What is the name of the membrane-bound sac that contains cell sap in plant and fungal cells?

The correct answer is vacuole, as it specifically refers to a membrane-bound sac within plant and fungal cells that stores cell sap—a mixture of water, ions, sugars, and other substances. The vacuole plays a crucial role in maintaining turgor pressure, which is essential for maintaining cell structure and support in plants. This pressure helps to keep the plant upright and is crucial for its overall health. In addition, vacuoles are involved in regulating the internal balance of nutrients and waste products, influencing metabolic processes.

Other options do not fit the description provided. The cell wall is a rigid outer layer that provides structural support and protection but does not contain cell sap. The plasma membrane is a semi-permeable barrier surrounding the cell that regulates what enters and exits, but it is not responsible for storing materials like a vacuole does. Lastly, chloroplasts are organelles involved in photosynthesis specifically for converting light energy into chemical energy, not for storing cell sap. Hence, the vacuole is distinctly identified as the correct answer.