Fatty acid
Malonyl-CoA is then involved in a repeating series of reactions that lengthens the growing fatty acid chain by two carbons at a time. Almost all natural fatty acids, therefore, have even numbers of carbon atoms. When synthesis is complete the free fatty acids are nearly always combined with glycerol (three fatty acids to one glycerol molecule) to form triglycerides, the main storage form of fatty acids, and thus of energy in animals. However, fatty acids are also important components of the phospholipids that form the phospholipid bilayers out of which all the membranes of the cell are constructed (the cell wall, and the membranes that enclose all the organelles within the cells, such as the nucleus, the mitochondria, endoplasmic reticulum, and the Golgi apparatus).
Saturation (chemistry)
The term saturation is applied similarly to the fatty acid constituents of fats, which can be either saturated or unsaturated, depending on whether the constituent fatty acids contain carbon-carbon double bonds. Tallow consists mainly of triglycerides (fats), whose major constituents are derived from the saturated stearic and monounsaturated oleic acids. Many vegetable oils contain fatty acids with one ("monounsaturated") or more ("polyunsaturated") double bonds in them.