What is the membrane of a living cell made of and what properties does it possess?

Cell membranes protect and organize cells. All cells have an outer plasma membrane that regulates not only what enters the cell, but also how much of any given substance exits. Unlike prokaryotes, eukaryotic cells also have inner membranes that contain organelles and control the exchange of essential cell components.

Both types of membranes have a specialized structure that makes them easier to function. The membranes are composed of glycerophospholipids, glycerol molecules, a phosphate group, and two fatty acid chains. Glycerin is a three-carbon molecule that functions as the backbone of these membrane lipids. Within a single glycerophospholipid, fatty acids are attached to the first and second carbons, and the phosphate group is attached to the third carbon of the glycerol backbone. Variable head groups are attached to phosphate. The space-filling patterns of these molecules show their cylindrical shape, which allows the glycerophospholipids to align side-by-side to form wide sheets.