Ozmotikus

Ozmotikus (osmotic) refers to phenomena related to osmosis, the movement of a solvent, usually water, across a semipermeable membrane in response to differences in solute concentration. The term derives from the Greek osmos, meaning "push" or impulse, and is used across biology, chemistry, and medicine to describe processes governed by solute gradients that produce net water flow.

Mechanism and osmotic pressure: Osmosis occurs when a membrane allows solvent passage but restricts most solutes. Water migrates from the side with lower solute concentration to the side with higher solute concentration, generating an opposing hydrostatic pressure that eventually balances the gradient. The pressure that would stop osmotic flow is the osmotic pressure, which for dilute solutions can be estimated by van't Hoff's law: π = iCRT, where i is the van't Hoff factor, C the molar concentration of solute, R the gas constant, and T the absolute temperature.

Osmolality and osmolarity: Osmolality (osmolality) measures solute particles per kilogram of solvent; osmolarity measures per liter of solution. In humans, typical extracellular and intracellular fluids are roughly 280–300 mOsm/kg, and tonicity describes the effective osmolality relative to the extracellular fluid, dictating the direction of water movement across cell membranes. Hypertonic, hypotonic, and isotonic solutions describe relative tonicity.

Clinical and physiological relevance: Osmotic processes underlie plant cell turgor, animal cell volume regulation, kidney function, and fluid therapy. Clinically, intravenous fluids are chosen for their osmolarity and tonicity (for example, isotonic saline, hypotonic dextrose solutions, or hypertonic saline) to restore or control body water and electrolyte balance. Osmometers measure osmolality in biological samples, and osmotic concepts intersect with regulation of thirst and osmoreceptors in the brain.