lípíða

Lípíða refers to a broad class of hydrophobic organic compounds that are insoluble in water but soluble in nonpolar solvents. In biology, lipids include fats, oils, waxes, phospholipids, glycolipids, and sterols. They are mainly composed of carbon and hydrogen, with variable amounts of oxygen, phosphorus, and nitrogen, and they perform diverse roles in cells.

Lípíða are commonly classified as simple lipids (such as fatty acids, triglycerides, and waxes), compound lipids (phospholipids, glycolipids, sphingolipids), and derived lipids (steroids, fat-soluble vitamins, and eicosanoids). Triglycerides consist of glycerol esterified to three fatty acids; phospholipids have two fatty acids and a phosphate-containing head group; sterols such as cholesterol have a ring-based structure; waxes are esters of long-chain alcohols and fatty acids.

The functions of lipids include energy storage in adipose tissue, membrane structure and fluidity through phospholipids and cholesterol, insulation and waterproofing by waxes, and signaling via steroid hormones and eicosanoids.

In digestion, lipids are emulsified by bile acids and hydrolyzed by pancreatic lipases into fatty acids and monoglycerides, which are absorbed and reassembled into triglycerides for transport in lipoproteins. Lipids are transported in the bloodstream by chylomicrons and other lipoproteins (VLDL, LDL, HDL). Dietary lipids come from animal and plant sources, including fats, oils, and dairy. Essential fatty acids, such as linoleic and alpha-linolenic acids, must be obtained from the diet.