Eukaryotic components
1. The Cell Wall (The Outer Layer) The cell wall is a rigid, protective layer found outside the plasma membrane in plants, fungi, and some protists. Composition: Algae: Contains cellulose, galactans, mannans, and calcium carbonate. Land Plants: Primarily hemicelluloses, pectin, lipids, and proteins. Strength: Cellulose microfibrils provide the primary structural rigidity. Special Depositions: Depending on the plant's needs, the wall may contain: Silica: Provides grit and strength (e.g., grass stems). Cutin & Wax: Prevents water loss (epidermal cells). Suberin: Acts as a waterproof seal (root endodermal cells). Lignin: Provides wood-like structural support. Function: It determines cell shape and acts as a shield against mechanical injury and infection.