Membranes

Membranes are thin, flexible layers that act as barriers to control what enters and exits a cell or structure. They are made mostly of lipids and proteins, forming a selective boundary that allows essential nutrients and oxygen to come in, waste products to go out, and helps communicate signals. This selective permeability is vital for maintaining a stable internal environment, or homeostasis. Membranes are found in all living organisms, including cell membranes in animals and plants, as well as in organelles inside cells, ensuring proper function and protection.