digplanet beta 1: Athena
Share digplanet:

Agriculture

Applied sciences

Arts

Belief

Business

Chronology

Culture

Education

Environment

Geography

Health

History

Humanities

Language

Law

Life

Mathematics

Nature

People

Politics

Science

Society

Technology

Cell biology
The animal cell
Animal Cell.svg
Components of a typical animal cell:
  1. Nucleolus
  2. Nucleus
  3. Ribosome (little dots)
  4. Vesicle
  5. Rough endoplasmic reticulum
  6. Golgi apparatus (or "Golgi body")
  7. Cytoskeleton
  8. Smooth endoplasmic reticulum
  9. Mitochondrion
  10. Vacuole
  11. Cytosol (fluid that contains organelles)
  12. Lysosome
  13. Centrosome
  14. Cell membrane

The cytoplasm comprises cytosol (the gel-like substance enclosed within the cell membrane) – and the organelles – the cell's internal sub-structures. All of the contents of the cells of prokaryote organisms (such as bacteria, which lack a cell nucleus) are contained within the cytoplasm. Within the cells of eukaryote organisms the contents of the cell nucleus are separated from the cytoplasm, and are then called the nucleoplasm. The cytoplasm is about 80% water and usually colorless.[1]

It is within the cytoplasm that most cellular activities occur, such as many metabolic pathways including glycolysis, and processes such as cell division. The concentrated inner area is called the endoplasm and the outer layer is called the cell cortex or the ectoplasm.

Movement of calcium ions in and out of the cytoplasm is thought to be a signaling activity for metabolic processes.[2]

In plants, movements of the cytoplasm around vacuoles are known as cytoplasmic streaming.

Physical nature of cytoplasm[edit]

The physical properties of the cytoplasm have been contested in recent years.[citation needed] It remains uncertain how the varied components of the cytoplasm interact to allow movement of particles and organelles while maintaining the cell’s structure. The flow of cytoplasmic components plays an important role in many cellular functions which are dependent on the permeability of the cytoplasm.[3] An obvious 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.[4] 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.[5] The irregular dynamics of such particles have given rise to various theories on the nature of the cytoplasm.

Cytoplasm as a sol-gel[edit]

There has long been evidence that the cytoplasm behaves like a sol-gel.[6] 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). 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 as a glass[edit]

Recently it has been proposed that the cytoplasm behaves like a glass-forming liquid approaching the glass transition.[5] 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).[5] A cell's ability to vitrifiy in the absence of metabolic activity, as in dormant periods, may be beneficial as a defence strategy. 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.[5]

Other perspectives[edit]

There has been research examining the motion of cytoplasmic particles independent of the nature of the cytoplasm. In such an alternative approach, the aggregate random forces within the cell caused by motor proteins explain the non-Brownian motion of cytoplasmic constituents.[7]

Constituents[edit]

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

Cytosol[edit]

Main article: Cytosol

The cytosol is the portion of the cytoplasm not contained within membrane-bound organelles. Cytosol makes up about 70% of the cell volume and is a complex mixture of cytoskeleton filaments, dissolved molecules, and water. 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.[8] The inner, granular and more fluid portion of the cytoplasm is referred to as endoplasm.

Proteins in different cellular compartments and structures tagged with green fluorescent protein

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

Organelles[edit]

Main article: Organelles

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

Cytoplasmic inclusions[edit]

Main article: Cytoplasmic inclusion

The inclusions are small particles of insoluble substances suspended in the cytosol. A huge range of inclusions exist in different cell types, and range from crystals of calcium oxalate or silicon dioxide in plants,[9][10] to granules of energy-storage materials such as starch,[11] glycogen,[12] or polyhydroxybutyrate.[13] 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.[14] 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.

Controversy and research[edit]

The cytoplasm, mitochondria and most organelles are contributions to the cell from the maternal gamete. 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.[15]

The material properties of the cytoplasm remain an ongoing investigation. Recent measurements using force spectrum microscopy reveal that the cytoplasm can be likened to an elastic solid, rather than a viscoelastic fluid.

See also[edit]

References[edit]

