Cell Surface Membrane.
The cell surface membrane: a unique barrier that divides the activities occurring inside the cell from the world outside, at the same time acting as a semi-permeable, letting certain molecules and substances to pass, while preventing others. Although its functions seem to be simple, its configuration and the activities that transpire to help it carry out its purpose are far more complicated.
But to understand how it works we must first understand, its structure. The main outline of the membrane consists of phospholipids, which contain a hydrophobic hydrocarbon and a hydrophilic phosphate and its due to this fact that the membrane obtains its shape from. Since the environment that surround the membrane embodies mainly water, the hydrophilic head will be consistently attracted to water and the hydrophobic tails will be continually try to get away from water. This causes the phospholipids to line up (tail to tail, heads facing away from each other), in the position were the tails can have the least interaction with water and the heads can have the most (look at figure 1). Yet unlike normal molecules these do not remain stationary, but they have the ability to move along in between and among the other phospholipids, giving the membrane a certain sense of fluidity. Also located among the phospholipids, are proteins, some are situated so that each end of the protein is on either side of the membrane, while others are positioned on or beneath the surface of the membrane. Extended out from the surface membrane is tree like structure called glycolipids, (also there are similar tree like structure that extend from the proteins with are called glycoproteins). In all the structure of the membrane should look like figure 2.
