Figure 1.6 A glycerophospholipid showing the amphipathic nature of lipids (A). Self-assembly of lipids producing a lipid bilayer (B).

The amphipathic nature of the lipids allows them to self-assemble in aqueous solutions to form a bilayer (Figure 1.6B). The assembled lipid bilayer has polar head groups interacting with water molecules whereas non-polar hydrocarbon regions are buried inside making the membrane core highly hydrophobic that acts as a barrier for polar and charged chemical species. It is this barrier that separates a cell from the external environment. A cell, however, needs to communicate and exchange material with its environment. To accomplish these tasks, biological membranes have acquired specialized proteins.

Having reviewed the structures of the four major biomolecules, we are now ready to look at the bioanalytical techniques that have gained importance in recent times (Lecture 2) and to go through them in detail in the following lectures.