Which structure provides a rigid structural support around the cell membrane?

• A. Cytoskeleton
• B. Nucleus
• C. Cell walls
• D. Ribosomes

Answer: (C)

Rigid external support around the plasma membrane is provided by the cell wall. It sits outside the membrane and gives plants, fungi, and many bacteria their shape and protection, helping resist osmotic pressure that could swell and burst the cell. The cytoskeleton is an internal network that helps maintain cell shape and move organelles, but it doesn’t encase the cell. The nucleus houses DNA, and ribosomes synthesize proteins. The cell wall’s composition varies by organism (cellulose in plants, chitin in fungi, peptidoglycan in bacteria), but its key role is to provide that firm, protective shell around the membrane.