Puoliläpäisykalvo

Puoliläpäisykalvo, often translated as semipermeable membrane or selectively permeable membrane, is a type of biological or synthetic membrane that allows certain molecules or ions to pass through it by diffusion, and occasionally specialized facilitated processes, along with, in some cases, significantly reduced rates of diffusion for some molecular species, and blocking or slowing the passage of other molecules or ions. The principle governing the passage of substances across a semipermeable membrane is osmosis.

In biology, cell membranes are prime examples of semipermeable membranes. These membranes are crucial for maintaining cellular integrity and regulating the internal environment of a cell. They control the movement of water, nutrients, and waste products in and out of the cell, ensuring that the cell can function properly. For instance, the cell membrane prevents essential molecules from leaking out while allowing necessary substances to enter.

Synthetic semipermeable membranes are used in various industrial and scientific applications. These include water purification (e.g., reverse osmosis), dialysis, and gas separation. In reverse osmosis, pressure is applied to force water through a semipermeable membrane, leaving behind dissolved salts and other impurities. Dialysis machines use semipermeable membranes to remove waste products from the blood of patients with kidney failure. The effectiveness of these applications relies on the precise control over which substances can and cannot pass through the membrane.