The lipid bi layer is a universal component of all cell membranes. Its role is critical because its structural components provide the barrier that marks the boundaries of a cell. The structure is called a "lipid bi layer" because it is composed of two layers of fat cells organized in two sheets.
We see the so called " near side " of the moon. Because the moon spins in the exact rotational period we see the same side of the moon every time we look at it .
