Polysaccharides (), or polycarbohydrates, are the most abundant
carbohydrate
A carbohydrate () is a biomolecule
, showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958, for which they received a ...
found in
food
Food is any substance consumed to provide Nutrient, nutritional support for an organism. Food is usually of plant, animal or Fungus, fungal origin, and contains essential nutrients, such as carbohydrates, fats, protein (nutrient), proteins, vi ...

. They are long chain
polymeric
A polymer (; Greek '' poly-'', "many" + '' -mer'', "part")
is a substance
Substance may refer to:
* Substance (Jainism), a term in Jain ontology to denote the base or owner of attributes
* Chemical substance, a material with a definite chemical ...
carbohydrates composed of
monosaccharide
Monosaccharides (from Greek#REDIRECT Greek
Greek may refer to:
Greece
Anything of, from, or related to Greece
Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is ap ...
units bound together by
glycosidic linkages. This carbohydrate can react with water (
hydrolysis
Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution
Substitution may refer to:
Arts and media
*Chord substitution, in music, swapping one chord for ...

) using
amylase enzymes as catalyst, which produces constituent sugars (
monosaccharides
Monosaccharides (from Greek
Greek may refer to:
Greece
Anything of, from, or related to Greece
Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 ...
, or
oligosaccharide
An oligosaccharide (/ˌɑlɪgoʊˈsækəˌɹaɪd/; from the Greek ὀλίγος ''olígos'', "a few", and σάκχαρ ''sácchar'', "sugar") is a saccharide
is a disaccharide
A disaccharide (also called a double sugar or ''biose'') is the sug ...
s). They range in structure from linear to highly branched. Examples include storage polysaccharides such as
starch
Starch or amylum is a consisting of numerous units joined by s. This is produced by most green s for energy storage. Worldwide, it is the most common carbohydrate in human diets, and is contained in large amounts in s like , es, (corn), , ...
,
glycogen
Glycogen is a multibranched polysaccharide
Polysaccharides (), or polycarbohydrates, are the most abundant found in . They are long chain carbohydrates composed of units bound together by . This carbohydrate can react with water () usi ...

and
and structural polysaccharides such as
cellulose
Cellulose is an organic compound with the chemical formula, formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of glycosidic bond, β(1→4) linked glucose, D-glucose units. Cellulose is an important stru ...

and
chitin
units that repeat to form long chains in β-(1→4)-linkage.
of the chitin molecule.
Chitin ( carbon, C8H13O5N)n ( ) is a long-chain polymer
A polymer (; Greek ''wikt:poly-, poly-'', "many" + ''wikt:-mer, -mer'', "part")
is a Chemical su ...

.
Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure, these
macromolecule
macromolecule
A macromolecule is a very large molecule
File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings.
A molecule is an electrically neu ...
s can have distinct properties from their monosaccharide building blocks. They may be
amorphous
In condensed matter physics
Condensed matter physics is the field of physics
Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science th ...

or even
insoluble
In chemistry
Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds composed of atom ...
in water.
When all the monosaccharides in a polysaccharide are the same type, the polysaccharide is called a ''homopolysaccharide'' or ''homoglycan'', but when more than one type of monosaccharide is present they are called ''heteropolysaccharides'' or ''heteroglycans''.
Natural saccharides are generally composed of simple carbohydrates called
monosaccharide
Monosaccharides (from Greek#REDIRECT Greek
Greek may refer to:
Greece
Anything of, from, or related to Greece
Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is ap ...
s with general formula (CH
2O)
''n'' where ''n'' is three or more. Examples of monosaccharides are
glucose
Glucose is a simple with the . Glucose is the most abundant , a subcategory of s. Glucose is mainly made by and most during from water and carbon dioxide, using energy from sunlight, where it is used to make in s, the most abundant carbohydr ...

,
fructose
Fructose, or fruit sugar, is a ketonic simple sugar
Monosaccharides (from Greek language, Greek ''wikt:μόνος, monos'': single, ''sacchar'': sugar), also called simple sugars, are the simplest form of sugar and the most basic units (monomers ...

, and
glyceraldehyde
Glyceraldehyde (glyceral) is a triose is an aldotriose because the carbonyl group is at the end of the chain
Image:Dihydroxyacetone.png">150px, Dihydroxyacetone is a ketone, ketotriose because the carbonyl group is the center of the chain.
A tr ...

