Cell theory states that living things are composed of one or more cells, that the cell is the basic unit of life, and that cells arise from existing cells.
A cell is the smallest unit of life. Most cells are so tiny that they cannot be seen with the naked eye. Therefore, scientists use microscopes to study cells. The first microscopes were used in the 1600s by Antonie van Leeuwenhoek, a Dutch shopkeeper who had great skill in crafting lenses. Despite the limitations of his now-ancient lenses, van Leeuwenhoek observed the movements of protista (a type of single-celled organism) and sperm, which he collectively termed “animalcules.”
In a 1665 scientist Robert Hooke coined the term “cell” for the box-like structures he observed when viewing cork tissue through a lens. This was followed in the 1670s when van Leeuwenhoek discovered bacteria and protozoa using his microscopes. Later advances in lenses, microscope construction, and staining techniques enabled other scientists to see some components inside cells discovering organelles.
By the late 1830s, botanist Matthias Schleiden and zoologist Theodor Schwann were studying tissues and proposed the unified cell theory. This states that all living things are composed of one or more cells, the cell is the basic unit of life, and new cells arise from existing cells.
The generally accepted portions of the modern Cell Theory are:
- The cell is the fundamental unit of structure and function in living things.
- All organisms are made up of one or more cells.
- Cells arise from other cells through cellular division.
Key Points
• The cell theory describes the basic properties of all cells.
• Cells were first discovered by Robert Hooke using a microscope to examine cork (wood).
• The three scientists that contributed to the development of cell theory are Matthias Schleiden, Theodor Schwann, and Rudolf Virchow.
Key Terms
unified cell theory: The scientific theory that all living organisms are made of cells as the smallest functional unit.
Antonie van Leeuwenhoek: a Dutch businessman and scientist known as “the Father of Microbiology”
protista: a kingdom that comprises mostly single-celled organisms such as the protozoa, simple algae and fungi
Robert Hooke: a 17th-century scientist who imaged cork through a microscope lens and discovered cells
cell: the smallest structural and functional unit of an organism, typically microscopic and consisting of cytoplasm and a nucleus enclosed in a membrane