Which statement about the lipid bilayer of the cell membrane is true?

• A. Most membrane proteins freely diffuse across the bilayer by flipping between leaflets (transverse diffusion) without assistance.
• B. Cholesterol decreases membrane fluidity at all temperatures by tightly packing phospholipid tails.
• C. Phospholipids arrange with hydrophilic heads facing the aqueous environment and hydrophobic tails facing inward toward each other.
• D. The lipid bilayer is a rigid, covalently cross-linked sheet that prevents any lateral movement of membrane components.

Answer: (C)