What does osmosis refer to?

Osmosis specifically refers to the process in which water molecules move across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration. This movement occurs in order to equalize solute concentrations on both sides of the membrane. The key characteristic of osmosis is that it involves the selective passage of water while solutes cannot freely pass through the membrane, making it a critical process for maintaining cellular homeostasis.

In contrast, the other options describe different biological and chemical processes. The movement of solutes across a cell membrane refers to general diffusion or active transport, which does not specifically pertain to water. The active transport of minerals involves energy use to move substances against their concentration gradient, while the passive movement of gases relates to gas diffusion rather than the specific movement of water in osmosis. Hence, the definition of osmosis is accurately captured by the diffusion of water across a semipermeable membrane.