Now, one part of that phospholipid found inside the membrane is polar and that is known as the polar head. And these are shown in blue. And the polar heads basically orient themselves to the outside or the inside because the outside and inside contains an aqueous polar environment. But the non polar hydrophobic region shown in red of these lipids basically aggregate at the center of that cell membrane. And as we can see from the diagram, the non polar region of the membrane basically predominates and that makes the membrane predominantly non polar. And so what that implies is the cell membrane basically serves as a barrier for polar and charged molecules.