How is osmosis defined?

Osmosis is specifically defined as the movement of water across a selectively permeable membrane. This process occurs when there is a difference in water concentration on either side of the membrane, typically resulting in water moving from an area of lower solute concentration (where there is a higher concentration of water) to an area of higher solute concentration (where there is a lower concentration of water). This movement of water continues until there is an equilibrium in solute concentration on both sides of the membrane.

The unique aspect of osmosis is that it involves the diffusion of water rather than solutes. While nutrients, solutes, and gases can also move across membranes, they are not the primary focus in the context of osmosis. The selective permeability of the membrane allows certain substances to pass while restricting others, specifically functioning to facilitate the balance of water concentration essential for cellular homeostasis. This understanding is crucial for various biological processes, including the regulation of cell volume and the movement of fluids in and out of cells.