Organisms must be able to maintain homeostasis, or a constant internal environment, in order to survive. Cells achieve homeostasis by creating a barrier to the outside world—a cell membrane—that enables them to protect their internal environment from external forces. In fact, cells “die” when the cell membrane’s integrity is destroyed or compromised. In this unit, you will learn about the membrane and its properties. You will discover that it serves as much more than just a wall—it also transports nutrients, exports waste, carries signals, and much more.