A biomembrane is a thin, flexible barrier that surrounds and protects cells and organelles within living organisms. Composed mainly of phospholipids and proteins, these membranes regulate the movement of substances in and out of cells, maintaining a stable internal environment. This selective permeability is crucial for cellular functions and communication. Biomembranes also play a vital role in various biological processes, such as cell signaling, energy production, and metabolism. They can form structures like vesicles and liposomes, which are important for transporting materials within cells. Overall, biomembranes are essential for life, enabling cells to interact with their surroundings effectively.