What substance is important in maintaining cell integrity and preventing excessive water uptake in plant cells?

Cellulose is the correct choice because it is a key structural component of the plant cell wall. This polysaccharide provides rigidity and strength to the cell wall, enabling the plant cells to maintain their shape and structural integrity. By forming a strong framework, cellulose prevents excessive water uptake by creating a barrier that can withstand osmotic pressure. When water enters a plant cell, the pressure increases, but the rigid cellulose wall helps stabilize the cell and prevents it from bursting under this pressure.

Pectin also plays a role in plant cell walls but primarily serves to bind cells together and contribute to the flexibility and permeability of the walls rather than offering the rigidity necessary to prevent excessive water uptake. Chlorophyll is involved in photosynthesis and does not contribute to cell wall structure. Starch, while a form of stored energy in plants, does not contribute to maintaining cell integrity or preventing water uptake.