puoliläpäisevyyden

Puoliläpäisevyys, also known as semipermeability or selective permeability, is a characteristic of a membrane that allows certain molecules or ions to pass through it by diffusion, and occasionally specialized facilitated diffusion. The rate of passage depends on the pressure, concentration, and temperature of the molecules or solutes on either side, as well as the permeability of the membrane to each solute.

Biological membranes, such as cell membranes, are a prime example of puoliläpäisevyys. These membranes are composed of a phospholipid bilayer with embedded proteins. This structure allows essential molecules like oxygen and carbon dioxide to cross freely, while regulating the passage of other substances like water, ions, and larger molecules. This selective nature is crucial for maintaining cellular homeostasis, nutrient uptake, and waste removal.

In industrial and laboratory settings, synthetic semipermeable membranes are used in various separation processes. These include reverse osmosis for water purification, dialysis for medical treatments, and nanofiltration for removing specific contaminants. The effectiveness of these processes relies heavily on the precise pore size and chemical properties of the chosen membrane, which dictates which substances can pass through and which are retained. The concept is fundamental to understanding osmosis, the movement of solvent molecules through a semipermeable membrane from a region of higher solvent concentration to a region of lower solvent concentration.