define cell in biology
Answers
Answer:
The cell (from Latin cella, meaning "small room"[1]) is the basic structural, functional, and biological unit of all known organisms. A cell is the smallest unit of life. Cells are often called the "building blocks of life". The study of cells is called cell biology, cellular biology, or cytology.
Cell
Wilson1900Fig2.jpg
Onion (Allium cepa) root cells in different phases of the cell cycle (drawn by E. B. Wilson, 1900)
Celltypes.svg
A eukaryotic cell (left) and prokaryotic cell (right)
Identifiers
MeSH
D002477
TH
H1.00.01.0.00001
FMA
686465
Anatomical terminology
[edit on Wikidata]
Cells consist of cytoplasm enclosed within a membrane, which contains many biomolecules such as proteins and nucleic acids.[2] Most plant and animal cells are only visible under a microscope, with dimensions between 1 and 100 micrometres.[3] Organisms can be classified as unicellular (consisting of a single cell such as bacteria) or multicellular (including plants and animals).[4] Most unicellular organisms are classed as microorganisms.
The number of cells in plants and animals varies from species to species; it has been estimated that humans contain somewhere around 40 trillion (4×1013) cells.[a][5] The human brain accounts for around 80 billion of these cells.[6]
Cells were discovered by Robert Hooke in 1665, who named them for their resemblance to cells inhabited by Christian monks in a monastery.[7][8] 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 cells are the fundamental unit of structure and function in all living organisms, and that all cells come from pre-existing cells.[9] Cells emerged on Earth at least 3.5 billion years ago.[10][11][12]
Cell types
Subcellular components
Structures outside the cell membrane
Cellular processes
Multicellularity
Origins
History of research
See also
References
Notes
Further reading
External links
Last edited 3 days ago by Citation bot
RELATED ARTICLES
Organelle
Specialized subunit within a cell that has a specific function
Outline of cell biology
Overview of and topical guide to cell biology
Prokaryote
Unicellular organism that lacks a membrane-bound nucleus
Cells are the structural, functional, and biological units of all living beings. A cell can replicate itself independently.