Figure 8.18. Carboxylic Acid Salt (Soap)When placed in aqueous solution, soap molecules arrange themselves into spherical structures
called micelles, as shown in Figure 8.19. The polar heads face outward, where they can be solvated
by water, and the nonpolar hydrocarbon chains are oriented toward the inside of the sphere,
protected from the solvent. Nonpolar molecules, such as grease, dissolve in the hydrocarbon
interior of the spherical micelle; the micelle as a whole then dissolves in water due to the polarity of
its exterior surface.
Figure 8.19. Soap Micelle
The polar heads interact with the hydrophilic environment; the nonpolar tails are oriented toward
the interior of the micelle.BRIDGE
The formation of the phospholipid bilayer, micelles, and liposomes are all contingent on the
bipolar nature of carboxylic acids with long hydrocarbon chains. These structures are
discussed in Chapter 5 of MCAT Biochemistry Review.MCAT Concept Check 8.2: