Question

The membrane of a cell is made mostly of a phospholipid bilayer (with proteins and other molecules embedded in it). Explain how the chemical properties of phospholipids make the cell membrane an effective barrier against ions while at the same time allowing non-polar molecules like oxygen to cross freely.

Answer 1

Phopholipid bilayer of cell is made up of a lipid containing a phosphate group on one end, named as “head,” and two side-by-side chains made up of  fatty acids called as tails.The head portion of the phospholipid bilayer is water loving or hydrophilic where as the tail portion is water fearing or hydrophobic. In the cell membrane structure the hydrophobic tails are sandwiched between the hydrophilic heads.

One of the main function of this cell membrane is to regulate the concentration of the substances within the cell and in this case the the phopholipid layer palys a impostant role because it has a hydrophobic interior that create a selectively permeable environment allowing only substances meeting certain criteria to pass through the lipid bilayer of the cell membrane. Only relatively small non polar elements like other lipids, oxygen and carbon dioxide,gases, and alcohol can pass through the cell membrane by simple diffusion but the polar , water soluble elements like glucose, amino acids, and electrolytes—need some assistance to pass throgh the membrane because they are repelled by the hydrophobic tails of the phospholipid bilayer. Like this the phospholipid bilayer make the cell membrane an effective barrier against the ions.