lipiidien

Lipidien, the Finnish term for lipids, are a diverse group of hydrophobic or amphipathic biomolecules essential to life. They include fatty acids, triglycerides, phospholipids, sterols, and waxes. Lipids serve multiple roles in cells and organisms, such as energy storage, membrane structure, insulation, and signaling.

Major classes and characteristics. Fatty acids are long hydrocarbon chains with a carboxyl group; they can be saturated or unsaturated. Triglycerides, composed of glycerol esterified to three fatty acids, store most metabolic energy. Phospholipids contain two fatty acids, a glycerol backbone, and a phosphate group, making them amphipathic and suitable for forming cellular membranes. Sterols, including cholesterol, provide membrane rigidity and serve as precursors to hormones. Waxes are esters of long-chain fatty acids with long-chain alcohols, offering protective barriers.

Structure and properties. The hydrophobic tails of lipids drive assembly into membranes and storage droplets, while polar head groups in phospholipids enable interface formation in aqueous environments. The degree of unsaturation in fatty acids influences fluidity of membranes and the energy yield upon oxidation.

Metabolism and transport. Dietary lipids are emulsified by bile, digested by lipases, and absorbed as fatty acids and monoglycerides. They are transported in the bloodstream inside lipoproteins and stored in adipose tissue. Beta-oxidation in mitochondria generates usable energy from fatty acids.

Dietary and health aspects. Lipids are essential but must be consumed in balance; unsaturated fats are generally favored over saturated fats, and trans fats are discouraged due to health risks. Lipidomics is the study of lipid species and their roles in biology.