The role of the cell membrane in maintaining homeostasis is critical, as it regulates the movement of substances in and out of the cell. Composed of a phospholipid bilayer with embedded proteins, the cell membrane acts as a selective barrier, allowing essential nutrients and ions to enter while keeping harmful substances out. It also facilitates communication between cells and their external environment. By controlling osmotic pressure, nutrient uptake, and waste removal, the cell membrane plays a crucial part in balancing the internal environment, ensuring that cellular processes function optimally and maintaining overall cellular health.