The cell membrane is made up of a lipid bilayer as shown in the model. Structure of the cell membrane, with the lipid bilayer labeled. One side of the membrane is labeled “OUTSIDE OF CELL.” The other side is labeled “INSIDE OF CELL (CYTOPLASM)” The outer surfaces of the membrane are made up of small spheres. Two lines extend from the spheres to the inside of the membrane. Pink capsules and tubes are embedded in the membrane.

Which of the following describes the structure and function of the cell membrane?

A. The hydrophilic head groups of the lipid molecules are exposed to the outside of the cell and the cytoplasm, which is a water-like environment. The hydrophobic tails form an oily layer inside the membrane that keeps water out of the cell.
B. The hydrophilic head groups of the lipid molecules are exposed to the outside of the cell and the cytoplasm, which is a water-like environment. The hydrophobic tails form an oily layer inside the membrane that allows water to enter the cell.
C. The hydrophobic head groups of the lipid molecules are exposed to the outside of the cell, which is a water-like environment. The hydrophilic tails form an oily layer inside the membrane that keeps water out of the cell.
D. The hydrophobic head groups of the lipid molecules are exposed to the outside of the cell, which is a water-like environment. The hydrophilic tails form an oily layer inside the membrane that allows water to enter the cell.