Why is cell theory not a law

Overview of the history of cell theory

Address well-known scientists (biography, performance, technical tools / devices) of them.

Before I give an overview of the history of cell theory, I would first like to explain the structure of the cell.

The cell is the basic component of all living things. It is the smallest structural and functional unit of living beings and as such has the basic properties of living matter: metabolism, reproduction, heredity and irritation. The size of the cells is in the range of 0.01 mm. Their shape can often be quite different. The cells can look spherical, plate-shaped, cube-shaped, spindle-shaped or barrel-like. The main control center of the cell is the nucleus. It contains important genetic information. The cytoplasm fills the cell and serves to transport and store substances. The cell plasma contains mitochondria, which are responsible for cell respiration; Vacuoles, which are used to store the cell sap, and starch granules, which can also store substances. The cell membrane holds the cell together; it forms the outer closure of the cell. The plant cells also have a cell wall, which takes on a protective function, and chloroplasts, which can convert light into chemical energy.

The historical development of cell and tissue theory is naturally dependent to a decisive extent on the development of optical aids. The first microscope was developed by Hans and Zacharias Janssen in Holland around 1600. But this microscope had been inferior to good, simple lenses in terms of resolution. Anton van Leeuwenhoek from Holland succeeded for the first time in producing a lens with sufficient magnification to be able to recognize cells with it. Around 1680 he recognized unicellular animals, sperm cells, red blood cells and even bacteria in dental plaque. Robert Hooke was also a well-known cell biologist. As early as 1665 he discovered a cellular structure in bottle cork by chance and described it as "cells", since he noticed that plant bodies are built up from tiny spaces.

Next, Marcello Molpighi 1675-79 and Nehemia Grew 1671-82 described the structure of plant cells. The interest of naturalists was directed from the 18th century. more on the cell content, which is proven by the following observations: in 1774 the evidence of movement phenomena in the cell interior by Corti, in 1831 the discovery of the cell nucleus by the English botanist Robert Brown and in 1839 the naming of the cell interior as protoplasm by J.E. Purkinje.

Theodor Schwann and Matthias Jacob Schleiden were able to prove that the cell nucleus was involved in cell division in 1838 and thus became the founders of the Schleiden-Schwann cell theory. It was not until 1840 that Matthias Schleiden proved for plant objects and Theodor Schwann for animal objects that all organisms are made up of cells and that it is not the walls that were discovered first, but the cell body that are the carriers of life. With that the doctrine of cells was founded. The doctrine of cells says: ,, _ All living beings

- as different as they may be - are made up of cells and their products _All cells agree in the basic features of their structure _The performance of living beings is the result of the performance of their cells _Cells consist only of cells that already exist.

In 1855 Rudolf Virchow recognized that cells only arise from cells (omnis cellula e cellula). This recognized the importance of the cell as the smallest, viable unit. Friedrich Miescher discovered nucleic acids in 1869/71.

The introduction of fixation and staining methods into microbiology made it possible at the end of the 19th century. further insights into the construction of cells and led to various theories about the protoplasmic structure. In 1865/1867, Frommann advocated a scaffolding or network theory, while Flemming made a distinction between filar mass and interfilar mass in 1882. From 1890, R. Altmann and C. Benda researched the mitochondria with the help of suitable fixation and staining methods. Another important event in 1903/04 was the explanation of the chromosome theory of inheritance and the establishment of cytogenetics by W.S.Sutton, T.Boveri and Correns.

In 1931, M. Knoll and E. Ruska in Berlin developed a microscope that used electron beams to dissolve structures. As a result, the magnification range was increased to 0.3 nm and the fine detail of the cells could now be examined. A rapid development in biochemistry and molecular biology was also associated with this discovery. Despite this electron microscope, the light microscope, which is one of the most important aids in cell biology, has not lost its importance because it has a wide range of possible applications and is easy to use.

Well-known cytobiologists

Robert Hooke was born on July 18th, 1635 in Freshwater and died on March 3rd, 1703 in London. He was an English natural scientist who formulated the law of elastic elongation named after him, declared the melting point of water to be 0 ° and referred to the "little boxes" as "cells".

Antonie van Leeuwenhoe lived from 1632 to 1723 and was a Dutch naturalist. With the help of microscopes he made himself, he discovered single-celled animals and bacteria.

Theodor Schwanngebar on December 7th, 1810 and lived until January 14th, 1882. He was a botanist and cytobiologist. He proved that animal objects are made up of cells.

Sources: Linder Biology; "Cell biology" by Haus Kleinig / Peter Sitte; "Classical writings on cell theory" by Wilhelm Ostwald