11(E)-Eicosenoic acid is a very long-chain ω-9 fatty acid that is a trans monounsaturated isomer of arachidic acid. 11(E)-Eicosenoic acid is one of several monounsaturated 20-carbon fatty acids, and is used to study phospholipid membranes. The combined C20:1 isomers constitute 70% of the total fatty acid pool in jojoba seed oil isolated from plants in the Arizona desert. 11(E)-Eicosenoic acid has been shown to inhibit glycerophosphate acyltransferase, cholinephosphotransferase and ethanolaminephosphotransferase in V79-R cells. 11(E)-Eicosenoic acid lacks the cis-double bond and has virtually no effect on telomerase activity (unlike cis-Unsaturated C20 fatty acids, which demonstrate strong telomerase inhibition and have been studied as a promising cancer therapeutic target).