From Wikipedia for FEVERv2
Jump to navigation Jump to search


Cell biologyCytoplasm_header_cell_0_0_0

In cell biology, the cytoplasm is all of the material within a cell, enclosed by the cell membrane, except for the cell nucleus. Cytoplasm_sentence_0

The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. Cytoplasm_sentence_1

The main components of the cytoplasm are cytosol (a gel-like substance), the organelles (the cell's internal sub-structures), and various cytoplasmic inclusions. Cytoplasm_sentence_2

The cytoplasm is about 80% water and usually colorless. Cytoplasm_sentence_3

The submicroscopic ground cell substance, or cytoplasmatic matrix which remains after exclusion the cell organelles and particles is groundplasm. Cytoplasm_sentence_4

It is the hyaloplasm of light microscopy, and high complex, polyphasic system in which all of resolvable cytoplasmic elements of are suspended, including the larger organelles such as the ribosomes, mitochondria, the plant plastids, lipid droplets, and vacuoles. Cytoplasm_sentence_5

Most cellular activities take place within the cytoplasm, such as many metabolic pathways including glycolysis, and processes such as cell division. Cytoplasm_sentence_6

The concentrated inner area is called the endoplasm and the outer layer is called the cell cortex or the ectoplasm. Cytoplasm_sentence_7

Movement of calcium ions in and out of the cytoplasm is a signaling activity for metabolic processes. Cytoplasm_sentence_8

In plants, movement of the cytoplasm around vacuoles is known as cytoplasmic streaming. Cytoplasm_sentence_9

History Cytoplasm_section_0

The term was introduced by Rudolf von Kölliker in 1863, originally as a synonym for protoplasm, but later it has come to mean the cell substance and organelles outside the nucleus. Cytoplasm_sentence_10

There has been certain disagreement on the definition of cytoplasm, as some authors prefer to exclude from it some organelles, especially the vacuoles and sometimes the plastids. Cytoplasm_sentence_11

Physical nature Cytoplasm_section_1

The physical properties of the cytoplasm have been contested in recent years. Cytoplasm_sentence_12

It remains uncertain how the varied components of the cytoplasm interact to allow movement of particles and organelles while maintaining the cell's structure. Cytoplasm_sentence_13

The flow of cytoplasmic components plays an important role in many cellular functions which are dependent on the permeability of the cytoplasm. Cytoplasm_sentence_14

An example of such function is cell signalling, a process which is dependent on the manner in which signaling molecules are allowed to diffuse across the cell. Cytoplasm_sentence_15

While small signaling molecules like calcium ions are able to diffuse with ease, larger molecules and subcellular structures often require aid in moving through the cytoplasm. Cytoplasm_sentence_16

The irregular dynamics of such particles have given rise to various theories on the nature of the cytoplasm. Cytoplasm_sentence_17

As a sol-gel Cytoplasm_section_2

There has long been evidence that the cytoplasm behaves like a sol-gel. Cytoplasm_sentence_18

It is thought that the component molecules and structures of the cytoplasm behave at times like a disordered colloidal solution (sol) and at other times like an integrated network, forming a solid mass (gel). Cytoplasm_sentence_19

This theory thus proposes that the cytoplasm exists in distinct fluid and solid phases depending on the level of interaction between cytoplasmic components, which may explain the differential dynamics of different particles observed moving through the cytoplasm. Cytoplasm_sentence_20

A papers suggested that at length scale smaller than 100 nm, the cytoplasm acts like a liquid, while in a larger length scale, it acts like a gel. Cytoplasm_sentence_21

As a glass Cytoplasm_section_3

Recently it has been proposed that the cytoplasm behaves like a glass-forming liquid approaching the glass transition. Cytoplasm_sentence_22

In this theory, the greater the concentration of cytoplasmic components, the less the cytoplasm behaves like a liquid and the more it behaves as a solid glass, freezing larger cytoplasmic components in place (it is thought that the cell's metabolic activity is able to fluidize the cytoplasm to allow the movement of such larger cytoplasmic components). Cytoplasm_sentence_23

A cell's ability to vitrify in the absence of metabolic activity, as in dormant periods, may be beneficial as a defence strategy. Cytoplasm_sentence_24

A solid glass cytoplasm would freeze subcellular structures in place, preventing damage, while allowing the transmission of very small proteins and metabolites, helping to kickstart growth upon the cell's revival from dormancy. Cytoplasm_sentence_25

Other perspectives Cytoplasm_section_4

There has been research examining the motion of cytoplasmic particles independent of the nature of the cytoplasm. Cytoplasm_sentence_26

In such an alternative approach, the aggregate random forces within the cell caused by motor proteins explain the non-Brownian motion of cytoplasmic constituents. Cytoplasm_sentence_27

Constituents Cytoplasm_section_5

The three major elements of the cytoplasm are the cytosol, organelles and inclusions. Cytoplasm_sentence_28

Cytosol Cytoplasm_section_6

Main article: Cytosol Cytoplasm_sentence_29

The cytosol is the portion of the cytoplasm not contained within membrane-bound organelles. Cytoplasm_sentence_30

Cytosol makes up about 70% of the cell volume and is a complex mixture of cytoskeleton filaments, dissolved molecules, and water. Cytoplasm_sentence_31

The cytosol's filaments include the protein filaments such as actin filaments and microtubules that make up the cytoskeleton, as well as soluble proteins and small structures such as ribosomes, proteasomes, and the mysterious vault complexes. Cytoplasm_sentence_32

The inner, granular and more fluid portion of the cytoplasm is referred to as endoplasm. Cytoplasm_sentence_33

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. Cytoplasm_sentence_34

This crowding effect alters how the components of the cytosol interact with each other. Cytoplasm_sentence_35

Organelles Cytoplasm_section_7

Main article: Organelle Cytoplasm_sentence_36

Organelles (literally "little organs"), are usually membrane-bound structures inside the cell that have specific functions. Cytoplasm_sentence_37

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. Cytoplasm_sentence_38

Cytoplasmic inclusions Cytoplasm_section_8

Main article: Cytoplasmic inclusion Cytoplasm_sentence_39

The inclusions are small particles of insoluble substances suspended in the cytosol. Cytoplasm_sentence_40

A huge range of inclusions exist in different cell types, and range from crystals of calcium oxalate or silicon dioxide in plants, to granules of energy-storage materials such as starch, glycogen, or polyhydroxybutyrate. Cytoplasm_sentence_41

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. Cytoplasm_sentence_42

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. Cytoplasm_sentence_43

Controversy and research Cytoplasm_section_9

The cytoplasm, mitochondria and most organelles are contributions to the cell from the maternal gamete. Cytoplasm_sentence_44

Contrary to the older information that disregards any notion of the cytoplasm being active, new research has shown it to be in control of movement and flow of nutrients in and out of the cell by viscoplastic behavior and a measure of the reciprocal rate of bond breakage within the cytoplasmic network. Cytoplasm_sentence_45

The material properties of the cytoplasm remain an ongoing investigation. Cytoplasm_sentence_46

A method of determining the mechanical behaviour of living cell mammalian cytoplasm with the aid of optical tweezers has been described. Cytoplasm_sentence_47

See also Cytoplasm_section_10


Credits to the contents of this page go to the authors of the corresponding Wikipedia page: