until equilibrium is reached. Osmosis is the movement of water through selectively permeable membranes, flowing toward the side with a higher concentration of solute molecules. Facilitated diffusion uses protein channels to move molecules that cannot pass through the membrane by simple diffusion. Active transport requires energy to move substances against their concentration gradient using pumps and coupled channels.

8. Osmotic Pressure

9. Osmotic Pressure (cont.)

10. Osmotic Pressure (cont.)