. Polysaccharides, meanwhile, have a general formula of C
''x''(H
2O)
''y'' where ''x'' is usually a large number between 200 and 2500. When the repeating units in the polymer backbone are
six-carbon monosaccharides, as is often the case, the general formula simplifies to (C
6H
10O
5)
''n'', where typically .
As a rule of thumb, polysaccharides contain more than ten monosaccharide units, whereas
oligosaccharide
An oligosaccharide (/ˌɑlɪgoʊˈsækəˌɹaɪd/; from the Greek ὀλίγος ''olígos'', "a few", and σάκχαρ ''sácchar'', "sugar") is a saccharide
is a disaccharide
A disaccharide (also called a double sugar or ''biose'') is the sug ...
s contain three to ten monosaccharide units; but the precise cutoff varies somewhat according to convention. Polysaccharides are an important class of
biological polymers. Their
function
Function or functionality may refer to:
Computing
* Function key
A function key is a key on a computer
A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations automatically. Modern comp ...
in living organisms is usually either structure- or storage-related.
Starch
Starch or amylum is a consisting of numerous units joined by s. This is produced by most green s for energy storage. Worldwide, it is the most common carbohydrate in human diets, and is contained in large amounts in s like , es, (corn), , ...
(a polymer of glucose) is used as a storage polysaccharide in plants, being found in the form of both
amylose
Amylose is a polysaccharide
, a beta-glucan polysaccharide
Image:amylose 3Dprojection.svg">350px, Amylose is a linear polymer of glucose mainly linked with α(1→4) bonds. It can be made of several thousands of glucose units. It is one of the two ...

and the branched
amylopectin
Amylopectin is a water-soluble Subscription required for online access. polysaccharide and highly branched polymer of α-glucose units found in plants. It is one of the two components of starch, the other being amylose.
Glucose units are linke ...
. In animals, the structurally similar glucose polymer is the more densely branched
glycogen
Glycogen is a multibranched polysaccharide
Polysaccharides (), or polycarbohydrates, are the most abundant found in . They are long chain carbohydrates composed of units bound together by . This carbohydrate can react with water () usi ...

, sometimes called "animal starch". Glycogen's properties allow it to be metabolized more quickly, which suits the active lives of moving animals. In
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 ...

, they play an important role in bacterial multicellularity.
Cellulose
Cellulose is an organic compound with the chemical formula, formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of glycosidic bond, β(1→4) linked glucose, D-glucose units. Cellulose is an important stru ...

and
chitin
units that repeat to form long chains in β-(1→4)-linkage.
of the chitin molecule.
Chitin ( carbon, C8H13O5N)n ( ) is a long-chain polymer
A polymer (; Greek ''wikt:poly-, poly-'', "many" + ''wikt:-mer, -mer'', "part")
is a Chemical su ...

are examples of structural polysaccharides. Cellulose is used in the
cell wall
A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane
cell membrane
vs. Prokaryotes
The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to a ...
s of plants and other organisms and is said to be the most abundant
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, catenate (form chains with other carbon ...
on Earth. It has many uses such as a significant role in the paper and textile industries, and is used as a feedstock for the production of rayon (via the
viscose
Rayon is a synthetic fiber
Synthetic fiber or synthetic fibre (in British English; American and British English spelling differences#-re, -er, see spelling differences) are fibers made by humans through chemical synthesis, as opposed to natur ...
process), cellulose acetate, celluloid, and nitrocellulose. Chitin has a similar structure, but has
nitrogen
Nitrogen is the chemical element
upright=1.0, 500px, The chemical elements ordered by link=Periodic table
In chemistry
Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...

-containing side branches, increasing its strength. It is found in
arthropod
An arthropod (, (gen. ποδός)) is an invertebrate
Invertebrates are animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This includes all animals apart fr ...
exoskeleton
An exoskeleton (from Greek έξω, ''éxō'' "outer" and σκελετός, ''skeletós'' "skeleton") is the external skeleton
A skeleton is a structural frame that supports an animal
Animals (also called Metazoa) are multicellular ...

s and in the cell walls of some
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 ...

. It also has multiple uses, including
surgical thread
Surgical suture is a medical device
Artificial pacemaker, a Class III device in the United States
A medical device is any device intended to be used for medical purposes. Medical devices benefit patients by helping health care providers diagnos ...
s. Polysaccharides also include
callose
Callose is a plant polysaccharide
, a beta-glucan
is an example of a (1→4)-β-D-glucan composed of glucose
Glucose is a simple sugar with the Chemical formula#Molecular formula, molecular formula . Glucose is the most abundant monosaccharide ...

or
laminarin
The molecule laminarin (also known as laminaran) is a storage glucan (a polysaccharide
, a beta-glucan polysaccharide
Image:amylose 3Dprojection.svg">350px, Amylose is a linear polymer of glucose mainly linked with α(1→4) bonds. It can be mad ...
,
chrysolaminarin
Chrysolaminarin is a linear polymer
A polymer (; Greek '' poly-'', "many" + '' -mer'', "part")
is a substance or material consisting of very large molecule
File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of penta ...
,
xylan
Xylan (; ) (CAS number
A CAS Registry Number, also referred to as CASRN or CAS Number, is a unique numerical identifier
An identifier is a name that identifies (that is, labels the identity of) either a unique object or a unique ''class'' of ...

