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Encyclopedia > Cell (biology)
Drawing of the structure of cork as it appeared under the microscope to Robert Hooke from Micrographia which is the origin of the word "cell" being used to describe the smallest unit of a living organism
Cells in culture, stained for keratin (red) and DNA (green)
Cells in culture, stained for keratin (red) and DNA (green)

The cell is the structural and functional unit of all known living organisms. It is the smallest unit of an organism that is classified as living, and is sometimes called the building block of life.[1] Some organisms, such as bacteria, are unicellular (consist of a single cell). Other organisms, such as humans, are multicellular. (Humans have an estimated 100 trillion or 1014 cells; a typical cell size is 10 µm; a typical cell mass is 1 nanogram.) The largest known cell is an ostrich egg. In 1837 before the final cell theory was developed, a Czech Jan Evangelista Purkyňe observed small "granules" while looking at the plant tissue through a microscope. 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. All cells come from preexisting cells. Vital functions of an organism occur within cells, and all cells contain the hereditary information necessary for regulating cell functions and for transmitting information to the next generation of cells. Image File history File links Download high-resolution version (811x1170, 213 KB) Schem. ... Image File history File links Download high-resolution version (811x1170, 213 KB) Schem. ... Cork cambium is a tissue found in woody plants as part of the periderm. ... Robert Hooke, FRS (July 18, 1635 – March 3, 1703) was an English polymath who played an important role in the scientific revolution, through both experimental and theoretical work. ... Hookes drawing of a flea Micrographia is a historical book by Robert Hooke, detailing the then twenty-eight year-old Hookes observations through various lenses. ... Cultured MDCK epithelial cells were stained for keratin, desmoplakin, and DNA. The stained cells were visualized by scanning laser confocal microscopy. ... Cultured MDCK epithelial cells were stained for keratin, desmoplakin, and DNA. The stained cells were visualized by scanning laser confocal microscopy. ... Staining is a biochemical technique of adding a class-specific (DNA, proteins, lipids, carbohydrates) dye to a substrate to qualify or quantify the presence of a specific compound. ... Not to be confused with kerogen or carotene. ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... For other uses, see Life (disambiguation). ... “Life on Earth” redirects here. ... Phyla Actinobacteria Aquificae Chlamydiae Bacteroidetes/Chlorobi Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Lentisphaerae Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Verrucomicrobia Bacteria (singular: bacterium) are unicellular microorganisms. ... A microorganism or microbe is an organism that is so small that it is microscopic (invisible to the naked eye). ... This article is about modern humans. ... Multicellular organisms are those organisms containing more than one cell, and having differentiated cells that perform specialized functions. ... A micrometre (American spelling: micrometer, symbol µm) is an SI unit of length equal to one millionth of a metre, or about a tenth of the diameter of a droplet of mist or fog. ... The nanogram is an SI unit of mass (symbol ng) defined as: 1 ng = 1 × 10-12 kilogram (1 × 10-9 gram) A nanogram is one billionth (1/1,000,000,000) of a gram. ... // Binomial name Carolus Linnaeus, 1758 The present-day distribution of Ostriches. ... In most birds and reptiles, an egg (Latin ovum) is the zygote, resulting from fertilization of the ovum. ... A prokaryote, a simple cell Cell theory is a scientific theory that is one of the foundations of biology. ... Die Entwickelung der Meduse (The Development of the Medusas), in Schleidens Das Meer Matthias Jakob Schleiden (April 5, 1804 - June 23, 1881) was a German botanist and co-founder of cell theory. ... Theodore Schwann Theodor Schwann (December 7, 1810 in Neuss, Prussia - January 11, 1882, in Cologne) was a German physiologist, histologist and cytologist. ... This article is about the general scientific term. ...


The word cell comes from the Latin cellula, meaning, a small room. The descriptive name for the smallest living biologial structure was chosen 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.[2] For other uses, see Latin (disambiguation). ... Robert Hooke, FRS (July 18, 1635 – March 3, 1703) was an English polymath who played an important role in the scientific revolution, through both experimental and theoretical work. ... Year 1665 (MDCLXV) was a common year starting on Thursday (link will display the full calendar) of the Gregorian calendar (or a common year starting on Sunday of the 10-day slower Julian calendar). ... A cork stopper for a wine bottle Champagne corks Varnished cork tiles can be used for flooring, as a substitute for linoleum or tiles. ...

Contents

Preamble

Each cell is at least somewhat self-contained and self-maintaining: it can take in nutrients, convert these nutrients into energy, carry out specialized functions, and reproduce as necessary. Each cell stores its own set of instructions for carrying out each of these activities. A nutrient is either a chemical element or compound used in an organisms metabolism or physiology. ...

Mouse cells grown in a culture dish. These cells grow in large clumps, but each individual cell is about 10 micrometres across

All cells have several different abilities:[3] Image of cell with size scale from wikibook Cell Biology textbook (licensed under the GFDL): http://wikibooks. ... Image of cell with size scale from wikibook Cell Biology textbook (licensed under the GFDL): http://wikibooks. ... A micrometre (American spelling: micrometer, symbol µm) is an SI unit of length equal to one millionth of a metre, or about a tenth of the diameter of a droplet of mist or fog. ...

Some prokaryotic cells contain important internal membrane-bound compartments,[4] but eukaryotic cells have a highly specialized endomembrane system characterized by regulated traffic and transport of vesicles.[5]
This does not adequately cite its references or sources. ... Binary fission Binary fission is the form of asexual reproduction in single-celled organisms by which one cell divides into two cells of the same size, used by most prokaryotes. ... Mitosis divides genetic information during cell division. ... For the figure of speech, see meiosis (figure of speech). ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... For a non-technical introduction to the topic, see Introduction to Genetics. ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... For other uses, see Gene (disambiguation). ... The life cycle of an mRNA in a eukaryotic cell. ... Figure 1: Ribosome structure indicating small subunit (A) and large subunit (B). ... A few of the metabolic pathways in a cell. ... 3D (left and center) and 2D (right) representations of the terpenoid molecule atisane. ... A by-product is a secondary or incidental product deriving from a manufacturing process or chemical reaction, and is not the primary product or service being produced. ... In biochemistry, a metabolic pathway is a series of chemical reactions occurring within a cell. ... In biology, signal transduction refers to any process by which a cell converts one kind of signal or stimulus into another, most often involving ordered sequences of biochemical reactions inside the cell, that are carried out by enzymes and linked through second messengers resulting in what is thought of as... For other uses, see PH (disambiguation). ... Look up cell membrane in Wiktionary, the free dictionary. ... This fluid lipid bilayer cross section is made up entirely of phosphatidyl choline. ... Prokaryotes are unicellular (in rare cases, multicellular) organisms without a nucleus. ... Kingdoms Eukaryotes are organisms with complex cells, in which the genetic material is organized into membrane-bound nuclei. ... The endomembrane system is the system of internal membranes within eukaryotic cells that divide the cell into functional and structural compartments, or organelles. ... The kinesin dimer attaches to, and moves along, microtubules. ... In cell biology, a vesicle is a relatively small and enclosed compartment, separated from the cytosol by at least one lipid bilayer. ...


Anatomy of cells

There are two types of cells: eukaryotic and prokaryotic. Prokaryotic cells are usually independent, while eukaryotic cells are usually found in multicellular organisms.


