Which description best explains how phospholipids are arranged in the cell membrane lipid bilayer?

• A. They form a bilayer with hydrophobic tails facing the extracellular fluid and cytosol, and hydrophilic heads facing inward toward each other.
• B. They form micelles in which the hydrophilic heads cluster at the center and the hydrophobic tails point outward toward water.
• C. They form a single layer with all hydrophilic heads facing the cytosol and all hydrophobic tails facing the extracellular fluid.
• D. They form a bilayer with hydrophilic (polar) heads facing the extracellular fluid and cytosol, and hydrophobic (nonpolar) fatty acid tails facing inward toward each other.

Answer: (D)