cytoplasm
American Heritage Dictionary:
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cy·to·plasm
(sī'tə-plăz'əm) 
n.
The protoplasm outside the nucleus of a cell.
cytoplasmic cy'to·plas'mic (-plăz'mĭk) adj.
cytoplasmically cy'to·plas'mi·cal·ly adv.
n.
The protoplasm outside the nucleus of a cell.
cytoplasmic cy'to·plas'mic (-plăz'mĭk) adj.
cytoplasmically cy'to·plas'mi·cal·ly adv.
Britannica Concise Encyclopedia:
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cytoplasm
Portion of a eukaryotic cell outside the nucleus. The cytoplasm contains all the organelles ( eukaryote). The organelles include the mitochondria, chloroplasts, endoplasmic reticulum, Golgi apparatus, lysosomes, and peroxisomes. The cytoplasm also contains the cytoskeleton and the cytosol (the fluid mass that surrounds the various organelles).
For more information on cytoplasm, visit Britannica.com.
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That portion of living cells bordered externally by the plasma membrane (cell membrane) and internally by the nuclear envelope. In the terminology of classical cytology, the substance in living cells and in living organisms not compartmentalized into cells was called protoplasm. It was assumed at the time that the protoplasm of various cells was similar in structure and chemistry. Results of research on cell chemistry and ultrastructure after about 1960 showed that each cell type had a recognizably different “protoplasm.” Primarily for that reason, the term protoplasm gradually fell into disuse in contemporary biology. The terms cytoplasm and nucleoplasm have been retained and are used descriptively; they are used almost synonymously with the terms cytosome (body of cytoplasm) and nucleus, respectively.
Many cells, especially the single-celled organisms or protistans, have regional cytoplasmic differentiation. The outer region is the cortex or ectoplasm, and the inner region is the endoplasm. In many cases the cortical layer is a gel made up of a meshwork of cytoskeletal fibers.
Cytoplasm contains mostly water, from 80 to 97% in different cells, except for spores and other inactive forms of living material, in which water may be present in lesser amounts. The dry mass of cells consists mainly of macromolecules: proteins, carbohydrates, nucleic acids, and lipids associated with membranes. The small molecules present in cells are mainly metabolites or metabolic intermediates. The principal ions other than the hydrogen and hydroxyl ions of water are the cations of potassium, sodium, magnesium, and calcium, and the anions chloride and bicarbonate. Many other elements are present in cytoplasm in smaller amounts. Iron is found in cytochrome pigments in mitochondria; magnesium is present in chlorophyll in chloroplasts; copper, zinc, iodine, bromine, and several other elements are present in trace quantities. See also Cytochemistry.
Sedimentation of cells by centrifugation shows that organelles and inclusions can be separated from the ground cytoplasm, the fluid phase of the cytoplasm in which they are suspended. The ground cytoplasm in turn has been shown to consist of a cytoskeletal network and the cytosol, the fluid in which the cytoskeleton is bathed. The cytoskeleton consists of several biopolymers of wide distribution in cells. Microtubules have been observed in electron micrographs of a vast number of different cell types. They consist of the protein tubulin, and are frequently covered by a fuzzy layer of microtubule-associated proteins. See also Cytoskeleton.
In most cells the smaller particles exhibit Brownian motion due to thermal agitation. In some cells lacking extensive cytoskeletal structure, particles can be moved freely around the cell by Brownian motion. In others they are restricted by their surrounding cytoskeletal elements. Particles of various types may also undergo saltatory motions which carry them farther than Brownian motion possibly could. Such excursions result from the interaction of a particle with an element of the cytoskeleton such as one or more microtubules or microfilaments. See also Cell (biology).
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That part of a cell inside the cell surface membrane, but outside the nucleus. It consists of a watery fluid, the cytosol, in which cell organelles are suspended.
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(seye-tuh-plaz-uhm)
The material within a biological cell that is not contained in the nucleus or other organelles.
Oxford Dictionary of Biochemistry:
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cytoplasm
all the protoplasm of a living cell excluding the nucleus and the plasma membrane but including the other intracellular organelles and structures. Some authors currently also exclude mitochondria, chloroplasts, or other structures containing independently replicating DNA. The term is not synonymous with cytoplasmic fraction. See also cytosol.
—cytoplasmic adj.
| cytophotometry, cytophilic antibody, cytophilic | |
| cytoplasmic droplet, cytoplasmic fraction, cytoplasmic gene |
Saunders Veterinary Dictionary:
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cytoplasm
The protoplasm of a cell surrounding the nucleus (nucleoplasm).
Random House Word Menu:
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categories related to 'cytoplasm'
- Cell Structure and Function - cytoplasm: entire contents of cell excluding nucleus
Wikipedia on Answers.com:
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Cytoplasm
(1) Nucleolus
(2) Nucleus
(3) Ribosomes (little dots)
(4) Vesicle
(5) Rough endoplasmic reticulum (ER)
(6) Golgi apparatus
(7) Cytoskeleton
(8) Smooth ER
(9) Mitochondria
(10) Vacuole
(11) Cytosol
(12) Lysosome
(13) Centrioles within Centrosome
The cytoplasm is the gel-like substance residing between the cell membrane holding all the cell's internal sub-structures (called organelles), except for the nucleus. All the contents of the cells of prokaryote organisms (which lack a cell nucleus) are contained within the cytoplasm. Within the cells of eukaryote organisms the contents of the cell nucleus are separated from the cytoplasm, and are then called the nucleoplasm. The cytoplasm is about 80% water and usually transparent.