Prokaryotic cells

Main article: Prokaryote
Diagram of a typical prokaryotic cell
Diagram of a typical prokaryotic cell

Prokaryotes are distinguished from eukaryotes on the basis of nuclear organization, specifically their lack of a nuclear membrane. Prokaryotes also lack most of the intracellular organelles and structures that are characteristic of eukaryotic cells (an important exception is the ribosome, which are present in both prokaryotic and eukaryotic cells). Most functions of organelles, such as mitochondria, chloroplasts, and the Golgi apparatus, are taken over by the prokaryotic plasma membrane. Prokaryotic cells have three architectural regions: appendages called flagella and pili — proteins attached to the cell surface; a cell envelope consisting of a capsule, a cell wall, and a plasma membrane; and a cytoplasmic region that contains the cell genome (DNA) and ribosomes and various sorts of inclusions. Other differences include: Prokaryotic bacteria cell structure Prokaryotes (IPA: //) are a group of organisms that lack a cell nucleus (= karyon), or any other membrane-bound organelles. ... Image File history File links Prokaryote_cell_diagram. ... Image File history File links Prokaryote_cell_diagram. ... Prokaryotes are unicellular (in rare cases, multicellular) organisms without a nucleus. ... Prokaryotic bacteria cell structure Prokaryotes (IPA: //) are a group of organisms that lack a cell nucleus (= karyon), or any other membrane-bound organelles. ... A flagellum (plural, flagella) is a whip-like organelle that many unicellular organisms, and some multicellular ones, use to move about. ... Image of bacteriological pili or fimbriae A pilus (Latin; plural : pili) is a hairlike structure on the surface of a cell, especially Gram-negative bacteria, a protein appendage required for bacterial conjugation. ... The cell envelope is the cell membrane and cell wall plus an outer membrane, if one is present. ... A cell wall is a fairly rigid layer surrounding a cell, located external to the cell membrane, that provides the cell with structural support, protection, and a filtering mechanism. ... Drawing of a cell membrane A component of every biological cell, the cell membrane (or plasma membrane) is a thin and structured bilayer of phospholipid and protein molecules that envelopes the cell. ... Organelles. ... In biology the genome of an organism is the whole hereditary information of an organism that is encoded in the DNA (or, for some viruses, RNA). ...

  • The plasma membrane (a phospholipid bilayer) separates the interior of the cell from its environment and serves as a filter and communications beacon.
  • Most prokaryotes have a cell wall (some exceptions are Mycoplasma (a bacterium) and Thermoplasma (an archaeon)). It consists of peptidoglycan in bacteria, and acts as an additional barrier against exterior forces. It also prevents the cell from "exploding" (cytolysis) from osmotic pressure against a hypotonic environment. A cell wall is also present in some eukaryotes like plants (cellulose) and fungi, but has a different chemical composition.
  • A prokaryotic chromosome is usually a circular molecule (an exception is that of the bacterium Borrelia burgdorferi, which causes Lyme disease). Even without a real nucleus, the DNA is condensed in a nucleoid. Prokaryotes can carry extrachromosomal DNA elements called plasmids, which are usually circular. Plasmids can carry additional functions, such as antibiotic resistance.

A cell wall is a fairly rigid layer surrounding a cell, located external to the cell membrane, that provides the cell with structural support, protection, and a filtering mechanism. ... Species M. genitalium M. hominis M. pneumoniae etc. ... Species Darland , 1970 Sergerer , 1988 Thermoplasma is a genus of archaea. ... Peptidoglycan, also known as murein, is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of eubacteria. ... Cytolysis is the lysis, or death, of cells due to the rupture of the cell membrane. ... This article or section does not adequately cite its references or sources. ... This article does not cite any references or sources. ... Divisions Chytridiomycota Zygomycota Ascomycota Basidiomycota The Fungi (singular: fungus) are a large group of organisms ranked as a kingdom within the Domain Eukaryota. ... Lyme disease, or borreliosis, is an emerging infectious disease caused by spirochete bacteria from the genus Borrelia. ... Extrachromosomal DNA (sometimes called extranuclear DNA or nonchromosomal DNA) is DNA located or maintained in a cell apart from the chromosomes. ... Figure 1: Illustration of a bacterium with plasmids enclosed showing chromosomal DNA and plasmids. ... Antibiotic resistance is the ability of a micro-organism to withstand the effects of an antibiotic. ...

Eukaryotic cells

Main article: Eukaryote
Diagram of a typical eukaryotic cell, showing subcellular components. Organelles: (1) nucleolus (2) nucleus (3) ribosome (4) vesicle (5) rough endoplasmic reticulum (ER) (6) Golgi apparatus (7) Cytoskeleton (8) smooth ER (9) mitochondria (10) vacuole (11) cytoplasm (12) lysosome (13) centrioles
Diagram of a typical eukaryotic cell, showing subcellular components. Organelles: (1) nucleolus (2) nucleus (3) ribosome (4) vesicle (5) rough endoplasmic reticulum (ER) (6) Golgi apparatus (7) Cytoskeleton (8) smooth ER (9) mitochondria (10) vacuole (11) cytoplasm (12) lysosome (13) centrioles

Eukaryotic cells are about 10 times the size of a typical prokaryote and can be as much as 1000 times greater in volume. The major difference between prokaryotes and eukaryotes is that eukaryotic cells contain membrane-bound compartments in which specific metabolic activities take place. Most important among these is the presence of a cell nucleus, a membrane-delineated compartment that houses the eukaryotic cell's DNA. It is this nucleus that gives the eukaryote its name, which means "true nucleus". Other differences include: Kingdoms Animalia - Animals Fungi Plantae - Plants Chromalveolata Protista Alternative phylogeny Unikonta Opisthokonta Metazoa Choanozoa Eumycota Amoebozoa Bikonta Apusozoa Cabozoa Rhizaria Excavata Corticata Archaeplastida Chromalveolata Animals, plants, fungi, and protists are eukaryotes (IPA: ), organisms whose cells are organized into complex structures by internal membranes and a cytoskeleton. ... Image File history File links Biological_cell. ... Image File history File links Biological_cell. ... Kingdoms Eukaryotes are organisms with complex cells, in which the genetic material is organized into membrane-bound nuclei. ... Schematic of typical animal cell, showing subcellular components. ... The nucleolus is contained within the cell nucleus. ... HeLa cells stained for DNA with the Blue Hoechst dye. ... Figure 1: Ribosome structure indicating small subunit (A) and large subunit (B). ... In cell biology, a vesicle is a relatively small and enclosed compartment, separated from the cytosol by at least one lipid bilayer. ... The endoplasmic reticulum or ER is an organelle found in all eukaryotic cells that is an interconnected network of tubules, vesicles and cisternae that is responsible for several specialized functions: Protein translation, folding, and transport of proteins to be used in the cell membrane (e. ... Micrograph of Golgi apparatus, visible as a stack of semicircular black rings near the bottom. ... The eukaryotic cytoskeleton. ... Electron micrograph of a mitochondrion showing its mitochondrial matrix and membranes In cell biology, a mitochondrion (plural mitochondria) is a membrane-enclosed organelle that is found in most eukaryotic cells. ... Schematic of typical animal cell, showing subcellular components. ... Organelles. ... Organelles labeled at upper left. ... A centriole is a barrel shaped organelle[1] found in most eukaryotic cells, though absent in higher plants and fungi. ... Kingdoms Animalia - Animals Fungi Plantae - Plants Chromalveolata Protista Alternative phylogeny Unikonta Opisthokonta Metazoa Choanozoa Eumycota Amoebozoa Bikonta Apusozoa Cabozoa Rhizaria Excavata Corticata Archaeplastida Chromalveolata Animals, plants, fungi, and protists are eukaryotes (IPA: ), organisms whose cells are organized into complex structures by internal membranes and a cytoskeleton. ... HeLa cells stained for DNA with the Blue Hoechst dye. ...

