Problems of worldoutlook and methodology of the natural-science knowledge are considered basing on the analysis of tendencies in the development of the membrane theory of cell processes and the use of principles of biological membrane functioning when solving some scientific and applied problems pertaining to different branches of chemistry and biology. The notion scientific knowledge integration is defined as interpenetration of approaches, methods and ideas of different branches of knowledge and enrichment on this basis of their content resulting in knowledge augmentation in each field taken separately. These processes are accompanied by appearance of new branches of knowledge - sciences "on junction" and their subsequent differentiations. The analysis of some gnoseological situations shows that integration of sciences contributes to coordination and some agreement of thinking styles of different specialists, puts forward keen personality of a scientist demanding, in particular, his high professional mobility. Problems of scientific activity organization are considered, which involve social sciences into the integration processes. The role of philosophy in the integration processes is emphasized.