what is a membrane

A membrane is a thin, selective barrier that separates two environments. It can be found in biological systems, separating cells from their surroundings and regulating the passage of substances. In cells, the plasma membrane controls the entry and exit of various molecules, maintaining internal conditions necessary for life. Membranes are made of lipids, proteins, and other molecules, allowing for processes like diffusion, osmosis, and active transport to occur. Additionally, membranes can be artificial, used in technologies like filtration systems and batteries. Their selective permeability is essential for maintaining homeostasis and facilitating various biological and technological processes.