The primary function of the cell wall is to provide structural support and protection to plant cells, bacteria, fungi, and some protists. It helps maintain cell shape, prevent osmotic lysis, and protects against physical damage and pathogens. The composition of cell walls varies: for plants, it mainly contains cellulose; for fungi, primarily chitin. Additionally, the cell wall plays a role in regulating interactions with the environment and other cells, which is crucial for growth and development.