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Sterol

 

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Sterol



 
 
Sterols are an important class of organic molecules. They occur naturally in plants, animals and fungi, with the most familiar type of animal sterol being cholesterol
Cholesterol

Cholesterol is a lipidic, waxy alcohol found in the cell membranes and transported in the blood plasma of all animals. It is an essential component of mammalian cell membranes where it is required to establish proper membrane permeability and membrane fluidity....
, which has been shown to contribute to high blood pressure and heart disease. Within the past decade, interest in plant sterols
Phytosterol

Phytosterols are a group of sterol, phytochemicals naturally occurring in plants. They are white powders with mild, characteristic odor, insoluble in water and soluble in alcohols....
 as a dietary supplement has increased, due to studies showing that they can contribute to lower cholesterol levels.

ols of plant
Plant

Plants are Life organisms belonging to the Kingdom Plantae. They include familiar organisms such as trees, herbs, bushes, grasses, vines, ferns, mosses, and green algae....
s are called phytosterol
Phytosterol

Phytosterols are a group of sterol, phytochemicals naturally occurring in plants. They are white powders with mild, characteristic odor, insoluble in water and soluble in alcohols....
s
and sterols of animal
Animal

Animals are a major group of multicellular, eukaryotic organisms of the Kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life....
s are called zoosterols.






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Encyclopedia


Sterols are an important class of organic molecules. They occur naturally in plants, animals and fungi, with the most familiar type of animal sterol being cholesterol
Cholesterol

Cholesterol is a lipidic, waxy alcohol found in the cell membranes and transported in the blood plasma of all animals. It is an essential component of mammalian cell membranes where it is required to establish proper membrane permeability and membrane fluidity....
, which has been shown to contribute to high blood pressure and heart disease. Within the past decade, interest in plant sterols
Phytosterol

Phytosterols are a group of sterol, phytochemicals naturally occurring in plants. They are white powders with mild, characteristic odor, insoluble in water and soluble in alcohols....
 as a dietary supplement has increased, due to studies showing that they can contribute to lower cholesterol levels.

Types of sterols

Sterols of plant
Plant

Plants are Life organisms belonging to the Kingdom Plantae. They include familiar organisms such as trees, herbs, bushes, grasses, vines, ferns, mosses, and green algae....
s are called phytosterol
Phytosterol

Phytosterols are a group of sterol, phytochemicals naturally occurring in plants. They are white powders with mild, characteristic odor, insoluble in water and soluble in alcohols....
s
and sterols of animal
Animal

Animals are a major group of multicellular, eukaryotic organisms of the Kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life....
s are called zoosterols. Important zoosterols are cholesterol
Cholesterol

Cholesterol is a lipidic, waxy alcohol found in the cell membranes and transported in the blood plasma of all animals. It is an essential component of mammalian cell membranes where it is required to establish proper membrane permeability and membrane fluidity....
 and some steroid hormone
Steroid hormone

Steroid hormones are steroids that act as hormones. Steroid hormones can be grouped into five groups by the receptor s to which they bind: glucocorticoids, mineralocorticoids, androgens, estrogens, and progestagens....
s; notable phytosterols include campesterol, sitosterol, and stigmasterol
Stigmasterol

Stigmasterol is a phytosterol with a molecular weight of 412.691 and a formula of C29H48O. It is also known as Wulzen anti-stiffness factor....
. Ergosterol
Ergosterol

Ergosterol , a sterol, is a biological precursor to Vitamin D. It is turned into viosterol by ultraviolet light, and is then converted into ergocalciferol, which is a form of Vitamin D....
 is a sterol present in the cell membrane
Cell membrane

The cell membrane is the interface between the cellular machinery inside the cell and the fluid outside.It is a semipermeable lipid bilayer found in all cell ....
 of fungi
Fungus

A fungus is a Eukaryote organism that is a member of the Kingdom Fungi . The fungi are a monophyletic group, also called the Eumycota , that is phylogeny distinct from the morphologically similar slime molds and water molds ....
, where it serves a role similar to cholesterol in animal cells.

