Eukaryote - Revision history

DavidB4-bot: clean up & uniformity

2016-07-13T12:12:08Z

clean up & uniformity

JimmyRa: Introduces evolutionist idea without proper balance

2011-05-12T17:33:02Z

Introduces evolutionist idea without proper balance

WesleyS: link to de-orphan

2009-02-26T23:08:13Z

link to de-orphan

WesleyS: link to de-orphan

2009-02-18T23:18:13Z

link to de-orphan

Corry at 18:46, July 3, 2008

2008-07-03T18:46:44Z

Aschlafly: wikify

2008-03-02T20:00:05Z

wikify

Lukecorlando at 02:32, November 15, 2007

2007-11-15T02:32:34Z

Ed Poor: the nucleus, consists of a nucleoplasm

2007-09-18T21:21:10Z

the nucleus, consists of a nucleoplasm

Ed Poor at 21:20, September 18, 2007

2007-09-18T21:20:31Z

Dcollier: de-orphan

2007-09-18T16:59:22Z

de-orphan

@@ Line 1: / Line 1: @@
-'''Eukaryotes ''' are organisms whose [[cell]]s are organized into complex structures by internal [[membrane|membranes]] and a [[cytoskeleton]]. [[animal|animals]], [[plant|plants]] and [[fungus|fungi]] are all eukaryotes, but [[bacteria]] are not.
+'''Eukaryotes ''' are organisms whose [[cell]]s are organized into complex structures by internal [[membrane]]s and a [[cytoskeleton]]. [[animal]]s, [[plant]]s and [[fungus|fungi]] are all eukaryotes, but [[bacteria]] are not.
-The most characteristic feature of a eukaryotic cell, the nucleus, consists of a [[nucleoplasm]] surrounded by a double nuclear membrane pierced by nuclear pores. <ref>http://biotech.icmb.utexas.edu/search/dict-search.html</ref><ref>http://www.iscid.org/encyclopedia/Eukaryote</ref> The nucleoplasm contains the (linear) chromosomes of the cell, which are organised into [[heterochromatin]], which stains only a little, and euchromatin, which stains more densely. The most important euchromatic area is the nucleolus, in which ribosomes are formed.
+The most characteristic feature of a eukaryotic cell, the nucleus, consists of a [[nucleoplasm]] surrounded by a double nuclear membrane pierced by nuclear pores.<ref>http://biotech.icmb.utexas.edu/search/dict-search.html</ref><ref>http://www.iscid.org/encyclopedia/Eukaryote</ref> The nucleoplasm contains the (linear) chromosomes of the cell, which are organised into [[heterochromatin]], which stains only a little, and euchromatin, which stains more densely. The most important euchromatic area is the nucleolus, in which ribosomes are formed.
 #εύ-καρυον (eu-karyon) - true [[kernel]].
@@ Line 9: / Line 9: @@
 #They can grow 'large' because cytoplasmic streaming allows rapid transport across the cell - 100 μm.
-[[Image:Animal_cell.png‎ |center||Animal cell: eukaryotic cells are characterised by the possession of a nucleus and membrane bound organelles.]]
+[[Image:Animal_cell.png‎|center||Animal cell: eukaryotic cells are characterised by the possession of a nucleus and membrane bound organelles.]]
 The role of the nucleus is three-fold:
@@ Line 19: / Line 19: @@
 [[DNA]] storage takes up about 10% of the cell of both prokaryotes (nucleoid area) and eukaryotes (nucleus). However, don't forget that some of the genome lives elsewhere: plasmids, endosymbionts (mitochondria), etc. The nucleus of eukaryotes also protects the genome from the cytoskeleton. Condensation of genome during mitosis is required to withstand these stresses. This is not relevant in prokaryotes, as they lack a cytoskeleton. The existence of the nucleus permits processing of mRNA, and therefore defers translation. Alternative splicing can be performed to generate different proteins from the same RNA primary transcript. mRNA is capped and tailed to permit it to exit the nucleus. rRNA and tRNA are also heavily processed by RNA editing, i.e. base modification (this also occurs to some mRNA in trypanosomes). rRNA modification occurs in the nucleolus, where ribosomes are constructed.
-The nucleus is bound by a double-membrane, which is contiguous through the nuclear pores, known as the nuclear envelope. The pores are required to allow RNA out and membrane lipids in (which is needed for growth during S phase).<ref> Berg, Jeremy M.; Tymoczko, John L.; and Stryer, Lubert."Biochemistry". W. H. Freeman and Co. ; c2002 </ref>
+The nucleus is bound by a double-membrane, which is contiguous through the nuclear pores, known as the nuclear envelope. The pores are required to allow RNA out and membrane lipids in (which is needed for growth during S phase).<ref>Berg, Jeremy M.; Tymoczko, John L.; and Stryer, Lubert."Biochemistry". W. H. Freeman and Co. ; c2002</ref>
