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Sterol is an
organic compound In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior and the changes they undergo during ...
with formula , whose molecule is derived from that of
gonane Gonane is a chemical compound with formula , whose molecule can be described as three molecules of cyclohexane Cyclohexane is a cycloalkane with the molecular formula C6H12. Cyclohexane is non-polar. Cyclohexane is a colorless, flammable liqu ...

gonane
by replacement of a
hydrogen Hydrogen is the chemical element with the Symbol (chemistry), symbol H and atomic number 1. Hydrogen is the lightest element. At standard temperature and pressure, standard conditions hydrogen is a gas of diatomic molecules having the che ...

hydrogen
atom in position 3 by a
hydroxyl A hydroxy or hydroxyl group is a functional group with the chemical formula -OH and composed of one oxygen Oxygen is the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the ...

hydroxyl
group. It is therefore an
alcohol In , alcohol is an that carries at least one (−OH) bound to a atom. The term alcohol originally referred to the primary alcohol (ethyl alcohol), which is and is the main alcohol present in s. An important class of alcohols, of which ...
of gonane. More generally, any compounds that contain the gonane structure, additional
functional groups In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the r ...
, and/or modified ring systems derived from gonane are called
steroids , a steroid with 27 carbon atoms. Its core ring system (ABCD), composed of 17 carbon atoms, is shown with IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations ...

steroids
. Therefore, sterols are a subgroup of the steroids. They occur naturally in most eukaryotes, including
plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, through cellular respiration, can later be released to fuel ...

plant
s,
animal Animals (also called Metazoa) are multicellular A multicellular organism is an organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells ...

animal
s, and
fungi A fungus (plural The plural (sometimes abbreviated An abbreviation (from Latin ''brevis'', meaning ''short'') is a shortened form of a word or phrase, by any method. It may consist of a group of letters, or words taken from the full ...

fungi
, and can also be produced by some
bacteria Bacteria (; common noun bacteria, singular bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typ ...

bacteria
(however likely with different functions). The most familiar type of animal sterol is
cholesterol Cholesterol is any of a class of certain organic Organic may refer to: * Organic, of or relating to an organism, a living entity * Organic, of or relating to an anatomical organ (anatomy), organ Chemistry * Organic matter, matter that has co ...

cholesterol
, which is vital to cell membrane structure, and functions as a precursor to fat-soluble
vitamin A vitamin is an organic molecule , CH4; is among the simplest organic compounds. In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen chemical bond, bonds. Due to carbon's ability to Catenation, ...
s and
steroid hormone A steroid hormone is a steroid , hypothetical a steroid with 32 carbon atoms. Its core ring system (ABCD), composed of 17 carbon atoms, is shown with IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international ...
s. While technically alcohols, sterols are classified by
biochemist Biochemists are scientists who are trained in biochemistry Biochemistry or biological chemistry, is the study of chemical process In a scientific Science (from the Latin Latin (, or , ) is a classical language belonging to the Ital ...
s as
lipid In and , a lipid is a macro that is soluble in solvents. are typically s used to dissolve other naturally occurring hydrocarbon lipid s that do not (or do not easily) dissolve in water, including s, es, s, fat-soluble s (such as vitamins A, ...
s (
fat In nutrition Nutrition is the biochemical Biochemistry or biological chemistry, is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided ...

fat
s in the broader sense of the term).


Types

Sterols of plants are called ''
phytosterol Phytosterols are phytosteroids, similar to cholesterol, that serve as structural components of biological membranes of plants. They encompass plant sterols and stanol ester, stanols. More than 250 sterols and related compounds have been identified. ...

phytosterol
s'' and sterols of animals are called ''zoosterols''. The most important zoosterol is
cholesterol Cholesterol is any of a class of certain organic Organic may refer to: * Organic, of or relating to an organism, a living entity * Organic, of or relating to an anatomical organ (anatomy), organ Chemistry * Organic matter, matter that has co ...

cholesterol
; notable phytosterols include
campesterol Campesterol is a phytosterol whose chemical structure is similar to that of cholesterol, and is one of the ingredients for E number E499. Natural occurrences Many vegetables, fruits, nuts, and seeds contain campesterol, but in low concentratio ...

campesterol
,
sitosterol β-Sitosterol (beta-sitosterol) is one of several phytosterolPhytosterols, which encompass plant sterols and stanols, are phytosteroid Phytosteroids, also known as plant steroids, are naturally occurring steroid , a steroid with 27 carbon a ...

sitosterol
, and
stigmasterol Stigmasterol – a plant sterol ('' phytosterol'') – is among the most abundant of plant sterol Sterol is a chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, mole ...

stigmasterol
.
Ergosterol Ergosterol (ergosta-5,7,22-trien-3β-ol) is a sterol Sterol is a chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one ...

