GED Science: Lipids
Lipids, as a group, include fats, oils, and waxes. They are used as a reserve fuel source, as a major component of cell membranes, and as a digestive aid for other lipids. Lipids cushion internal organs, and provide insulation in cold weather. While one nutritional recommendation is to remove excess fats from the diet through “fat-free” or “reduced fat” foods, it is important to note that animals need fats (lipids) to live. Fats are used in a number of metabolic structures and functions.
Chemically, lipids are molecules that are generally hydrophobic (not attracted to water). Vegetable oil is a fat. You can easily see that it is not attracted to water by the way it beads up when you put vegetable oil in water. The reason why lipids are hydrophobic is because the non-polar covalent bonds linking their carbons and hydrogens aren’t attracted to the polar bonds of water (see the chemistry lessons for reviews of polar and non-polar bonds). The four major groups of lipids include fatty acids, triglycerides, phospholipids, and sterols.