One of the interesting things that I found about cell biology was the plasma membrane. The plasma membrane is a selective hydrophobic barrier, meaning some substances can easily pass, whereas other particles trying to cross the membrane must enter VIA a type of facilitated diffusion. The membrane is composed of hydrophobic tails which point inward, and hydrophilic heads pointing outward. Several other membrane components typically make up the cell membrane and are referred to as the fluid mosaic model.This plays an important role in the way the human body can regulate intake of proteins, glucose, carbohydrates, steroids and other important biological molecules.