A Level Biology Practice Exam

What does turgor refer to in plant cells?

1. The pressure exerted by the cell wall

2. The pressure exerted by the cell-surface membrane against the cell wall

3. The amount of water within a cell

4. The structure of the cell wall

The correct answer is: The pressure exerted by the cell-surface membrane against the cell wall

Turgor refers specifically to the pressure that the fluid (usually water) inside the cell exerts against the cell wall. This pressure is vital for maintaining the structural integrity of plant cells, keeping them rigid and fully expanded. When the cell is full of water, the contents push against the cell-surface membrane, which in turn pushes against the cell wall. This pressure helps support the plant and allows it to maintain its shape. The other options do not accurately define turgor. The pressure exerted by the cell wall does not capture the dynamic interaction between the cell's contents and the wall itself. While the amount of water within a cell relates to turgor, it does not define what turgor is, since turgor specifically pertains to the pressure created by the water inside the cell pressing against the cell wall. Lastly, the structure of the cell wall itself is a separate characteristic that does not directly relate to the concept of turgor.