Phospholipids are a class of lipids and are a major component of all cell membranes as they can form lipid bi-layers. Phospholipids are a type of large group of organic compounds called “Lipids”. Lipids are a broad group of naturally occurring molecules with fats, waxes, fat-soluble vitamins (such as vitamins A, D, E and K), phospholipids and others. The main biological functions of lipids include energy storage, as structural components of cell membranes and as important signaling molecules. The cell membrane is a biological membrane that separates the interior of all cells from the outside environment. The main role of the phospholipids in living organism is that they make up the cell membrane.
Lipids form a large and varied group of compounds that contain carbon (C), oxygen (O) and hydrogen (H) and are insoluble in water, or they do not dissolve in water. All lipids fall into one of 2 groups-fats or oils. The only difference between these groups is that fats are solid at room temperature while oils are a liquid. Phospholipids are defined as phosphorus that contains fats.
The first phospholipid identified, as such, in biological tissues was “lecithin”, in the egg yolk, by Theodore Nicolas Gobley, a French chemist and pharmacist, in the year 1847.
The chemical structure of lipids varies between the many different types. Most are “triglycerides”, or they are formed from the 3 fatty acid chains attached to a glycerol molecule. Triglycerides are the chemical formation of animal and vegetable fats. In molecular form, 3 molecules of fatty acids (acids produced when fats are broken, which are known as good fats) combine with glycerol (glycerin) to form triglycerides. In human body, these are carried through the blood plasma and unused molecules are stored in the body as fat. All fatty acids are made up of a carboxyl group (-COOH) attached to a hydrocarbon chain, made up of carbon and hydrogen atoms. The hydrocarbon chains can vary in length and are hydrophobic, or repel water.
Phospholipids are not triglycerides. There is a small but very important difference in the structure of phospholipids compared to triglycerides. Instead of having 3 fatty acids attached to the glycerol molecule, one is replaced by a phosphate group, made up of phosphorus, oxygen and hydrogen. The phosphate group is hydrophilic, or it is attracted by water, in contrast to the rest of the molecule. The fact that one part of the molecule attracts water while the rest repels it affects the role of phospholipids in the cell membrane. Most phospholipids contain a “diglyceride”, a phosphate group and a simple organic molecule such as choline, which is a water-soluble essential nutrient.
In water based solution, the phospholipids automatically arrange themselves into a double layer, or as a “phospholipid bi layer”. The fatty acids, which repel water, are found in the middle of the bi layer. The hydrophilic heads, which contain the phosphate group, face outwards along the bi layer and line either side of it. Due to this formation, some substances will be able to pass through the bi layer and others won’t. So, it performs as a natural boundary.
The function of cell membrane is to act as a boundary between the inside of the cell ad its surrounding environment. It is made up almost entirely of a phopholipid bi layer and proteins. Molecules that are water soluble are unable to pass though the phospholipid bi layer due to the hydrophobic internal. The duty of some of the proteins found within the bi layer is to allow transport across it, both in and out of the cell. In this way, the phospholipids and proteins control what enters and leaves the You do not have access to view this node.