Role in biochemistry

Sterols and related compounds play essential roles in the physiology of eukaryotic
Eukaryote

Animals, plants, fungus, and protists are eukaryotes , organisms whose Cell are organized into complex structures enclosed within Cell membrane....
 organisms. For example, cholesterol forms part of the cellular membrane in animals, where it affects the cell membrane's fluidity and serves as second messenger in developmental signaling. In humans and other animals, corticosteroids, such as cortisol
Cortisol

Cortisol is a corticosteroid hormone or glucocorticoid produced by the adrenal cortex, that is part of the adrenal gland . It is usually referred to as the "stress hormone" as it is involved in response to stress and anxiety, controlled by Corticotropin-releasing hormone....
 act as signalling compounds in cellular communication and general metabolism.

As a nutritional supplement

Phytosterol
Phytosterol

Phytosterols are a group of sterol, phytochemicals naturally occurring in plants. They are white powders with mild, characteristic odor, insoluble in water and soluble in alcohols....
s, more commonly known as plant sterols, have been shown in clinical trials to block cholesterol absorption sites in the human intestine, thus helping to reduce cholesterol in humans. They are currently approved by the U.S. Food and Drug Administration
Food and Drug Administration

The U.S. Food and Drug Administration is an Government agency of the United States Department of Health and Human Services and is responsible for regulating and supervising the safety of foods, dietary supplements, Medications, vaccines, Biopharmaceutical, blood transfusion, medical devices, Electromagnetic radiation-emitting devices, veteri...
 for use as a food additive, however, there is some concern that they may block absorption, not only of cholesterol, but of other important nutrients as well. At present the American Heart Association
American Heart Association

The American Heart Association is a non-profit organization in the United States that fosters appropriate Heart care in an effort to reduce disability and deaths caused by cardiovascular disease and stroke....
 has recommended that supplemental plant sterols be taken only by the those diagnosed with elevated cholesterol, and has particularly recommended that they not be take by pregnant women or nursing mothers.

Chemical classification and structure

Sterol Skeleton
Sterols are also known as steroid alcohols. They are a subgroup of steroid
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....
s with a hydroxyl group at the 3-position of the A-ring. They are amphipathic lipids
Amphipathic lipids

Amphipathic lipids are molecules that are mostly lipid-like in structure, but at one end have a region that is polar or ionic . The hydrophilic region is usually referred to as the head group, and the lipid portion is know as the tail....
 synthesized from acetyl-coenzyme A via the HMG-CoA reductase
HMG-CoA reductase

HMG-CoA reductase is the rate controlling enzyme of the mevalonate pathway, the metabolic pathway that produces cholesterol and other isoprenoids....
 pathway. The overall molecule is quite flat. The hydroxyl group on the A ring is polar
Chemical polarity

In chemistry, polarity refers to the dipole-dipole intermolecular forces between the slightly electric charge end of one molecule to the negative end of another or the same molecule....
. The rest of the aliphatic chain is non-polar
Chemical polarity

In chemistry, polarity refers to the dipole-dipole intermolecular forces between the slightly electric charge end of one molecule to the negative end of another or the same molecule....
.

See also

  • Cholesterol
    Cholesterol

    Cholesterol is a lipidic, waxy alcohol found in the cell membranes and transported in the blood plasma of all animals. It is an essential component of mammalian cell membranes where it is required to establish proper membrane permeability and membrane fluidity....
  • Phytosterol
    Phytosterol

    Phytosterols are a group of sterol, phytochemicals naturally occurring in plants. They are white powders with mild, characteristic odor, insoluble in water and soluble in alcohols....
  • Ergosterol
    Ergosterol

    Ergosterol , a sterol, is a biological precursor to Vitamin D. It is turned into viosterol by ultraviolet light, and is then converted into ergocalciferol, which is a form of Vitamin D....
  • Hopanoids
    Hopanoids

    Hopanoids are pentacyclic compounds similar to sterols, whose primary function is to improve plasma membrane fluidity in Bacteria. Cholesterol serves a similar function in eukaryotes ....


External links

  • Cyberlipid.org