,
arabinoxylanArabinoxylan is a hemicellulose found in both the primary and secondary cell walls of plants, including woods and cereal grains, consisting of copolymers of two pentose sugars: arabinose and xylose.
Structure
Arabinoxylan chains contain a large numb ...
,
mannan,
fucoidan Fucoidan is a long chain sulfate
The sulfate or sulphate ion is a polyatomic anion
An ion () is an atom
An atom is the smallest unit of ordinary matter
In classical physics and general chemistry, matter is any substance that has m ...

and
galactomannan
A segment of galactomannan showing mannose backbone (below) with a branching galactose unit (top)
Galactomannans are polysaccharide
, a beta-glucan polysaccharide
Image:amylose 3Dprojection.svg">350px, Amylose is a linear polymer of glucose mainl ...

.
Function
Structure
Nutrition polysaccharides are common sources of energy. Many organisms can easily break down starches into glucose; however, most organisms cannot metabolize cellulose or other polysaccharides like
cellulose
Cellulose is an organic compound with the chemical formula, formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of glycosidic bond, β(1→4) linked glucose, D-glucose units. Cellulose is an important stru ...

,
chitin
units that repeat to form long chains in β-(1→4)-linkage.
of the chitin molecule.
Chitin ( carbon, C8H13O5N)n ( ) is a long-chain polymer
A polymer (; Greek ''wikt:poly-, poly-'', "many" + ''wikt:-mer, -mer'', "part")
is a Chemical su ...

and
arabinoxylans. These carbohydrate types can be metabolized by some bacteria and protists.
Ruminant
Ruminants (suborder Ruminantia) are large ungulate, hoofed herbivorous grazing or browsing mammals that are able to acquire nutrients from plant-based food by Enteric fermentation, fermenting it in a specialized stomach prior to digestion, princi ...
s and
termite
Termites are Eusociality, eusocial insects that are classified at the Taxonomy (biology), taxonomic rank of infraorder Isoptera, or alternatively as Taxonomic rank#All ranks, epifamily Termitoidae, within the order Blattodea (along with cockroa ...

s, for example, use microorganisms to process
cellulose
Cellulose is an organic compound with the chemical formula, formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of glycosidic bond, β(1→4) linked glucose, D-glucose units. Cellulose is an important stru ...

.
Even though these complex polysaccharides are not very digestible, they provide important dietary elements for humans. Called
dietary fiber
Dietary fiber (British spelling fibre) or roughage is the portion of plant-derived food that cannot be completely broken down by human digestive enzyme
Digestive may refer to: Biology
*Digestion
Digestion is the breakdown of large insolub ...
, these carbohydrates enhance digestion among other benefits. The main action of dietary fiber is to change the nature of the contents of the
gastrointestinal tract
The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system
The human digestive system consists of the gastrointestinal tract
The gastrointestinal tract, (GI tract, GIT, d ...
, and to change how other nutrients and chemicals are absorbed.
[ Soluble fiber binds to ]bile acids
Bile acids are 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 federatio ...
in the small intestine, making them less likely to enter the body; this in turn lowers 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 ...

levels in the blood. Soluble fiber also attenuates the absorption of sugar, reduces sugar response after eating, normalizes blood lipid levels and, once fermented in the colon, produces short-chain fatty acidShort-chain fatty acids (SCFAs) are fatty acids with fewer than six carbon atoms. Derived from intestine, intestinal microbe, microbial fermentation of indigestible foods, SCFAs are the main energy source of Gastrointestinal_tract#Mucosa, colonocytes ...
s as byproducts with wide-ranging physiological activities (discussion below). Although insoluble fiber is associated with reduced diabetes risk, the mechanism by which this occurs is unknown.
Not yet formally proposed as an essential macronutrient (as of 2005), dietary fiber is nevertheless regarded as important for the diet, with regulatory authorities in many developed countries recommending increases in fiber intake.
Storage polysaccharides
Starch
Starch
Starch or amylum is a consisting of numerous units joined by s. This is produced by most green s for energy storage. Worldwide, it is the most common carbohydrate in human diets, and is contained in large amounts in s like , es, (corn), , ...
is a glucose
Glucose is a simple with the . Glucose is the most abundant , a subcategory of s. Glucose is mainly made by and most during from water and carbon dioxide, using energy from sunlight, where it is used to make in s, the most abundant carbohydr ...

polymer in which glucopyranose
Glucose is a simple sugar
Sugar is the generic name for Sweetness, sweet-tasting, soluble carbohydrates, many of which are used in food. Table sugar, granulated sugar, or regular sugar, refers to sucrose, a disaccharide composed of glucose and ...

units are bonded by ''alpha''-linkages. It is made up of a mixture of amylose
Amylose is a polysaccharide
, a beta-glucan polysaccharide
Image:amylose 3Dprojection.svg">350px, Amylose is a linear polymer of glucose mainly linked with α(1→4) bonds. It can be made of several thousands of glucose units. It is one of the two ...

