The cell wall helps determine the shape of a bacterium and provides strong structural support to keep the cell from bursting or collapsing due to osmotic pressure.

• A. Capsule
• B. Nucleoid
• C. Cell wall
• D. Plasma membrane

Answer: (C)

The cell wall provides the rigid support that shapes the bacterial cell and resists the pressure from water trying to swell the cell. This rigid lattice, made of peptidoglycan in most bacteria, counteracts osmotic influx and prevents lysis, giving the cell its defined form. The capsule sits outside this wall as a protective, slimy layer that helps with protection and adherence but does not supply the mechanical rigidity needed to withstand osmotic stress. The nucleoid is simply the region containing the chromosome and doesn’t influence shape or structural strength. The plasma membrane is a flexible barrier that controls what enters and leaves the cell; while important for many functions, it isn’t the rigid scaffold that maintains shape or prevents bursting under osmotic pressure.