Secondary metabolism

antibiotics, pigments and scents. The opposite of secondary metabolites are primary metabolites

microbes, plants, fungi and animals, usually living in crowded habitats, where chemical defense represents a better option than physical escape.^[2] It is very hard to distinguish primary and secondary metabolites due to often overlapping of the intermediates and pathways of primary and secondary metabolism. As an example can serve sterols, that are products of secondary metabolism, and, at the same time, represent a base for a cell structure.^[3]