Cell (biology) From Wikipedia, the free encyclopedia Page semi-protected Onion (Allium) cells in different phases of the cell cycle The cells of eukaryotes (left) and prokaryotes (right) The cell is the basic structural, functional and biological unit of all known li ving organisms. Cells are the smallest unit of life that is classified as a livi ng thing, and are often called the "building blocks of life". Cells consist of a protoplasm enclosed within a membrane, which contains many bi omolecules such as proteins and nucleic acids.[1] Organisms can be classified as unicellular (consisting of a single cell; including most bacteria) or multicell ular (including plants and animals). While the number of cells in plants and ani mals varies from species to species, humans contain about 100 trillion (1014) ce lls.[2] Most plant and animal cells are between 1 and 100 micrometres and theref ore are visible only under the microscope.[3] The cell was discovered by Robert Hooke in 1665. The cell theory, first develope d in 1839 by Matthias Jakob Schleiden and Theodor Schwann, states that all organ isms are composed of one or more cells, that all cells come from preexisting cel ls, that vital functions of an organism occur within cells, and that all cells c ontain the hereditary information necessary for regulating cell functions and fo r transmitting information to the next generation of cells.[4] Cells emerged on Earth at least 3.5 billion years ago.[5][6][7] The word cell comes from the Latin cella, meaning "small room".[8] It was coined by Robert Hooke in his book Micrographia (1665), in which he compared the cork cells he saw through his microscope to the small rooms monks lived in.[9] Contents [hide] 1 Anatomy 1.1 Prokaryotic cells 1.2 Eukaryotic cells 2 Subcellular components 2.1 Membrane 2.2 Cytoskeleton 2.3 Genetic material 2.4 Organelles 2.4.1 Eukaryotic 2.4.2 Eukaryotic and prokaryotic 3 Structures outside the cell membrane 3.1 Cell wall 3.2 Prokaryotic 3.2.1 Capsule 3.2.2 Flagella 3.2.3 Fimbriae (pili) 4 Growth and metabolism 5 Replication 6 Protein synthesis 7 Movement or motility 8 Origins 8.1 Origin of the first cell 8.2 Origin of eukaryotic cells 9 History of research 10 See also 11 References 12 External links 12.1 Textbooks Anatomy

There are two types of cells, eukaryotes, which contain a nucleus, and prokaryot es, which do not. Prokaryotic cells are usually single-celled organisms, while e ukaryotic cells can be either single-celled or part of multicellular organisms. Table 1: Comparison of features of prokaryotic and eukaryotic cells Prokaryotes Eukaryotes Typical organisms bacteria, archaea protists, fungi, plants, animals Typical size ~ 1 5 m[10] ~ 10 100 m[10] Type of nucleus nucleoid region; no true nucleus true nucleus with double membrane DNA circular (usually) linear molecules (chromosomes) with histone prot eins RNA/protein synthesis coupled in the cytoplasm RNA synthesis in the nuc leus protein synthesis in the cytoplasm Ribosomes 50S and 30S 60S and 40S Cytoplasmic structure very few structures highly structured by endomembran es and a cytoskeleton Cell movement flagella made of flagellin flagella and cilia containing mi crotubules; lamellipodia and filopodia containing actin Mitochondria none one to several thousand (though some lack mitochondria) Chloroplasts none in algae and plants Organization usually single cells single cells, colonies, higher multicell ular organisms with specialized cells Cell division Binary fission (simple division) Mitosis (fission or budd ing) Meiosis Prokaryotic cells Main article: Prokaryote Diagram of a typical prokaryotic cell Prokaryotic cells were the first form of life on Earth. They are simpler and sma ller than eukaryotic cells, and lack membrane-bound organelles such as the nucle us. Prokaryotes include two of the domains of life, bacteria and archaea. The DN A of a prokaryotic cell consists of a single chromosome that is in direct contac t with the cytoplasm. The nuclear region in the cytoplasm is called the nucleoid . A prokaryotic cell has three architectural regions: On the outside, flagella and pili project from the cell's surface. These are str uctures (not