What occurs during osmosis?

During osmosis, water molecules move across a semi-permeable membrane from an area of low solute concentration to an area of high solute concentration. This process occurs in response to differences in solute concentration on either side of the membrane. The semi-permeable nature of the membrane allows water to pass through while restricting the movement of solute particles.

Osmosis is a crucial biological process for maintaining cell turgor and homeostasis. For example, when a cell is placed in a hypotonic solution (where the external solute concentration is lower than that inside the cell), water flows into the cell, causing it to swell. Conversely, in a hypertonic solution, water exits the cell, leading to cell shrinkage.

The other options describe different biological processes. The first option refers to the movement of solutes, which is not the focus of osmosis. The third option describes active transport, which requires energy input to move substances against their concentration gradient, making it distinct from osmosis. Finally, the fourth option mentions passive diffusion, which generally applies to solutes moving until equilibrium is achieved and does not specifically relate to water movement as in osmosis.