A cell wall is a fairly rigid layer surrounding a cell, located external to the cell membrane, which provides the cell with structural support, protection, and acts as a filtering mechanism. The cell wall also prevents over-expansion when water enters the cell. They are found in plants, bacteria, archaea, fungi, and algae. Animals and most protists do not have cell walls.
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Noun 1. a thin membrane around the cytoplasm of a cell; controls passage of substances in and out of the cell (synonym) cell membrane, cytomembrane, plasma membrane (hypernym) semipermeable membrane (part-holonym) cell