Cell theory  

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Cell theory refers to the idea that cells are the basic unit of structure in every living thing. Development of this theory during the mid 17th century was made possible by advances in microscopy. This theory is one of the foundations of biology. The theory says that new cells are formed from other existing cells, and that the cell is a fundamental unit of structure, function and organization in all living organisms.


Contents

Classical interpretation

  1. All living organisms are made up of one or more cells.
  2. Cells are the basic unit of life.
  3. All cells arise from pre-existing cells.
  4. The cell is the unit of structure, physiology, and organization in living things.
  5. The cell retains a dual existence as a distinct entity and a building block in the construction of organisms.

Modern interpretation

The generally accepted parts of modern cell theory include:

  1. The cell is the fundamental unit of structure and function in living organisms.
  2. All cells arise from pre-existing cells by division.
  3. Energy flow (metabolism and biochemistry) occurs within cells.
  4. Cells contain hereditary information (DNA) which is passed from cell to cell during cell division.
  5. All cells are basically the same in chemical composition in organisms of similar species.
  6. All known living things are made up of one or more cells.
  7. Some organisms are made up of only one cell and are known as unicellular organisms.
  8. Others are multicellular, composed of a number of cells.
  9. The activity of an organism depends on the total activity of independent cells.

Types of cells

Cells can be subdivided into the following subcategories:

  1. Prokaryotes: Prokaryotes lack a nucleus (though they do have circular DNA) and other membrane-bound organelles (though they do contain ribosomes). Bacteria and Archaea are two domains of prokaryotes.
  2. Eukaryotes: Eukaryotes, on the other hand, have distinct nuclei bound by a nuclear membrane and membrane-bound organelles (mitochondria, chloroplasts, lysosomes, rough and smooth endoplasmic reticulum, vacuoles). In addition, they possess organized chromosomes which store genetic material.

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Unless indicated otherwise, the text in this article is either based on Wikipedia article "Cell theory" or another language Wikipedia page thereof used under the terms of the GNU Free Documentation License; or on research by Jahsonic and friends. See Art and Popular Culture's copyright notice.

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