What extracellular structure protects plant cells and helps maintain their shape?

The cell wall is the extracellular structure that protects plant cells and helps maintain their shape. It is primarily composed of cellulose, a polysaccharide that provides rigidity and strength, allowing plants to withstand various environmental stresses such as wind, water pressure, and mechanical support from gravity. The cell wall also plays a crucial role in determining the overall morphology of the plant, contributing to the structural integrity required for supporting leaves, stems, and roots.

In contrast, the plasma membrane and cell membrane refer to the same structure: a phospholipid bilayer that regulates the movement of substances in and out of the cell but does not provide the same level of structural support as the cell wall. Chloroplasts are organelles involved in photosynthesis and are not relevant to the protection or shape maintenance of the plant cell structure. Thus, the cell wall is essential for protecting plant cells and maintaining their form and function.