(15–20%) and amylopectin
Amylopectin is a water-soluble Subscription required for online access. polysaccharide and highly branched polymer of α-glucose units found in plants. It is one of the two components of starch, the other being amylose.
Glucose units are linke ...
(80–85%). Amylose consists of a linear chain of several hundred glucose molecules, and Amylopectin is a branched molecule made of several thousand glucose units (every chain of 24–30 glucose units is one unit of Amylopectin). Starches are insoluble
In chemistry
Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds composed of atom ...
in water
Water (chemical formula H2O) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known li ...

. They can be digested by breaking the ''alpha''-linkages (glycosidic bonds). Both humans and other animals have amylases, so they can digest starches. Potato
The potato is a starch#Food, starchy tuber of the plant ''Solanum tuberosum'' and is a root vegetable native to the Americas. The plant is a perennial plant, perennial in the nightshade family Solanaceae.
Wild potato species can be found thro ...

, rice
Rice is the seed
A seed is an embryonic
''Embryonic'' is the twelfth studio album by experimental rock band the Flaming Lips released on October 13, 2009, on Warner Bros. Records, Warner Bros. The band's first double album, it was relea ...

, wheat
Wheat is a grass widely cultivated for its seed, a cereal grain which is a worldwide staple food. The many species of wheat together make up the genus ''Triticum''; the most widely grown is common wheat
Common wheat (''Triticum aestivum'' ...

, and maize
Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It can also be ...

are major sources of starch in the human diet. The formations of starches are the ways that plants store glucose
Glucose is a simple with the . Glucose is the most abundant , a subcategory of s. Glucose is mainly made by and most during from water and carbon dioxide, using energy from sunlight, where it is used to make in s, the most abundant carbohydr ...

.
Glycogen
Glycogen serves as the secondary long-term energy storage in 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 ...

and fungal
A fungus (plural
The plural (sometimes list of glossing abbreviations, abbreviated ), in many languages, is one of the values of the grammatical number, grammatical category of number. The plural of a noun typically denotes a quantity great ...

cells, with the primary energy stores being held in adipose tissue
Adipose tissue, body fat, or simply fat is a loose connective tissue
Connective tissue is one of the many basic types of animal
Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biolo ...

. Glycogen is made primarily by the liver
The liver is an organ
Organ may refer to:
Biology
* Organ (anatomy)
An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems.
A given organ's t ...

and the muscle
Skeletal muscles (commonly referred to as muscles) are organs
An organ is a group of tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems.
A given organ's tissues can be broadly cat ...

s, but can also be made by glycogenesis
Glycogenesis is the process of glycogen
A view of the atomic structure of a single branched strand of glucose units in a glycogen molecule.
Glycogen is a multibranched polysaccharide of glucose that serves as a form of energy storage in an ...

within the brain
A brain is an organ
Organ may refer to:
Biology
* Organ (anatomy)
An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems.
A given organ's tis ...

and stomach
The stomach is a muscular, in the of humans and many other animals, including several s. The stomach has a dilated structure and functions as a vital organ. In the digestive system the stomach is involved in the second phase of digestion, ...

.
Glycogen is analogous to starch
Starch or amylum is a consisting of numerous units joined by s. This is produced by most green s for energy storage. Worldwide, it is the most common carbohydrate in human diets, and is contained in large amounts in s like , es, (corn), , ...
, a glucose polymer in 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 ...

s, and is sometimes referred to as ''animal starch'', having a similar structure to amylopectin
Amylopectin is a water-soluble Subscription required for online access. polysaccharide and highly branched polymer of α-glucose units found in plants. It is one of the two components of starch, the other being amylose.
Glucose units are linke ...
but more extensively branched and compact than starch. Glycogen is a polymer of α(1→4) glycosidic bonds linked, with α(1→6)-linked branches. Glycogen is found in the form of granules in the cytosol
The cytosol, also known as cytoplasmic matrix or groundplasm, is one of the liquids found inside cells
Cell most often refers to:
* Cell (biology), the functional basic unit of life
Cell may also refer to:
Closed spaces
* Monastic cell, a s ...
/cytoplasm in many cell types, and plays an important role in the glucose cycle
The glucose cycle (also known as the hepatic futile cycle) occurs primarily in the liver
The liver is an organ only found in vertebrates which detoxifies various metabolites, synthesizes proteins and produces biochemicals necessary for diges ...
. Glycogen forms an energy
In physics
Physics is the that studies , its , its and behavior through , and the related entities of and . "Physical science is that department of knowledge which relates to the order of nature, or, in other words, to the regula ...

