Membrane Structure

The cell has to have boundaries that keep all of its' components close together.  But it has to be constructed in such a way so that it could regulate what and when materials can come in and leave the cell.  It must also be able to survive a watery environment

The cell membrane has both a polar end and a nonpolar end.  The cell membrane is called the phospholipid membrane because it has a non-polar lipid end and a polar phosphate end.  The polar phosphate is called hydrophillic because it will align itself automatically so that it touches the polar water molecule.  It seeks water.  The non-polar lipid end of the phospholipid molecule consists of 2 strands of fatty acids that extend from the phosphate head.  The fatty acid tail is said to be hydrophobic because it will align itself in a direction away from water.  Most lipids are hydrophobic .  This is why water and vegetable oil will not mix.  There are more components in the phospholipid membrane than just phospholipids.  There are proteins in the membrane.  The type of protein depends the function of that protein for that cell.  There are 3 types of membrane proteins.  These include integral proteins, channel (pore) proteins and surface proteins.  Along with those proteins are molecules of cholesterol the function of which is structural integrity of the membrane.  The membrane is said to be fluid, in that the particles are able to move around a little within the structure of the membrane.  The proteins and cholesterol molecules are placed in the membrane in a random fashion.  It is like a mosaic tile pattern on a wall or floor.  It is because of these two factors that the membrane is said to be a fluid mosaic.

Back              Next