Case Study: Membranes

Membranes are essential to cellular organisms. They are like fortresses in that they provide a barrier between the inside and outside with guarded drawbridges in the form of proteins that regulate the influx and efflux of material. Unlike the rigid walls of a fortress, membranes are fluid and are able to bend and move. The bricks forming a membrane, called lipids, freely move. Plasma membranes enclose and define the boundaries of a cell, maintaining a barrier between the interior of a cell, the cytosol, and the extracellular environment. In eukaryotic cells, membranes also surround specialized organelles such as the mitochondria, nucleus, and other membrane bound