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Steroid



  A steroid is a terpenoid lipid characterized by a carbon skeleton with four fused rings, generally arranged in a 6-6-6-5 fashion.

Steroids vary by the functional groups attached to these rings and the oxidation state of the rings. Hundreds of distinct steroids are found in plants, animals, and fungi. All steroids are made in cells either from the sterol lanosterol (animals and fungi) or the sterol cycloartenol (plants). Both sterols are derived from the cyclization of the triterpene squalene.[1]

Additional recommended knowledge

Contents

Origin

  Steroids include estrogen (US spelling) or oestrogen (UK/AUS spelling), progesterone and testosterone. Estrogen and progesterone are made primarily in the ovary and in the placenta during pregnancy and testosterone in the testes. Testosterone is also converted into estrogen to regulate the supply of each, in the bodies of both females and males. Certain neurons and glia in the central nervous system (CNS) express the enzymes that are required for the local synthesis of pregnane neurosteroids, either de novo or from peripherally derived sources. The rate limiting step of steroid synthesis is the conversion of cholesterol to pregnenolone which occurs inside the mitochondrion.[2]

Classification

Taxonomical/Functional

Some of the common categories of steroids:

Structural

It is also possible to classify steroids based upon their chemical composition. One example of how MeSH performs this classification is available at the Wikipedia MeSH catalog. Examples from this classification include:

Class Examples Number of carbon atoms
Cholstanes cholesterol 27
Cholanes cholic acid 22
Pregnanes progesterone 22
Androstanes testosterone 19
Estranes estradiol 18

See also

  • Steroid biosynthesis
  • List of steroid abbreviations

References

  1. ^ http://www.chem.qmul.ac.uk/iubmb/enzyme/reaction/terp/lanost.html
  2. ^ Rossier MF (2006). "T channels and steroid biosynthesis: in search of a link with mitochondria". Cell Calcium. 40 (2): 155-64. doi:10.1016/j.ceca.2006.04.020. PMID 16759697.
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Steroid". A list of authors is available in Wikipedia.
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