Cytoplasm: Wikis


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From Wikipedia, the free encyclopedia

Schematic showing the cytoplasm, with major components of a typical animal cell (organelles):
(1) nucleolus
(2) nucleus
(3) ribosomes (little dots)
(4) vesicle
(5) rough endoplasmic reticulum (ER)
(6) Golgi apparatus
(7) Cytoskeleton
(8) smooth ER
(9) mitochondria
(10) vacuole
(11) cytosol
(12) lysosome
(13) centrioles within centrosome

The cytoplasm is the part of a cell that is enclosed within the cell membrane. In eukaryotic cells, the contents of the cell nucleus are not part of the cytoplasm and are instead called the nucleoplasm. Also in eukaryotic cells, the cytoplasm contains organelles, such as mitochondria, which are filled with liquid that is kept separate from the rest of the cytoplasm by biological membranes. The cytoplasm is the site where most cellular activities occur, such as many metabolic pathways like glycolysis, and processes such as cell division. The inner, granular mass is called the endoplasm and the outer, clear and glassy layer is called the cell cortex or the ectoplasm.

The part of the cytoplasm that is not held within organelles is called the cytosol. The cytosol is a complex mixture of cytoskeleton filaments, dissolved molecules, and water that fills much of the volume of a cell. The cytosol is a gel, with a network of fibers dispersed through water. Due to this network of pores 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.



The cytoplasm has three major elements; the cytosol, organelles and inclusions.


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

The cytosol is the portion of a cell that is not enclosed within membrane-bound organelles. The cytosol is a translucent fluid in which the other cytoplasmic elements are suspended. Cytosol makes up about 70 % of the cell volume and is composed of water, salts and organic molecules.[1] The cytoplasm also contains the protein filaments that make up the cytoskeleton, as well as soluble proteins and small structures such as ribosomes, proteasomes, and the mysterious vault complexes.[2] The inner, granular and more fluid portion of the cytoplasm is referred to as endoplasm.


Organelles are membrane-bound compartments within the cell that have specific functions. Some major organelles that are suspended in the cytosol are the mitochondria, the endoplasmic reticulum, the Golgi apparatus, ribosomes, vacuoles, lysosomes, and in plant cells chloroplasts.

Cytoplasmic inclusions

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,[3][4] to granules of energy-storage materials such as starch,[5] glycogen,[6] or polyhydroxybutyrate.[7] 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.[8] 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.


  1. ^ Cytoplasm Composition
  2. ^ 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. 
  3. ^ 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. 
  4. ^ Prychid, C. J.; Rudall, P. J.; Gregory, M. (2003). "Systematics and Biology of Silica Bodies in Monocotyledons". The Botanical Review 69 (4): 377–440. doi:10.1663/0006-8101(2004)069[0377:SABOSB2.0.CO;2]. 
  5. ^ 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. 
  6. ^ Shearer J, Graham TE (April 2002). "New perspectives on the storage and organization of muscle glycogen". Can J Appl Physiol 27 (2): 179–203. PMID 12179957. 
  7. ^ Anderson AJ, Dawes EA (1 December 1990). "Occurrence, metabolism, metabolic role, and industrial uses of bacterial polyhydroxyalkanoates". Microbiol. Rev. 54 (4): 450–72. PMID 2087222. PMC 372789. 
  8. ^ Murphy DJ (September 2001). "The biogenesis and functions of lipid bodies in animals, plants and microorganisms". Prog. Lipid Res. 40 (5): 325–438. doi:10.1016/S0163-7827(01)00013-3. PMID 11470496. 

Further reading

  • Alberts, Bruce et al. (2003). Essential Cell Biology, 2nd ed., Garland Science, 2003, ISBN 081533480X.
  • Human Anatomy & Physiology, seventh edition By; Elain N Marieb and Latja Hoehn.

