EVERYDAY SCIENCE

Detailed explanation-1: -The lipid bilayer of many cell membranes is not composed exclusively of phospholipids, however; it often also contains cholesterol and glycolipids. Eucaryotic plasma membranes contain especially large amounts of cholesterol (Figure 10-10)-up to one molecule for every phospholipid molecule.

Detailed explanation-2: -Phospholipid bilayers are critical components of cell membranes. The lipid bilayer acts as a barrier to the passage of molecules and ions into and out of the cell. However, an important function of the cell membrane is to allow selective passage of certain substances into and out of cells.

Detailed explanation-3: -Phospholipids spontaneously form stable bilayers, with their polar head groups exposed to water and their hydrophobic tails buried in the interior of the membrane.