Final answer:
The amount of pressure needed to prevent the movement of water across a cell membrane is known as osmotic pressure. This pressure is equal to the osmotic pressure of the solution and is crucial for maintaining cellular function and structure, especially in plant cells where it helps maintain turgor pressure.
Step-by-step explanation:
The term for the amount of pressure needed to prevent the movement of water across a cell membrane is called osmotic pressure. This is a fundamental concept in biology, particularly within the context of how cells regulate their internal environment through a semipermeable membrane. Osmosis refers to the movement of water from an area of lower solute concentration to one of higher solute concentration. To prevent this natural flow of water, an external pressure must be applied that is equivalent to the osmotic pressure of the solution. This osmotic pressure is also a colligative property of the solution, meaning that it depends on the solute concentration but not on the type of solute particles.
Plant cells are particularly relevant examples of osmotic pressure, as they utilize this process for maintaining turgor pressure, which is crucial for plant structure and function. For instance, when a plant cell is placed in a hypertonic solution, water moves out, and the cell may shrink. The pressure that needs to be applied to prevent this movement of water is the osmotic pressure, essential for the plant's ability to maintain shape and structural integrity.