reserve that can be quickly mobilized to meet a sudden need for glucose, but one that is less compact and more immediately available as an energy reserve than triglycerides
300px, Example of an unsaturated fat triglyceride (C55H98O6). Left part: glycerol; right part, from top to bottom: palmitic acid, oleic acid">palmitic_acid.html" ;"title="glycerol; right part, from top to bottom: palmitic acid">glycerol; right par ...
(lipids).
In the liver hepatocyte
A hepatocyte is a cell of the main parenchymal tissue of the liver. Hepatocytes make up 80% of the liver's mass.
These cells are involved in:
* Protein biosynthesis, Protein synthesis
* Storage protein, Protein storage
* Transformation of carbohyd ...
s, glycogen can compose up to 8 percent (100–120 grams in an adult) of the fresh weight soon after a meal. Only the glycogen stored in the liver can be made accessible to other organs. In the muscle
Skeletal muscles (commonly referred to as muscles) are organs
An organ is a group of tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems.
A given organ's tissues can be broadly cat ...

s, glycogen is found in a low concentration
In chemistry
Chemistry is the scientific
Science () is a systematic enterprise that builds and organizes knowledge
Knowledge is a familiarity or awareness, of someone or something, such as facts
A fact is an occurrence in t ...

of one to two percent of the muscle mass. The amount of glycogen stored in the body—especially within the muscles
Skeletal muscles (commonly referred to as muscles) are Organ (biology), organs of the vertebrate muscular system that are mostly attached by tendons to bones of the skeleton. The muscle cells of skeletal muscles are much longer than in the other ...

, liver
The liver is an organ
Organ may refer to:
Biology
* Organ (anatomy)
An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems.
A given organ's t ...

, and red blood cells
Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek ''erythros'' for "red" and ''kytos'' for "holl ...

—varies with physical activity, basal metabolic rate, and eating habits such as intermittent fasting
Intermittent fasting, also known as intermittent energy restriction, is any of various meal timing schedules that cycle between voluntary fasting (or reduced calorie intake) and non-fasting over a given period. Methods of intermittent fasting inc ...

. Small amounts of glycogen are found in the kidney
The kidneys are two reddish-brown bean-shaped organs
An organ is a group of tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems.
A given organ's tissues can be broadly categorized ...

s, and even smaller amounts in certain glial
Glia, also called glial cells (singular ''gliocyte'') or neuroglia, are non-neuron
A neuron or nerve cell is an membrane potential#Cell excitability, electrically excitable cell (biology), cell that communicates with other cells via specializ ...
cells in the brain
A brain is an organ
Organ may refer to:
Biology
* Organ (anatomy)
An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems.
A given organ's tis ...

and white blood cells
White blood cells, also called leukocytes or leucocytes, are the cell (biology), cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. All white blood cells are produced and de ...
. The uterus also stores glycogen during pregnancy, to nourish the embryo.
Glycogen is composed of a branched chain of glucose residues. It is stored in liver and muscles.
*It is an energy reserve for animals.
*It is the chief form of carbohydrate stored in animal body.
*It is insoluble in water. It turns brown-red when mixed with iodine.
*It also yields glucose on hydrolysis
Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution
Substitution may refer to:
Arts and media
*Chord substitution, in music, swapping one chord for ...

.
File:Glycogen structure.svg, Schematic 2-D cross-sectional view of glycogen. A core protein of glycogenin is surrounded by branches of glucose
Glucose is a simple with the . Glucose is the most abundant , a subcategory of s. Glucose is mainly made by and most during from water and carbon dioxide, using energy from sunlight, where it is used to make in s, the most abundant carbohydr ...

units. The entire globular granule may contain approximately 30,000 glucose units.
File:Glycogen spacefilling model.jpg, A view of the atom
An atom is the smallest unit of ordinary matter
In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of ato ...

ic structure of a single branched strand of glucose
Glucose is a simple with the . Glucose is the most abundant , a subcategory of s. Glucose is mainly made by and most during from water and carbon dioxide, using energy from sunlight, where it is used to make in s, the most abundant carbohydr ...

units in a glycogen molecule
A molecule is an electrically
Electricity is the set of physical phenomena associated with the presence and motion
Image:Leaving Yongsan Station.jpg, 300px, Motion involves a change in position
In physics, motion is the phenomenon ...

.
Galactogen
Galactogen is a polysaccharide of galactose
Galactose (, '' galacto-'' + ''-ose
The suffix
In linguistics
Linguistics is the science, scientific study of language. It encompasses the analysis of every aspect of language, as well as the methods for studying and modeling them.
Th ...
that functions as energy storage in pulmonate
Pulmonata, or "pulmonates", is an informal group (previously an order
Order or ORDER or Orders may refer to:
* Orderliness
Orderliness is associated with other qualities such as cleanliness
Cleanliness is both the abstract state of being clean ...

snails and some Caenogastropoda
Caenogastropoda is a taxonomic clade
A clade (; from grc, , ''klados'', "branch"), also known as a monophyletic group or natural group, is a group of organisms that are monophyly, monophyletic—that is, composed of a common ancestor and al ...

