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  • Cell, a room or hut in which a monk or nun lives.
  • Cell group, a discipleship gathering in the Christian non-denomination Government of 12 (G12)movement. Very popular in Bogata, Columbia and southwest United States.

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The Cell microprocessor is frequently credited to IBM, although Sony and Toshiba are also significantly involved in the chip's development. The project (and the company alliance) was announced in 2000, and the project lasted four years. Currently the architecture is "finished" if not highly in-use.

The Cell architecture is intended to be highly scalable, usable for the simplest and the most complex of computing devices. Conceptually, it consists of an array of processing units around a central processing core - a 64-bit PowerPC core. The satellite units are what makes the architecture scalable, and chip design has taken heavy considerations toward things like power consumption and ease of programming.

Although the Cell is touted to be an end-all-be-all microchip for even the most powerful applications, e.g. weather and disaster prediction, the PlayStation 3 is currently the most exciting thing anyone plans to use it in.

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Simple English

[[File:|thumb|right|Epithelial Cells (from skin)]]

In biology, the cell is the basic structure of organisms. All cells are made by other cells.

The environment outside of the cell and the inside of the cell are separated by the cell membrane. Inside some cells, some parts of the cell stay separate from other parts by plasma membranes. These separate parts are called organelles (like small organs). They each do different things in the cell. Two examples are the nucleus (where DNA is), and mitochondria (where usable energy is created).[1][2]

Contents

Kinds of cells

There are two basic kinds of cells: prokaryotic cells and eukaryotic cells. Prokaryotes, bacteria and archaea, are simple cells with no organelles, but with bacterial microcompartments instead.

Eukaryotes are complex cells with many organelles and other structures in the cell. Eukaryotes store their genetic information (DNA) in the cell nucleus. In a prokaryotic cell the DNA is not separated from the rest of the cell. In general, all living things (organisms) that are made up of multiple cells are eukaryotes.

Kinds of prokaryotic organisms

The only kinds of prokaryotic organisms that survived to the present are bacteria and archaea.[3] Prokaryotic organisms evolved before eukaryotic organisms, so at one point the world consisted of nothing but prokaryotic organisms.

Kinds of eukaryotic organisms

Unicellular

[[File:|thumb|right|A paramecium]] Unicellular organisms are made up of one cell. Examples of unicellular organisms are:

Unicellular organisms live without other cells to help them. Many of these organisms need to:

All organisms must:

  • get rid of waste
  • reproduce (make more of itself)
  • grow

Some may:

  • get their energy from the sun (e.g., cyanobacteria)
  • ferment (e.g., yeasts)
  • use anaerobic respiration (e.g. C. botulinum)

Multicellular

Multicellular organisms are made from many cells. They are complex organisms. This can be a small number of cells, or millions of cells. All plants and animals are multicellular organisms. The cells of a multicellular organism are not all the same. They have different shapes and sizes, and do different work in the organism. The cells are specialized. This means they do only some kinds of work. By themselves, they cannot do everything that the organism needs to live. They need other cells to do other work. They live together, but cannot live alone.

Cell history

Cells were discovered by Robert Hooke (1635–1703). He used a compound microscope with two lenses to look at the structure of cork, and to look at leaves and some insects. He did this from about 1660, and reported it in his book Micrographica in 1665. He named cells after the Latin word cella, meaning room. He did this because he thought cells looked like small rooms.

Many other naturalists and philosophers tried out the new instrument. The structure of plants was investigated by Nehemiah Grew (1641–1712) and Marcello Malpighi (1628–1694). Grew's major work was The anatomy of plants (1682).[4] It is not clear who first saw animal cells, Malpighi, Jan Swammerdam (1637–1680) or Antonie van Leeuwenhoek (1632–1723). There is no doubt Swammerdam was looking at red blood cells by 1682, and probably earlier. Malpighi's observations of blood were earlier, but are less clear. [4]p17

Leeuwenhoek's discoveries and drawings of 'little animalules' opened up a whole new world for naturalists. Protozoa, and microorganisms generally were discovered, and the discoveries about them are still going on today. Christian Gottfried Ehrenberg's book Die Infusionsthierchen summarised what was known in 1838. Lorenz Oken (1779–1851) in 1805 wrote that infusoria (microscopic forms) were the basis of all life.

The work of the Czech Jan Purkyně (1787–1869) and his student and collaborator Gabriel Valentin (1810–1883) was unjustly denigrated by the nationalistic Germans. They have a claim to some priority in the cell theory.[4]Chapter 9 Johannes Müller (1801–1858) also made great contributions. It was, however, his student Theodor Schwann (1810–1882) and Matthias Schleiden (1804–1881) who got the credit for the cell theory, despite the fact that some of their observations were not correct, and their credits to previous workers were "a travesty".[4]p97 As understood now, the cell theory includes these important ideas:

  1. All living things are made of cells.
  2. The cell is the basic unit of structure and function in all organisms.
  3. Every cell comes from another cell that lived before it.
  4. The nucleus is the core element of the cell.

Their key works were published in 1838 and 1839. These ideas still are the basic ideas of cell theory.[5]

Cell reproduction

The body cells of metazoans divide by simple mitotic cell division. Sexual reproduction is ancestral in eukaryotes, and in metazoa it is carried out by specialised sex cells in a process called meiosis.

Prokaryotic cells reproduce using binary fission, where the cell simply splits in half. For both mitosis and binary fission the cell must replicate all of its genetic information (DNA) so that each new cell will have a copy.

References

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  1. Alberts B, Johnson A. Lewis J. Raff M. Roberts K. Walter P. 2002. Molecular biology of the cell, 4th ed. Garland.
  2. Lodish H. Berk A. Matsudaira P. Kaiser CA. Krieger M. Scott MP. Zipurksy SL. Darnell J. 2004. Molecular cell biology, 5th ed. WH Freeman: NY.
  3. and viruses
  4. 4.0 4.1 4.2 4.3 Harris H. The birth of the cell. Yale 1999.
  5. Gall JG & McIntosh JR eds 2001. Landmark papers in cell biology. Bethesda MD and Cold Spring Harbor NY: The American Society for Cell Biology and Cold Spring Harbor Laboratory Press.

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