<P> About 500 million years ago, some nervous cells and some gut cells of vertebrates, migrated and specialized in a more complex nervous system: the brain, and in uptake and storage of iodocompounds: the follicular thyroid . In the PUFAs, the presence of a double bond between two carbons (or carbon - carbon double bond) provides them with the possibility of changing their molecular structure through enzymes such as phospholipases, cyclooxygenases and lipoxygenases, etc . The resulting substances, called eicosanoids: prostaglandins (PG), leukotrienes (LT), lipoxins and thromboxane (TX); and docosanoids: resolvins, protectins, and maresins, are powerful lipid mediators that produce specific actions in the organism; they organize inflammation, hemodynamic, immune response and the repair of tissue . </P> <P> Many PUFAs cannot be synthesized by animal organisms and are considered essential, and therefore should be incorporated into diets . These are: linoleic acid (C18: 2 n - 6), omega - 6 and alpha - linolenic (C18:3 n - 3) omega - 3, arachidonic acid (AA)--omega--6 (C20: 4n - 6), and docosahexaenoic acid (DHA)--omega - 3 (C22: 6n - 3). These PUFAs are incorporated into the phospholipidic membrane of all the cells of an organism . In parallel, ectodermic cells, differentiated into neuronal cells, became the primitive nervous system and brain . Both these cells synthesized iodolipids, as novel words of the chemical lipid language developed among cell membranes during the evolution of life . These biochemical signals among cells, since contact and modification of membranes in multicellular organisms formed the bases of adaptation to terrestrial environments, and their alterations are important in the mechanism of apoptosis, carcinogenesis and degenerative diseases, as well as for understand some problems discussed regarding human evolution (as Aquatic ape hypothesis). </P> <P> Phospholipids and glycolipids consist of two long, nonpolar (hydrophobic) hydrocarbon chains linked to a hydrophilic head group . </P> <P> The heads of phospholipids are phosphorylated and they consist of either: </P>

A major type of lipid found in cell membranes