How does the cell membrane carry out its functions?
The cell membrane, or plasma membrane as it is sometimes called is possibly the most important aspect of the cell and without it life could not exist in any form. The membrane allows an organism to be enclosed and separated from the surroundings. The membrane is selectively permeable in that it only allows certain molecules through whilst others may not pass through it: the reason for this will be discussed later. The membrane means that concentrations of some molecules in the cell can be increased or decreased as well as the separation of certain reactions. A good example of this is the way that the mitocondrion is completely enclosed and so can perform catabolic reactions such as citric acid cycle and fatty acid degradation whereas in the cytoplasm other reactions, including fatty acid synthesis can take place and it is easy to see how this can be beneficial to the cell as a whole. The membrane itself can be described as a bilayer as it contains two leaflets of phospholipids. Each ph
