View source for Glucose

{{about|the naturally-occuring <small>D</small>-form of glucose|the <small>L</small>-form|L-Glucose}}
{{FixBunching|beg}}
{{chembox
| Name = <small>D</small>-Glucose
| ImageFileL1 = D-glucose-2D-skeletal-hexagon.png
|   ImageStyleL1 = padding 30px 5px 5px 5px
|   ImageSizeL1 = 120px
| ImageFileR1 = DGlucose Fischer.svg
|   ImageSizeR1 = 60px
| ImageFile2 = D-glucose-chain-2D-skeletal.png
|   ImageSize2 = 220px
| IUPACName = <small>D</small>-Glucose
|   OtherNames = Dextrose
| Section1 = {{Chembox Identifiers
|   Abbreviations = Glc
|   CASNo = 50-99-7
|    CASNo_Ref = {{cascite}}
|   EINECS = 200-075-1
|   PubChem = 5793
|   ChemSpiderID = 5589
|   HMDB = HMDB00122
|   SMILES = OC[C@@H](O1)[C@@H](O)[C@H](O)[C@@H](O)[C@@H](O)1 (glucopyranose) ;
OC[C@@H](O)[C@@H](O)[C@H](O)[C@@H](O)C=O (acyclic glucose).
  }}
| Section2 = {{Chembox Properties
|   Reference = <ref>{{citation | url = http://oru.edu/cccda/sl/solubility/allsolvents.php?solute=D-glucose | title = Solubility of D-glucose in non-aqueous solvents}}.</ref>
|   Formula = C<sub>6</sub>H<sub>12</sub>O<sub>6</sub>
|   MolarMass = 180.16 g/mol
|   ExactMass = 180.063388
|   MeltingPt = 146 °C
|   Density = 1.54 g/cm<sup>3</sup>
|   Solubility = 91 g/100 ml (25 °C)
|   Solubility1 = 0.037 M
|    Solvent1 = methanol
|   Solubility2 = 0.006 M
|    Solvent2 = ethanol
|   Solubility3 = 0.016 M
|    Solvent3 = tetrahydrofuran
  }}
| Section3 = {{Chembox Thermochemistry
|   Reference = <ref>{{citation | last1 = Ponomarev | first1 = V. V. | last2 = Migarskaya | first2 = L. B. | title = Heats of combustion of some amino-acids | journal = Russ. J. Phys. Chem. (Engl. Transl.) | year = 1960 | volume = 34 | pages = 1182–83}}. {{citation | last = Boerio-Goates | first = Juliana | title = Heat-capacity measurements and thermodynamic functions of crystalline α-D-glucose at temperatures from 10K to 340K | journal = J. Chem. Thermodynam. | year = 1991 | volume = 23 | issue = 5 | pages = 403–9 | doi = 10.1016/S0021-9614(05)80128-4}}.</ref>
|   DeltaHf = −1271 kJ/mol
|   DeltaHc = −2805 kJ/mol
|   Entropy = 209.2 J&thinsp;K<sup>−1</sup>&thinsp;mol<sup>−1</sup>
  }}
| Section7 = {{Chembox Hazards
|   ExternalMSDS = [http://www.inchem.org/documents/icsc/icsc/eics0865.htm ICSC 0865]
|   EUIndex = not listed
  }}
}}
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{{chembox
| Name = α-<small>D</small>-Glucopyranose
| IUPACName = α-<small>D</small>-Glucopyranose
| Section1 = {{Chembox Identifiers
|   InChI = 1/C6H12O6/c7-1-2-3(8)4(9)5(10)6(11)12-2/h2-11H,1H2/t2-,3-,4+,5-,6+/m1/s1
|   StdInChI = 1S/C6H12O6/c7-1-2-3(8)4(9)5(10)6(11)12-2/h2-11H,1H2/t2-,3-,4+,5-,6+/m1/s1
|   InChIKey = WQZGKKKJIJFFOK-DVKNGEFBBQ
|   StdInChIKey = WQZGKKKJIJFFOK-DVKNGEFBSA-N
|   CASNo = 492-62-6
|    CASNo_Ref = {{cascite}}
|   EC-number = 207-757-8
|   ChemSpiderID = 71358
  }}
}}
{{FixBunching|mid}}
{{chembox
| Name = β-<small>D</small>-Glucopyranose
| IUPACName = β-<small>D</small>-Glucopyranose
| Section1 = {{Chembox Identifiers
|   InChI = 1/C6H12O6/c7-1-2-3(8)4(9)5(10)6(11)12-2/h2-11H,1H2/t2-,3-,4+,5-,6-/m1/s1
|   StdInChI = 1S/C6H12O6/c7-1-2-3(8)4(9)5(10)6(11)12-2/h2-11H,1H2/t2-,3-,4+,5-,6-/m1/s1
|   InChIKey = WQZGKKKJIJFFOK-VFUOTHLCBI
|   StdInChIKey = WQZGKKKJIJFFOK-VFUOTHLCSA-N
|   CASNo = 492-61-5
|    CASNo_Ref = {{cascite}}
|   EC-number = 207-756-2
|   ChemSpiderID = 58238
  }}
}}
{{FixBunching|end}}