present in all prokaryotes) made of proteins that facilitate moveme nt and communication between cells. Enclosing the cell is the cell envelope generally consisting of a cell wall cove ring a plasma membrane though some bacteria also have a further covering layer c alled a capsule. The envelope gives rigidity to the cell and separates the inter ior of the cell from its environment, serving as a protective filter. Though mos t prokaryotes have a cell wall, there are exceptions such as Mycoplasma (bacteri a) and Thermoplasma (archaea). The cell wall consists of peptidoglycan in bacter ia, and acts as an additional barrier against exterior forces. It also prevents the cell from expanding and bursting (cytolysis) from osmotic pressure due to a hypotonic environment. Some eukaryotic cells (plant cells and fungal cells) also have a cell wall. Inside the cell is the cytoplasmic region that contains the genome (DNA), riboso mes and various sorts of inclusions. The prokaryotic chromosome is usually a cir cular molecule (an exception is that of the bacterium Borrelia burgdorferi, whic h causes Lyme disease).[11] Though not forming a nucleus, the DNA is condensed i n a nucleoid. Prokaryotes can carry extrachromosomal DNA elements called plasmid s, which are usually circular. Plasmids encode additional genes, such as antibio tic resistance genes. Eukaryotic cells

Main article: Eukaryote Plants, animals, fungi, slime moulds, protozoa, and algae are all eukaryotic. Th ese cells are about fifteen times wider than a typical prokaryote and can be as much as a thousand times greater in volume. The main distinguishing feature of e ukaryotes as compared to prokaryotes is compartmentalization: the presence of me mbrane-bound compartments in which specific metabolic activities take place. Mos t important among these is a cell nucleus, a membrane-delineated compartment tha t houses the eukaryotic cell's DNA. This nucleus gives the eukaryote its name, w hich means "true nucleus." Other differences include: The plasma membrane resembles that of prokaryotes in function, with minor differ ences in the setup. Cell walls may or may not be present. The eukaryotic DNA is organized in one or more linear molecules, called chromoso mes, which are associated with histone proteins. All chromosomal DNA is stored i n the cell nucleus, separated from the cytoplasm by a membrane. Some eukaryotic organelles such as mitochondria also contain some DNA. Many eukaryotic cells are ciliated with primary cilia. Primary cilia play import ant roles in chemosensation, mechanosensation, and thermosensation. Cilia may th us be "viewed as a sensory cellular antennae that coordinates a large number of cellular signaling pathways, sometimes coupling the signaling to ciliary motilit y or alternatively to cell division and differentiation."[12] Eukaryotes can move using motile cilia or flagella. Eukaryotic flagella are less complex than those of prokaryotes. Structure of a typical animal cell Structure of a typical plant cell Table 2: Comparison of structures between animal and plant cells Typical animal cell Typical plant cell Organelles Nucleus Nucleolus (within the nucleus) Rough endoplasmic reticulum (ER) Smooth endoplasmic reticulum Ribosomes Cytoskeleton Golgi apparatus Cytoplasm Mitochondria Vesicles Lysosomes Centrosome Centrioles Nucleus Nucleolus (within the nucleus) Rough endoplasmic reticulum Smooth endoplasmic reticulum Ribosomes Cytoskeleton Golgi apparatus (dictiosomes) Cytoplasm Mitochondria Plastids and their derivatives Vacuole(s) Cell wall Subcellular components All cells, whether prokaryotic or eukaryotic, have a membrane that envelops the cell, separates its interior from its environment, regulates what moves in and o

