What is a cell?

The cell is the fundamental unit of all forms of independent life on this planet.

We consider cells to be simple building blocks that create an organism together. But, that is not all.

Each cell comprises of a dynamic network of interacting macromolecules, and this individual cell in itself behaves like an organism in itself.

Each cell works in a highly coordinated, exquisitely regulated and beautifully choreographed manner to function correctly as a single unit within a large multicellular organism.

A limiting membrane, the plasma membrane, encloses the contents of the cell and allows the host of enzymatic reactions to occur within a confined, regulated environment.

So, what is this limiting membrane?

Well, the major component of the limiting membrane is a lipid bilayer and the major component of the lipid bilayer are amphipathic phospholipids.

Simple animal cell

Amphipathic molecules have one part that is water soluble (hydrophilic) and another part that is water insoluble (hydrophobic). So, because of this property, when these amphipathic compounds are in aqueous solution, they spontaneously organise themselves so that the hydrophobic regions face one another shielding them from water, leaving the hydrophilic regions (also called the head groups) to the side of water. 

So, what does this limiting membrane contain within itself?

Even though the contents are in aqueous nature, its not just water! The contents of the cell comprise of a vast range of biomolecules, and cell organelles.