- The cell membrane is a
semipermeable membrane that acts as a barrier
between the external environment and the internal
environment of the cell.
- It is composed of a bilipid layer
of phospholipids. These orient themselves in such
a way that the hydrophobic ends are withinthe
internal part of the bilipid structure.
- Apart from the phospholipids, a
number of proteins are also found in the cell
membrane. Some proteins are found partially
submerged on each side of the membrane, whilst
others span the membrane.
- Proteins and lipiods are free to
move accross the membrane and hence the strucutre
is called the fluid-mosaic model.
- The proteins found in the cell
membrane have various functions including
support, transport of molecules, signalling and
- In addition to lipids and
proteins, the cell membrane has a number of
carbohydrates atatched either to the
phospholipids (glycolipids) opr ot the proteins
(glycoproteins). These carbohydrates act as
signalling structures between cells.
- Another important aspect of the
cell membrane is the fact that it can act as a
semipermeable membrane. A semi-permeable
membrane, as the name implies, is a membrane that
is permeable to some solutes but not to others. Osmosis
and osmotic pressure is an important aspect
of semi-permable membranes.