ut (selectively permeable), and maintains the electric potential of the cell. In side the membrane, a salty cytoplasm takes up most of the cell volume. All cells (except red blood cells which lack a cell nucleus and most organelles to accomm odate maximum space for hemoglobin) possess DNA, the hereditary material of gene s, and RNA, containing the information necessary to build various proteins such as enzymes, the cell's primary machinery. There are also other kinds of biomolec ules in cells. This article lists these primary components of the cell, then bri efly describes their function. Membrane Main article: Cell membrane The cell membrane, or plasma membrane, surrounds the cytoplasm of a cell. In ani mals, the plasma membrane is the outer boundary of the cell, while in plants and prokaryotes it is usually covered by a cell wall. This membrane serves to separ ate and protect a cell from its surrounding environment and is made mostly from a double layer of phospholipids, which are amphiphilic (partly hydrophobic and p artly hydrophilic). Hence, the layer is called a phospholipid bilayer, or someti mes a fluid mosaic membrane. Embedded within this membrane is a variety of prote in molecules that act as channels and pumps that move different molecules into a nd 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 r eceptor proteins that allow cells to detect external signaling molecules such as hormones. Cytoskeleton Main article: Cytoskeleton A fluorescent image of an endothelial cell. Nuclei are stained blue, mitochondri a are stained red, and microfilaments are stained green. The cytoskeleton acts to organize and maintain the cell's shape; anchors organel les in place; helps during endocytosis, the uptake of external materials by a ce ll, and cytokinesis, the separation of daughter cells after cell division; and m oves parts of the cell in processes of growth and mobility. The eukaryotic cytos keleton is composed of microfilaments, intermediate filaments and microtubules. There are a great number of proteins associated with them, each controlling a ce ll's structure by directing, bundling, and aligning filaments. The prokaryotic c ytoskeleton is less well-studied but is involved in the maintenance of cell shap e, polarity and cytokinesis.[13] Genetic material Two different kinds of genetic material exist: deoxyribonucleic acid (DNA) and r ibonucleic acid (RNA). Most cells use DNA for their long-term information storag e. The biological information contained in an organism is encoded in its DNA seq uence. RNA is used for information transport (e.g., mRNA) and enzymatic function s (e.g., ribosomal RNA). Transfer RNA (tRNA) molecules are used to add amino aci ds during protein translation. Prokaryotic genetic material is organized in a simple circular DNA molecule (the bacterial chromosome) in the nucleoid region of the cytoplasm. Eukaryotic genet ic material is divided into different, linear molecules called chromosomes insid e a discrete nucleus, usually with additional genetic material in some organelle s like mitochondria and chloroplasts (see endosymbiotic theory). A human cell has genetic material contained in the cell nucleus (the nuclear gen ome) and in the mitochondria (the mitochondrial genome). In humans the nuclear g enome is divided into 46 linear DNA molecules called chromosomes, including 22 h omologous chromosome pairs and a pair of sex chromosomes. The mitochondrial geno me is a circular DNA molecule distinct from the nuclear DNA. Although the mitoch ondrial DNA is very small compared to nuclear chromosomes, it codes for 13 prote ins involved in mitochondrial energy production and specific tRNAs. 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 D NA is not inserted into the cell's genome, or stable, if it is. Certain viruses

also insert their genetic material into the genome. Organelles Main article: Organelle Organelles are parts of the cell which are adapted and/or specialized for carryi ng out one or more vital functions, analogous to the organs of the human body (s uch as the heart, lung, and kidney, with each organ performing a different funct ion). Both eukaryotic and prokaryotic cells have organelles, but prokaryotic org anelles are generally simpler and are not membrane-bound. There are several types of organelles in a cell. Some (such as the nucleus and g olgi apparatus) are typically solitary, while others (such as mitochondria, pero xisomes and lysosomes) can be numerous (hundreds to thousands). The cytosol is t he gelatinous fluid that fills the cell and surrounds the organelles. Eukaryotic Human cancer cells with