What do we call the network of protein filaments that helps maintain the cell's shape?

The network of protein filaments that helps maintain the cell's shape is referred to as the cytoskeleton. This dynamic structure is made up of three major components: microfilaments, intermediate filaments, and microtubules. Each of these components plays a critical role in providing structural support, facilitating cellular movement, and organizing the internal architecture of the cell.

The cytoskeleton not only helps maintain the cell's shape but also supports various cellular functions, such as the transport of organelles within the cell, the formation of the mitotic spindle during cell division, and the ability of cells to change shape and move. This combination of structural integrity and functional versatility underscores the importance of the cytoskeleton in cellular biology.

In contrast, other choices like cytoplasm, nucleus, and plasma membrane do not serve the primary role of maintaining the cell's shape. The cytoplasm is the gel-like substance within the cell that contains organelles, the nucleus houses genetic material, and the plasma membrane is the outer barrier of the cell that controls what enters and exits. Thus, the cytoskeleton is uniquely positioned to fulfill the role of maintaining the cell's structure and enabling its various functions.