A student adds purified phospholipids to water and observes that they spontaneously self-assemble into bilayer sheets and vesicles without energy input. The teacher asks why this organization happens spontaneously when water is the solvent on both sides.
Which property of phospholipids drives the spontaneous formation of the bilayer shown?
- A
ATP hydrolysis builds the bilayer molecule by molecule
- Bcheck_circle
Amphipathic structure: hydrophilic heads face water; hydrophobic tails face inward
- C
Phospholipids are entirely hydrophobic and avoid water
- D
Phospholipids are entirely hydrophilic and bind water tightly
Explanation
Each phospholipid has a polar head and nonpolar tails; in water, tails self-associate away from water while heads contact it, generating a bilayer without energy input.