nuclei (specifically the DNA) stained blue. The central and rightmost cell are in interphase, so the entire nuclei are labeled. The cell on the left is going through mitosis and its DNA has condensed. Cell nucleus: A cell's information center, the cell nucleus is the most conspicu ous organelle found in a eukaryotic cell. It houses the cell's chromosomes, and is the place where almost all DNA replication and RNA synthesis (transcription) occur. The nucleus is spherical and separated from the cytoplasm by a double mem brane called the nuclear envelope. The nuclear envelope isolates and protects a cell's DNA from various molecules that could accidentally damage its structure o r interfere with its processing. During processing, DNA is transcribed, or copie d into a special RNA, called messenger RNA (mRNA). This mRNA is then transported out of the nucleus, where it is translated into a specific protein molecule. Th e nucleolus is a specialized region within the nucleus where ribosome subunits a re assembled. In prokaryotes, DNA processing takes place in the cytoplasm. Mitochondria and Chloroplasts: the power generators: Mitochondria are self-repli cating organelles that occur in various numbers, shapes, and sizes in the cytopl asm of all eukaryotic cells. Mitochondria play a critical role in generating ene rgy in the eukaryotic cell. Respiration occurs in the cell mitochondria, which g enerate the cell's energy by oxidative phosphorylation, using oxygen to release energy stored in cellular nutrients (typically pertaining to glucose) to generat e ATP. Mitochondria multiply by binary fission, like prokaryotes. Chloroplasts c an only be found in plants and algae, and they capture the sun's energy to make ATP. Diagram of an endomembrane system Endoplasmic reticulum: The endoplasmic reticulum (ER) is a transport network for molecules targeted for certain modifications and specific destinations, as comp ared to molecules that float freely in the cytoplasm. The ER has two forms: the rough ER, which has ribosomes on its surface that secrete proteins into the ER, and the smooth ER, which lacks ribosomes. The smooth ER plays a role in calcium sequestration and release. (See Endoplasmic reticulum) Golgi apparatus: The primary function of the Golgi apparatus is to process and p ackage the macromolecules such as proteins and lipids that are synthesized by th e cell. (See Golgi apparatus) Lysosomes and Peroxisomes: Lysosomes contain digestive enzymes (acid hydrolases) . They digest excess or worn-out organelles, food particles, and engulfed viruse s or bacteria. Peroxisomes have enzymes that rid the cell of toxic peroxides. Th e cell could not house these destructive enzymes if they were not contained in a membrane-bound system. (See Lysosome and Peroxisome) the cytoskeleton organiser: The centrosome produces the microtubules Centrosome 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, whic h 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 som

e fungi and algae cells. (See Centrosome) Vacuoles: Vacuoles store food and waste. Some vacuoles store extra water. They a re often described as liquid filled space and are surrounded by a membrane. Some cells, most notably Amoeba, have contractile vacuoles, which can pump water out of the cell if there is too much water. The vacuoles of eukaryotic cells are us ually larger in those of plants than animals. (See Vacuole) Eukaryotic and prokaryotic Ribosomes: The ribosome is a large complex of RNA and protein molecules. They ea ch consist of two subunits, and act as an assembly line where RNA from the nucle us is used to synthesise proteins from amino acids. Ribosomes can be found eithe r floating freely or bound to a membrane (the rough endoplasmatic reticulum in e ukaryotes, or the cell membrane in prokaryotes).