Introduction
Learning Objectives
By the end of this section, you will be able to:
- recognise key similarities and differences between eukaryotic and prokaryotic cells
- discuss the importance of cell structure and functions
- explain key terms such as autophagy, cytokinesis, DNA
- describe why it is necessary to understand cell physiology
Introduction
Life takes many forms, from the Australian mountain ash (Eucalyptus regnans), a tree that grows over 100 metres tall to the smallest known microorganisms, which measure only a few billionths of a metre. Humans have pondered life’s origins and debated the defining characteristics of life, but our understanding of these concepts has changed radically since the invention of the microscope. In the 17th century, observations of microscopic life led to the development of the cell theory: the idea that the fundamental unit of life is the cell, that all organisms contain at least one cell, and that cells only come from other cells.
While most cells have some similar or common structures such as cell walls, cell membranes and genetic information, these structures or elements can vary in composition and function to allow the cells to carry out their particular and specific function. These cellular functions can vary widely and include reproduction, defence, communication with other cells or movement of substances into and out of the cell as well as many other facets of life.