  • The plasma membrane resembles that of prokaryotes in function, with minor differences in the setup. Cell walls may or may not be present.
  • The eukaryotic DNA is organized in one or more linear molecules, called chromosomes, which are associated with histone proteins. All chromosomal DNA is stored in the cell nucleus, separated from the cytoplasm by a membrane. Some eukaryotic organelles also contain some DNA.
  • Eukaryotes can move using cilia or flagella. The flagella are more complex than those of prokaryotes.
Table 1: Comparison of features of prokaryotic and eukaryotic cells
  Prokaryotes Eukaryotes
Typical organisms bacteria, archaea protists, fungi, plants, animals
Typical size ~ 1-10 µm ~ 10-100 µm (sperm cells, apart from the tail, are smaller)
Type of nucleus nucleoid region; no real nucleus real nucleus with double membrane
DNA circular (usually) linear molecules (chromosomes) with histone proteins
RNA-/protein-synthesis coupled in cytoplasm RNA-synthesis inside the nucleus
protein synthesis in cytoplasm
Ribosomes 50S+30S 60S+40S
Cytoplasmatic structure very few structures highly structured by endomembranes and a cytoskeleton
Cell movement flagella made of flagellin flagella and cilia made of tubulin
Mitochondria none one to several dozen (though some lack mitochondria)
Chloroplasts none in algae and plants
Organization usually single cells single cells, colonies, higher multicellular organisms with specialized cells
Cell division Binary fission (simple division) Mitosis (fission or budding)
Meiosis
Table 2: Comparison of structures between animal and plant cells
Typical animal cell Typical plant cell
Organelles
Additional structures

Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division. ... Schematic representation of the assembly of the core histones into the nucleosome. ... HeLa cells stained for DNA with the Blue Hoechst dye. ... Schematic of typical animal cell, showing subcellular components. ... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ... Phyla Crenarchaeota Euryarchaeota Korarchaeota Nanoarchaeota ARMAN The Archaea (), or archaebacteria, are a major group of microorganisms. ... Typical phyla Chromalveolata Chromista Heterokontophyta Haptophyta Cryptophyta (cryptomonads) Alveolata Dinoflagellata Apicomplexa Ciliophora (ciliates) Cabozoa Excavata Euglenozoa Percolozoa Metamonada Rhizaria Radiolaria Foraminifera Cercozoa Archaeplastida (in part) Rhodophyta (red algae) Glaucophyta (basal archaeplastids) Amoebozoa Choanozoa Many others; classification varies Protists (IPA: (RP); (GenAm)), Greek protiston -a meaning the (most) first of all... Subkingdom/Phyla Chytridiomycota Blastocladiomycota Neocallimastigomycota Glomeromycota Zygomycota Dikarya (inc. ... For other uses, see Plant (disambiguation). ... For other uses, see Animal (disambiguation). ... A micrometre (American spelling: micrometer, symbol µm) is an SI unit of length. ... A micrometre (American spelling: micrometer, symbol µm) is an SI unit of length. ... A spermatozoon or spermatozoan ( spermatozoa), from the ancient Greek σπέρμα (seed) and (living being) and more commonly known as a sperm cell, is the haploid cell that is the male gamete. ... HeLa cells stained for DNA with the Blue Hoechst dye. ... In prokaryotic lifeforms, the nucleoid region is the part of the cell that contains the DNA molecule. ... Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division. ... Schematic representation of the assembly of the core histones into the nucleosome. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Organelles. ... Figure 1: Ribosome structure indicating small subunit (A) and large subunit (B). ... The eukaryotic cytoskeleton. ... Chemotaxis is a kind of taxis, in which bodily cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemicals in their environment. ... For the insect anatomical structure, see Antenna (biology). ... Helicobacter pylori electron micrograph, showing multiple flagella on the cell surface Flagellin is a protein that arranges itself in a hollow cylinder to form the filament in bacterial flagellum. ... Not to be confused with Psyllium. ... Tubulin is the protein which makes up microtubules. ... In cell biology, a mitochondrion is an organelle found in the cells of most eukaryotes. ... Chloroplasts are organelles found in plant cells and eukaryotic algae that conduct photosynthesis. ... Algae have conventionally been regarded as simple plants within the study of botany. ... For other uses, see Plant (disambiguation). ... This does not adequately cite its references or sources. ... Binary fission Binary fission is the form of asexual reproduction in single-celled organisms by which one cell divides into two cells of the same size, used by most prokaryotes. ... Mitosis divides genetic information during cell division. ... For the figure of speech, see meiosis (figure of speech). ... HeLa cells stained for DNA with the Blue Hoechst dye. ... The nucleolus is contained within the cell nucleus. ... The endoplasmic reticulum or ER is an organelle found in all eukaryotic cells that is an interconnected network of tubules, vesicles and cisternae that is responsible for several specialized functions: Protein translation, folding, and transport of proteins to be used in the cell membrane (e. ... The endoplasmic reticulum or ER (endoplasmic means within the cytoplasm, reticulum means little net) is an organelle found in all eukaryotic cells. ... Figure 1: Ribosome structure indicating small subunit (A) and large subunit (B). ... The eukaryotic cytoskeleton. ... Micrograph of Golgi apparatus, visible as a stack of semicircular black rings near the bottom. ... Organelles. ... Electron micrograph of a mitochondrion showing its mitochondrial matrix and membranes In cell biology, a mitochondrion (plural mitochondria) is a membrane-enclosed organelle that is found in most eukaryotic cells. ... In cell biology, a vesicle is a relatively small and enclosed compartment, separated from the cytosol by at least one lipid bilayer. ... Organelles labeled at upper left. ... The centrosome is the main microtubule organizing center (MTOC) of the cell as well as a regulator of cell-cycle progression. ... A centriole is a barrel shaped organelle[1] found in most eukaryotic cells, though absent in higher plants and fungi. ... Schematic of typical animal cell, showing subcellular components. ... HeLa cells stained for DNA with the Blue Hoechst dye. ... The nucleolus is contained within the cell nucleus. ... Figure 1: Ribosome structure indicating small subunit (A) and large subunit (B). ... The eukaryotic cytoskeleton. ... Micrograph of Golgi apparatus, visible as a stack of semicircular black rings near the bottom. ... In cell biology, the Golgi apparatus, Golgi body, Golgi complex, or dictyosome is an organelle found in most eukaryotic cells, including those of plants and animals (but not most fungi). ... Organelles. ... Electron micrograph of a mitochondrion showing its mitochondrial matrix and membranes In cell biology, a mitochondrion (plural mitochondria) is a membrane-enclosed organelle that is found in most eukaryotic cells. ... In cell biology, a vesicle is a relatively small and enclosed compartment, separated from the cytosol by at least one lipid bilayer. ... Chloroplasts are organelles found in plant cells and eukaryotic algae that conduct photosynthesis. ... Plant cells with visible chloroplasts. ... Vacuoles are large membrane-bound compartments within some eukaryotic cells where they serve a variety of different functions: capturing food materials or unwanted structural debris surrounding the cell, sequestering materials that might be toxic to the cell, maintaining fluid balance (called turgor) within the cell, exporting unwanted substances from the... Vacuoles are large membrane-bound compartments within some eukaryotic cells where they serve a variety of different functions: capturing food materials or unwanted structural debris surrounding the cell, sequestering materials that might be toxic to the cell, maintaining fluid balance (called turgor) within the cell, exporting unwanted substances from the... Basic structure of a peroxisome Peroxisomes are ubiquitous organelles in eukaryotes that participate in the metabolism of fatty acids and other metabolites. ... Schematic of typical animal cell, showing subcellular components. ... A membrane-surrounded plant cell organelle, especially found in germinating seeds, and involved in the breakdown and conversion of fatty acids to acetyl-CoA for the glyoxylate bypass. ... Drawing of a cell membrane A component of every biological cell, the cell membrane (or plasma membrane) is a thin and structured bilayer of phospholipid and protein molecules that envelopes the cell. ... For the insect anatomical structure, see Antenna (biology). ... Not to be confused with Psyllium. ... Drawing of a cell membrane A component of every biological cell, the cell membrane (or plasma membrane) is a thin and structured bilayer of phospholipid and protein molecules that envelopes the cell. ... For the insect anatomical structure, see Antenna (biology). ... A cell wall is a fairly rigid layer surrounding a cell, located external to the cell membrane, that provides the cell with structural support, protection, and a filtering mechanism. ... Plasmodesmata (Singular, plasmodesma) are small cell junctions in a plant cell which connect the cytoplasm of adjacent plant cells, forming a circulatory and communication system connecting the cells in plant tissue. ...

Subcellular components

The cells of eukaryotes (left) and prokaryotes (right).
The cells of eukaryotes (left) and prokaryotes (right).

