Figure 1 of
Bicknell, Mol Vis 2002;
Figure 1. Biosynthetic pathways for polyunsaturated fatty acid families
A simplified scheme of the biosynthetic pathways for n-3 and n-6 polyunsaturated fatty acid families. *Alternate pathways, proposed by Voss et al.  and Mohammed et al.  in rat liver and Alvarez et al.  in canine retina, involve 24-carbon PUFAs as intermediates in the synthesis of 22:6n-3 and 22:5n-6.