Final answer:
Water crosses a membrane relatively impermeable to a solute through osmosis, moving from an area with high water concentration to one with low water concentration to equalize solute levels.
Step-by-step explanation:
If a membrane is relatively impermeable to a particular solute that dissolves in water, then water can cross the membrane in the direction of the solute by means of osmosis. Osmosis is a type of diffusion in which water moves from an area of high water concentration (low solute concentration) to an area of low water concentration (high solite concentration) through a semipermeable membrane. The process is driven by the goal to equalize the solute concentrations on both sides of the membrane, effectively letting water move to the side where it is less concentrated.
This phenomenon is extremely important in biological systems as it allows cells to maintain proper pressure and volume, and to adapt to changes in their environment. Aquaporins facilitate the transport of water, enabling faster water movement across cell membranes during osmosis.