celtheorie

Celtheorie, or cell theory, is a foundational concept in biology that states that all living organisms are composed of cells, that the cell is the basic unit of life, and that cells arise from pre-existing cells. The theory provides a framework for understanding the organization of organisms, from single-celled bacteria to complex multicellular forms.

Origin and development: In the 1830s, Matthias Schleiden and Theodor Schwann formulated the first widely accepted version, proposing that all plants and animals are composed of cells. In 1855 Rudolf Virchow added the principle that all cells arise from existing cells, completing the classic three tenets. Later refinements incorporated cellular metabolism, genetic material, and the unity of chemical composition across cells.

Modern perspective and exceptions: The cell theory has been extended to include that cells carry hereditary information in DNA and that metabolic processes occur within cells, with energy flow through cellular compartments. While most life is cellular, viruses and some non-cellular aggregates challenge the boundary, as viruses require host cells for replication and are not considered cells themselves. The theory underpins modern biology, medicine, and genetics, guiding research from cellular pathology to developmental biology.