[14] Structures outside the cell membrane Many cells also have structures which exist wholly or partially outside the cell membrane. These structures are notable because they are not protected from the external environment by the impermeable cell membrane. In order to assemble thes e structures, their components must be carried across the cell membrane by expor t processes. Cell wall Many types of prokaryotic and eukaryotic cells have a cell wall. The cell wall a cts to protect the cell mechanically and chemically from its environment, and is an additional layer of protection to the cell membrane. Different types of cell have cell walls made up of different materials; plant cell walls are primarily made up of pectin, fungi cell walls are made up of chitin and bacteria cell wall s are made up of peptidoglycan. Prokaryotic Capsule A gelatinous capsule is present in some bacteria outside the cell membrane and c ell wall. The capsule may be polysaccharide as in pneumococci, meningococci or p olypeptide as Bacillus anthracis or hyaluronic acid as in streptococci. (See Bac terial capsule.) Capsules are not marked by normal staining protocols and can be detected by India ink or Methyl blue; which allows for higher contrast between the cells for observation.[15]:87 Flagella Flagella are organelles for cellular mobility. The bacterial flagellum stretches from cytoplasm through the cell membrane(s) and extrudes through the cell wall. They are long and thick thread-like appendages, protein in nature. Are most com monly found in bacteria cells but are found in animal cells as well. Fimbriae (pili) They are short and thin hair-like filaments, formed of protein called pilin (ant igenic). Fimbriae are responsible for attachment of bacteria to specific recepto rs of human cell (adherence). There are special types of pili called (sex pili) involved in conjunction. (See Pilus.) Growth and metabolism Main articles: Cell growth and Metabolism Between successive cell divisions, cells grow through the functioning of cellula r metabolism. Cell metabolism is the process by which individual cells process n utrient molecules. Metabolism has two distinct divisions: catabolism, in which t he 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 th e organism can be broken down into a less chemically complex sugar molecule call ed glucose. Once inside the cell, glucose is broken down to make adenosine triph osphate (ATP), a form of energy, through two different pathways. The first pathway, glycolysis, requires no oxygen and is referred to as anaerobi c metabolism. Each reaction produces ATP and NADH, which are used in cellular fu nctions, as well as two pyruvate molecules that derive from the original glucose molecule. In prokaryotes, all energy is produced by glycolysis.

The second pathway, called the Krebs cycle or citric acid cycle, is performed on ly by eukaryotes and involves further breakdown of the pyruvate produced in glyc olysis. It occurs inside the mitochondria and generates much more energy than gl ycolysis, mostly through oxidative phosphorylation. Replication

Bacteria divide by binary fission, while eukaryotes divide by mitosis or meiosis . Main article: Cell division Cell division involves a single cell (called a mother cell) dividing into two da ughter cells. This leads to growth in multicellular organisms (the growth of tis sue) and to procreation (vegetative reproduction) in unicellular organisms. Prok aryotic cells divide by binary fission, while 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 c ells, usually four. Haploid cells serve as gametes in multicellular organisms, f using to form new diploid cells. DNA replication, or the process of duplicating a cell's genome, always happens w hen a cell divides through mitosis or binary fission. This occurs during the S p hase of the cell cycle. In meiosis, the DNA is replicated only once, while the cell divides twice. DNA r eplication only occurs before meiosis I. DNA replication does not occur when the cells divide the second time, in meiosis II.