Which process describes the movement of water across a selectively permeable membrane?

• A. Diffusion
• B. Active transport
• C. Osmosis
• D. Facilitated diffusion

Answer: (C)

The movement of water across a selectively permeable membrane is specifically described by the process known as osmosis. Osmosis is a type of passive transport that involves the movement of water molecules from an area of lower solute concentration to an area of higher solute concentration. This occurs to equalize solute concentrations on both sides of the membrane, facilitating the balance of water and solutes across cellular structures.

Unlike simple diffusion, which involves the movement of any type of solute, osmosis is solely focused on water. This distinction is crucial because it highlights that osmosis is driven by the concentration gradient of water itself, rather than the solutes. While facilitated diffusion refers to the process of moving larger or polar molecules across a membrane through specific channel proteins, and active transport involves energy input to move substances against their concentration gradient, osmosis does not require energy and is specific to the movement of water.

Overall, when examining the transport of water through a selectively permeable membrane, osmosis accurately defines the process based on its principles of movement in response to solute concentration differences.