A cell (cell) is a minute chamber-like substructure of all living things. A basic unit in terms of structure and function of living organisms. At the same time, it can also be called a living organism.
The etymology of the English word "cell", which means cell, is the Greek word for "small room." In his book "Micrographia Plates-Microworld Illustrations" (Hyakushosha) published by Robert Hooke in 1665, "When I observed the bark of the cork oak, many small rooms (cells) were lined up." Reported, this is the origin of cells that came to be called cells.
A cell is a basic unit that constitutes an individual itself in a single-celled organism (bacteria, protist, etc.), which is a primitive form of an organism, and a tissue in a complex multicellular organism. All living things consist of this small chamber-like substructure "cell", which is generally recognized as "the most basic building block of living things", and having cells is sometimes one of the definitions of living things. In this view, viruses and viroids are not considered organisms because they do not have cells, do not metabolize, and cannot self-proliferate.
The cell is surrounded by a membrane structure that separates the cytoplasm from the outside world, and inside it has an organ that carries out metabolic pathways such as glycolysis and citric acid cycle and constantly performs life activities, and self-regenerates and replicates. It has the genetic information for it and the function to express it.
Organisms are diverse and there are multiple domains to classify. Of these, cells and organisms are classified into two types depending on the form in which DNA, which is a common substance responsible for heredity, is placed. Those that do not have a clear structure that holds DNA are called prokaryotes (prokaryotes), and they do not have other organelles. Such cells are called prokaryotic cells (prokaryotic cells / naked nuclei cells). On the other hand, cells with a clear nucleus that wraps DNA are eukaryotic cells (nucleated cells / nucleated cells), and clear organelles can also be seen. In cell division, eukaryotic cells undergo mitosis, whereas prokaryotic cells do not.
Furthermore, in living organisms, from single-celled organisms in which each cell lives independently, to organisms in which similar cells gather to form a colony and live together, and each cell. There are various morphologies, from multicellular organisms consisting of cells that are so specialized that they cannot live.
The name "cell" in English begins with "Micrographia" and "Micrographia" by Robert Hooke.
In 1665, he first discovered this structure while observing small pieces of the cork layer of Quercus suber under his own microscope, and thought that the organism was made of cells. However, what he actually observed was the cell wall after the contents were lost. He then performed cell observations under a high-performance microscope invented by Antonie van Leeuwenhoek.
From the results of observation of plant tissue by Matthias Jakob Schleiden in 1838 and animal tissue by Theodor Schwann the following year, it is said that organisms are basically composed of cells, and cells have a common structure. He proposed the "cell theory", which is the basic unit of development. The cell theory did not explain how cells develop, but in 1855 Rudolf Virchow Karl Wilhyo published the theory that "cells divide and multiply," and in 1860 Louis. Pasts