Phospholipid Bilayer - Anatomy & Physiology

Introduction

The phospholipid bilayer is the fundamental structure which makes up the cell membrane. It is made of 2 sheets of phospholipid molecules which are said to have hydrophillic heads and hydrophobic tails. Therefore molecules on opposite sheets face back to back to protect their hydrophobic area from the surrounding intra or extracellular fluid. This creates a region inside the membrane which is hydrophobic. 50% of the mass of the membrane is protein. Differant varieties of these fulfill a vast range of functions including those of transport. Such as the cotransporters, the ATPases and the Ion channels.

The Impact of the Structure on Transport

The region of hydrophobic molecules means that it is only lipid soluble molecules which are able to cross the membrane. Polar molecules and ions struggle to cross the membrane without some kind of help. Hence the need for water filled protein ion channels.