All cells, whether prokaryotic or eukaryotic, have a membrane that envelops the cell, separates its interior from its environment, regulates what moves in and out (selectively permeable), and maintains the electric potential of the cell. Inside the membrane, a salty cytoplasm takes up most of the cell volume. All cells possess DNA, the hereditary material of genes, and RNA, containing the information necessary to build various proteins such as enzymes, the cell's primary machinery. There are also other kinds of biomolecules in cells. This article will list these primary components of the cell, then briefly describe their function. Image File history File links This is a lossless scalable vector image. ... Image File history File links This is a lossless scalable vector image. ... Prokaryotes are unicellular (in rare cases, multicellular) organisms without a nucleus. ... Kingdoms Eukaryotes are organisms with complex cells, in which the genetic material is organized into membrane-bound nuclei. ... Look up cell membrane in Wiktionary, the free dictionary. ... In biological cells that are electrically at rest, the cytosol possesses a uniform electric potential or voltage compared to the extracellular solution. ... For other uses, see Salt (disambiguation). ... Organelles. ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... For other uses, see Gene (disambiguation). ... Ribonucleic acid or RNA is a nucleic acid polymer consisting of nucleotide monomers that plays several important roles in the processes that translate genetic information from deoxyribonucleic acid (DNA) into protein products; RNA acts as a messenger between DNA and the protein synthesis complexes known as ribosomes, forms vital portions... Gene expression, or simply expression, is the process by which the inheritable information which comprises a gene, such as the DNA sequence, is made manifest as a physical and biologically functional gene product, such as protein or RNA. Several steps in the gene expression process may be modulated, including the... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ...


Cell membrane: A cell's defining boundary

Main article: Cell membrane

The cytoplasm of a cell is surrounded by a plasma membrane. The plasma membrane in plants and prokaryotes is usually covered by a cell wall. This membrane serves to separate and protect a cell from its surrounding environment and is made mostly from a double layer of lipids (hydrophobic fat-like molecules) and hydrophilic phosphorus molecules. Hence, the layer is called a phospholipid bilayer. It may also be called a fluid mosaic membrane. Embedded within this membrane is a variety of protein molecules that act as channels and pumps that move different molecules into and out of the cell. The membrane is said to be 'semi-permeable', in that it can either let a substance (molecule or ion) pass through freely, pass through to a limited extent or not pass through at all. Cell surface membranes also contain receptor proteins that allow cells to detect external signalling molecules such as hormones. Look up cell membrane in Wiktionary, the free dictionary. ... A cell wall is a fairly rigid layer surrounding a cell, located external to the cell membrane, that provides the cell with structural support, protection, and a filtering mechanism. ... This fluid lipid bilayer cross section is made up entirely of phosphatidyl choline. ... In chemistry, hydrophobic or lipophilic species, or hydrophobes, tend to be electrically neutral and nonpolar, and thus prefer other neutral and nonpolar solvents or molecular environments. ... The adjective hydrophilic describes something that likes water (from Greek hydros = water; philos = friend). ... General Name, symbol, number phosphorus, P, 15 Chemical series nonmetals Group, period, block 15, 3, p Appearance waxy white/ red/ black/ colorless Standard atomic weight 30. ... A DPPC bilayer simulation Color scheme: PO4 = green, N(CH3)3 = violet, water = blue, terminal CH3 = yellow, O = red, glycol C = brown, chain C = grey In biology and chemistry, a lipid bilayer is a membrane or zone of membrane composed only of lipid. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... 3D (left and center) and 2D (right) representations of the terpenoid molecule atisane. ... This article is about the electrically charged particle. ... In biochemistry, a receptor is a protein on the cell membrane or within the cytoplasm or cell nucleus that binds to a specific molecule (a ligand), such as a neurotransmitter, hormone, or other substance, and initiates the cellular response to the ligand. ... Norepinephrine A hormone (from Greek όρμή - to set in motion) is a chemical messenger from one cell (or group of cells) to another. ...


Cytoskeleton: A cell's scaffold

Main article: Cytoskeleton

The cytoskeleton acts to organize and maintain the cell's shape; anchors organelles in place; helps during endocytosis, the uptake of external materials by a cell, and cytokinesis, the separation of daughter cells after cell division; and moves parts of the cell in processes of growth and mobility. The eukaryotic cytoskeleton is composed of microfilaments, intermediate filaments and microtubules. There is a great number of proteins associated with them, each controlling a cell's structure by directing, bundling, and aligning filaments. The prokaryotic cytoskeleton is less well-studied but is involved in the maintenance of cell shape, polarity and cytokinesis.[6] The eukaryotic cytoskeleton. ... It has been suggested that Endocytic cycle be merged into this article or section. ... A cell that has almost completed cytokinesis. ... This does not adequately cite its references or sources. ... This article or section should be merged with actin Microfilaments or actin filaments are made up of two twisted monomeric actin subunits. ... // Intermediate filaments (IFs) are important structural proteins which are located both in the cytoplasm and the nucleus. ... Microtubules are one of the components of the cytoskeleton. ...


Genetic material

Two different kinds of genetic material exist: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Most organisms use DNA for their long-term information storage, but some viruses (e.g., retroviruses) have RNA as their genetic material. The biological information contained in an organism is encoded in its DNA or RNA sequence. RNA is also used for information transport (e.g., mRNA) and enzymatic functions (e.g., ribosomal RNA) in organisms that use DNA for the genetic code itself. The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... Ribonucleic acid or RNA is a nucleic acid polymer consisting of nucleotide monomers that plays several important roles in the processes that translate genetic information from deoxyribonucleic acid (DNA) into protein products; RNA acts as a messenger between DNA and the protein synthesis complexes known as ribosomes, forms vital portions... An RNA virus is a virus that either uses RNA as its genetic material, or whose genetic material passes through an RNA intermediate during replication. ... Genera Alpharetrovirus Betaretrovirus Gammaretrovirus Deltaretrovirus Epsilonretrovirus Lentivirus Spumavirus A retrovirus is any virus belonging to the viral family Retroviridae. ... For a non-technical introduction to the topic, see Introduction to Genetics. ... The interaction of mRNA in a eukaryote cell. ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... Figure 1: Ribosome structure indicating small subunit (A) and large subunit (B). ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ...


Prokaryotic genetic material is organized in a simple circular DNA molecule (the bacterial chromosome) in the nucleoid region of the cytoplasm. Eukaryotic genetic material is divided into different, linear molecules called chromosomes inside a discrete nucleus, usually with additional genetic material in some organelles like mitochondria and chloroplasts (see endosymbiotic theory). Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division. ... In prokaryotic lifeforms, the nucleoid region is the part of the cell that contains the DNA molecule. ... Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division. ... In cell biology, a mitochondrion is an organelle found in the cells of most eukaryotes. ... Chloroplasts are organelles found in plant cells and eukaryotic algae which conduct photosynthesis. ... It has been suggested that Proto-mitochondrion be merged into this article or section. ...


A human cell has genetic material in the nucleus (the nuclear genome) and in the mitochondria (the mitochondrial genome). In humans the nuclear genome is divided into 46 linear DNA molecules called chromosomes. The mitochondrial genome is a circular DNA molecule separate from the nuclear DNA. Although the mitochondrial genome is very small, it codes for some important proteins. In biology the genome of an organism is the whole hereditary information of an organism that is encoded in the DNA (or, for some viruses, RNA). ... The mitochondrial genome is the genetic material of the mitochondria. ...


Foreign genetic material (most commonly DNA) can also be artificially introduced into the cell by a process called transfection. This can be transient, if the DNA is not inserted into the cell's genome, or stable, if it is. Transfection describes the introduction of foreign material into eukaryotic cells. ... In biology the genome of an organism is the whole hereditary information of an organism that is encoded in the DNA (or, for some viruses, RNA). ...


Organelles

Main article: Organelle

The human body contains many different organs, such as the heart, lung, and kidney, with each organ performing a different function. Cells also have a set of "little organs," called organelles, that are adapted and/or specialized for carrying out one or more vital functions. Membrane-bound organelles are found only in eukaryotes. Schematic of typical animal cell, showing subcellular components. ... This article is about the biological unit. ... Schematic of typical animal cell, showing subcellular components. ...

