What is the impact of the phosphocholine head group on the function of sphingomyelin?

• A. It enhances the solubility of sphingomyelin in water.
• B. It decreases the permeability of the membrane to ions.
• C. It increases the fluidity of the lipid bilayer.
• D. It contributes to the structural integrity and signaling functions of cell membranes.

Answer: (D)