Cell membranes separate the contents of a cell from their external enviroment, controlling exchange of material such as nutrients and waste products between the two.
Membranes are partially permeable since water, gases, glucose, aminoacids, fatty acids glycerol and ions diffuse through membranes. If only water and gases could cross the cell membrane then it would be called semipermeable.
Membrane are made out of proteins and lipids. This is because only organic compounds can diffuse through it like alchool or chloroforn. This suggests that membranes are non-polar.
|