Cell nucleus (a cell's information center) 
The cell nucleus is the most conspicuous organelle found in a eukaryotic cell. It houses the cell's chromosomes, and is the place where almost all DNA replication and RNA synthesis occur. The nucleus is spherical in shape and separated from the cytoplasm by a double membrane called the nuclear envelope. The nuclear envelope isolates and protects a cell's DNA from various molecules that could accidentally damage its structure or interfere with its processing. During processing, DNA is transcribed, or copied into a special RNA, called mRNA. This mRNA is then transported out of the nucleus, where it is translated into a specific protein molecule. In prokaryotes, DNA processing takes place in the cytoplasm.
Diagram of a cell nucleus
Mitochondria and Chloroplasts (the power generators) 
Mitochondria are self-replicating organelles that occur in various numbers, shapes, and sizes in the cytoplasm of all eukaryotic cells. As mitochondria contain their own genome that is separate and distinct from the nuclear genome of a cell, they play a critical role in generating energy in the eukaryotic cell, they give the cell energy by the process of respiration, adding oxygen to food (typicially pertaining to glucose and ATP) to release energy. Organelles that are modified chloroplasts are broadly called plastids, and are often involved in storage. Since they contain their own genome, they are thought to have once been separate organisms, which later formed a symbiotic relationship with the cells. Chloroplasts are the counter-part of the mitochondria. Instead of giving off CO2 and H2O Plants give off glucose, oxygen, 6 molecules of water (compared to 12 in respiration) this process is called photosynthesis.
Endoplasmic reticulum and Golgi apparatus (macromolecule managers) 
The endoplasmic reticulum (ER) is the transport network for molecules targeted for certain modifications and specific destinations, as compared to molecules that will float freely in the cytoplasm. The ER has two forms: the rough ER, which has ribosomes on its surface, and the smooth ER, which lacks them. Also the Golgi apparatus's ends "pinch" off and become new vacuoles in the animal cell.
Ribosomes (the protein production centers in the cell) 
The ribosome is a large complex, composed of many molecules, in prokaryotes only exist floating freely in the cytosol, whereas in eukaryotes they can be found either free or bound to membranes.
Lysosomes and Peroxisomes (of the eukaryotic cell) 
The cell could not house such destructive enzymes if they were not contained in a membrane-bound system. These organelles are often called a "suicide bag" because of their ability to detonate and destroy the cell.
Centrosome (the cytoskeleton organiser) 
The centrosome produces the microtubules of a cell - a key component of the cytoskeleton. It directs the transport through the ER and the Golgi apparatus. Centrosomes are composed of two centrioles, which separate during cell division and help in the formation of the mitotic spindle. A single centrosome is present in the animal cells. They are also found in some fungi and algae cells.
Vacuoles 
Vacuoles store food and waste. Some vacuoles store extra water. They are often described as liquid filled space and are surrounded by a membrane. Some cells, most notably Amoeba, have contractile vacuoles, which are able to pump water out of the cell if there is too much water.

Cell functions

Cell growth and metabolism

Main articles: Cell growth and Metabolism

Between successive cell divisions, cells grow through the functioning of cellular metabolism. HeLa cells stained for DNA with the Blue Hoechst dye. ... Kingdoms Eukaryotes are organisms with complex cells, in which the genetic material is organized into membrane-bound nuclei. ... This article is about the biological chromosome. ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... Ribonucleic acid or RNA is a nucleic acid polymer consisting of nucleotide monomers that plays several important roles in the processes that translate genetic information from deoxyribonucleic acid (DNA) into protein products; RNA acts as a messenger between DNA and the protein synthesis complexes known as ribosomes, forms vital portions... Synthesis (from the ancient Greek σύν (with) and θεσις (placing), is commonly understood to be an integration of two or more pre-existing elements which results in a new creation. ... The nuclear envelope (also known as the perinuclear envelope, nuclear membrane, nucleolemma or karyotheca) is the double membrane of the nucleus that encloses genetic material in eukaryotic cells. ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... A micrograph of ongoing gene transcription of ribosomal RNA illustrating the growing primary transcripts. ... Ribonucleic acid or RNA is a nucleic acid polymer consisting of nucleotide monomers that plays several important roles in the processes that translate genetic information from deoxyribonucleic acid (DNA) into protein products; RNA acts as a messenger between DNA and the protein synthesis complexes known as ribosomes, forms vital portions... The interaction of mRNA in a eukaryote cell. ... Organelles. ... Image File history File links Diagram_human_cell_nucleus_no_text. ... Electron micrograph of a mitochondrion showing its mitochondrial matrix and membranes In cell biology, a mitochondrion (plural mitochondria) is a membrane-enclosed organelle that is found in most eukaryotic cells. ... General Name, symbol, number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, period, block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Standard atomic weight 15. ... Glucose (Glc), a monosaccharide (or simple sugar), is an important carbohydrate in biology. ... Adenosine 5-triphosphate (ATP) is a multifunctional nucleotide that is most important as a molecular currency of intracellular energy transfer. ... Plant cells with visible chloroplasts. ... The endoplasmic reticulum or ER is an organelle found in all eukaryotic cells that is an interconnected network of tubules, vesicles and cisternae that is responsible for several specialized functions: Protein translation, folding, and transport of proteins to be used in the cell membrane (e. ... Micrograph of Golgi apparatus, visible as a stack of semicircular black rings near the bottom. ... Image File history File links Endomembrane_system_diagram_no_text_nucleus. ... Figure 1: Ribosome structure indicating small subunit (A) and large subunit (B). ... Lysosomes are organelles in eukaryotic cells that contain digestive enzymes to digest macromolecules. ... Peroxisomes are ubiquitous organelles in eukaryotes. ... The centrosome is the main microtubule organizing center (MTOC) of the cell as well as a regulator of cell-cycle progression. ... Microtubules are protein structures found within cells. ... The eukaryotic cytoskeleton. ... The endoplasmic reticulum or ER is an organelle found in all eukaryotic cells that is an interconnected network of tubules, vesicles and cisternae that is responsible for several specialized functions: Protein translation, folding, and transport of proteins to be used in the cell membrane (e. ... Micrograph of Golgi apparatus, visible as a stack of semicircular black rings near the bottom. ... A centriole in biology is a hollow cylindrical organelle found in most animal cells, and cells of fungi and algae though not frequently in plants. ... This does not adequately cite its references or sources. ... Micrograph showing condensed chromosomes in blue and the mitotic spindle in green during prometaphase of mitosis The mitotic spindle (a. ... A three-dimensional diagram of the animal cell, including its organelles. ... Schematic of typical animal cell, showing subcellular components. ... Alternate meanings: Amoeboid, Amoebozoa For other uses, see Amoeba (disambiguation). ... The term cell growth is used in two different ways in biology. ... A few of the metabolic pathways in a cell. ...


Cell metabolism is the process by which individual cells process nutrient molecules. Metabolism has two distinct divisions: catabolism, in which the cell breaks down complex molecules to produce energy and reducing power, and anabolism, in which the cell uses energy and reducing power to construct complex molecules and perform other biological functions. Complex sugars consumed by the organism can be broken down into a less chemically-complex sugar molecule called glucose. Once inside the cell, glucose is broken down to make adenosine triphosphate (ATP), a form of energy, via two different pathways. Anabolism is the aspect of metabolism that contributes to growth. ... Anabolism is the metabolic process that builds larger molecules from smaller ones. ... Glucose (Glc), a monosaccharide (or simple sugar), is an important carbohydrate in biology. ... Adenosine 5-triphosphate (ATP) is a multifunctional nucleotide that is most important as a molecular currency of intracellular energy transfer. ...


