Cell compartment

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As cell compartments in the are Biology various spaces within a cell , respectively. Even within the organelles, individual compartments are structurally separated from one another. In contrast to the term ' organelle ', which always refers to a single object (such as a mitochondrion ), the term compartment is used for the sum of all similar cellular spaces. A cell can therefore have many mitochondria, but only one mitochondrial compartment. The cytoplasm is also a compartment, but not an organelle.

Further compartments of the eukaryotes are made up of the components of the endomembrane system (such as the interior of the endoplasmic reticulum ), the cell nucleus ( karyoplasm or nuclear matrix ), the mitochondria ( matrix ), and - if present, as in plants and green algae - the chloroplasts and other plastids ( Stroma ) as well as the vacuoles and the interiors of the thylakoid . The lytic compartment is also a special form .

Compartments are usually separated from each other by biomembranes , but areas of the cell that are not separated by a biomembrane can also represent compartments, such as the heterochromatic and the euchromatic compartment in the cell nucleus. With the aid of the compartmentalization rule proposed by Eberhard Schnepf , compartments can be assigned to the plasmatic or the non-plasmatic phase .

Meaning of cell compartments

The cell is divided into different reaction spaces (compartments) so that different metabolic reactions are possible in a very small space. Different microenvironments are created. Many of the organelles have biomembranes. The bio-membranes represent a demarcation of the smallest areas from the environment and, thanks to their controllable permeability, enable selective permeability . Different processes can take place in such separated compartments, e.g. B. detoxification processes, biochemical reactions that would interfere with each other and thus the chemistry of the entire cell.

In addition, concentration gradients can be built up through the membranes of the different compartments . This means that the concentrations of dissolved substances (e.g. ions such as potassium ions or calcium ions) differ on the two sides of the membrane. This concentration gradient can, for. B. be used by proteins to synthesize substances or to transport other ions through the membrane in exchange for ions.

The presence of compartments enables an intracellular division of labor, through which an enormous differentiation and performance increase of the specialized cell is made possible. At the cellular level, compartmentalization is therefore the evolutionary prerequisite for the development of complex, differentiated organisms.

The division of the cell into reaction spaces (compartmentalization) also enables a considerable acceleration of metabolic reactions. The concentration of the metabolite particles in smaller cell subspaces leads to an increase in the collision probability and the reaction rate due to the smaller diffusion distances (see Fick's law ).

But many prokaryotic cells also have compartments. One of the best-researched is the periplasmic space of the proteobacteria , which is located between the cytoplasmic membrane and the outer membrane . This compartment contains, among other things, the cell wall .

The inside of the cells of planctomycetes is also highly compartmentalized without any details about the function of the individual delimited spaces being known. Another bacterial compartment found in green non-sulfur bacteria are chlorosomes , which contain the light-absorbing pigments of these phototrophic bacteria.

Individual evidence

  1. Hans Kleinig , Peter Sitte: Cell Biology , 3rd ed .. edition, Gustav Fischer Verlag., 1992