As you may know, all living things around you, including yourself, are made up of cells. Furthermore, all cells have what’s known as a “cell membrane”. Technically, the cell membrane is a biological membrane that separates the interior of all cells from the outside environment.
Basically, it is an enclosure that sets up cell boundaries, and surrounds a cell. However, it does more than just surround the cells, and that is why it is nothing less than a miracle on its own. The most important function of the cell membrane is that it determines what enters and exits the cell, and also aids in cell to cell communication (yes, cells do communicate). Since the cell membrane allows certain substance to pass through, it is “selectively permeable”.
For the specific functions of the cell membrane, the structure of the membrane has to match. In this article, the contents found in the cell membrane will be discussed. The cell membrane itself is extremely thin, and is made of a double layer of fats which are known as phospholipids and have protein molecules embedded. Cell membranes also contain glycolipids and glycoproteins. These are lipids and proteins with a sugar part attached. They help the cell to recognize other cells of the body. Cholesterol is another molecule found in the cell membranes.
The membrane consists of a phospholipid bilayer. These phospholipids contain a hydrophilic head and a hydrophobic tail.
Proteins are organic compounds that are made up of amino acids. The proteins found in the cell membranes have various functions, and are of various types. Some proteins act as cell surface receptors, whereas others act as enzymes, surface antigens, and transport proteins.
The proteins found in the membranes responsible for transport decide and control what enters and exits the cell. They have specific structures that allow them to transport molecules across. The transport proteins are one type. They actively transport substances across the membranes. The word actively means that it uses energy. The other type of transport proteins are channel proteins. These are responsible for the passive flow of certain molecules which does not require energy.
Cholesterol is a fat, or lipid produced by the liver. The cholesterol present strengthens the membranes and reduces lipid fluidity. Without this molecule, the cell membranes would not be able to main their shape and either be too fluid, not firm enough and even too permeable. Cholesterol also helps in communication with other cells. Cholesterol also helps to secure the proteins in their place in the membranes.