[16] Replication, like all cellular activities, requires specialized proteins for carrying out the job. Protein synthesis An overview of protein synthesis. Within the nucleus of the cell (light blue), genes (DNA, dark blue) are transcri bed 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 nu cleus and into the cytoplasm (peach), where it undergoes translation into a prot ein. mRNA is translated by ribosomes (purple) that match the three-base codons o f the mRNA to the three-base anti-codons of the appropriate tRNA. Newly synthesi zed proteins (black) are often further modified, such as by binding to an effect or molecule (orange), to become fully active. Main article: Protein biosynthesis Cells are capable of synthesizing new proteins, which are essential for the modu lation and maintenance of cellular activities. This process involves the formati on of new protein molecules from amino acid building blocks based on information encoded in DNA/RNA. Protein synthesis generally consists of two major steps: tr anscription and translation. 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 p rotein-RNA complexes called ribosomes located in the cytosol, where they are tra nslated into polypeptide sequences. The ribosome mediates the formation of a pol ypeptide 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 f unctional three-dimensional protein molecule. Movement or motility Cells can move during many processes: such as wound healing, the immune response and cancer metastasis. For wound healing to occur, white blood cells and cells that ingest bacteria move to the wound site to kill the microorganisms that caus e infection. At the same time fibroblasts (connective tissue cells) move there to remodel dam

aged structures. In the case of tumor development, cells from a primary tumor mo ve away and spread to other parts of the body. Cell motility involves many recep tors, crosslinking, bundling, binding, adhesion, motor and other proteins.[17] T he process is divided into three steps protrusion of the leading edge of the cel l, adhesion of the leading edge and de-adhesion at the cell body and rear, and c ytoskeletal contraction to pull the cell forward. Each step is driven by physica l forces generated by unique segments of the cytoskeleton.[18][19] Origins Main article: Evolutionary history of life The origin of cells has to do with the origin of life, which began the history o f life on Earth. Origin of the first cell Stromatolites are left behind by cyanobacteria, also called blue-green algae. Th ey are the oldest known fossils of life on Earth. This one-billion-year-old foss il is from Glacier National Park in the United States. Further information: Abiogenesis and Evolution of cells There are several theories about the origin of small molecules that led to life on the early Earth. They may have been carried to Earth on meteorites (see Murch ison meteorite), created at deep-sea vents, or synthesized by lightning in a red ucing atmosphere (see Miller Urey experiment). There is little experimental data d efining what the first self-replicating forms were. RNA is thought to be the ear liest self-replicating molecule, as it is capable of both storing genetic inform ation and catalyzing chemical reactions (see RNA world hypothesis), but some oth er entity with the potential to self-replicate could have preceded RNA, such as clay or peptide nucleic acid.[20] Cells emerged at least 3.5 billion years ago.[5][6][7] The current belief is tha t these cells were heterotrophs. The early cell membranes were probably more sim ple and permeable than modern ones, with only a single fatty acid chain per lipi d. Lipids are known to spontaneously form bilayered vesicles in water, and could have preceded RNA, but the first cell membranes could also have been produced b y catalytic RNA, or even have required structural proteins before they could for m.[21] Origin of eukaryotic cells Further information: Evolution of sexual reproduction The eukaryotic cell seems to have evolved from a symbiotic community of prokaryo tic cells. DNA-bearing organelles like the mitochondria and the chloroplasts are descended from ancient symbiotic oxygen-breathing proteobacteria and cyanobacte ria, respectively, which were endosymbiosed by an ancestral archaean prokaryote. There is still considerable debate about whether organelles like the hydrogenoso me predated the origin of mitochondria, or vice versa: see the hydrogen hypothes is for the origin of eukaryotic cells. Sex, as the stereotyped choreography of meiosis and syngamy that persists in nea rly all extant eukaryotes, may have played a role in the transition from prokary otes to eukaryotes. One view, on the origin of sex in eukaryotic cells, is that eukaryotic sex evolved from a prokaryotic sexual process termed transformation. According to this view, bacterial transformation is an adaptation for repairing DNA damages that arise during stressful conditions, and this role has been maint ained in meiosis, where recombinational DNA repair is promoted. Thus the adaptiv e benefit of prokaryotic sex, recombinational repair, was maintained through the evolutionary transition from prokaryotes to single-celled eukaryotes.