The first pathway, glycolysis, requires no oxygen and is referred to as anaerobic metabolism. Each reaction is designed to produce some hydrogen ions that can then be used to make energy packets (ATP). In prokaryotes, glycolysis is the only method used for converting energy. The word glycolysis is derived from Greek γλυκύς (sweet) and λύσις (rupture). ... It has been suggested that this article or section be merged with Fermentation (food). ...


The second pathway, called the Krebs cycle, or citric acid cycle, occurs inside the mitochondria and is capable of generating enough ATP to run all the cell functions. Overview of the citric acid cycle The citric acid cycle (also known as the tricarboxylic acid cycle, the TCA cycle, or the Krebs cycle, after Hans Adolf Krebs who identified the cycle) is a series of chemical reactions of central importance in all living cells that use oxygen as part...

An overview of protein synthesis.Within the nucleus of the cell (light blue), genes (DNA, dark blue) are transcribed into RNA. This RNA is then subject to post-transcriptional modification and control, resulting in a mature mRNA (red) that is then transported out of the nucleus and into the cytoplasm (peach), where it undergoes translation into a protein. mRNA is translated by ribosomes (purple) that match the three-base codons of the mRNA to the three-base anti-codons of the appropriate tRNA. Newly-synthesized proteins (black) are often further modified, such as by binding to an effector molecule (orange), to become fully active.
An overview of protein synthesis.
Within the nucleus of the cell (light blue), genes (DNA, dark blue) are transcribed into RNA. This RNA is then subject to post-transcriptional modification and control, resulting in a mature mRNA (red) that is then transported out of the nucleus and into the cytoplasm (peach), where it undergoes translation into a protein. mRNA is translated by ribosomes (purple) that match the three-base codons of the mRNA to the three-base anti-codons of the appropriate tRNA. Newly-synthesized proteins (black) are often further modified, such as by binding to an effector molecule (orange), to become fully active.

Creation of new cells

Main article: Cell division

Cell division involves a single cell (called a mother cell) dividing into two daughter cells. This leads to growth in multicellular organisms (the growth of tissue) and to procreation (vegetative reproduction) in unicellular organisms. File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... HeLa cells stained for DNA with the Blue Hoechst dye. ... For other uses, see Gene (disambiguation). ... A micrograph of ongoing gene transcription of ribosomal RNA illustrating the growing primary transcripts. ... Ribonucleic acid or RNA is a nucleic acid polymer consisting of nucleotide monomers that plays several important roles in the processes that translate genetic information from deoxyribonucleic acid (DNA) into protein products; RNA acts as a messenger between DNA and the protein synthesis complexes known as ribosomes, forms vital portions... The interaction of mRNA in a eukaryote cell. ... Organelles. ... Translation is the second process of protein biosynthesis (part of the overall process of gene expression). ... Figure 1: Ribosome structure indicating small subunit (A) and large subunit (B). ... RNA codons. ... Transfer RNA Transfer RNA (abbreviated tRNA), first hypothesized by Francis Crick, is a small RNA chain (73-93 nucleotides) that transfers a specific amino acid to a growing polypeptide chain at the ribosomal site of protein synthesis during translation. ... This does not adequately cite its references or sources. ... Wild-type Caenorhabditis elegans hermaphrodite stained to highlight the nuclei of all cells Multicellular organisms are organisms consisting of more than one cell, and having differentiated cells that perform specialized functions. ... Biological tissue is a collection of interconnected cells that perform a similar function within an organism. ... Production of new individuals along a leaf margin of the air plant, Kalanchoë pinnata. ... A microorganism or microbe is an organism that is so small that it is microscopic (invisible to the naked eye). ...


Prokaryotic cells divide by binary fission. Eukaryotic cells usually undergo a process of nuclear division, called mitosis, followed by division of the cell, called cytokinesis. A diploid cell may also undergo meiosis to produce haploid cells, usually four. Haploid cells serve as gametes in multicellular organisms, fusing to form new diploid cells. Prokaryotic bacteria cell structure Prokaryotes (IPA: //) are a group of organisms that lack a cell nucleus (= karyon), or any other membrane-bound organelles. ... Binary fission Binary fission is the form of asexual reproduction in single-celled organisms by which one cell divides into two cells of the same size, used by most prokaryotes. ... Kingdoms Animalia - Animals Fungi Plantae - Plants Chromalveolata Protista Alternative phylogeny Unikonta Opisthokonta Metazoa Choanozoa Eumycota Amoebozoa Bikonta Apusozoa Cabozoa Rhizaria Excavata Corticata Archaeplastida Chromalveolata Animals, plants, fungi, and protists are eukaryotes (IPA: ), organisms whose cells are organized into complex structures by internal membranes and a cytoskeleton. ... Mitosis divides genetic information during cell division. ... A cell that has almost completed cytokinesis. ... Diploid (meaning double in Greek) cells have two copies (homologs) of each chromosome (both sex- and non-sex determining chromosomes), usually one from the mother and one from the father. ... For the figure of speech, see meiosis (figure of speech). ... Haploid (meaning simple in Greek) cells have only one copy of each chromosome. ... A gamete is a specialized germ cell that fuses with another gamete during fertilization (conception) in organisms that reproduce sexually. ...


DNA replication, or the process of duplicating a cell's genome, is required every time a cell divides. Replication, like all cellular activities, requires specialized proteins for carrying out the job. It has been suggested that DNA replicate, Replisome, Replication fork, Lagging strand, Leading strand be merged into this article or section. ...

Protein synthesis

Main article: Protein biosynthesis

Cells are capable of synthesizing new proteins, which are essential for the modulation and maintenance of cellular activities. This process involves the formation of new protein molecules from amino acid building blocks based on information encoded in DNA/RNA. Protein synthesis generally consists of two major steps: transcription and translation. An overview of protein synthesis. ... Phenylalanine is one of the standard amino acids. ... A micrograph of ongoing gene transcription of ribosomal RNA illustrating the growing primary transcripts. ... Translation is the second process of protein biosynthesis (part of the overall process of gene expression). ...


Transcription is the process where genetic information in DNA is used to produce a complementary RNA strand. This RNA strand is then processed to give messenger RNA (mRNA), which is free to migrate through the cell. mRNA molecules bind to protein-RNA complexes called ribosomes located in the cytosol, where they are translated into polypeptide sequences. The ribosome mediates the formation of a polypeptide sequence based on the mRNA sequence. The mRNA sequence directly relates to the polypeptide sequence by binding to transfer RNA (tRNA) adapter molecules in binding pockets within the ribosome. The new polypeptide then folds into a functional three-dimensional protein molecule. The life cycle of an mRNA in a eukaryotic cell. ... Figure 1: Ribosome structure indicating small subunit (A) and large subunit (B). ... The cytosol (cf. ... Transfer RNA Transfer RNA (abbreviated tRNA), first hypothesized by Francis Crick, is a small RNA chain (73-93 nucleotides) that transfers a specific amino acid to a growing polypeptide chain at the ribosomal site of protein synthesis during translation. ...

Cell movement or motility

Cell has the ability to move spontaneously during the process of wound healing, immune response and cancer metastasis. The fastest moving cells in the human body are the spermaculi, which enter and exit through the penis. This was proven when Professor Julia Ertmann of UCLA observed changes in the reproductive spermaculi in a lab environment (circa 2005). For wound healing to occur, white blood cells and cells that ingest bacteria move to the wound site to kill the microorganisms that cause infection. A the same time fibroblasts (connective tissue cells) move there to remodel damaged structures. In the case of tumor development, cells from a primary tumor move away and spread to other parts of the body. Cell motility involves many receptors, crosslinking, bundling, binding, adhesion, motor and other proteins.[7] The process is divided into three steps - protrusion of the leading edge of the cell, adhesion of the leading edge and deadhesion at the cell body and rear, and cytoskeletal contraction to pull the cell forward. Each of these steps is driven by physical forces generated by unique segments of the cytoskeleton. [8][9]

Origins of cells

Main article: Origin of life

The origin of cells has to do with the origin of life, and was one of the most important steps in the theory of evolution. The birth of the cell marked the passage from prebiotic chemistry to biological life. This article does not adequately cite its references or sources. ...

