Cellular compartment

[[File:Cell-organelles-labeled.png|thumb|Basic cellular compartments]]

'''Cellular compartments''' in [[cell biology]] comprise all of the closed parts within the [[cytosol]] of a [[eukaryotic]] [[cell (biology)|cell]], usually surrounded by a single or [[lipid bilayer|double lipid layer]] [[cell membrane|membrane]]. These compartments are often, but not always, defined as membrane-enclosed [[organelle]]s. The formation of cellular compartments is called '''compartmentalization'''.

Both [[organelle]]s, the [[mitochondria]] and [[chloroplast]]s (in photosynthetic organisms), are compartments that are believed to be of endosymbiotic origin. Other compartments such as [[peroxisome]]s, [[lysosome]]s, the [[endoplasmic reticulum]], the [[cell nucleus]] or the [[Golgi apparatus]] are not of endosymbiotic origin. Smaller elements like [[Vesicle (biology)|vesicles]], and sometimes even [[microtubules]] can also be counted as compartments.

It was thought that compartmentalization is not found in prokaryotic cells.,<ref name="campbell564">{{Cite book| title=Biology| last1=Campbell| last2=Reece| last3=Urry| last4=Cain| last5=Wasserman| last6=Minorsky| last7=Jackson| first1=Neil A.| first2=Jane B.| first3=Lisa A.| first4=Michael L.| first5=Steven A.| first6=Peter V.| first7=Robert B.| edition=8th| isbn=978-0-8053-6844-4| page=559| year=2008| publisher=Pearson Benjamin Cummings}}</ref> but the discovery of [[carboxysome]]s and many other [[bacterial microcompartment|metabolosomes]] revealed that prokaryotic cells are capable of making compartmentalized structures, albeit these are in most cases not surrounded by a lipid bilayer, but of pure proteinaceous built.<ref>{{cite journal |last1=Grant |first1=CR |last2=Wan |first2=J |last3=Komeili |first3=A |title=Organelle Formation in Bacteria and Archaea. |journal=Annual Review of Cell and Developmental Biology |date=6 October 2018 |volume=34 |pages=217–238 |doi=10.1146/annurev-cellbio-100616-060908 |pmid=30113887}}</ref><ref>{{cite journal |last1=Diekmann |first1=Y |last2=Pereira-Leal |first2=JB |title=Evolution of intracellular compartmentalization. |journal=The Biochemical Journal |date=15 January 2013 |volume=449 |issue=2 |pages=319–31 |doi=10.1042/BJ20120957 |pmid=23240612}}</ref><ref>{{cite journal |last1=Cornejo |first1=E |last2=Abreu |first2=N |last3=Komeili |first3=A |title=Compartmentalization and organelle formation in bacteria. |journal=Current Opinion in Cell Biology |date=February 2014 |volume=26 |pages=132–8 |doi=10.1016/j.ceb.2013.12.007 |pmid=24440431|pmc=4318566 }}</ref>

==Types== In general, there are 4 main cellular compartments, they are: # The nuclear compartment comprising the nucleus # The intercisternal space which comprises the space between the membranes of the endoplasmic reticulum (which is continuous with the nuclear envelope) # Organelles (the mitochondrion in all eukaryotes and the plastid in phototrophic eukaryotes) # The [[cytosol]]

==Function== Compartments have three main roles. One is to establish physical boundaries for biological processes that enables the cell to carry out different metabolic activities at the same time. This may include keeping certain biomolecules within a region, or keeping other molecules outside. Within the membrane-bound compartments, different [[intracellular pH]], different enzyme systems, and other differences are isolated from other organelles and cytosol. With mitochondria, the cytosol has an oxidizing environment which converts [[NADH]] to NAD+. With these cases, the compartmentalization is physical.

Another is to generate a specific micro-environment to spatially or temporally regulate a biological process. As an example, a yeast vacuole is normally acidified by proton transporters on the membrane.

A third role is to establish specific locations or cellular addresses for which processes should occur. For example, a [[transcription factor]] may be directed to a [[Cell nucleus|nucleus]], where it can promote [[Transcription (genetics)|transcription]] of certain [[genes]]. In terms of protein synthesis, the necessary organelles are relatively near one another. The nucleolus within the nuclear envelope is the location of ribosome synthesis. The destination of synthesized ribosomes for protein translation is [[endoplasmic reticulum#Rough Endoplasmic Reticulum|rough endoplasmic reticulum]] (rough ER), which is connected to and shares the same membrane with the nucleus. The [[Golgi body]] is also near the rough ER for packaging and redistributing. Likewise, intracellular compartmentalization allows specific sites of related eukaryotic cell functions isolated from other processes and therefore efficient.

== Establishment == Often, cellular compartments are defined by membrane enclosure. These membranes provide physical barriers to biomolecules. Transport across these barriers is often controlled in order to maintain the optimal concentration of biomolecules within and outside of the compartment.

==Emergence of the eukaryotic nucleus== The [[eukaryote|eukaryotic cell]] is thought to have arisen when an ancestral [[archaea|archaeal cell]] internalized an aerobic [[bacteria|bacterium]] (the [[proto-mitochondrion]]). Mans et al.<ref>Mans BJ, Anantharaman V, Aravind L, Koonin EV. Comparative genomics, evolution and origins of the nuclear envelope and nuclear pore complex. Cell Cycle. 2004 Dec;3(12):1612-37. doi: 10.4161/cc.3.12.1345. Epub 2004 Dec 20. PMID 15611647</ref> proposed that the evolutionary development of the eukaryotic [[cell nucleus]] was triggered by this archaeo-bacterial [[symbiosis]]. The [[nuclear envelope]] (membrane), a defining characteristic of the eukaryotic cell, was suggested to have arisen as an adaptation for segregating the original archaeal host DNA [[genome]] away from the proto-mitochondria, the main source of damaging [[reactive oxygen species]].<ref>Bernstein H, Bernstein C. Sexual communication in archaea, the precursor to meiosis. pp. 103-117 in Biocommunication of Archaea (Guenther Witzany, ed.) 2017. Springer International Publishing</ref>

==References== {{Reflist}}

==External links== *{{Commons category-inline|Cell compartmentation}}

{{DEFAULTSORT:Cellular Compartment}} [[Category:Cell anatomy]] [[Category:Eukaryotic cell anatomy]]