What term refers to the network of protein filaments and tubules that maintain the shape of the cell?

The term that refers to the network of protein filaments and tubules maintaining the shape of the cell is the cytoskeleton. The cytoskeleton is a dynamic structure composed of microfilaments, intermediate filaments, and microtubules, which work together to provide support, shape, and organization to the cell. It plays crucial roles in cellular functions such as transportation of materials within the cell, cell division, and muscle contraction.

In contrast, the cytoplasm is the gel-like substance within the cell membrane that contains organelles, but it does not specifically refer to the structure maintaining cell shape. The cell membrane, while providing an outer boundary and some structural integrity, primarily functions to protect the cell and regulate the movement of substances in and out. The extracellular matrix refers to materials outside of the cell that provide structural and biochemical support, but it is not part of the cell's internal structure responsible for maintaining its shape. Therefore, the cytoskeleton's role as the framework that gives the cell its shape and facilitates various cellular processes makes it the correct choice.