'''Glucose''' (Glc), a [[monosaccharide]] (or simple [[sugar]]) also known as '''grape sugar''', '''blood sugar''', or '''corn sugar''', is a very important [[carbohydrate]] in [[biology]]. The living [[Cell (biology)|cell]] uses it as a source of energy and metabolic intermediate. Glucose is one of the main products of [[photosynthesis]] and starts [[cellular respiration]] in both [[prokaryote]]s ([[bacteria]] and [[archaea]]) and [[eukaryote]]s ([[animal]]s, [[plant]]s, [[fungus|fungi]], and [[protist]]s).

The name "glucose" comes from the [[Greek language|Greek]] word ''glukus'' ({{lang|el|γλυκύς}}), meaning "sweet", and the suffix "-ose," which denotes a sugar.

Two [[stereoisomerism|stereoisomer]]s of the [[aldohexose]] sugars are known as glucose, only one of which (<small>D</small>-glucose) is biologically active. This form (<small>D</small>-glucose) is often referred to as '''dextrose monohydrate''', or, especially in the [[food industry]], simply '''dextrose''' (from ''[[dextrorotatory]] glucose''<ref>{{citation | contribution = dextrose | url = http://www.m-w.com/dictionary/dextrose | title = Merriam-Webster Online Dictionary | accessdate = 2009-09-02}}.</ref>).  This article deals with the <small>D</small>-form of glucose. The mirror-image of the molecule, [[L-Glucose|<small>L</small>-glucose]], cannot be metabolized by cells in the biochemical process known as [[glycolysis]].

== Structure ==
Glucose (C<sub>6</sub>H<sub>12</sub>O<sub>6</sub>) contains six [[carbon]] [[atom]]s, one of which is part of an [[aldehyde group]]. Therefore glucose is an [[Hexose|aldohexose]]. In solution, the glucose molecule can exist in an open-chain (acyclic) form and a ring (cyclic) form (in equilibrium). The cyclic form is the result of a covalent bond between the aldehyde C atom and the C-5 [[hydroxyl]] group to form a six-membered cyclic [[hemiacetal]]. At [[pH]]&nbsp;7 the cyclic form is predominant. In the solid phase, glucose assumes the cyclic form. Because the ring contains five carbon atoms and one oxygen atom (like [[pyran]]), the cyclic form of glucose is also referred to as glucopyranose. In this ring, each carbon is linked to a hydroxyl side group with the exception of the fifth atom, which links to a sixth carbon atom outside the ring, forming a CH<sub>2</sub>OH group. Glucose is commonly available in the form of a white substance or as a solid crystal. It can also be dissolved in water as an aqueous solution.    
   
=== Isomers ===
[[Aldohexose]] sugars have four [[chirality (chemistry)|chiral centers]], giving 2<sup>4</sup> = 16 [[stereoisomers]]. These are split into two groups, <small>L</small> and <small>D</small>, with eight sugars in each. Glucose is one of these sugars, and <small>L</small>-glucose and <small>D</small>-glucose are two of the stereoisomers. Only seven of these are found in living organisms, of which <small>D</small>-glucose (Glu), <small>D</small>-[[galactose]] (Gal) and <small>D</small>-[[mannose]] (Man) are the most important. These eight isomers (including glucose itself) are related as [[diastereoisomer]]s and belong to the [[Monosaccharide#Isomerism|<small>D</small> series]].    
  
An additional asymmetric center at C-1 (called ''the anomeric carbon atom'') is created when glucose cyclizes and two ring structures called [[anomer]]s are formed as α-glucose and β-glucose. These anomers differ structurally by the relative positioning of the hydroxyl group linked to C-1 and the group at C-6, which is termed the reference carbon. When <small>D</small>-glucose is drawn as a [[Haworth projection]] or in the standard chain conformation, the designation α means that the hydroxyl group attached to C-1 is positioned trans to the -CH<sub>2</sub>OH group at C-5, while β means that it is cis. An inaccurate but superficially attractive alternative method of distinguishing α from β is observing whether the C-1 hydroxyl is below or above the plane of the ring; this may fail if the glucose ring is drawn upside down or in an alternative chair conformation. The α and β forms interconvert over a timescale of hours in aqueous solution, to a final stable ratio of α:β 36:64, in a process called [[mutarotation]].<ref>{{McMurry2nd | page = 866}}.</ref> The ratio would be α:β 11:89 if it were not for the influence of the [[anomeric effect]].<ref>{{citation | title = The Anomeric Effect | last1 = Juaristi | first1 = Eusebio | first2 = Gabriel | last2 = Cuevas | year = 1995 | publisher = CRC Press | pages = 9–10 | isbn = 0849389410}}.</ref>   
  
