Advanced Placement (AP) Biology Practice Exam

Which vacuole type is important for maintaining turgor pressure in plant cells?

1. Food vacuole

2. Contractile vacuole

3. Central vacuole

4. Storage vacuole

The correct answer is: Central vacuole

The central vacuole is crucial for maintaining turgor pressure in plant cells. Turgor pressure is the pressure exerted by the fluid (mainly water) inside the vacuole against the cell wall, which helps maintain the structure and rigidity of the plant. When the plant cells take up water, the central vacuole fills and expands, pushing the cytoplasm against the cell wall. This pressure is essential for keeping the plant upright and is vital for growth and development. A well-hydrated central vacuole contributes to the overall health of the plant, as it supports various cellular functions and processes. Other types of vacuoles, like food vacuoles or contractile vacuoles, serve different roles such as nutrient storage or expelling excess water from cells, and thus do not play a significant part in maintaining the turgor pressure necessary for plant cell stability and growth. Storage vacuoles can store substances but are not directly involved in creating pressure against the cell wall like the central vacuole.