Which statement is true regarding the movement of water across the plasma membrane?

Facilitated diffusion is a key process in the movement of water across plasma membranes, and it refers specifically to the passive transport of molecules across a membrane via transmembrane proteins. This movement does not require energy in the form of ATP because it relies on the inherent kinetic energy of the molecules and the concentration gradient.

In the case of water, aquaporins—specialized channel proteins—facilitate its movement in and out of cells. Since water generally moves from an area of lower solute concentration to an area of higher solute concentration, it follows the concentration gradient, allowing for rapid and efficient transport without expending energy. This means that facilitated diffusion effectively enables cells to regulate their water balance based on osmotic pressures, contributing to homeostasis.

The other options incorrectly describe the mechanisms of water movement: ATP-dependent mechanisms refer to active transport processes that require energy, which is not the case for water movement through facilitated diffusion. While some forms of transport may use active transport, water primarily moves passively. The statement that movement occurs solely through active transport overlooks the significant role of passive processes like facilitated diffusion. Lastly, stating that water movement is independent of concentration gradients misrepresents how diffusion functions, as the movement is inherently linked to these gradients.