The cytoskeleton is best described as

• A. A network of fibers that holds the cell together, helps the cell to keep its shape, and aids in movement
• B. The outer boundary of the cell
• C. The fluid inside the nucleus
• D. A group of ribosomes attached to the rough endoplasmic reticulum

Answer: (A)

The cytoskeleton is a dynamic internal framework made of protein filaments that runs throughout the cytoplasm. This network gives the cell its shape and mechanical strength, helping it resist deformation and maintain integrity. It also serves as tracks for movement and transport, with motor proteins carrying cargo along actin filaments and microtubules, which enables intracellular organization and cell locomotion. In addition, the cytoskeleton positions and anchors organelles and plays a key role in cell division by forming structures like the spindle apparatus. It’s not the outer boundary of the cell (that’s the plasma membrane), nor is it the fluid inside the nucleus (the nucleoplasm), nor a cluster of ribosomes on the rough endoplasmic reticulum.