fedtsyre

Fedtsyre is a carboxylic acid with a long hydrophobic hydrocarbon chain. The carbon chain is typically even-numbered, often ranging from about 14 to 22 carbon atoms in dietary fats, though shorter and longer chains occur. The molecule bears a terminal carboxyl group (–COOH) and a nonpolar tail. Fatty acids may be saturated, lacking double bonds, or unsaturated, containing one or more carbon–carbon double bonds. Unsaturated fatty acids commonly have cis-configured double bonds; trans configurations may arise in partially hydrogenated fats but are rare in nature.

They can exist as free fatty acids or as components of larger lipids, notably triglycerides, phospholipids, and cholesterol esters. In triglycerides, three fatty acids are esterified to glycerol; in phospholipids, one fatty acid is replaced by a phosphate-containing group, giving amphipathic properties essential for membranes.

Some fatty acids are essential in humans; linoleic acid (18:2, n-6) and alpha-linolenic acid (18:3, n-3) cannot be synthesized de novo and must be obtained from the diet. The body can elongate and desaturate these to other long-chain fatty acids such as arachidonic acid (20:4, n-6), EPA (20:5, n-3), and DHA (22:6, n-3).

Functions include energy storage in adipose tissue as triglycerides, cell membrane structure and fluidity, and signaling as precursors to eicosanoids. Fatty acids are digested and absorbed as free fatty acids and monoglycerides, transported in the bloodstream mainly by lipoproteins, and oxidized in mitochondria via beta-oxidation to generate energy.