One of the essential structures required by every living organism is a membrane that encompasses the cytoplasm (the contents of the cell). Membranes, not only have a very important role in sustaining contacts with the outside world, but also in protecting the cell against it. Whilst membranes have to be quite resistant to the stressful environment surrounding the cell, they also have to enable uptake of substrates and extrusion of waste products. ....
Zie: Summary