Which structure provides support and shape to a plant cell?

The cell wall is the structure that provides support and shape to a plant cell. It is a rigid outer layer made primarily of cellulose, which gives the plant cell its firmness and defines its shape. This rigidity is important for maintaining the cell's integrity and protecting it from mechanical stress. The cell wall also plays a critical role in regulating intake of water and nutrients, contributing to overall cell stability and health. In addition to structural support, the cell wall aids in communication between cells and contributes to the plant's overall ability to withstand environmental pressures.

The other structures listed have different functions: the cell membrane acts as a barrier that regulates the movement of substances in and out of the cell; the nucleus houses genetic material and controls cellular activities; the cytoplasm is the gel-like substance that fills the cell, providing a medium for chemical reactions, but it does not provide the rigid support that the cell wall does.