A diverse group of small organic compounds occurring in living organisms that are insoluble or hydrophobic in water due to the fact they are composed of methylene. They include fats and oils (concentrated means of storing energy), fat-soluble vitamins (e.g. vitamins A, D, E and K), waxes (provide waterproofing of of body surfaces), hormones, phosolipids (major building blocks of cells), as well as cholesterol (and other steroids). Their main functions consist of not only of energy storage, but also the provision of structural components for cells, and as signaling molecules. When metabolized, lipids are oxydized to release large amounts of energy. When lipids combine with proteins lipoproteins can be formed (e.g., cell membranes). Sometimes, the term lipid is used as a synonym for fats, but they are in fact a sub-group of fats called triglycerides. In essence, lipids are essential to organic life.
See Amniotic fluid, Biochemistry, Cholesterol, Fatty acid, Fibroblasts, Growth hormone (or somatotropin), Hormones, Montgomery’s areaolar glands, Muscle fiber, Nicotine, Phosolipids, Polarizer, Steroids