Discovery of the Cell

The Cell Theory …also, by the early part of the 19th century enough biological material had been observed to begin to make generalizations.

Matthias Jakob Schleiden A botanist and microscopist In 1838 declared that the plant organism is made of cells He accepted the importance of the nucleus, discovered by Robert Brown (1773-1858), and speculated on its role in cell division 1804-1881, Germany

Theodor Schwann He was a zoologist and a microscopist Physiologist and microanatomist Discovered the connection between yeast and fermentation Following Schleiden’s pronouncement, declared that animals, too, are made of cells as the fundamental building blocks 1810-1882, Germany

Virchow and Remak Virchow’s cell theory Rudolph Carl Virchow (1821-1902, Germany) suggested that disease is a cellular problem He stated that all cells come from pre-existing cells, a theory stated earlier by Robert Remak (1815-1865, Poland) Virchow (1821-1902) Remak (1815-1865)

The Cell Theory by 1858 All living organisms are composed of one or more cells. The cell is the most basic unit of structure, function, and organization in all organisms. All cells come from pre-existing, living cells.

Histology and Paul Ehrlich Aniline dyes had been derived from coal tars in the early part of 19th Century Karl Weigert (1845-1904, Germany) used an aniline dye to stain bacteria Ehrlich experimented with staining human tissues He used chemical treatments to serve as the first chemotherapy (used Methylene Blue for syphilis) 1854-1915, Germany The use of aniline dye to stain white blood cells

Development of Optical Staining Bright field Polarized light Darkfield Phase-Contrast Differential Interference Contrast Fluorescence Imaging

The Cell Cycle: Mitosis

Reduction Division: Meiosis First described by Oskar Hertwig (1849-1922, Germany) in 1876 in the formation of sea urchin eggs. Described again by Edouard van Beneden (1846-1910, Belgium) in 1890 in the formation of Ascaris eggs. August Weismann (1834-1914, Germany) noted in 1911 that the reduction of chromosome numbers, employing meiosis, was necessary if nuclei were to fuse in sexual reproduction

Meiosis

Electron Microscopy Two types: Transmission (TEM) and Scanning (SEM)

Transmission Electron Microscopy Leo Szilard (1928) filed patent for electron microscope in concept The prototype built in 1931 by Ruska and Knoll Resolution limit for light microscope ~2,000X; but the limit for TEM ~2 millionX Max Knoll (1897-1969, Germany, left) and Ernst Ruska(1906-1988, Germany, right) with first TEM

Scanning Electron Microscopy Vladimir Kosmich Zworykin (1888-1982, Russia and USA) invented SEM and television (both based on raster principle) With early television (kinetoscope) in 1929

Details of Subcellular Structures with EM Membranes

Details of Subcellular Structures with EM Nucleus

Molecular details of the nuclear envelope by Mahamid et al. (2016) A new method for visualizing molecular cellular components using TEM

Details of Subcellular Structures with EM Chloroplast

Details of Subcellular Structures with EM Mitochondria

Details of Subcellular Structures with EM Endoplasmic Reticulum

Details of Subcellular Structures with EM Flagellum or Cilium

Current View of the Cell Theory All known living things are made up of one or more cells. All living cells arise from pre-existing cells by division. The cell is the fundamental unit of structure and function in all living organisms. The activity of an organism depends on the total activity of independent cells. Energy flow occurs within cells. Cells contain hereditary information (DNA) which is passed from cell to cell during cell division. All cells are basically the same in chemical composition in organisms of similar species.