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Multiple Choice
Why do phospholipids spontaneously form a bilayer when mixed with water?
A
Because their hydrophilic tails attract water and their hydrophobic heads repel water.
B
Because their hydrophobic tails repel water and their hydrophilic heads attract water.
C
Because they are completely hydrophilic and dissolve in water.
D
Because they are completely hydrophobic and avoid water entirely.
Verified step by step guidance
1
Understand the structure of phospholipids: Phospholipids have a hydrophilic (water-attracting) head and two hydrophobic (water-repelling) tails.
Recognize the behavior of hydrophilic and hydrophobic regions: In an aqueous environment, the hydrophilic heads of phospholipids are attracted to water, while the hydrophobic tails avoid water.
Consider the arrangement in water: To minimize the exposure of hydrophobic tails to water, phospholipids arrange themselves in a bilayer, with hydrophobic tails facing inward, shielded from water, and hydrophilic heads facing outward, interacting with the water.
Visualize the bilayer formation: The bilayer structure is stable because it satisfies the affinity of the hydrophilic heads for water and the aversion of the hydrophobic tails to water.
Conclude the spontaneous formation: This self-assembly into a bilayer is driven by the amphipathic nature of phospholipids, where the dual affinity for water and avoidance of water leads to a stable, energetically favorable structure.