What structure gives protection and shape to the cell?

The cell wall is a vital structure that provides both protection and shape to plant cells, fungi, and some bacteria. Unlike animal cells, which only have a cell membrane, the presence of a cell wall adds an additional layer of structure. Made primarily of cellulose in plants, the cell wall serves to maintain the integrity of the cell, prevent excessive water uptake, and protect the cell from mechanical stress and pathogens. This rigid outer layer is crucial for maintaining the overall architecture of the plant, enabling it to stand upright and retain its shape, especially in environments where water availability can fluctuate.

Other options do serve essential functions within the cell, but they do not provide the external protection and rigidity that the cell wall does. The cell membrane, for instance, regulates the movement of substances into and out of the cell; cytoplasm supports cellular components and facilitates metabolic processes; and the nucleus houses genetic material and controls cellular activities. However, none of these structures can take on the role of providing a physical barrier and shape like the cell wall does.