Origin of the first cell

For more information RNA world hypothesis

In a gene-centered view of evolution, life is regarded in terms of replicators—that is DNA molecules in the organism. In this paradigm, cells satisfy two fundamental conditions: protection from the outside environment and confinement of biochemical activity. The former condition is needed to maintain the stability of fragile DNA chains in a varying and sometimes aggressive environment, and may have been the main reason for which cells evolved. The latter is fundamental for the evolution of complexity. If freely-floating DNA molecules that code for enzymes are not enclosed in cells, the enzymes that benefit a given replicator (for example, by producing nucleotides) may do so less efficiently, and may in fact benefit competing replicators. If the entire DNA molecule of a replicator is enclosed in a cell, then the enzymes coded from the molecule will be kept close to the DNA molecule itself. The replicator will directly benefit from its encoded enzymes. RNA with its nitrogenous bases to the left and DNA to the right. ... The gene-centered view of evolution, gene selection theory or selfish gene theory holds that natural selection acts through differential survival of competing genes, increasing the frequency of those alleles whose phenotypic effects successfully promote their own propagation. ... Survival machine is a concept, first proposed by Richard Dawkins in The Selfish Gene, whereby all organisms should be considered as the protection genes construct to survive their surroundings in order to propagate. ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... The evolution of complexity is an important outcome of the process of evolution. ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ...


Biochemically, cell-like spheroids formed by proteinoids are observed by heating amino acids with phosphoric acid as a catalyst. They bear many of the basic features provided by cell membranes. Proteinoid-based protocells enclosing RNA molecules may have been the first cellular life forms on Earth. Phospholipid bilayer membranes can contain water, and are a probable precursor to the modern cell membrane.[10] Proteinoids are protein-like molecules formed inorganically from amino acids. ... Phenylalanine is one of the standard amino acids. ... This article is about orthophosphoric acid. ... It has been suggested that this article or section be merged into Catalysis. ... Look up cell membrane in Wiktionary, the free dictionary. ... Phospholipid Two schematic representations of a phospholipid. ... This fluid lipid bilayer cross section is made up entirely of phosphatidyl choline. ...

Origin of eukaryotic cells

The eukaryotic cell seems to have evolved from a symbiotic community of prokaryotic cells. It is almost certain that DNA-bearing organelles like the mitochondria and the chloroplasts are what remains of ancient symbiotic oxygen-breathing proteobacteria and cyanobacteria, respectively, where the rest of the cell seems to be derived from an ancestral archaean prokaryote cell – a theory termed the endosymbiotic theory. For other uses, see Symbiosis (disambiguation). ... In cell biology, a mitochondrion is an organelle found in the cells of most eukaryotes. ... Chloroplasts are organelles found in plant cells and eukaryotic algae which conduct photosynthesis. ... Orders Alpha Proteobacteria    Caulobacterales - e. ... Orders The taxonomy of the Cyanobacteria is currently under revision. ... Phyla Crenarchaeota Euryarchaeota Korarchaeota Nanoarchaeota ARMAN The Archaea (), or archaebacteria, are a major group of microorganisms. ... It has been suggested that Proto-mitochondrion be merged into this article or section. ...


There is still considerable debate about whether organelles like the hydrogenosome predated the origin of mitochondria, or viceversa: see the hydrogen hypothesis for the origin of eukaryotic cells. A hydrogenosome is an organelle of ciliates, trichomonads and fungi. ... In cell biology, a mitochondrion is an organelle found in the cells of most eukaryotes. ... The Hydrogen hypothesis is a model that describes how the first eukaryotic cell may have developed. ...


Sex, as the stereotyped choreography of meiosis and syngamy that persists in nearly all extant eukaryotes, may have played a role in the transition from prokaryotes to eukaryotes. An 'origin of sex as vaccination' theory suggests that the eukaryote genome accreted from prokaryan parasite genomes in numerous rounds of lateral gene transfer. Sex-as-syngamy (fusion sex) arose when infected hosts began swapping nuclearized genomes containing coevolved, vertically transmitted symbionts that conveyed protection against horizontal infection by more virulent symbionts.[11]

History

See also

References

  1. ^ Cell Movements and the Shaping of the Vertebrate Body in Chapter 21 of Molecular Biology of the Cell fourth edition, edited by Bruce Alberts (2002) published by Garland Science.
    The Alberts text discusses how the "cellular building blocks" move to shape developing embryos. It is also common to describe small molecules such as amino acids as "molecular building blocks".
  2. ^ a b "... I could exceedingly plainly perceive it to be all perforated and porous, much like a Honey-comb, but that the pores of it were not regular [..] these pores, or cells, [..] were indeed the first microscopical pores I ever saw, and perhaps, that were ever seen, for I had not met with any Writer or Person, that had made any mention of them before this. . ." – Hooke describing his observations on a thin slice of cork. Robert Hooke
  3. ^ The Universal Features of Cells on Earth in Chapter 1 of the Alberts textbook (reference #1, above).
  4. ^ L.M., Mashburn-Warren; Whiteley, M. (2006). "Special delivery: vesicle trafficking in prokaryotes.". Mol Microbiol 61 (4): 839-46. 
  5. ^ A. Rose, S. J. Schraegle, E. A. Stahlberg and I. Meier (2005) "Coiled-coil protein composition of 22 proteomes--differences and common themes in subcellular infrastructure and traffic control" in BMC evolutionary biology Vulume 5 article 66. Entrez PubMed 16288662
    Rose et al. suggest that coiled-coil alpha helical vesicle transport proteins are only found in eukaryotic organisms.
  6. ^ Michie K, Löwe J (2006). "Dynamic filaments of the bacterial cytoskeleton". Annu Rev Biochem 75: 467-92. PMID 16756499. 
  7. ^ http://www.biolsci.org/v03p0303.htm
  8. ^ Alberts B, Johnson A, Lewis J. et al. Molecular Biology of the Cell, 4e. Garland Science. 2002
  9. ^ Ananthakrishnan R, Ehrlicher A. The Forces Behind Cell Movement. Int J Biol Sci 2007; 3:303-317. http://www.biolsci.org/v03p0303.htm
  10. ^ http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/P/Phospholipids.html
  11. ^ Sterrer W (2002). "On the origin of sex as vaccination". Journal of Theoretical Biology 216: 387-396. 
  • This article contains material from the Science Primer published by the NCBI, which, as a U.S. government publication, is in the public domain.

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Online textbooks

  • Alberts B, Johnson A, Lewis J, Raff M, Roberts K, Walter P (2002). Molecular Biology of the Cell, 4th ed., Garland. ISBN 0815332181. 
  • Lodish H, Berk A, Matsudaira P, Kaiser CA, Krieger M, Scott MP, Zipurksy SL, Darnell J (2004). Molecular Cell Biology, 5th ed., WH Freeman: New York, NY. ISBN 978-0716743668. 
  • 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; 2001. Commentaries and links to original research papers published in the ASCB Image & Video Library

