BIOC 405 Midterm: The hydrophobic effect and amphiphilic molecules
Document Summary
Water molecules near the hydrophobic alkyl chains aren"t able to form hydrogen bond networks, so they are restricted in rotational freedom. There is an entropy loss in these specific water molecules. Only the parts of the water molecules that are in contact with the non-polar tails have reduced entropy. If you cluster the hydrophobic groups together, fewer water molecules are in contact with the lipid portions than in the sum of three individual lipids, so fewer water molecules are restricted in rotational freedom. Clustering lipids increases the entropy of the system. Lipids tend to spontaneously form micelles in solution, in which the polar groups are entirely facing the water molecules and the nonpolar tails face inward. Compared to the cluster, even fewer water molecules are in contact with the lipid portions than in the sum of individual lipids. The entropy of the system is further increased.
