Fettstoffer

Fettstoffer, or lipider, are a diverse group of organic compounds that are predominantly insoluble in water and soluble in nonpolar solvents. They include triglycerides (fats and oils), phospholipids, sterols, waxes, and derived lipids such as fatty acids and fat-soluble vitamins. Lipids are characterized by their hydrophobic or amphipathic nature and contribute to energy storage, membrane structure, and signaling.

Classification commonly divides lipids into simple lipids (esters of fatty acids with alcohols, such as triglycerides and waxes), compound lipids (phospholipids and glycolipids), and derived lipids (steroids, fat-soluble vitamins, eicosanoids). Fatty acids vary by chain length and degree of saturation: saturated, monounsaturated, and polyunsaturated; essential fatty acids include linoleic acid (omega-6) and alpha-linolenic acid (omega-3).

Key roles include energy storage in adipose tissue, insulation and cushioning, and serving as structural components of cell membranes (phospholipids and cholesterol). Lipids also act as signaling molecules, with steroids and eicosanoids influencing numerous physiological processes. Dietary lipids supply energy and essential fatty acids and assist in the absorption of fat-soluble vitamins.

Metabolism involves digestion by pancreatic lipases and bile salts, emulsification, and absorption in the intestine, followed by transport via lipoproteins. Fatty acids undergo beta-oxidation in mitochondria to acetyl-CoA for energy, with ketone bodies produced during fasting. Lipid synthesis (lipogenesis) occurs mainly in liver and adipose tissue and is regulated by hormones such as insulin and glucagon.

Abnormal lipid levels are associated with health issues including hyperlipidemia and atherosclerosis. Examples of lipids include palmitic and stearic acids, oleic acid, linoleic acid, and cholesterol.