Polyunsaturated fatty acids

Definition

Fatty acids containing two or more carbon–carbon double bonds in their hydrocarbon backbone. In arthropods, PUFAs are critical membrane components that maintain fluidity at low temperatures, serve as precursors for eicosanoid signaling molecules regulating immunity and reproduction, and are essential dietary nutrients for many insects that cannot synthesize linoleic acid (18:2) and α-linolenic acid (18:3) de novo. The degree of unsaturation varies with thermal adaptation—polar and high-elevation arthropods typically accumulate more PUFAs to preserve membrane function in the cold.

Etymology

From Greek poly- (many) + Latin saturare (to fill), referring to multiple unfilled (unsaturated) carbon bonds; fatty acid from Latin adeps (fat) + acidus (sharp, sour).

Example

The Antarctic midge Belgica antarctica elevates membrane phospholipid polyunsaturation to maintain cellular function at sub-zero temperatures; dietary PUFA availability also limits growth and fecundity in phytophagous insects like the cabbage looper Trichoplusia ni, which must obtain linoleic acid from host plants.

Synonyms

• PUFA
• polyene fatty acid

Related Terms

• essential fatty acid
• eicosanoid
• phospholipid
• cold hardiness
• lipid metabolism
• linoleic acid
• alpha-linolenic acid
• membrane fluidity

Usage Notes

Distinguish from monounsaturated fatty acids (one double bond) and saturated fatty acids (none). In entomological literature, "PUFA" is the standard abbreviation; "essential fatty acid" is a functional subset that cannot be synthesized by the organism. The 18:2 and 18:3 designations refer to carbon chain length and double bond count. Some specialist contexts distinguish omega-3 and omega-6 PUFAs by the position of the first double bond from the methyl end.