Molecular model of cyclooxygenase-1 enzyme (COX-1, grey and blue spirals) complexed with linoleic acid (yellow spheres). Linoleic acid is a polyunsaturated omega-6 fatty acid, classified as an essential fatty acid that must be obtained through a dietary source. COX-1 catalyses the reaction that converts linoleic acid into prostaglandins: lipids used in the body for tissue repair and mediating inflammation. COX-1 also has a protoporphyrin IX ring (grey spheres) with cobalt (blue) in the centre.