The functions of the phospholipids are somewhat obscure, they are probably multiple and different for each phospholipid. Except in pathological states, the sphingosine and carbohydrate containing lipids are found most concentrated in nervous tissues. Through their concentration in cell membranes they may somehow be involved in the transport of hydrophobic constituents into and out of cells. Some blood serum phospholipid may originate in the liver, postprandial serum phospholipid containing dietary fatty acids and glycerol, arises in extrahepatic tissue, probable the intestinal mucosa. The presence of phospholipids in mitochondria is probably not adventitious, by may well play a role in fatty acid oxidation.
Lipids are present in all living cells, but the proportion varies from tissue to tissue.
The more complex lipids occur closely linked with protein in the membranes of the cell and of subcellular particles. Human skin is a sensitive and complex organ utilizing miriad cell processes to function. In today's world, cosmetics are intended not merely to superficially improve the appearance of skin, but to care for, cleanse and maintain the functions of the skin. Phospholipids play an important role in cosmetics because they possess and chemical properties that are needed for the care and maintenance of healthy skin. Phospholipids contain naturally occurring essential polysaturated fatty acids, which can contribute to the activation of cellular metabolism.