This high purity monounsaturated fatty acid is ideal as a standard and for biological systems. It has a cis double bond at an even carbon (carbon 10) and therefore cannot be enzymatically degraded via the usual beta-oxidation pathway. Instead, a reductase-isomerase or an epimerase pathway must be employed in the metabolism of this fatty acid.1 Pentadecenoic acid (cis-10) is not usually found in nature and is therefore a good monounsaturated internal standard.