Learning Outcomes:

After this lesson, you should be able to:

• Explain the role of osmosis and osmotic pressure in controlling water movement across the plasma membrane. Illustrate the differences among hypotonic, isotonic, and hypertonic solutions regarding water movement.

Osmosis

The osmosis process refers to the movement of a solvent, the dissolving medium, across a selectively permeable membrane from a solution with a lower solute concentration (high solvent concentration) to a solution with a higher solute concentration (low solvent concentration). Like diffusion, osmosis is a passive process. In the human body, the solvent is water, and the membrane is the plasma membrane.

Solutions (mediums) with a high solute concentration have a high osmotic pressure (pulling force). Solutions with a low solute concentration have a low osmotic pressure.



Solutions (mediums) with a high solute concentration have a high osmotic pressure (pulling force). Solutions with a low solute concentration have a low osmotic pressure.