How does pospholipids behave in water?

Answer 1

Considering that phospholipids are amphiphilic molecules, such as soaps and detergents, form "micelles" (globular aggregates whose hydrocarbon groups are out of contact with water). This molecular arrangements eliminates unfavorable contacts between water and hydrophobic tails (the fatty acids) of the phospholipids and yet permits the solvation of the polar head groups (the phosphate group).

Now, we have to consider that micelle formation is a cooperative formation, that is, an assembly of just a few amphiphiles cannot shield its tails form contact with water. Consequently, dilute aqueous solutions of amphiphiles do not form micelles until their concentrations surpasses a certain critical micelle concentration (cmc). According to this, above the cmc, almost all added amphiphiles aggregates to form micelles. The value of the cmc depends on the identity of the amphiphile and the solution conditions, for example, biollogical lipids, most of which have two large hydrophobic tails (the fatty acids), the cmc values are generally < 10-6 M.