 The inner face of the inner nuclear envelope (INE) is coated by the nuclear lamina, which contains intermediate fibres called lamins A, B and C (at least in mammals). Phosphorylation of lamins by kinases cause nuclear envelope breakdown during prometaphase. Chromosomes occupy definite positions within the nucleus because of the interaction between lamins and telomeres, for example the Rabl conformation in yeast.
@@ Line 33: / Line 33: @@
 Photosynthetic eukaryotes also have chloroplasts, which are the remains of cyanobacteria that also became endosymbiotic. They have a triple membrane system. The outer membrane surrounds the inner membrane, which itself surrounds the stroma, in which are embedded a number of thylakoid membranes, some of which occur in stacks called grana. Those that are unstacked are termed intergrana. The thylakoids surround another compartment, termed the lumen. Chloroplasts are one of several different sorts of plastid. Others include proplasts (immature plastids), chromoplasts (full of pigments), etioplasts (formed in the dark) and amyloplasts (full of starch). Plastids carry out photosynthesis, converting light energy into ATP and NADH.
-[[Image:Plant_cell.png|center||Plant cell: The cell wall vs the cell membrane found in animal cells.]]
+[[Image:Plant_cell.png|center|Plant cell: The cell wall vs the cell membrane found in animal cells.]]
 Eukaryotes have a cytoskeleton, which is composed of a number of interacting fibre types. The first are the actin microfilaments, which, with the motor protein myosin, form the muscles of the cytoskeleton (and in sarcosomes, form actual muscles too). The actin cytoskeleton forms a cortex beneath the plasmalemma of most eukaryotic cells, which is involved in changes to the external shape of the cell (such as the formation of pseudopodia in [[amoebas]]).The second fibre type are intermediate filaments, composed of spectrin, keratin, vimentin, nuclear lamins and other proteins. The intermediate filaments help maintain the relative positions of organelles and give the cell mechanical strength. The third type of cytoskeletal filament are the microtubules, which form the spindle during cell divisions (meiosis and mitosis), and give structure to the cell membrane, forming microvilli. They also form undulipodia, which are waving structures with a typical 9+2 structure, found in cilia (short undulipodia) and flagella (longer ones). The microtubules are composed of tubulin, and are organised by a microtubule organising centre (the centrosome and centrioles in animals), in which the − ends of the microtubules (which grow more slowly than the + ends) are embedded. Vesicles traffic along the microtubules under the influence of motor proteins such as kinesin (which transports items from the −→+ ends, i.e. away from the MTOC) and dynein (which traffics items from +→−). Tubulin is homologous to the FtsZ protein that is involved in bacterial fission.
@@ Line 47: / Line 47: @@
 The rough ER differs from the smooth ER morphologically. The RER's cytoplasmic surface is studded with ribosomes, and it has flattened cisternae (rather than tubular ones). The RER is denser than SER due to presence of ribosomes. Consequently, disrupted ER 'microsomes' can be separated using density gradient centrifugation.
-[[Image:Density_gradient_er.png|center||SER microsomes are less dense than RER microsomes, so can be separated by centrifugation.]]
+[[Image:Density_gradient_er.png|center|SER microsomes are less dense than RER microsomes, so can be separated by centrifugation.]]
 Other proteins are destined for the endolysosome system. Material engulfed from outside by [[phagocytosis]] (solids) and pinocytosis (liquids) are packaged into phagosomes, and internal organelles destined for destruction are packed into autophagosomes. Endolysosomes containing digestive enzymes fuse with the phagosomes and digest their contents. The fused organelles produced are the cells disposal system, and are called lysosomes. Very large lysosomes are found in plants where they help to bulk the cell with water. Here they are called vacuoles, and are surrounded by a membrane called to tonoplast. Other vacuoles are involved in osmoregulation: for example contractile vacuoles in Amoeba.
@@ Line 65: / Line 65: @@
 [[Category:Molecular Biology]]
 [[Category:Cellular Biology]]
-[[Category:microbiology]]
+[[Category:Microbiology]]

