Animal Cells
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing (except virus, which consists only from DNA/RNA covered by protein and lipids), and is often called the building block of life. Organisms can be classified as unicellular (consisting of a single cell; including most bacteria) or multicellular (including plants and animals). Humans contain about 10 trillion (1013) cells. Most plant and animal cells are between 1 and 100 µm and therefore are visible only under the microscope.
The cell was discovered by Robert Hooke in 1665. The cell theory, first developed in 1839 by Matthias Jakob Schleiden and Theodor Schwann, states that all organisms are composed of one or more cells, that all cells come from preexisting cells, that vital functions of an organism occur within cells, and that all cells contain the hereditary information necessary for regulating cell functions and for transmitting information to the next generation of cells.
The word cell comes from the Latin cella, meaning "small room". The descriptive term for the smallest living biological structure was coined by Robert Hooke in a book he published in 1665 when he compared the cork cells he saw through his microscope to the small rooms monks lived in.
Read more about Animal Cells: Anatomy, Subcellular Components, Structures Outside The Cell Membrane, Movement or Motility, Origins, History of Research
Famous quotes containing the words animal and/or cells:
“When we reflect upon the cruelties daily practised upon such of the animal creation as are given us for food, or which we ensnare for our diversion, we shall be obliged to own that there is more of the savage in human nature than we are aware of.”
—Samuel Richardson (1689–1761)
“They are sworn enemies of lyric poetry.
In prison they accompany the jailer,
Enter cells to hear confessions.
Their short-end comes down
When you least expect it.”
—Charles Simic (b. 1938)