Semipermeable Membrane
Definition and meaning of Semipermeable Membrane in chemistry.
A semipermeable membrane is a biological or synthetic polymeric material that allows certain specific molecules or ions to pass through it by diffusion while selectively blocking others. It serves as the essential physical barrier in the fundamental thermodynamic process of osmosis.
In more detail
The selective permeability of this membrane depends on several chemical and physical factors, including pore size, solute solubility, molecular weight, and electrical charge. In the process of osmosis, solvent molecules, typically water, move spontaneously across the membrane from a region of lower solute concentration to a region of higher solute concentration to achieve equilibrium. These specialized membranes are widely utilized in industrial water purification systems, critical medical devices such as kidney dialysis machines, and occur naturally in all living organisms in the form of the cellular phospholipid bilayer.
Key facts
| Field | Physical Chemistry |
|---|---|
| Mechanism | Selective diffusion |
| Application | Reverse osmosis and dialysis |
The phospholipid bilayer of a human cell membrane is a semipermeable membrane, which allows small uncharged water molecules to pass freely while blocking large proteins and charged ions.
Frequently asked questions
What determines what can pass through a semipermeable membrane?
Pore size, molecular charge, and the specific chemical affinity of the solute to the membrane material dictate overall permeability.