What is the process called when particles move across a semipermeable membrane?

The correct answer is osmosis, which is a specific type of movement that involves the transfer of water molecules across a semipermeable membrane. In osmosis, water molecules move from an area of lower solute concentration to an area of higher solute concentration in order to achieve equilibrium in solute levels on both sides of the membrane. This process is vital for maintaining cell turgor and overall homeostasis in biological systems.

In contrast, diffusion refers to the movement of particles (larger solute molecules or gases) from an area of higher concentration to an area of lower concentration, but it does not specifically pertain to water or semipermeable membranes. Filtration involves the separation of particles from a fluid by passing the fluid through a filter, which can remove larger particles but does not typically involve the specific movement driven by concentration gradients. Adsorption is a surface phenomenon where molecules adhere to the surface of a solid or liquid, rather than moving across a membrane.

Understanding osmosis is crucial as it plays a key role in biological systems, particularly in how cells manage their internal environments by regulating water movement.