Odd chain fatty acids are those that contain an odd number of carbon atoms in the structure. Almost all animal fatty acid synthesis is done by assembling two 2C Acetyl-CoA molecules together. Because the segments are each two carbons in length the resulting fatty acid has an even number of carbon atoms in it. Some plant-based fatty acids, however, have an odd number of carbon atoms, and Phytanic fatty acid absorbed from plant chlorophyll has multiple methyl branch points. As a result, it breaks down into three odd numbered 3C Propionyl segments as well as three even numbered 2C Acetyl segments and one even numbered 4C Isobutynoyl segment.