Comparative investigation of lipid and fatty acid composition of fish gills and mammalian lungs. A model of the membrane lipid component areas.

The lipid and fatty acid composition of gills and lungs were studied in 18 fish species and seven mammalian species. Different relationships among individual phospholipids and different molar ratios between phospholipids and cholesterol (2:1 in fish and 3:1 in mammals) were found. Conformational analysis of the main phospholipid and cholesterol molecules was carried out using a molecular mechanics method. The model of "one unit fragment of the membrane lipid component" accommodates 19 lipid molecules in fish and 42 in mammals. The areas of the molecule projections of the main phospholipids do not differ from each other by more than 2-3%. It may be suggested that the closely packed lipids in membranes of the aerohaematic barrier protect the organism of mammals from the high oxygen content in the environment.