. This polysaccharide is exclusive of the reproduction and is only found in the albumen gland from the female snail reproductive system and in the perivitelline fluid of eggs.
Galactogen serves as an energy reserve for developing embryos and hatchlings, which is later replaced by glycogen
Glycogen is a multibranched polysaccharide
Polysaccharides (), or polycarbohydrates, are the most abundant found in . They are long chain carbohydrates composed of units bound together by . This carbohydrate can react with water () usi ...

in juveniles and adults.
Inulin
Inulin
Inulins are a group of naturally occurring polysaccharides produced by many types of plants, industrially most often extracted from chicory. The inulins belong to a class of dietary fibers known as fructans. Inulin is used by some plants as a mean ...

is a naturally occurring polysaccharide complex carbohydrate
is a disaccharide found in animal milk. It consists of a molecule of galactose, D-galactose and a molecule of glucose, D-glucose bonded by beta-1-4 glycosidic linkage.
A carbohydrate () is a biomolecule consisting of carbon (C), hydrogen (H) an ...
composed of fructose
Fructose, or fruit sugar, is a ketonic simple sugar
Monosaccharides (from Greek language, Greek ''wikt:μόνος, monos'': single, ''sacchar'': sugar), also called simple sugars, are the simplest form of sugar and the most basic units (monomers ...

, a plant-derived food that cannot be completely broken down by human digestive enzymes.
Structural polysaccharides
Arabinoxylans
ArabinoxylanArabinoxylan is a hemicellulose found in both the primary and secondary cell walls of plants, including woods and cereal grains, consisting of copolymers of two pentose sugars: arabinose and xylose.
Structure
Arabinoxylan chains contain a large numb ...
s are found in both the primary and secondary cell walls of plants and are the copolymers of two sugars: arabinose
Arabinose is an aldopentose – a monosaccharide
Monosaccharides (from Greek '' monos'': single, ''sacchar'': sugar), also called simple sugars, are the simplest form of sugar
Sugar is the generic name for Sweetness, sweet-tasting, soluble ...

and xylose
Xylose ( grc, ξύλον, , "wood") is a sugar first isolated from wood, and named for it. Xylose is classified as a of the type, which means that it contains five atoms and includes an . It is derived from , one of the main constituents o ...

. They may also have beneficial effects on human health.
Cellulose
The structural components of 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 ...

s are formed primarily from cellulose
Cellulose is an organic compound with the chemical formula, formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of glycosidic bond, β(1→4) linked glucose, D-glucose units. Cellulose is an important stru ...

. Wood is largely cellulose and lignin
Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and Bark (botany), bark, because they l ...

, while paper
Paper is a thin sheet material
Material is a substance
Substance may refer to:
* Substance (Jainism), a term in Jain ontology to denote the base or owner of attributes
* Chemical substance, a material with a definite chemical composition
...

and cotton
Cotton is a soft, fluffy staple fiber
Fiber or fibre (from la, fibra, links=no) is a natural
Nature, in the broadest sense, is the natural, physical, material world or universe
The universe ( la, universus) is all of s ...

are nearly pure cellulose. Cellulose is a polymer
A polymer (; Greek ''poly-
Poly, from the Greek :wikt:πολύς, πολύς meaning "many" or "much", may refer to:
Businesses
* China Poly Group Corporation, a Chinese business group, and its subsidiaries:
** Poly Property, a Hong Kong inc ...

made with repeated glucose units bonded together by ''beta''-linkages. Humans and many animals lack an enzyme to break the ''beta''-linkages, so they do not digest cellulose. Certain animals such as termite
Termites are Eusociality, eusocial insects that are classified at the Taxonomy (biology), taxonomic rank of infraorder Isoptera, or alternatively as Taxonomic rank#All ranks, epifamily Termitoidae, within the order Blattodea (along with cockroa ...

s can digest cellulose, because bacteria possessing the enzyme are present in their gut. Cellulose is insoluble in water. It does not change color when mixed with iodine. On hydrolysis, it yields glucose. It is the most abundant carbohydrate in nature.
Chitin
Chitin
Chitin (carbon, C8hydrogen, H13oxygen, O5nitrogen, N)n ( ) is a long-chain polymer of N-Acetylglucosamine, ''N''-acetylglucosamine, an amide derivative of glucose. The second most abundant polysaccharide in nature (behind only cellulose), it ...

is one of many naturally occurring polymers
A polymer (; Greek ''wikt:poly-, poly-'', "many" + ''wikt:-mer, -mer'', "part")
is a Chemical substance, substance or material consisting of very large molecules, or macromolecules, composed of many Repeat unit, repeating subunits. Due to thei ...