[22][23] T his view is also presented in the Wikipedia articles Transformation (genetics), Evolution of sexual reproduction and Sex. In another view, an 'origin of sex as vaccination' theory suggests that the euka ryote genome accreted from prokaryan parasite genomes in numerous rounds of late ral gene transfer. Sex-as-syngamy (fusion sex) arose when infected hosts began s wapping nuclearized genomes containing co-evolved, vertically transmitted symbio nts that conveyed protection against horizontal infection by more virulent symbi

onts.[24] History of research 1632 1723: Antonie van Leeuwenhoek teaches himself to make lenses, constructs simp le microscopes and draws protozoa, such as Vorticella from rain water, and bacte ria from his own mouth. 1665: Robert Hooke discovers cells in cork, then in living plant tissue using an early compound microscope.[9] 1839: Theodor Schwann and Matthias Jakob Schleiden elucidate the principle that plants and animals are made of cells, concluding that cells are a common unit of structure and development, and thus founding the cell theory. 1855: Rudolf Virchow states that new cells come from pre-existing cells by cell division (omnis cellula ex cellula). 1859: The belief that life forms can occur spontaneously (generatio spontanea) i s contradicted by Louis Pasteur (1822 1895) (although Francesco Redi had performed an experiment in 1668 that suggested the same conclusion). 1931: Ernst Ruska builds the first transmission electron microscope (TEM) at the University of Berlin. By 1935, he has built an EM with twice the resolution of a light microscope, revealing previously unresolvable organelles. 1953: Watson and Crick made their first announcement on the double helix structu re of DNA on February 28. 1981: Lynn Margulis published Symbiosis in Cell Evolution detailing the endosymb iotic theory. See also Wikimedia Commons has media related to: Cell biology Main article: Topic outline of cell biology Cell biology Cell culture Cell type Cellular component Cytorrhysis Cytotoxicity Plasmolysis Stem cell Syncytium References ^ Cell Movements and the Shaping of the Vertebrate Body in Chapter 21 of Molecul ar 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 deve loping embryos. It is also common to describe small molecules such as amino acid s as "molecular building blocks". ^ Lodish (2007). Molecular Cell Biology,6e. W.H.Freeman and Company. ISBN 0-7167 -7601-4. ^ Campbell, Neil A.; Brad Williamson; Robin J. Heyden (2006). Biology: Exploring Life. Boston, Massachusetts: Pearson Prentice Hall. ISBN 0-13-250882-6. ^ Maton, Anthea; Hopkins, Jean Johnson, Susan LaHart, David Quon Warner, Maryann a Wright, Jill D (1997). Cells Building Blocks of Life. New Jersey: Prentice Hal l. ISBN 0-13-423476-6. ^ a b Schopf, JW, Kudryavtsev, AB, Czaja, AD, and Tripathi, AB. (2007). Evidence of Archean life: Stromatolites and microfossils. Precambrian Research 158:141-1 55. ^ a b Schopf, JW (2006). Fossil evidence of Archaean life. Philos Trans R Soc Lo nd B Biol Sci 29;361(1470):869-85. ^ a b Peter Hamilton Raven; George Brooks Johnson (2002). Biology. McGraw-Hill E ducation. p. 68. ISBN 978-0-07-112261-0. Retrieved 7 July 2013. ^ "Cell". Online Etymology Dictionary. Retrieved 31 December 2012. ^ a b "... I could exceedingly plainly perceive it to be all perforated and poro

