OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What is turgor pressure?

1. The pressure that causes a plant to wilt

2. The internal pressure of a cell against its wall

3. The force resulting from water loss in cells

4. A measurement of water content in plants

The correct answer is: The internal pressure of a cell against its wall

Turgor pressure refers specifically to the internal pressure exerted by the fluid (typically water) inside a plant cell against its cell wall. This pressure is vital for maintaining the structural integrity of the plant, as it helps keep cells firm and upright. When a plant takes up water through osmosis, the central vacuole fills with water, pushing the cell membrane against the rigid cell wall, which creates turgor pressure. This pressure counteracts the external pressure and also contributes to maintaining the plant's shape. In contrast, the other options describe various aspects of plant health or cell function but do not accurately define turgor pressure. While turgor pressure is essential for preventing wilting and maintaining cell shape, it is more precise to say it is the pressure within the cell itself rather than the worsening conditions that lead to wilting or water loss impacts. Water content measurement in plants relates to turgor pressure but does not capture its mechanical aspect or function within the cell.