The head of the phospholipid molecule is hydrophilic which means it can easily be wetted by water or it can dissolve in water but the long fatty acid chain which is non polar in nature do not mix with water any way and thus, it is insoluble in water.
The phsopholipid molecuel in the cell membrane prevents the dissolution of cell organelled and its other component in water through this nonpolar, insoluble long fatty acid chain