External links


Up to date as of January 23, 2010
(Redirected to Cell Biology/Glossary article)

From Wikibooks, the open-content textbooks collection

Alpha Helix
DNA forms a specific formation called a alpha helix.
Amino Acid
The basic subunit of proteins.
One unit of a given element.
One of the common elements found in organic matter and living things.
Cell Wall
found in prokaryotic plants and it provides structural support and protection.
convert light/food into usable energy. (ATP production)
Found in cell membranes, affects the rigidity of the membrane. Also a basic compound used to form man hormones.
A group of genes/DNA that are contiguous, a functional unit. Humans have 23 pairs chromosomes.
Hair-like structures.
The flatten sacs of the Rough Endoplasmic Reticulum.
Genetics term for chromosomes literally crossing over DNA from one chromosome to another.
One type of prokaryote (cell without a nucleus).
the protoplasm outside the nucleus
Microtubules, actin and intermediate filaments. This produces the support structure/shape of cells. Of course plant cells have a much more rigid shape due to the cell wall.
The 'fluid' portion of the cell, it is made up of water and many free proteins and other elements - all except the organelles.
Deoxyribonucleic Acid, made up of 4 nucleotides: Adenine, Guanine, Thymine, and Cytosine (A,G,T,C).
Element is one atom of a particular substance found on the periodic table. (Things such as Carbon, Hydrogen, Oxygen, etc.)
Endoplasmic Reticulum (ER)
Important for protein synthesis. It is a transport network for molecules destined for specific modifications and locations. There are two types: Rough ER - has ribosomes, and tends to be more in 'sheets'. Smooth ER - Does not have ribosomes and tends to be more of a tubular network.
A Cell with a nucleus.
Genetic Material
Globular Protein
Golgi Apparatus
important for glycosylation, secretion.
A common element in organic and living organisms.
'likes water' (hydro = water; philic = like). Meaning that a hydrophilic molecule or portion would be attracted to water. Much like the opposite poles of a magnet pulling each other together.
'fears water' (hydro = water; phobic = fear). Meaning that a hydrophobic molecule or portion would be repulsed/push-away a water molecule. This would be like trying to put together the same pole of two magnets. Examples: oils, fatty acids (i.e. the 'tails' of phospholipids), cholesterol.
Digestive sacks - the main point of digestion, these are only found in animal cells.
is a type of cell division. See section on meiosis. This occurs for formation of egg/sperm cells, which in the end have 1/2 the normal number of chromosomes, only 1 copy of each chromosome.
A unit of measure in the metric system. 10^-6 meters.
made from tubulin, and make up centrioles,cilia,etc.
A unit of measure in the metric system. 10^-3 meters.
convert foods into usable energy. (ATP production) A mitochondrion does this through aerobic respiration. They have 2 membranes, the inner membranes shapes differ between different types of cells, but they form projections called cristae. The mitochondrion is about the size of a bacteria, and it carries its own genetic material and ribosomes.
The cell division, that is found in most non-reproductive cells.
A unit of measure in the metric system. 10^-9 meters.
A common element in organic and living organisms.
Nucleic Acid
Basic Building block for DNA.
Or densely packed portion of the Nucleus.
(only in eukaryotes) - where genetic material (DNA) is located, RNA is transcribed.
(which also have membranes) in 'higher' eukaryote organisms:
A common element in organic and living organisms.
This is the main component of prokaryotic cell walls, it is made from a large protein polymer and sugar.
Use oxygen to carry out catabolic reactions, in both plant and animals.
See the section of the course on Cell Membranes and specifically phospholipids.
A common element in organic and living organisms.
Plasma membrane
The surface around the cell made up of phospholipids, proteins, cholesterol, etc.. See the section on the Cell Membrane
Cells without a nucleus.
the living material in the cell
literally means 'False foot'
Ribonucleic Acid
half are on the Endoplasmic Reticulum, the other half are 'free' in the cytosol, this is where the RNA goes for translation into proteins.
A common element in organic and living organisms.
Transfer RNA, cool 3D structure. It works with the ribosome and mRNA to form proteins (called translation). It has a 'anti-codon' which will match codons of the mRNA, and also has a amino-acid. The tRNA is a key to the having the Amino-acid match a specific codon on the mRNA, See the Codon Table to see how these are matched in general. Please NOTE: There are differences in how the matches take place in mitochondria and bacteria.

Simple English

The cytoplasm is a semi-liquid substance that contains a eukaryotic cell's organelles. It refers to both the cytosol (the actual liquid), a cells organelles, but not the nucleus (or the cell membrane). The cytoplasm surrounds the nucleus, and is home to the other organelles. The cytoplasm consists mainly of cytosol, and crucial chemical reactions happen with it. It is usually what remains when a cell dies. In simpler prokaryotic cells, there is no distinction between individual organelles and the cytoplasma. Rather, enzymes, DNA and RNA float around. Prokaryotic cytoplasm is capable of flow, unlike eukaryote cells. The simplest way to consider cytoplasm is to view it as the "goo" of a cell, including its functional organelles but excluding the nucleus.

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