<gallery>   
Image:D-glucose-chain-2D-Fischer.png|<center>The [[Fischer projection]] of the chain form of <small>D</small>-glucose</center>   
Image:D-glucose-chain-2D-skeletal-numbers.png|<center>The chain form of <small>D</small>-glucose</center>   
Image:Alpha-D-glucopyranose-2D-skeletal.png|<center>α-<small>D</small>-<br>glucopyranose</center>   
Image:Beta-D-glucopyranose-2D-skeletal.png|<center>β-<small>D</small>-<br>glucopyranose</center>   
Image:D-glucose-chain-3D-balls.png|<center>Chain form: [[ball-and-stick model]]</center>   
Image:D-glucose-chain-3D-vdW.png|<center>Chain form: [[space-filling model]]</center>   
File:Alpha-D-glucose-from-xtal-1979-3D-balls.png|<center>α-<small>D</small>-<br>glucopyranose</center>   
File:Beta-D-glucose-from-xtal-3D-balls.png|<center>β-<small>D</small>-<br>glucopyranose</center>   
</gallery>

===Rotamers===
Within the cyclic form of glucose, rotation may occur around the O6-C6-C5-O5 torsion angle, termed the ''ω''-angle, to form three rotamer conformations as shown in the diagram below. In referring to the orientations of the ''ω''-angle and the O6-C6-C5-C4 angle, the three stable staggered rotamer conformations are termed ''gauche''-''gauche'' (gg), ''gauche''-''trans'' (gt) and ''trans''-''gauche'' (tg). For methyl α-<small>D</small>-glucopyranose at equilibrium the ratio of molecules in each rotamer conformation is reported as 57:38:5 gg:gt:tg.<ref>{{citation | last1 = Kirschner | first1 = Karl N. | last2 = Woods | first2 = Robert J. | title = Solvent interactions determine carbohydrate conformation | journal = Proc. Natl. Acad. Sci. USA | year = 2001 | volume = 98 | issue = 19 | pages = 10541–45 | pmid = 11526221 | doi = 10.1073/pnas.191362798 }}.</ref>   
This tendency for the ''ω''-angle to prefer to adopt a ''gauche'' conformation is attributed to the [[gauche effect]].    
[[Image:Glc rotamers.jpeg|center|thumb|600px|Rotamer conformations of ''α''-<small>D</small>-glucopyranose]]

==Production==<!-- This section is linked from [[Sake]] -->
===Natural===
#Glucose is one of the products of [[photosynthesis]] in [[plants]] and some [[prokaryote]]s.
#In animals and fungi, glucose is the result of the breakdown of [[glycogen]], a process known as [[glycogenolysis]]. In plants the breakdown substrate is [[starch]].
#In animals, glucose is synthesized in the [[liver]] and [[kidney]]s from non-carbohydrate intermediates, such as [[pyruvate]] and [[glycerol]], by a process known as [[gluconeogenesis]].
#In some deep-sea [[bacteria]] glucose is produced by [[chemosynthesis]].

===Commercial===
Glucose is produced commercially via the [[enzyme|enzymatic]] [[hydrolysis]] of starch. Many crops can be used as the source of starch. [[Maize]], [[rice]], [[wheat]], [[cassava]], [[corn husk]] and [[sago]] are all used in various parts of the world. In the [[United States]], [[cornstarch]] (from maize) is used almost exclusively.

<gallery>
image:Glucose 1.jpg|Glucose
image:Glucose 2.jpg|Glucose tablets
</gallery>

==Function==
[[File:Glucose metabolism.svg|thumb|250px|Glucose metabolism and various forms of it in the process.
<br>-Glucose-containing compounds and [[isomer]]ic forms are digested and taken up by the body in the intestines, including [[:en:starch|starch]], [[:en:glycogen|glycogen]], [[:en:disaccharide|disaccharides]] and [[:en:monosaccharide|monosaccharides]].
<br>-Glucose is stored in mainly the liver and muscles as glycogen.
<br>-It is distributed and utilized in tissues as free glucose.
]]

Scientists can speculate on the reasons why glucose, and not another monosaccharide such as [[fructose]] (Fru), is so widely used in organisms. One reason might be that glucose has a lower tendency, as compared to other hexose sugars, to non-specifically react with the [[amine|amino]] groups of [[protein]]s. This reaction ([[glycation]]) reduces or destroys the function of many [[enzyme]]s. The low rate of glycation is due to glucose's preference for the less reactive cyclic [[isomer]]. Nevertheless, many of the long-term complications of [[diabetes mellitus|diabetes]] (e.g., [[blindness]], [[renal failure]], and [[peripheral neuropathy]]) are probably due to the glycation of proteins or lipids. In contrast, [[enzyme]]-regulated addition of glucose to proteins by [[glycosylation]] is often essential to their function.{{Fact|date=June 2009}}