us, 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 observation s on a thin slice of cork. Robert Hooke ^ a b Campbell Biology Concepts and Connections. Pearson Education. 2009. p. 320. ^ European Bioinformatics Institute, Karyn's Genomes: Borrelia burgdorferi, part of 2can on the EBI-EMBL database. Retrieved 5 August 2012 ^ Satir, Peter; Christensen, ST; Sren T. Christensen (2008-03-26). "Structure and function of mammalian cilia". Histochemistry and Cell Biology (Springer Berlin / Heidelberg) 129 (6): 687 693. doi:10.1007/s00418-008-0416-9. PMC 2386530. PMID 1 8365235. 1432-119X. Retrieved 2009-09-12. ^ Michie K, Lwe J (2006). "Dynamic filaments of the bacterial cytoskeleton". Annu Rev Biochem 75: 467 92. doi:10.1146/annurev.biochem.75.103004.142452. PMID 167564 99. ^ Mntret JF, Schaletzky J, Clemons WM, et al., CW; Akey (December 2007). "Ribosome binding of a single copy of the SecY complex: implications for protein transloc ation". Mol. Cell 28 (6): 1083 92. doi:10.1016/j.molcel.2007.10.034. PMID 18158904 . ^ Prokaryotes. Newnes. Apr 11, 1996. ISBN 9780080984735. ^ Campbell Biology Concepts and Connections. Pearson Education. 2009. p. 138. ^ Revathi Ananthakrishnan1 *, Allen Ehrlicher2 ?. "The Forces Behind Cell Moveme nt". Biolsci.org. Retrieved 2009-04-17. ^ Alberts B, Johnson A, Lewis J. et al. Molecular Biology of the Cell, 4e. Garla nd Science. 2002 ^ Ananthakrishnan R, Ehrlicher A. The Forces Behind Cell Movement. Int J Biol Sc i 2007; 3:303 317. http://www.biolsci.org/v03p0303.htm ^ Orgel LE (1998). "The origin of life--a review of facts and speculations". Tre nds Biochem Sci 23 (12): 491 5. doi:10.1016/S0968-0004(98)01300-0. PMID 9868373. ^ Griffiths G (December 2007). "Cell evolution and the problem of membrane topol ogy". Nature reviews. Molecular cell biology 8 (12): 1018 24. doi:10.1038/nrm2287. PMID 17971839. ^ Bernstein H, Bernstein C. (2010) Evolutionary Origin of Recombination during M eiosis. BioScience 60(7):498-505. doi: http://dx.doi.org/10.1525/bio.2010.60.7.5 ^ Bernstein H, Bernstein C, Michod RE (2012). DNA repair as the primary adaptive function of sex in bacteria and eukaryotes. Chapter 1: pp.1-49 in: DNA Repair: New Research, Sakura Kimura and Sora Shimizu editors. Nova Sci. Publ., Hauppauge , N.Y. ISBN 978-1-62100-808-8 https://www.novapublishers.com/catalog/product_inf o.php?products_id=31918 ^ Sterrer W (2002). "On the origin of sex as vaccination". Journal of Theoretica l Biology 216 (4): 387 396. doi:10.1006/jtbi.2002.3008. PMID 12151256. This article incorporates public domain material from the NCBI document "Scienc e Primer". External links Inside the Cell - a science education booklet by National Institutes of Health, in PDF and ePub. Cells Alive! Cell Biology in "The Biology Project" of University of Arizona. Centre of the Cell online The Image & Video Library of The American Society for Cell Biology, a collection of peer-reviewed still images, video clips and digital books that illustrate th e structure, function and biology of the cell. HighMag Blog, still images of cells from recent research articles. New Microscope Produces Dazzling 3D Movies of Live Cells, March 4, 2011 - Howard Hughes Medical Institute. WormWeb.org: Interactive Visualization of the C. elegans Cell lineage - Visualiz e the entire cell lineage tree of the nematode C. elegans Textbooks

Alberts B, Johnson A, Lewis J, Raff M, Roberts K, Walter P (2002). Molecular Bio logy of the Cell (4th ed.). Garland. ISBN 0-8153-3218-1. Lodish H, Berk A, Matsudaira P, Kaiser CA, Krieger M, Scott MP, Zipurksy SL, Dar nell J (2004). Molecular Cell Biology (5th ed.). WH Freeman: New York, NY. ISBN 978-0-7167-4366-8. Cooper GM (2000). The cell: a molecular approach (2nd ed.). Washington, D.C: ASM Press. ISBN 0-87893-102-3. [show] v t e Structures of the cell / organelles (TH H1.00.01.2-3) [show] v t e Hierarchy of life Categories: Cell biology Navigation menu Create accountLog inArticleTalkReadView sourceView history Search Main page Contents Featured content Current events Random article Donate to Wikipedia Interaction Help About Wikipedia Community portal Recent changes Contact Wikipedia Toolbox Print/export Languages ???????? Afrikaans ???? nglisc ??????? Aragons Az?rbaycanca ????? Bn-lm-g ????????? ?????????? ?????????? (???????????)? ????????? Bosanski Brezhoneg Catal Cesky ChiShona Cymraeg Dansk Deutsch Eesti ???????? Espaol Esperanto Estremeu Euskara ????? Fiji Hindi Froyskt

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