【非選題】 3. Please plot the structure of arachidonic acid (C20:4Δ6). Please depict how arachidonic acid is synthesized from linoleic acid (C18:2Δ6) in mammals. Please describe your answer including "Δ5 desaturase”, “Δ6 desaturase”, and “elongation". Please define the structure of each intermediate. (15%)