Fats are the simplest and most common lipids. Their molecules are formed as a result of the addition of three carboxylic acid residues (most often higher) to the glycerol alcohol molecule, which may be the same or different. Phospholipids are similar in structure to fats, but in their molecule one carboxylic acid residue is replaced by a radical containing a phosphoric acid residue. Phospholipids are the main component of cell membranes. Lipids also include waxes, which perform a mainly protective function in the body of plants and animals. Another group of lipids are steroids. Their molecules do not contain carboxylic acid residues.
One of the main functions of lipids is energy. With the complete oxidation of 1 g of fat to carbon dioxide and water, about 39 kJ of energy is released, which is much more compared to the complete oxidation of the same amount of carbohydrates. In addition, the oxidation of 1 g of fat produces 1.05-1.1 g of water.
An important function of lipids is construction (structural). Phospholipids, cholesterol, lipoproteins, glycolipids are the most important components of cell membranes.
The protective function of lipids is that they protect internal organs from mechanical damage (for example, a person’s kidneys are covered with a fat layer that protects them from injuries, tremors when walking and jumping).
Accumulating in subcutaneous fat, fats perform a heat-insulating function.
Regulatory function. Sex hormones and corticosteroids regulate the processes of development and reproduction, metabolism. Vitamins of group D, which are derivatives of cholesterol, play an important role in the metabolism of calcium and phosphorus. Bile acids are involved in digestion: they provide emulsification of food fats and absorption of their breakdown products.
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