Lipids are a wide category of compounds that are known as biomolecules. Lipids include neutral fats, steroids, oils and waxes. They are created by the body naturally to be used in a variety of biological membranes and reactions.
Lipids perform a variety of functions in a biological system. They contribute to the structure of plasma membranes that enclose both cells and cellular organelles. Lipids also protect the organism from drying out. In humans, lipids are found in skin cells, where they prevent dry skin and keep water molecules inside of the body. Lipids insulate organisms against extreme environments, and they also regulate the activities of many hormones and enzymes.