So what differentiates one fatty acid from another fatty acid? Well, basically, the length of that hydrocarbon chain. So the number of carbon atoms within that fatty acid. So, in humans and other animals, the dominant types of fatty acids are palmitic acid, which basically contains 16 carbons, as well as Olake acid, which contains 18 carbons. But in animals as well as humans, we can have fatty acids ranging anywhere from 14 to 24 carbon atoms. So, although the most common fatty acids in biological systems such as our cells are the 16 and 18 carbon fatty acids.