@@ Line 41: / Line 41: @@
 The endomembranes and plasmalemma form a continuous membrane system in the eukaryote cell. The cell contains a rich diversity of membranes, in addition to those found in the endosymbiotic organelles. The outer cell membrane or plasmalemma, controls what gets in and out of the cell by the use of pores, symports, antiports and pumps. It is composed of a fluid mosaic of proteins embedded in a phospholipid bilayer, as are all membranes. The plasmalemma also interacts with the extracellular space through receptors, gap junctions, plasmodesmata, and synapses.
-The endomembranes include the nuclear membrane, already mentioned, and the rough and smooth endoplasmic reticula (RER and SER). The lamellae of the rough endoplasmic reticulum are continuous throughout the cell, and also contiguous with the nuclear membrane. They are the site of synthesis for proteins destined for the endomembrane system and the extracellular space, with which its lumen (the cisternal space) is topologically identical. The tubules of the SER are responsible for steroid and lipid synthesis. After translation on ribosomes attached to the RER, proteins are carried in small transport vesicles to the Golgi bodies (dictyosomes), where they go undergo modification to the glycosylation they received as they were imported into the RER. After modification, some proteins are exported from the trans-Golgi network in export vesicles to the extracellular space. The ER is continuous with the nuclear envelope, and probably evolved at the same time, possibly by invaginations of the sort seen in the mesosomes of bacteria.
+The endomembranes include the nuclear membrane, already mentioned, and the rough and smooth endoplasmic reticula (RER and SER). The lamellae of the rough endoplasmic reticulum are continuous throughout the cell, and also contiguous with the nuclear membrane. They are the site of synthesis for proteins destined for the endomembrane system and the extracellular space, with which its lumen (the cisternal space) is topologically identical. The tubules of the SER are responsible for steroid and lipid synthesis. After translation on ribosomes attached to the RER, proteins are carried in small transport vesicles to the Golgi bodies (dictyosomes), where they go undergo modification to the glycosylation they received as they were imported into the RER. After modification, some proteins are exported from the trans-Golgi network in export vesicles to the extracellular space.
 [[Image:Endomembranes_evolution.png‎|center||Endomembranes probably evolved from invaginations of the plasmalemma, as seen in bacterial mesosomes, thylakoids and chromatophores.]]

@@ Line 1: / Line 1: @@
 '''Eukaryotes ''' are organisms whose [[cell]]s are organized into complex structures by internal [[membrane|membranes]] and a [[cytoskeleton]]. [[animal|animals]], [[plant|plants]] and [[fungus|fungi]] are all eukaryotes, but [[bacteria]] are not.
-The most characteristic feature of a eukaryotic cell, the nucleus, consists of a [[nucleoplasm]] surrounded by a double nuclear membrane pierced by nuclear pores. <ref>http://biotech.icmb.utexas.edu/search/dict-search.html</ref><ref>http://www.iscid.org/encyclopedia/Eukaryote</ref> The nucleoplasm contains the (linear) chromosomes of the cell, which are organised into heterochromatin, which stains only a little, and euchromatin, which stains more densely. The most important euchromatic area is the nucleolus, in which ribosomes are formed.
+The most characteristic feature of a eukaryotic cell, the nucleus, consists of a [[nucleoplasm]] surrounded by a double nuclear membrane pierced by nuclear pores. <ref>http://biotech.icmb.utexas.edu/search/dict-search.html</ref><ref>http://www.iscid.org/encyclopedia/Eukaryote</ref> The nucleoplasm contains the (linear) chromosomes of the cell, which are organised into [[heterochromatin]], which stains only a little, and euchromatin, which stains more densely. The most important euchromatic area is the nucleolus, in which ribosomes are formed.
 #εύ-καρυον (eu-karyon) - true [[kernel]].

