There are a number of types of cell membrane phospholipids. Most of them are made out of modified glycerol lipids and phosphate, though there are some that are constructed from sphingo molecules. Cell membrane phospholipids are an important component of cell biology.
The most common cell membrane phospholipids are lecithin and cephalin. To form a lecithin molecule, an ammonium salt of choline is joined to a phosphate and its two lipid tails. These molecules can be extracted from soybeans to be used as an emulsifier, aiding in the mixing of various oils with water. Cephalin cell membrane phospholipids are found in nerve cells and blood platelets. They are important in the formation of blood clots.
Phosphatiadates are common cell membrane phospholipids that have three roles. These molecules attract cytosolic proteins, which deliver instructions to cells. Another of its roles is to shape the cell membrane. Phosphatiadates also help in the synthesis of various lipids, and it is possible for one of these molecules to perform more than one of these roles at once.
Sphingomyelin is the most abundant type of sphinosine-based phospholipid found in animal cells. About 10% of cell membrane phospholipids in the brain are made from this molecule. In addition to its role in building cell membranes, sphingomyelin acts as a messenger because it is easily able to attract and distribute cholesterol. Sphingomyelin is also central to the sphingomyelin cycle, which creates a number of different molecules involved in cellular construction and communication, including sphingosine and sphingosine-1-phosphate.
Sphingosine is a molecule that can be attached to a phospholipid. When combined, the resulting molecule is known as sphingosine-1-phosphate which is a cellular messenger. One of the primary roles of this messenger molecule is to instruct a cell to divide into two sister cells. This molecule, though essential to normal cellular function, has been linked to cancer because it instructs all cells to divide, including cancer cells.
Most cell membrane phospholipids are comprised of a hydrophilic head and two hydrophobic tails made of fatty acids. Lipids, which are normally comprised of three strings of fatty acids, are modified into phospholipids when one of these fatty acids is replaced with a phosphate group. The phosphate group forms the head and the two remaining fatty acids, the tails. Cell membrane phospholipids are arranged in two rows with the heads facing outward and the tails towards each other.