What structure provides support and shape to plant cells?

The structure that provides support and shape to plant cells is the cell wall. The cell wall is composed primarily of cellulose, which is a polysaccharide that forms a rigid structure surrounding the cell membrane. This rigid layer protects the plant cell, giving it its defined shape and preventing excessive water uptake that could lead to cell lysis. Furthermore, the cell wall plays a crucial role in maintaining the overall integrity of plant tissues, allowing plants to stand upright and grow towards sunlight.

In contrast, the cell membrane, which is present in both plant and animal cells, acts as a selective barrier that controls the movement of substances in and out of the cell but does not provide structural support. The plasma membrane is another term used to reference the cell membrane, and it serves the same function without contributing to the shape of plant cells. The nucleus, while vital for housing genetic material and regulating cellular activities, does not play a role in providing structural support or shape to the cell. Therefore, the cell wall is the correct answer as it is specifically suited to fulfill this key function in plant cells.