Best Answer: The fluidity of a cell membrane means that it is flexible. The greater the concentration of unsaturated fatty acids, the more fluid it is and vice versa.
Unsaturated lipids and cholesterol increases the fluidity of a plasma membrane. And also Like other membranes, plasma membranes are essentially lipid bilayers and exhibit a dynamic organization and fluidity characteristic of such "liquid crystalline" structures. The predominant lipids found in most plasma membranes include phospholipid and glycolipid; those in animal cells also contain significant amounts of cholesterol. Since cholesterol is a stiff, planar molecule and is thought to have a stabilizing influence on plasma membranes, scientists speculate its presence represents an adaptation by animal cells to the absence of the external cell wall that surrounds bacterial and plant cells. Plasma membranes also contain protein and glycoprotein in addition to lipid, of both the integral and peripheral varieties. These proteins perform the major functions associated with plasma membrane and they account for the major differences in plasma membranes among different cells of an organism.