@@ Line 49: / Line 49: @@
 [[Image:Density_gradient_er.png|center||SER microsomes are less dense than RER microsomes, so can be separated by centrifugation.]]
-Other proteins are destined for the endolysosome system. Material engulfed from outside by phagocytosis (solids) and pinocytosis (liquids) are packaged into phagosomes, and internal organelles destined for destruction are packed into autophagosomes. Endolysosomes containing digestive enzymes fuse with the phagosomes and digest their contents. The fused organelles produced are the cells disposal system, and are called lysosomes. Very large lysosomes are found in plants where they help to bulk the cell with water. Here they are called vacuoles, and are surrounded by a membrane called to tonoplast. Other vacuoles are involved in osmoregulation: for example contractile vacuoles in Amoeba.
+Other proteins are destined for the endolysosome system. Material engulfed from outside by [[phagocytosis]] (solids) and pinocytosis (liquids) are packaged into phagosomes, and internal organelles destined for destruction are packed into autophagosomes. Endolysosomes containing digestive enzymes fuse with the phagosomes and digest their contents. The fused organelles produced are the cells disposal system, and are called lysosomes. Very large lysosomes are found in plants where they help to bulk the cell with water. Here they are called vacuoles, and are surrounded by a membrane called to tonoplast. Other vacuoles are involved in osmoregulation: for example contractile vacuoles in Amoeba.
 Finally, a number of smaller vesicles are found in the cytosol. They are called microsomes, and most seem to be peroxisomes, containing the enzyme catalase, which degrades hydrogen peroxide produced by respiration. In germinating plant seed, many glyoxysomes are present, which perform fat oxidation for growth. Some vesicles also contain food reserves, such as fat droplets.

@@ Line 59: / Line 59: @@
 RNApol-III - tRNA and 5S rRNA.
 RNA is heavily processed in the nucleus, which allows deferred translation. They possess large 80S ribosomes.
 ==References==

@@ Line 3: / Line 3: @@
 The most characteristic feature of a eukaryotic cell, the nucleus, consists of a [[nucleoplasm]] surrounded by a double nuclear membrane pierced by nuclear pores. <ref>http://biotech.icmb.utexas.edu/search/dict-search.html</ref><ref>http://www.iscid.org/encyclopedia/Eukaryote</ref> The nucleoplasm contains the (linear) chromosomes of the cell, which are organised into heterochromatin, which stains only a little, and euchromatin, which stains more densely. The most important euchromatic area is the nucleolus, in which ribosomes are formed.
-#εύ-καρυον (eu-karyon) - true kernel.
+#εύ-καρυον (eu-karyon) - true [[kernel]].
-#Double-membrane bound nucleus containing linear chromosomes.
+#Double-membrane bound nucleus containing linear [[chromosome]]s.
-#Complex 9+2-type undulipodium, cytoskeleton, cytosis and mitosis.
+#Complex 9+2-type undulipodium, cytoskeleton, [[cytosis]] and [[mitosis]].
 #Many membrane-bound organelles and double membrane-bound endosymbionts.
 #They can grow 'large' because cytoplasmic streaming allows rapid transport across the cell - 100 μm.

← Older revision		Revision as of 02:32, November 15, 2007
Line 1:		Line 1:
−	'''Eukaryotes ''' are organisms whose ~~cells~~ are organized into complex structures by internal [[membrane\|membranes]] and a [[cytoskeleton]]. [[animal\|animals]], [[plant\|plants]] and [[fungus\|fungi]] are all eukaryotes, but [[bacteria]] are not.	+	'''Eukaryotes ''' are organisms whose [[cell]]s are organized into complex structures by internal [[membrane\|membranes]] and a [[cytoskeleton]]. [[animal\|animals]], [[plant\|plants]] and [[fungus\|fungi]] are all eukaryotes, but [[bacteria]] are not.

	The most characteristic feature of a eukaryotic cell, the nucleus, consists of a [[nucleoplasm]] surrounded by a double nuclear membrane pierced by nuclear pores. <ref>http://biotech.icmb.utexas.edu/search/dict-search.html</ref><ref>http://www.iscid.org/encyclopedia/Eukaryote</ref> The nucleoplasm contains the (linear) chromosomes of the cell, which are organised into heterochromatin, which stains only a little, and euchromatin, which stains more densely. The most important euchromatic area is the nucleolus, in which ribosomes are formed.		The most characteristic feature of a eukaryotic cell, the nucleus, consists of a [[nucleoplasm]] surrounded by a double nuclear membrane pierced by nuclear pores. <ref>http://biotech.icmb.utexas.edu/search/dict-search.html</ref><ref>http://www.iscid.org/encyclopedia/Eukaryote</ref> The nucleoplasm contains the (linear) chromosomes of the cell, which are organised into heterochromatin, which stains only a little, and euchromatin, which stains more densely. The most important euchromatic area is the nucleolus, in which ribosomes are formed.

