Cellular compartments in

cell biology Cell biology (also cellular biology or cytology) is a branch of biology that studies the structure, function, and behavior of cells. All living organisms are made of cells. A cell is the basic unit of life that is responsible for the living a ...

comprise all of the closed parts within the

cytosol The cytosol, also known as cytoplasmic matrix or groundplasm, is one of the liquids found inside cells (intracellular fluid (ICF)). It is separated into compartments by membranes. For example, the mitochondrial matrix separates the mitochondrio ...

of a eukaryotic

cell Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Locations * Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery w ...

, usually surrounded by a single or double lipid layer membrane. These compartments are often, but not always, defined as

membrane-bound organelle In cell biology, an organelle is a specialized subunit, usually within a cell, that has a specific function. The name ''organelle'' comes from the idea that these structures are parts of cells, as organs are to the body, hence ''organelle,'' the ...

s. The formation of cellular compartments is called compartmentalization. Both

organelle In cell biology, an organelle is a specialized subunit, usually within a cell, that has a specific function. The name ''organelle'' comes from the idea that these structures are parts of cells, as organs are to the body, hence ''organelle,'' the ...

s, the mitochondria and

chloroplast A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant and algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, and stores it in ...

s (in photosynthetic organisms), are compartments that are believed to be of endosymbiotic origin. Other compartments such as

peroxisome A peroxisome () is a membrane-bound organelle, a type of microbody, found in the cytoplasm of virtually all eukaryotic cells. Peroxisomes are oxidative organelles. Frequently, molecular oxygen serves as a co-substrate, from which hydrogen pero ...

s, lysosomes, the endoplasmic reticulum, the

cell nucleus The cell nucleus (pl. nuclei; from Latin or , meaning ''kernel'' or ''seed'') is a membrane-bound organelle found in eukaryotic cells. Eukaryotic cells usually have a single nucleus, but a few cell types, such as mammalian red blood cells, h ...

or the Golgi apparatus are not of endosymbiotic origin. Smaller elements like

vesicles Vesicle may refer to: ; In cellular biology or chemistry * Vesicle (biology and chemistry), a supramolecular assembly of lipid molecules, like a cell membrane * Synaptic vesicle ; In human embryology * Vesicle (embryology), bulge-like features o ...

, and sometimes even

microtubules Microtubules are polymers of tubulin that form part of the cytoskeleton and provide structure and shape to eukaryotic cells. Microtubules can be as long as 50 micrometres, as wide as 23 to 27 nm and have an inner diameter between 11 a ...

can also be counted as compartments. It was thought that compartmentalization is not found in prokaryotic cells., but the discovery of

carboxysome Carboxysomes are bacterial microcompartments (BMCs) consisting of polyhedral protein shells filled with the enzymes ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO)—the predominant enzyme in carbon fixation and the rate limiting e ...

s and many other 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.

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

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 Nicotinamide adenine dinucleotide (NAD) is a coenzyme central to metabolism. Found in all living cells, NAD is called a dinucleotide because it consists of two nucleotides joined through their phosphate groups. One nucleotide contains an aden ...

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

nucleus Nucleus ( : nuclei) is a Latin word for the seed inside a fruit. It most often refers to: * Atomic nucleus, the very dense central region of an atom *Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA Nucl ...

, where it can promote 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

rough endoplasmic reticulum The endoplasmic reticulum (ER) is, in essence, the transportation system of the eukaryotic cell, and has many other important functions such as protein folding. It is a type of organelle made up of two subunits – rough endoplasmic reticulum ( ...

(rough ER), which is connected to and shares the same membrane with the nucleus. The

Golgi body The Golgi apparatus (), also known as the Golgi complex, Golgi body, or simply the Golgi, is an organelle found in most eukaryotic cells. Part of the endomembrane system in the cytoplasm, it packages proteins into membrane-bound vesicles insi ...

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 eukaryotic cell is thought to have arisen when an ancestral archaeal cell internalized an aerobic

bacterium Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

(the

proto-mitochondrion The proto-mitochondrion is the hypothetical ancestral bacterial endosymbiont from which all mitochondria in eukaryotes are thought to descend, after an episode of symbiogenesis which created the aerobic eukaryotes. Phylogeny The phylogenetic ana ...

). Mans et al. proposed that the evolutionary development of the eukaryotic

was triggered by this archaeo-bacterial

symbiosis Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasi ...

. 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.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

References

External links

* {{DEFAULTSORT:Cellular Compartment Cell anatomy