Cell Theory – Concept, history, postulates and principles

We explain what cell theory is, its postulates and principles. Also, the history of its background and how it was verified.

cell theory microscope
The cell theory explains that all organisms are made up of cells.

What is cell theory?

Cell theory is one of the most important and central postulates in the field of modern biology. It states that absolutely all living beings are made up of cells. This includes all organisms on our planet.

This theory, furthermore, describes the role of cells in the evolutionary history of life on the planet. From this he explains the main characteristics of living beings.

Cell theory forever revolutionized the way humans understand and organize life. Consequently, he opened numerous fields of specialized knowledge and solved many of the questions about his body and that of animals, which had accompanied him since ancient times.

From your demonstration, this theory shed light on the origin of life and on reproduction. In addition, it allowed us to understand the dynamics and processes of what is now considered the most basic physiological unit in biology: the cell.

What is the cell theory?

Cell theory, as we said before, focused the efforts of biology on the cell as the minimal structure of life. It understands that all forms of life are cell-based, that is, all the tissues of plants, animals and fungi can be decomposed into individual cells, although unique and differentiated.

However, the cells of animals, the cells of plants, or the cells of single-celled organisms are very different from each other. Furthermore, this perspective allowed us to understand the gigantic cellular diversity that exists, not just between primitive and single-celled life forms, but even within our own body.

On the other hand, all the studies regarding the basic processes of life, such as being born, growing, reproducing and dying, can not only be traced to the cellular level of the organism, but also occur, in turn, in each of cells of the body.

History of cell theory

Marcello Malpighi cell theory history
Marcelo Malpighi was the first to observe living cells. Image: Wellcome Collection

Cell theory has its antecedents in a long history of life studies that began in ancient civilizations. However, just with the invention of the microscope plant cells could be observed in the seventeenth century, as did the Italian biologist Marcello Malpighi (1628-1694).

It was then that the debate began regarding what exactly those structures were. Later, the English Robert Hooke (1635-1703) baptized them as cellulae, from the Latin “cell”, from his observations of cork cuts.

Later, the Dutch Anton van Leeuwenhoek (1632-1723), considered the father of microbiology, began to use various microscopes of his own responsibility to observe the quality of the fabrics he traded. But then he turned to the observation of other substances.

Thus, van Leeuwenhoek was the first to observe bacteria, protozoa, and sperm themselves. In this way he also gave the first blows to the prevailing theory regarding the spontaneous generation of life.

Other later scientists made significant contributions to the emergence of the cell theory. For example, French Xavier Bichat (1771-1802) was the first to define a tissue as a set of cells with similar form and function.

On the other hand, the Germans Theodor Schwann (1810-1882) and Matthias Jackob Schleiden (1804-1881), formulated the first principle of the cell theory: all living beings are made up of cells and their secretions. Then the german Rudolf Virchow (1821-1902), was the first to demonstrate cellular bipartition, that is, cells come from other cells.

Despite these discoveries, the cell theory was debated throughout the entire 19th century. Finally, into French Louis Pasteur (1822-1895) fully proved this theory with his experiments to show that life does not generate spontaneously.

Principles of cell theory

The principles that govern cell theory are roughly the same as those of modern biology. This implies the distinction between the living and the inert: living matter is capable of metabolizing (nourishing) and self-perpetuating (reproducing), for which it must have the necessary structures, present inside the cell.

Another important principle is that of inheritance: the transmission of biological information to descendants allows the persistence of a species. This process also depends on important cellular structures, such as the cell nucleus, where the DNA of the entire species is contained.

Finally, cells come together in multicellular organisms to form tissues, which are larger and homogeneous structures of cells of the same type. In doing so, they obey important diversification criteria, such as those that separate nerve, muscle, liver cells, etc.

Postulates of cell theory

cell theory division reproduction postulates
The cell theory holds that all cells come from other cells.

The cell theory can be reduced to three fundamental postulates:

  • All living things are made up of cells. Therefore, these are the minimum functional unit of life, in its different levels of structural complexity. One cell is enough to constitute an organism (unicellular), but many cells can organize themselves in colonies or in the same single organism (multicellular), diversifying their functions and reaching a very high margin of interdependence.
  • The vital functions of organisms take place within cells. Through biochemical processes, and are controlled by substances that cells secrete. Each cell operates as a unique open system, exchanging matter and energy with its environment in a controlled manner. Furthermore, in each cell of an organism the same vital functions occur as in the entire organism: birth, growth, reproduction, death.
  • All the cells that exist come from previous cells. By cell division or by formation from stem cells. The oldest and most primitive cells in the world are prokaryotes (without a cell nucleus).