arachidonic acid A polyunsaturated fatty acid, CH₃(CH₂)₃(CH₂CH:CH)₄(CH₂)₃COOH, that is essential for growth in mammals (see eicosanoid). It can be synthesized from linoleic acid. Arachidonic acid acts as a precursor to several biologically active compounds, including prostaglandins, and plays an important role in membrane production and fat metabolism. The release of arachidonic acid from membrane phospholipids, particularly diacylglycerol, is triggered by certain hormones. See essential fatty acids.

arachidonic acid A long chain polyunsaturated fatty acid (20 : 4 ω6). Not strictly an essential fatty acid, since it can be formed from linoleic acid, but three times more potent than linoleic acid in curing the signs of essential fatty acid deficiency. Found in animal tissues, especially fish, eggs, liver, and brain.

arachidonic acid (ă-rak-i-don-ik) n. see essential fatty acid.