What structure provides support to the cell by holding it together and maintaining its shape?

The cytoskeleton is the structure that provides support to the cell by maintaining its shape and holding its components together. Composed of a dynamic network of protein filaments and tubules, the cytoskeleton plays a crucial role in providing structural integrity. It enables the cell to resist deformation, contributes to intracellular transport, and is involved in cell movement.

Each of the other structures has specific functions, but they are distinct from the primary role of providing structural support. The cell wall, for example, is a rigid layer found in plant cells and some prokaryotes that offers additional support, but it is not present in all cell types. The plasma membrane serves as a barrier that regulates the passage of substances in and out of the cell while providing some structural support. The nucleus is primarily involved in housing genetic material and coordinating cell activities, not in maintaining cell shape. Therefore, the cytoskeleton is the best answer as it is universally involved in supporting various cell types throughout the biological kingdom.