What structure gives shape and protection to a cell?

The correct answer is the cell wall, which is a crucial structure that provides shape and protection to cells, particularly in plant cells, fungi, and certain prokaryotes. The cell wall is composed of cellulose in plants, chitin in fungi, and peptidoglycan in bacteria, offering rigidity and support. This structural characteristic allows the cell to maintain its form and withstand various stresses from the environment, such as osmotic pressure.

In contrast, while the cell membrane does provide a barrier to the external environment and plays a key role in regulating what enters and exits the cell, it does not provide rigidity or shape. The cytoplasm is the jelly-like substance within the cell that houses organelles but does not contribute to the cell's shape or structural integrity. The nucleoid is the region in prokaryotic cells where the genetic material is located, but it is not involved in providing shape or protection to the cell itself. Therefore, the cell wall is the structure specifically designed to offer both shape and protective functions to various types of cells.