The covalent bonds in water can be broken in cells. Water follows salt, i.e., water diffuses from a solution of low salt concentration to one of high salt concentration. Water absorbs heat effectively with little change in temperature. Water has a lower surface tension than most other ligands, causing water to have very low cohesion. Ice has a lower density than liquid water.
Hydrophobic interactions hold together the plasma membrane.
Some membrane proteins are held in place by attachment to the cytoskeleton. The cell membrane must be fluid to work properly. The only lipids found in the plasma membrane are phospholipids. It is rare for lipids or proteins to flip-flop transversely across the bilayer, switching from one phospholipid layer to the other. Phospholipids are found only in certain membranes.