Final answer:
The statement that the aggregation of hydrophobic lipid ends lowers the free energy in an aqueous solution is true, as this process minimizes their exposure to water while forming structures like micelles and phospholipid bilayers.
Step-by-step explanation:
The aggregation of the hydrophobic ends of lipids in water does indeed lower the free energy of the solution. This is true because in an aqueous environment, hydrophobic molecules, such as the tails of phospholipids, are energetically unfavorable when exposed to water. They aggregate to minimize their exposure to the water, which is a process driven by the hydrophobic effect.
This aggregation forms structures like micelles or the lipid bilayers of cell membranes. In micelles, the hydrophobic tails face inward, away from the water, while the hydrophilic heads face outwards. In a phospholipid bilayer, which composes the cell membrane, the hydrophobic tails are sandwiched inside between two layers of hydrophilic heads. This bilateral arrangement not only lowers the system's free energy but also provides a barrier for the cell against its aqueous environment.