Anton van Leeuwenhoek Anton van Leeuwenhoek (October 24, 1632 - August 30, 1723, full name Thonius Philips van Leeuwenhoek (pronounced Layewenhook) was a Dutch tradesman and scientist from Delft, Netherlands. ... This article is about the optical device. ... Robert Hookes microscope (1665) - an engineered device used to study living systems. ... Wikisource has an original article from the 1911 Encyclopædia Britannica about: Protozoa Protozoa (in Greek proto = first and zoa = animals) are single-celled eukaryotes (organisms whose cells have nuclei) that commonly show characteristics usually associated with animals, most notably mobility and heterotrophy. ... Species See text Vorticella is a genus of protozoa, with over 100 known species. ... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ... Robert Hooke, FRS (July 18, 1635 – March 3, 1703) was an English polymath who played an important role in the scientific revolution, through both experimental and theoretical work. ... Theodore Schwann Theodor Schwann (December 7, 1810 in Neuss, Prussia - January 11, 1882, in Cologne) was a German physiologist, histologist and cytologist. ... Die Entwickelung der Meduse (The Development of the Medusas), in Schleidens Das Meer Matthias Jakob Schleiden (April 5, 1804 - June 23, 1881) was a German botanist and co-founder of cell theory. ... Abiogenesis (Greek a-bio-genesis, non biological origins) is the formation of life from non-living matter. ... Louis Pasteur (December 27, 1822 – September 28, 1895) was a French chemist best known for his remarkable breakthroughs in microbiology. ... Redi is featured in many modern-day science textbooks due to his experiment. ... Dr. R.L.K. Virchow Rudolf Ludwig Karl Virchow (October 13, 1821, in Schivelbein, Pomerania - September 5, 1902, in Berlin) was a German doctor, pathologist, prehistorian, biologist, and politician. ... This does not adequately cite its references or sources. ... Ernst August Friedrich Ruska (December 25, 1906–May 25, 1988) was a German physicist. ... Transmission electron microscopy (TEM) is an imaging technique whereby a beam of electrons is focused onto a specimen causing an enlarged version to appear on a fluorescent screen or layer of photographic film (see electron microscope), or can be detected by a CCD camera. ... There is no institution called the University of Berlin, but there are four universities in Berlin, Germany: Humboldt University of Berlin (Humboldt-Universität zu Berlin) Technical University of Berlin (Technische Universität Berlin) Free University of Berlin (Freie Universität Berlin) Berlin University of the Arts (Universität der... James Dewey Watson (born April 6, 1928) is an American molecular biologist, best known as one of the co-discoverers of the structure of DNA. Watson, Francis Crick, and Maurice Wilkins were awarded the 1962 Nobel Prize for Physiology or Medicine for their discoveries concerning the molecular structure of nucleic... Francis Harry Compton Crick OM FRS (8 June 1916 – 28 July 2004) was an English molecular biologist, physicist, and neuroscientist, who is most noted for being one of the co-discoverers of the structure of the DNA molecule in 1953. ... A helix (pl: helices), from the Greek word έλικας/έλιξ, is a twisted shape like a spring, screw or a spiral (correctly termed helical) staircase. ... Lynn Margulis Dr. Lynn Margulis (born March 15, 1938) is a biologist and University Professor in the Department of Geosciences at the University of Massachusetts Amherst. ... It has been suggested that Proto-mitochondrion be merged into this article or section. ... Epithelial cells in culture, stained for keratin (red) and DNA (green) Cell culture is the process by which either prokaryotic or eukaryotic cells are grown under controlled conditions. ... A cell type is a distinct morphological or functional form of cell. ... Biological matter or biological material refers to the unique, highly organized substances of which cellular life is composed of, for instance membranes, proteins, and nucleic acids. ... Cytorrhysis is the complete collapse of a plant cells cell wall within plants due to the loss of water through osmosis. ... Cytotoxicity is the quality of being poisonous to cells. ... Plant cell structure Plant cells are quite different from the cells of the other eukaryotic kingdoms organisms. ... Before Plasmolysis. ... Mouse embryonic stem cells with fluorescent marker. ... In biology, a syncytium is a large region of cytoplasm that contains many nuclei. ... For other uses, see Embryo (disambiguation). ... Phenylalanine is one of the standard amino acids. ... The Entrez logo The Entrez Global Query Cross-Database Search System allows access to databases at the National Center for Biotechnology Information (NCBI) website. ... A coiled coil is a structural motif found in many proteins. ... National Center for Biotechnology Information logo The National Center for Biotechnology Information (NCBI) is part of the United States National Library of Medicine (NLM), a branch of the National Institutes of Health. ... The public domain comprises the body of all creative works and other knowledge—writing, artwork, music, science, inventions, and others—in which no person or organization has any proprietary interest. ... Image File history File links Commons-logo. ... Image File history File links Wikibooks-logo-en. ... Schematic of typical animal cell, showing subcellular components. ... In spermatozoa of many animals, the acrosome is an organelle that develops over the anterior half of the spermatozoons head. ... A cell wall is a fairly rigid layer surrounding a cell, located external to the cell membrane, that provides the cell with structural support, protection, and a filtering mechanism. ... Look up cell membrane in Wiktionary, the free dictionary. ... A centriole is a barrel shaped organelle[1] found in most eukaryotic cells, though absent in higher plants and fungi. ... Chloroplasts are organelles found in plant cells and eukaryotic algae that conduct photosynthesis. ... Not to be confused with Psyllium. ... For the insect anatomical structure, see Antenna (biology). ... The centrosome is the main microtubule organizing center (MTOC) of the cell as well as a regulator of cell-cycle progression. ... Organelles. ... The endoplasmic reticulum or ER is an organelle found in all eukaryotic cells that is an interconnected network of tubules, vesicles and cisternae that is responsible for several specialized functions: Protein translation, folding, and transport of proteins to be used in the cell membrane (e. ... In biology an endosome is a membrane-bound compartment inside cells. ... Micrograph of Golgi apparatus, visible as a stack of semicircular black rings near the bottom. ... Organelles labeled at upper left. ... In a biological cell, a melanosome is an organelle containing melanin, the most common light-absorbing pigment found in the animal kingdom. ... Electron micrograph of a mitochondrion showing its mitochondrial matrix and membranes In cell biology, a mitochondrion (plural mitochondria) is a membrane-enclosed organelle that is found in most eukaryotic cells. ... A diagram of the structure of a Myofybril Myofibrils (obsolete term: sarcostyles) are cylindrical organelles, found within muscle cells. ... HeLa cells stained for DNA with the Blue Hoechst dye. ... The nucleolus is contained within the cell nucleus. ... Parenthesomes are found in basidiomycete fungus. ... Basic structure of a peroxisome Peroxisomes are ubiquitous organelles in eukaryotes that participate in the metabolism of fatty acids and other metabolites. ... Plant cells with visible chloroplasts. ... Figure 1: Ribosome structure indicating small subunit (A) and large subunit (B). ... Schematic of typical animal cell, showing subcellular components. ... In cell biology, a vesicle is a relatively small and enclosed compartment, separated from the cytosol by at least one lipid bilayer. ... This article is about matter in physics and chemistry. ... “Life on Earth” redirects here. ... For other uses, see Life (disambiguation), Lives (disambiguation) or Living (disambiguation), Living Things (disambiguation) Look up life, living in Wiktionary, the free dictionary. ... This article is about the biological unit. ... Biological tissue is a group of cells that perform a similar function. ... Schematic of typical animal cell, showing subcellular components. ... 3D (left and center) and 2D (right) representations of the terpenoid molecule atisane. ... For other uses, see Atom (disambiguation). ... Helium atom (schematic) Showing two protons (red), two neutrons (green) and two electrons (yellow). ... For the novel, see The Elementary Particles. ...


  Results from FactBites:
 
The Biology Project: Cell Biology (405 words)
Cell Membranes Learn that membranes are fluid, with components that move, change, and perform vital physiological roles as they allow cells to communicate with each other and their environment.
The Cell Cycle & Mitosis Understand the events that occur in the cell cycle and the process of mitosis that divides the duplicated genetic material creating two identical daughter cells.
The Cytoskeleton Learn that the cytoskeleton acts both a muscle and a skeleton, and is responsible for cell movement, cytokinesis, and the organization of the organelles within the cell.
Cell (biology) - MSN Encarta (2372 words)
The smallest cell, a type of bacterium known as a mycoplasma, measures 0.0001 mm (0.000004 in) in diameter; 10,000 mycoplasmas in a row are only as wide as the diameter of a human hair.
Prokaryotic cells are among the tiniest of all cells, ranging in size from 0.0001 to 0.003 mm (0.000004 to 0.0001 in) in diameter.
The extraordinary biochemical diversity of prokaryotic cells is manifested in the wide-ranging lifestyles of the archaebacteria and the bacteria, whose habitats include polar ice, deserts, and hydrothermal vents—deep regions of the ocean under great pressure where hot water geysers erupt from cracks in the ocean floor.
  More results at FactBites »

 
 

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