← Older revision		Revision as of 21:20, September 18, 2007
Line 1:		Line 1:
−	'''Eukaryotes '''are ~~are eukaryotes~~ organisms whose cells are organized into complex structures by internal [[membrane\|membranes]] and a [[cytoskeleton]]. [[animal\|animals]], [[plant\|plants]] and [[fungus\|fungi]] are all eukaryotes, but [[bacteria]] are not.	+	'''Eukaryotes ''' are organisms whose cells are organized into complex structures by internal [[membrane\|membranes]] and a [[cytoskeleton]]. [[animal\|animals]], [[plant\|plants]] and [[fungus\|fungi]] are all eukaryotes, but [[bacteria]] are not.

	The most characteristic feature of a eukaryotic cell, the nucleus, consists of a nucleoplasm surrounded by a double nuclear membrane pierced by nuclear pores. <ref>http://biotech.icmb.utexas.edu/search/dict-search.html</ref><ref>http://www.iscid.org/encyclopedia/Eukaryote</ref> The nucleoplasm contains the (linear) chromosomes of the cell, which are organised into heterochromatin, which stains only a little, and euchromatin, which stains more densely. The most important euchromatic area is the nucleolus, in which ribosomes are formed.		The most characteristic feature of a eukaryotic cell, the nucleus, consists of a nucleoplasm surrounded by a double nuclear membrane pierced by nuclear pores. <ref>http://biotech.icmb.utexas.edu/search/dict-search.html</ref><ref>http://www.iscid.org/encyclopedia/Eukaryote</ref> The nucleoplasm contains the (linear) chromosomes of the cell, which are organised into heterochromatin, which stains only a little, and euchromatin, which stains more densely. The most important euchromatic area is the nucleolus, in which ribosomes are formed.

@@ Line 35: / Line 35: @@
 [[Image:Plant_cell.png|center||Plant cell: The cell wall vs the cell membrane found in animal cells.]]
-Eukaryotes have a cytoskeleton, which is composed of a number of interacting fibre types. The first are the actin microfilaments, which, with the motor protein myosin, form the muscles of the cytoskeleton (and in sarcosomes, form actual muscles too). The actin cytoskeleton forms a cortex beneath the plasmalemma of most eukaryotic cells, which is involved in changes to the external shape of the cell (such as the formation of pseudopodia in amoebae).The second fibre type are intermediate filaments, composed of spectrin, keratin, vimentin, nuclear lamins and other proteins. The intermediate filaments help maintain the relative positions of organelles and give the cell mechanical strength. The third type of cytoskeletal filament are the microtubules, which form the spindle during cell divisions (meiosis and mitosis), and give structure to the cell membrane, forming microvilli. They also form undulipodia, which are waving structures with a typical 9+2 structure, found in cilia (short undulipodia) and flagella (longer ones). The microtubules are composed of tubulin, and are organised by a microtubule organising centre (the centrosome and centrioles in animals), in which the − ends of the microtubules (which grow more slowly than the + ends) are embedded. Vesicles traffic along the microtubules under the influence of motor proteins such as kinesin (which transports items from the −→+ ends, i.e. away from the MTOC) and dynein (which traffics items from +→−). Tubulin is homologous to the FtsZ protein that is involved in bacterial fission.
+Eukaryotes have a cytoskeleton, which is composed of a number of interacting fibre types. The first are the actin microfilaments, which, with the motor protein myosin, form the muscles of the cytoskeleton (and in sarcosomes, form actual muscles too). The actin cytoskeleton forms a cortex beneath the plasmalemma of most eukaryotic cells, which is involved in changes to the external shape of the cell (such as the formation of pseudopodia in [[amoebas]]).The second fibre type are intermediate filaments, composed of spectrin, keratin, vimentin, nuclear lamins and other proteins. The intermediate filaments help maintain the relative positions of organelles and give the cell mechanical strength. The third type of cytoskeletal filament are the microtubules, which form the spindle during cell divisions (meiosis and mitosis), and give structure to the cell membrane, forming microvilli. They also form undulipodia, which are waving structures with a typical 9+2 structure, found in cilia (short undulipodia) and flagella (longer ones). The microtubules are composed of tubulin, and are organised by a microtubule organising centre (the centrosome and centrioles in animals), in which the − ends of the microtubules (which grow more slowly than the + ends) are embedded. Vesicles traffic along the microtubules under the influence of motor proteins such as kinesin (which transports items from the −→+ ends, i.e. away from the MTOC) and dynein (which traffics items from +→−). Tubulin is homologous to the FtsZ protein that is involved in bacterial fission.
 The body of the cell is composed of a heterogeneous mixture of proteins and solutes called the cytosol. The cytosol contains many 80S ribosomes, on which protein synthesis takes place.