. It forms a structural component of many animals, such as exoskeleton
An exoskeleton (from Greek έξω, ''éxō'' "outer" and σκελετός, ''skeletós'' "skeleton") is the external skeleton
A skeleton is a structural frame that supports an animal
Animals (also called Metazoa) are multicellular ...

s. Over time it is bio-degradable in the natural environment. Its breakdown may be catalyzed by enzyme
Enzymes () are proteins that act as biological catalysts (biocatalysts). Catalysts accelerate chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates in ...

s called chitinase
Chitinases (''chitodextrinase'', ''1,4-beta-poly-N-acetylglucosaminidase'', ''poly-beta-glucosaminidase'', ''beta-1,4-poly-N-acetyl glucosamidinase'', ''poly ,4-(N-acetyl-beta-D-glucosaminide)glycanohydrolase'', ''(1->4)-2-acetamido-2-deoxy-beta ...
s, secreted by microorganisms such as 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 ...

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 ...

and produced by some plants. Some of these microorganisms have receptors
Receptor may refer to:
*Sensory receptor, in physiology, any structure which, on receiving environmental stimuli, produces an informative nerve impulse
*Receptor (biochemistry), in biochemistry, a protein molecule that receives and responds to a ne ...
to simple sugars
Sugar is the generic name for Sweetness, sweet-tasting, soluble carbohydrates, many of which are used in food. Simple sugars, also called monosaccharides, include glucose, fructose, and galactose. Compound sugars, also called disaccharides o ...
from the decomposition of chitin. If chitin is detected, they then produce enzyme
Enzymes () are proteins that act as biological catalysts (biocatalysts). Catalysts accelerate chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates in ...

s to digest it by cleaving the glycosidic bond
A glycosidic bond or glycosidic linkage is a type of covalent bond that joins a carbohydrate (sugar) molecule to another group, which may or may not be another carbohydrate.
A glycosidic bond is formed between the hemiacetal or hemiketal group ...
s in order to convert it to simple sugars and ammonia
Ammonia is a chemical compound, compound of nitrogen and hydrogen with the chemical formula, formula NH3. A Binary compounds of hydrogen, stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct ch ...

.
Chemically, chitin is closely related to chitosan
Chitosan is a linear polysaccharide composed of randomly distributed β-(1→4)-linked Glucosamine, D-glucosamine (deacetylated unit) and N-Acetylglucosamine, ''N''-acetyl-D-glucosamine (acetylated unit). It is made by treating the chitin shells ...

(a more water-soluble derivative of chitin). It is also closely related to cellulose
Cellulose is an organic compound with the chemical formula, formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of glycosidic bond, β(1→4) linked glucose, D-glucose units. Cellulose is an important stru ...

in that it is a long unbranched chain of glucose
Glucose is a simple with the . Glucose is the most abundant , a subcategory of s. Glucose is mainly made by and most during from water and carbon dioxide, using energy from sunlight, where it is used to make in s, the most abundant carbohydr ...

derivatives. Both materials contribute structure and strength, protecting the organism.
Pectins
Pectin
Pectin (from grc, πηκτικός ', "congealed, curdled") is a structural acidic heteropolysaccharide contained in the primary and middle lamella
The middle lamella is a layer that cements together the primary cell wall
A cell wall is a ...

s are a family of complex polysaccharides that contain 1,4-linked α--galactosyl uronic acid residues. They are present in most primary cell walls and in the nonwoody parts of terrestrial plants.
Acidic polysaccharides
Acidic polysaccharides are polysaccharides that contain carboxyl group
A carboxylic acid is an organic acid that contains a carboxyl group (C(=O)OH) attached to an R-group. The general formula of a carboxylic acid is R−COOH or R−CO2H, with substituent, R referring to the alkyl, alkenyl, aryl, or other group. ...

s, phosphate groups and/or groups.
Bacterial polysaccharides
Pathogenic bacteria
Pathogenic bacteria are bacteria
Bacteria (; common noun bacteria, singular bacterium) are a type of biological cell
The cell (from Latin ''cella'', meaning "small room") is the basic structural, functional, and biological unit of a ...
commonly produce a thick, mucous-like, layer of polysaccharide. This "capsule" cloaks antigen
In immunology
Immunology is a branch of biology that covers the study of immune systems in all organisms. Immunology charts, measures, and contextualizes the Physiology, physiological functioning of the immune system in states of both health ...
ic protein
Proteins are large biomolecule
, showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958, for which they received a No ...

