Answer
The lipid bilayer of a plasma membrane is formed by two flat sheets of glycosylated phospholipid molecules. Each phospholipid molecule is comprised of two hydrophobic fatty acid chains esterified to a glycerol moitey. The phosphate group which is attached to the glycerol is connected to a hydrophilic entity such as inositol, serine, or choline, and these with the glycerol constitute the head of the phospholipid molecule. When suspended in water, the phospholipid molecules , because of energy considerations, naturally arrange themselves so that their hydropihilic heads face the aqueous environment, and their hydrophobic tails face away from it. This effect has been called the hydrophobic effect. It results in the formation of the flattish lipd bilatyer with the fatty acid tails in each layer approximating, and the hydrophilic heads facing away . This means that in a cell, the heads of the bilayer face aqueous extracellular and intracellular environments. The plasma membrane with its lipid bilayer is a permeability barrier that controls the transport of substances in and out of the cytosol.
Work Step by Step
The hydrophobic effect is the same effect that causes water and oil to naturally separate in a mixture of the two liquids. Hydrophobic regions aggregate to lessen the surface area exposed to a hydrophilic exterior.
