Biochemistry

Fats are solvents of vitamins A, D, E, K, F and contribute to their absorption. A number of biologically active substances enter the body with dietary fats: phosphatides, polyunsaturated fatty acids (PUFAs), sterols, etc. The fats included in the food improve its palatability, as well as increase the nutritional and energy value. In the human body, fat is in the form of structural (protoplasmic, constitutional) and reserve (fat of "fat depots"). Structural fat in cells is presented in complex lipids or forms relatively strong compounds with proteins - lipoprotein complexes . They are contained in the blood, participate in the construction of cellular organelles (nuclei, ribosomes, mitochondria). Protoplasmic fat is present in organs and tissues in a constant amount (about 25% of all lipids) that does not change even with complete starvation. Reserve fats are deposited in the so-called "fat depots" ( subcutaneous tissue, mesentery, fat capsule of the kidneys , etc.). They also form lipoprotein complexes, but are unstable, so their number decreases rapidly with starvation, some nervous and humoral disorders. In reserve fat, synthesis and decay constantly occur, however, it is a source of renewal of intracellular structural fat. Reserved fats act as a shock absorber, protecting the body from shock, jolts, and injuries. All internal organs have a fatty “ lining ” , but the largest are the kidneys and the heart. Reserve fat is involved in the thermal regulation of the body, it conducts heat poorly and, being deposited in the subcutaneous tissue, protects internal organs from hypothermia. The degree of accumulation of reserve fat depends on the nature of nutrition, the level of energy consumption, age, gender, constitutional characteristics of the body, and the state of its regulatory (nervous and humoral) systems. So, hard physical work, some diseases and malnutrition contribute to a decrease in fat stores. On the contrary, excess nutrition, physical inactivity, decreased genital and thyroid function contribute to an increase in its number. Fats are esters of glycerol and higher fatty acids . Natural fats also contain up to 2% of concomitant substances, on which their color, aroma and taste characteristics depend. According to the chemical composition of the lipids are divided into simple and complex (Fig. 6.1). LIPIDS 125 Figure 6.1 - Classification of lipids 124