Ergosterol
is a sterol present in the
cell membrane cell membrane vs. Prokaryotes A prokaryote is a typically unicellular organism that lacks a nuclear membrane-enclosed cell nucleus, nucleus. The word ''prokaryote'' comes from the Greek language, Greek (, 'before') and (, 'nut' or 'kernel').C ...

cell membrane
of fungi, 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 Eukaryotes () are organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interact ...

eukaryotic
organisms. For example, cholesterol forms part of the cellular membrane in animals, where it affects the cell membrane's fluidity and serves as
secondary messenger Second messengers are intracellular signaling molecules released by the cell in response to exposure to extracellular signaling molecules—the first messengers. (Intracellular signals, a non-local form or cell signaling, encompassing both first me ...
in developmental signaling. In humans and other animals,
corticosteroids Corticosteroids are a class of steroid hormone A steroid hormone is a steroid , hypothetical a steroid with 32 carbon atoms. Its core ring system (ABCD), composed of 17 carbon atoms, is shown with IUPAC The International Union of Pure a ...
such as
cortisol Cortisol is a steroid hormone, in the glucocorticoid class of hormones. When used as a medication, it is known as hydrocortisone. It is produced in many animals, mainly by the ''zona fasciculata'' of the adrenal cortex in the adrenal gland. ...

cortisol
act as signaling compounds in cellular communication and general metabolism. Sterols are common components of
human skin oils
human skin oils
.


Phytosterols as a nutritional supplement

Phytosterol Phytosterols are phytosteroids, similar to cholesterol, that serve as structural components of biological membranes of plants. They encompass plant sterols and stanol ester, stanols. More than 250 sterols and related compounds have been identified. ...

Phytosterol
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 absorption in humans. They are currently approved by the U.S.
Food and Drug Administration The United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, st ...
for use as a
food supplement A dietary supplement is a manufactured product intended to supplement one's diet by taking a pill, capsule, tablet, powder or liquid. A supplement can provide nutrient A nutrient is a substance used by an organism to survive, grow, and ...
; 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 The American Heart Association (AHA) is a nonprofit organization A nonprofit organization (NPO), also known as a non-business entity, not-for-profit organization, or nonprofit institution, is a legal entity organized and operated for a collectiv ...
has recommended that supplemental plant sterols be taken only by those diagnosed with elevated cholesterol, and has particularly recommended that they not be taken by pregnant women or nursing mothers. Preliminary research has shown that phytosterols may have anticancer effects.


Chemical classification and structure

Sterols are a subgroup of
steroid A steroid is a biologically active organic compound In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, ...

steroid
s with a
hydroxyl group A hydroxy or hydroxyl group is a functional group with the chemical formula -OH and composed of one oxygen Oxygen is the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the ...

hydroxyl group
at the 3-position of the A-ring. They are
amphipathic 250px, Cross-section view of the structures that can be formed by phospholipids, biological amphiphiles in aqueous solutions. Unlike this illustration, micelles are usually formed by non-biological, single-chain, amphiphiles, soaps or detergents, ...
lipid In and , a lipid is a macro that is soluble in solvents. are typically s used to dissolve other naturally occurring hydrocarbon lipid s that do not (or do not easily) dissolve in water, including s, es, s, fat-soluble s (such as vitamins A, ...
s synthesized from acetyl-coenzyme A via the
HMG-CoA reductase HMG-CoA reductase (3-hydroxy-3-methyl-glutaryl-coenzyme A reductase, official symbol HMGCR) is the rate-controlling enzyme Enzymes () are proteins that act as biological catalysts (biocatalysts). Catalysts accelerate chemical reactions. Th ...
pathway. The overall molecule is quite flat. The hydroxyl group on the A ring is
polar Polar may refer to: Geography Polar may refer to: * Geographical pole, either of two fixed points on the surface of a rotating body or planet, at 90 degrees from the equator, based on the axis around which a body rotates *Polar climate, the clim ...
. The rest of the
aliphatic In organic chemistry, hydrocarbon In organic chemistry, a hydrocarbon is an organic compound , CH4; is among the simplest organic compounds. In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen che ...
chain is non-polar.


See also

*
Cholesterol Cholesterol is any of a class of certain organic compound, organic molecules. A cholesterol is a sterol (or chemical modification, modified steroid), a type of lipid. Cholesterol is biosynthesis, biosynthesized by all animal Cell (biology)#Euk ...

Cholesterol
*
Ergosterol Ergosterol (ergosta-5,7,22-trien-3β-ol) is a sterol Sterol is a chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one ...

Ergosterol
*
HopanoidsHopanoids are a diverse subclass of Triterpene, triterpenoids with the same hydrocarbon skeleton as the compound hopane. This group of Pentacyclic compound, pentacyclic molecules therefore refers to simple hopenes, hopanols and hopanes, but also to e ...
* Hydroxysteroid *
Phytosterol Phytosterols are phytosteroids, similar to cholesterol, that serve as structural components of biological membranes of plants. They encompass plant sterols and stanol ester, stanols. More than 250 sterols and related compounds have been identified. ...

Phytosterol
*
Steroids A steroid is a biologically active organic compound with four rings arranged in a specific molecular configuration. Steroids have two principal biological functions: as important components of cell membranes which alter membrane fluidity; and ...
* Zoosterol


References


Further reading

*


External links


Sterols
Cyberlipid.org {{Authority control