It is within the cytoplasm that most cellular activities occur, such as many metabolic pathways including glycolysis, and processes such as cell division. The inner, granular mass is called the endoplasm and the outer, clear and glassy layer is called the cell cortex or the ectoplasm.
The part of the cytoplasm that its not held within organelles is called the cytosol. The cytosol is a complex mixture of cytoskeleton filaments, dissolved molecules, and water that fills much of the volume of a cell. The cytosol is a gel, with a network of fibers dispersed in water. Due to this network of fibres and high concentrations of dissolved macromolecules, such as proteins, an effect called macromolecular crowding occurs and the cytosol does not act as an ideal solution. This crowding effect alters how the components of the cytosol interact with each other.
Movement of calcium ions in and out of the cytoplasm is thought to be a signaling activity for metabolic processes.[1]
In plants, movements of the cytoplasm around vacuoles are known as cyclosis.
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Contents
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Constituents
The cytoplasm has three major elements; the cytosol, organelles and inclusions.
Cytosol
Main article: Cytosol
The cytosol is the portion of the cytoplasm not contained within membrane-bound organelles. Cytosol makes up about 70% of the cell volume and is composed of water, salts and organic molecules.[2] The cytoplasm also contains the protein filaments that make up the cytoskeleton, as well as soluble proteins and small structures such as ribosomes, proteasomes, and the mysterious vault complexes.[3] The inner, granular and more fluid portion of the cytoplasm is referred to as endoplasm.
Organelles
Main article: Organelles
Organelles, literally little organs, are membrane-bound structures inside the cell that have specific functions. Some major organelles that are suspended in the cytosol are the mitochondria, the endoplasmic reticulum, the Golgi apparatus, vacuoles, lysosomes, and in plant cells chloroplasts.
Cytoplasmic inclusions
Main article: Cytoplasmic inclusion
The inclusions are small particles of insoluble substances suspended in the cytosol. A huge range of inclusions exist in different cell types, and range from crystals of calcium oxalate or silicon dioxide in plants,[4][5] to granules of energy-storage materials such as starch,[6] glycogen,[7] or polyhydroxybutyrate.[8] A particularly widespread example are lipid droplets, which are spherical droplets composed of lipids and proteins that are used in both prokaryotes and eukaryotes as a way of storing lipids such as fatty acids and sterols.[9] Lipid droplets make up much of the volume of adipocytes, which are specialized lipid-storage cells, but they are also found in a range of other cell types.
Notes
- ^ C. Michael Hogan. 2010. Calcium. eds. A.Jorgensen, C. Cleveland. Encyclopedia of Earth. National Council for Science and the Environment.
- ^ Cytoplasm Composition
- ^ van Zon A, Mossink MH, Scheper RJ, Sonneveld P, Wiemer EA (September 2003). "The vault complex". Cell. Mol. Life Sci. 60 (9): 1828–37. doi:10.1007/s00018-003-3030-y. PMID 14523546.
- ^ Prychid, Christina J.; Rudall, Paula J. (1999). "Calcium Oxalate Crystals in Monocotyledons: A Review of their Structure and Systematics". Annals of Botany 84 (6): 725. doi:10.1006/anbo.1999.0975. http://aob.oxfordjournals.org/cgi/content/abstract/84/6/725.
- ^ Prychid, C. J.; Rudall, P. J.; Gregory, M. (2003). "Systematics and Biology of Silica Bodies in Monocotyledons". The Botanical Review 69 (4): 377–440. doi:10.1663/0006-8101(2004)069[0377:SABOSB]2.0.CO;2. http://www.bioone.org/perlserv/?request=get-abstract.
- ^ Ball SG, Morell MK (2003). "From bacterial glycogen to starch: understanding the biogenesis of the plant starch granule". Annu Rev Plant Biol 54: 207–33. doi:10.1146/annurev.arplant.54.031902.134927. PMID 14502990.
- ^ Shearer J, Graham TE (April 2002). "New perspectives on the storage and organization of muscle glycogen". Can J Appl Physiol 27 (2): 179–203. doi:10.1139/h02-012. PMID 12179957.
- ^ Anderson AJ, Dawes EA (1 December 1990). "Occurrence, metabolism, metabolic role, and industrial uses of bacterial polyhydroxyalkanoates". Microbiol. Rev. 54 (4): 450–72. PMC 372789. PMID 2087222. http://mmbr.asm.org/cgi/pmidlookup?view=long&pmid=2087222.
- ^ Murphy DJ (September 2001). "The biogenesis and functions of lipid bodies in animals, growth and microorganisms". Prog. Lipid Res. 40 (5): 325–438. doi:10.1016/S0163-7827(01)00013-3. PMID 11470496.
External links
- Luby-Phelps K. Cytoarchitecture and physical properties of cytoplasm: volume, viscosity, diffusion, intracellular surface area. Int Rev Cytol. 2000;192:189-221.
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