Introduction

A cell is the most basic structural unit of life and can exist by itself (unicellular, eg a bacterium) or as a group of cells (multicellular eg a human). There are different types of cells, based on their structure and origin (eg prokaryotic, eukaryotic) but these cell types have very similar components (eg nucleic acids, carbohydrates, proteins and lipids) albeit in varied proportions.

In the human body, cells of one type (with shared function) and that are closely interconnected, can form tissues and then these tissues can form organs (eg stomach, heart, brain), which in turn can combine to form organ systems (eg gastrointestinal (digestive) system, circulatory system), producing an entire organism.

As cells are the basic building blocks of all organisms, it is increasingly important to understand how the cell ‘works’ and understand the variety of functions that can occur which are directed and regulated by both the genome and the environment.