  1. ^ Franklin Institute (November 23, 2013). "Cytoplasm". fi.edu. 
  2. ^ C. Michael Hogan. 2010. Calcium. eds. A.Jorgensen, C. Cleveland. Encyclopedia of Earth. National Council for Science and the Environment.
  3. ^ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3519356/
  4. ^ http://www.sciencedirect.com/science/article/pii/S000634950474312X
  5. ^ a b c d http://www.cell.com/abstract/S0092-8674%2813%2901479-7
  6. ^ http://onlinelibrary.wiley.com/doi/10.1002/jez.1400370302/abstract
  7. ^ http://www.cell.com/abstract/S0092-8674%2814%2900924-6
  8. ^ van Zon A, Mossink MH, Scheper RJ, Sonneveld P, Wiemer EA (September 2003). "The vault complex". Cell. Mol. Life Sci. 60 (9): 1828–37. doi:10.1007/s00018-003-3030-y. PMID 14523546. 
  9. ^ Prychid, Christina J.; Rudall, Paula J. (1999). "Calcium Oxalate Crystals in Monocotyledons: A Review of their Structure and Systematics". Annals of Botany 84 (6): 725. doi:10.1006/anbo.1999.0975. 
  10. ^ Prychid, C. J.; Rudall, P. J.; Gregory, M. (2004). "Systematics and Biology of Silica Bodies in Monocotyledons". The Botanical Review 69 (4): 377–440. doi:10.1663/0006-8101(2004)069[0377:SABOSB]2.0.CO;2. JSTOR 4354467. 
  11. ^ Ball SG, Morell MK (2003). "From bacterial glycogen to starch: understanding the biogenesis of the plant starch granule". Annu Rev Plant Biol 54: 207–33. doi:10.1146/annurev.arplant.54.031902.134927. PMID 14502990. 
  12. ^ Shearer J, Graham TE (April 2002). "New perspectives on the storage and organization of muscle glycogen". Can J Appl Physiol 27 (2): 179–203. doi:10.1139/h02-012. PMID 12179957. 
  13. ^ Anderson AJ, Dawes EA (1 December 1990). "Occurrence, metabolism, metabolic role, and industrial uses of bacterial polyhydroxyalkanoates". Microbiol. Rev. 54 (4): 450–72. PMC 372789. PMID 2087222. 
  14. ^ Murphy DJ (September 2001). "The biogenesis and functions of lipid bodies in animals, growth and microorganisms". Prog. Lipid Res. 40 (5): 325–438. doi:10.1016/S0163-7827(01)00013-3. PMID 11470496. 
  15. ^ Feneberg, Wolfgang; Sackmann, Erich; Westphal, Monika (2001). "Dictyostelium cells' cytoplasm as an active viscoplastic body". European Biophysics Journal 30 (4): 284–94. doi:10.1007/s002490100135. PMID 11548131. 

External links[edit]


Original courtesy of Wikipedia: http://en.wikipedia.org/wiki/Cytoplasm — Please support Wikipedia.
This page uses Creative Commons Licensed content from Wikipedia. A portion of the proceeds from advertising on Digplanet goes to supporting Wikipedia.

3055 news items

Alzforum

Alzforum
Fri, 28 Aug 2015 14:53:52 -0700

Could a molecular traffic jam at the nuclear membrane explain one kind of motor neuron disease? Extensive hexanucleotide repeats in the C9ORF72 gene, which are transcribed into RNAs and translated into dipeptide oligomers, cause amyotrophic lateral ...

io9

io9
Wed, 02 Sep 2015 12:41:15 -0700

The copepod's back is covered with chitin, but beneath that are alternating layers of hexagonal crystals made of guanine and cytoplasm. Each layer of crystal reflects incoming light back out again. And through different species, the layers of cytoplasm ...

Blair Enterprise Publishing

Blair Enterprise Publishing
Wed, 02 Sep 2015 13:48:45 -0700

Students covered the cake base with white frosting to represent cytoplasm in both models. The cell membrane portion of the cells were modeled by licorice. A Fruit Roll-Up was added to the outside of the plant cell to represent the cell wall. Both plant ...
 
PR Newswire (press release)
Thu, 03 Sep 2015 04:03:45 -0700

Glycogen, a complex sugar, is known to accumulate in both the cytoplasm and lysosome of adult-onset Pompe patients; however, the currently approved enzyme-replacement product is limited to the lysosome for therapeutic activity. Armstrong said VAL-1221 ...

Nature.com

Nature.com
Wed, 02 Sep 2015 10:03:45 -0700

Transcription of this G4C2 hexanucleotide repeat expansion (HRE) produces RNA that assembles into harmful G-quadruplex structures that can remain in the nucleus or be exported to the cytoplasm. Three studies provide evidence suggesting that the G4C2 ...

R & D Magazine

R & D Magazine
Wed, 02 Sep 2015 12:41:15 -0700

The team's experiment involved measuring the reflectance of individual animals, and then measuring the thickness of the crystal and cytoplasm layers using cryogenic scanning microscopy. Additionally, the team discovered when certain Sapphirinidae ...
 
MarketWatch
Wed, 02 Sep 2015 04:26:15 -0700

Dicerna's proprietary RNAi molecules are known as Dicer substrate short-interfering RNA molecules, or DsiRNAs, so called because they are processed by the Dicer enzyme, which is the initiation point for RNAi in the human cell cytoplasm. Dicerna's ...

Phys.Org

Phys.Org
Thu, 27 Aug 2015 12:18:45 -0700

Their role in the transport of molecules between nucleus and cytoplasm has been extensively described. Such molecules also include building blocks that help decipher the genetic information stored within the nucleus and guide those that have to leave ...
Loading

Oops, we seem to be having trouble contacting Twitter

Support Wikipedia

A portion of the proceeds from advertising on Digplanet goes to supporting Wikipedia. Please add your support for Wikipedia!

Searchlight Group

Digplanet also receives support from Searchlight Group. Visit Searchlight