The cell is the basis of all living things, but cells are made up of smaller parts with different functions. Only a cell can make another cell.
In 1663, Robert Hooke was able to see and describe plant cells, seen in a thin slice of cork, examined under the microscope, and he estimated their size.
Hooke's estimate: in one inch, "near eleven hundred of them . . . in a Cubick Inch, above twelve hundred Millions, or 1 259 712 000, a thing most incredible".
René Joachim Henri Dutrochet was probably the first to offer us the theory that all living things are composed of cells, rather than Schleiden or Schwann.
In 1858, Rudolf Virchow ruled out spontaneous generation, saying that all cells arise from pre-existing cells, saying it in Latin: "Omnis cellula e cellula".
In 1860, Louis Pasteur stated his view that all living things come from living things, which he expressed in Latin, saying: "Omne vivum e vivo".
All the procaryotes have regions within them which are locally different, but they have no membrane-bound organelles inside the outer membrane.
The life forms we call procaryotes may also be considered as acellular, in that they contain a whole organism in a single container, rather than unicellular.
Saying that a cell is filled with cytoplasm is about as useful as saying a television set is filled with teleplasm: neither statement contains any information.
A cell membrane is a complex structure that interacts with the cells' contents and surroundings to play a major part in the operation of the cell.
The cell membrane is more than a bag: it is an important part of the cell which plays a major role in deciding what is, and is not, allowed into the cell.
Cells may take up material by active transport, where parts of the membrane select particular molecules and carry them into (or out of) the cell.
Cells may take up material by pinocytosis, where the cell membrane puckers in, surrounds a particle or some fluid, seals it off, and then releases it inside.
All of the organisms we call eucaryotes have membrane-bound organelles, including the nucleus, lysosomes, endoplasmic reticulum, Golgi bodies and mitochondria.
Serial endosymbiosis theory says the parts of eucaryotic cells were once separate simple organisms which linked together to form a complex organism.
In 1914, Warren H. Lewis and his wife, Margaret Lewis, used bright field microscopy to be the first to describe mitochondria and mitochondrial shape changes.
The role of the mitochondria is to generate energy in the cell, so the mitochondria are the centres where respiration is used to generate ATP from ADP.
The nucleus of a eucaryotic cell is visible under the light microscope, especially when it is treated with a DNA-specific dye that stains the chromosomes.
In 1956, Henry Borsook and Paul Charles Zamecnik established that the ribosomes of the endoplasmic reticulum were the site of protein synthesis.
The role of the ribosomes is to make protein as specified in accordance with the universal genetic code by the sequence of bases on a strand of messenger RNA