s on the bacterial surface that would otherwise provoke an immune response and thereby lead to the destruction of the bacteria. Capsular polysaccharides are water-soluble, commonly acidic, and have molecular weight
A molecule is an electrically
Electricity is the set of physical phenomena associated with the presence and motion
Image:Leaving Yongsan Station.jpg, 300px, Motion involves a change in position
In physics, motion is the phenomenon ...
s on the order of 100,000 to 2,000,000 daltons. They are linear and consist of regularly repeating subunits of one to six monosaccharide
Monosaccharides (from Greek#REDIRECT Greek
Greek may refer to:
Greece
Anything of, from, or related to Greece
Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is ap ...
s. There is enormous structural diversity; nearly two hundred different polysaccharides are produced by '''' alone. Mixtures of capsular polysaccharides, either conjugated or native, are used as vaccine
A vaccine is a biological preparation that provides active acquired immunity
The adaptive immune system, also referred as the acquired immune system, is a subsystem of the immune system
The immune system is a network of biological process ...

s.
Bacteria and many other microbes, including 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 ...

and algae
Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic
Photosynthesis is a process used by plants and other organisms to convert
Conversion or convert may refer to:
Arts, entertainment, and media
* Co ...

, often secrete polysaccharides to help them adhere to surfaces and to prevent them from drying out. Humans have developed some of these polysaccharides into useful products, including xanthan gum
Xanthan gum () is a polysaccharide with many industrial uses, including as a common food additive. It is an effective thickening agent and stabilizer (food), stabilizer to prevent ingredients from separating. It can be produced from monosacchar ...
, dextran
Dextran is a complex branched glucan (polysaccharide
, a beta-glucan polysaccharide
Image:amylose 3Dprojection.svg">350px, Amylose is a linear polymer of glucose mainly linked with α(1→4) bonds. It can be made of several thousands of glucose ...

, welan gum, gellan gum, diutan gum and pullulan. Levan-type exopolysaccharide produced by ''Pantoea agglomerans'' ZMR7 was reported to decrease the viability of rhabdomyosarcoma (RD) and breast cancer (MDA) cells compared with untreated cancer cells. In addition, it has high antiparasitic activity against the promastigote of ''Leishmania tropica.''
Most of these polysaccharides exhibit useful visco-elastic properties when dissolved in water at very low levels. This makes various liquids used in everyday life, such as some foods, lotions, cleaners, and paints, viscous when stationary, but much more free-flowing when even slight shear is applied by stirring or shaking, pouring, wiping, or brushing. This property is named pseudoplasticity or shear thinning; the study of such matters is called rheology.
:
Aqueous solutions of the polysaccharide alone have a curious behavior when stirred: after stirring ceases, the solution initially continues to swirl due to momentum, then slows to a standstill due to viscosity and reverses direction briefly before stopping. This recoil is due to the elastic effect of the polysaccharide chains, previously stretched in solution, returning to their relaxed state.
Cell-surface polysaccharides play diverse roles in bacterial ecology and physiology. They serve as a barrier between the cell wall
A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane
cell membrane
vs. Prokaryotes
The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to a ...
and the environment, mediate host-pathogen interactions. Polysaccharides also play an important role in formation of Biofilm, biofilms and the structuring of complex life forms in bacteria like ''Myxococcus xanthus'.''
These polysaccharides are synthesized from nucleotide-activated precursors (called nucleotide sugars) and, in most cases, all the enzymes necessary for biosynthesis, assembly and transport of the completed polymer are encoded by genes organized in dedicated clusters within the genome of the organism. Lipopolysaccharide is one of the most important cell-surface polysaccharides, as it plays a key structural role in outer membrane integrity, as well as being an important mediator of host-pathogen interactions.
The enzymes that make the ''A-band'' (homopolymeric) and ''B-band'' (heteropolymeric) O-antigens have been identified and the metabolic pathways defined. The exopolysaccharide alginate is a linear copolymer of β-1,4-linked -mannuronic acid and -guluronic acid residues, and is responsible for the mucoid phenotype of late-stage cystic fibrosis disease. The ''pel'' and ''psl'' loci are two recently discovered gene clusters that also encode exopolysaccharides found to be important for biofilm formation. Rhamnolipid is a biosurfactant whose production is tightly regulated at the Transcription (genetics), transcriptional level, but the precise role that it plays in disease is not well understood at present. Protein glycosylation, particularly of pilin and flagellin, became a focus of research by several groups from about 2007, and has been shown to be important for adhesion and invasion during bacterial infection.
Chemical identification tests for polysaccharides
Periodic acid-Schiff stain (PAS)
Polysaccharides with unprotected Diol#Vicinal diols, vicinal diols or amino sugars (where some hydroxyl groups are replaced with amines) give a positive periodic acid-Schiff stain (PAS). The list of polysaccharides that stain with PAS is long. Although mucins of epithelial origins stain with PAS, mucins of connective tissue origin have so many acidic substitutions that they do not have enough glycol or amino-alcohol groups left to react with PAS.
See also
*Glycan
*Oligosaccharide nomenclature
*Polysaccharide encapsulated bacteria
References
External links
Polysaccharide Structure
European Polysaccharide Network of Excellence
{{Authority control
Polysaccharides,
Carbohydrate chemistry