| Popis: |
Lipids are a heterogeneous group of chemical compounds that are found in all animal and plant organisms and combine based on common properties. The physiological role of lipids in fish is extremely important and diverse. They perform a number of functions, including energetical, structural, regulatory and others. The authors analyzed the data in the domestic and foreign literature on the structural and functional importance of lipids in fish. The role of lipids in the processes of adaptation of aquatic organisms to adverse factors of the aquatic environment (temperature, salinity, chemical pollution) by changing the ratio of certain classes of lipids, their fatty acid composition and spatial orientation of fatty acid "tails" in biological membranes. The regulatory role of lipids in the functioning of membrane enzymes is analyzed. The authors argue that to find the causes of reduced productivity of fish in a polluted aquatic environment, it is necessary to study bodily changes in lipid metabolism, which are one of the main structural and metabolic compounds, responsible for the formation of adaptive reactions. By adaptation to low temperatures the inclusion of polyene fatty acids in the membrane lipids increases and also increases desaturation. Caused by changes in the temperature of the adjustment in the composition of membrane lipids are aimed at maintaining the mobility of membranes. By adaptation to the temperature factor the level of saturated or unsaturated fatty acids, the ratio of the main classes of phospholipids and cholesterol, asymmetry in the distribution of proteins and lipids in the cell membrane may change. The effects of hydrostatic pressure and salinity of water on lipid metabolism in fish are analyzed. It has been established that phase transitions are largely determined by the same properties of membrane lipids as with temperature change. First of all, it is the degree of saturation of fatty acids, the length of their chain, the position of the double bond and the number of hydrocarbon atoms (pair or not pair). It is shown that in the organs and tissues or fish, involved in the processes of osmoregulation, during adaptation to salt water the lipid content increases. Under the influence of toxic factors in different species of fish a general adaptation strategy is traced, which consists of increasing the content of those lipid fractions, that maintain the energy status of fish for excretion and neutralization of toxicants, reducing the permeability of biological cell membranes to limit the entry of toxicants into fish organism. |
