Biology Regents Practice Exam 2025 - Free Practice Questions and Study Guide

Osmosis is specifically defined as the diffusion of water across a selectively permeable membrane. This process occurs when water molecules move from an area of higher water concentration (or lower solute concentration) to an area of lower water concentration (or higher solute concentration) in an effort to equalize the concentrations on both sides of the membrane.

The term "selectively permeable" indicates that the membrane allows certain substances, such as water, to pass through while restricting others, such as ions or larger solute molecules. This property is crucial for maintaining cell homeostasis and regulating internal conditions, as it enables cells to control water balance and, subsequently, the overall concentration of solutes.

Osmosis plays a vital role in various biological processes, including nutrient absorption, waste removal, and the maintenance of turgor pressure in plant cells, which contributes to their structure and rigidity. Understanding osmosis is essential for grasping how cells interact with their environment and manage their internal physiological states.