Role of blood lipoproteins. A, Simplified diagram of the role of low-density lipoprotein (LDL) in delivering cholesterol to cells. B, Proposed role of high-density lipoprotein (HDL) in removing cholesterol from cells.
Most fatty acids can be synthesized by the body. A certain number of the unsaturated fatty acids must be provided by the diet and are thus called essential fatty acids. Some of the essential fatty acids serve as a source within the body for synthesis of an important group of lipids called prostaglandins. These hormone-like compounds, first discovered in the 1930s from prostate fluids forming semen, have in recent years gained increasing recognition for their occurrence in various tissues, where they support a wide spectrum of biological activity. Certain essential fatty acids are also necessary for manufacturing the phospholipids in cell membranes and the myelin in nerve tissue .