===As an energy source===
Glucose is a ubiquitous fuel in [[biology]]. It is used as an energy source in most organisms, from bacteria to humans. Use of glucose may be by either [[aerobic respiration]], [[anaerobic respiration]], or [[Fermentation (biochemistry)|fermentation]]. Carbohydrates are the human body's key source of energy, through aerobic respiration, providing approximately 3.75&nbsp;[[kilocalorie]]s (16&nbsp;[[kilojoule]]s) of [[food energy]] per [[gram]].<ref>{{citation | title = Food energy - methods of analysis and conversion factors | url = 
http://www.fao.org/docrep/006/Y5022E/y5022e04.htm | chapter = Chapter 3: Calculation of the Energy Content of Foods – Energy Conversion Factors | series = FAO Food and Nutrition Paper 77 | publisher = Food and Agriculture Organization | location = Rome | year = 2003 | isbn = 92-5-105014-7}}.</ref> Breakdown of carbohydrates (e.g. starch) yields [[monosaccharide|mono-]] and [[disaccharide]]s, most of which is glucose.  Through [[glycolysis]] and later in the reactions of the [[citric acid cycle]] (TCAC), glucose is [[oxidize]]d to eventually form [[carbon dioxide|CO<sub>2</sub>]] and [[water]], yielding energy sources, mostly in the form of [[adenosine triphosphate|ATP]].  The insulin reaction, and other mechanisms, regulate the concentration of glucose in the blood. A high fasting blood sugar level is an indication of prediabetic and diabetic conditions.

Glucose is a primary source of energy for the brain, and hence its availability influences psychological processes. When [[Hypoglycaemia|glucose is low]], psychological processes requiring mental effort (e.g., [[self-control]], effortful decision-making) are impaired.<ref>{{citation | last1 = Fairclough | first1 = Stephen H. | last2 = Houston | first2 = Kim | title = A metabolic measure of mental effort | journal = Biol. Psychol.  | year = 2004 | volume = 66 | issue = 2 | pages = 177–90 | pmid = 15041139  | doi = 10.1016/j.biopsycho.2003.10.001}}.</ref><ref>{{citation | last1 = Gailliot | first1 = Matthew T. | last2 = Baumeister | first2 = Roy F. | last3 = DeWall | first3 = C. Nathan | last4 = Plant | first4 = E. Ashby | last5 = Brewer | first5 = Lauren E. | last6 = Schmeichel | first6 = Brandon J.  | last7 = Tice | first7 = Dianne M. | last8 = Maner | first8 = Jon K. | title = Self-Control Relies on Glucose as a Limited Energy Source: Willpower is More than a Metaphor| journal = J. Personal. Soc. Psychol. | year = 2007 | volume = 92 | issue = 2 |  pages = 325–36 | pmid = 17279852 | doi = 10.1037/0022-3514.92.2.325}}.</ref><ref>{{citation | last1 = Gailliot | first1 = Matthew T. | last2 = Baumeister | first2 = Roy F.  | title = The Physiology of Willpower: Linking Blood Glucose to Self-Control | journal = Personal. Soc. Psychol. Rev. | year = 2007 | volume = 11 | issue = 4 | pages = 303–27 | doi = 10.1177/1088868307303030 | pmid = 18453466}}.</ref><ref>{{citation | last1 = Masicampo | first1 = E. J. | last2 = Baumeister | first2 = Roy F. | title = Toward a Physiology of Dual-Process Reasoning and Judgment: Lemonade, Willpower, and Expensive Rule-Based Analysis | journal = Psychol. Sci. | year = 2008 | volume = 19 | issue = 3 | pages = 255–60 | doi = 10.1111/j.1467-9280.2008.02077.x}}.</ref>

===Glucose in glycolysis===
{|width=370px align=right
|{{Enzymatic Reaction
|foward_enzyme=[[Hexokinase]]
|reverse_enzyme=
|substrate=α-<small>D</small>-Glucose
|product=α-<small>D</small>-[[Glucose-6-phosphate]]
|reaction_direction_(forward/reversible/reverse)=forward
|minor_foward_substrate(s)=[[Adenosine triphosphate|ATP]]
|minor_foward_product(s)=[[Adenosine diphosphate|ADP]]
|minor_reverse_substrate(s)=
|minor_reverse_product(s)=
|substrate_image=D-glucose wpmp.png
|product_image=Glucose-6-phosphate_wpmp.png
}}
|-
|{{KEGG compound|C00031}} {{KEGG enzyme|2.7.1.1}} {{KEGG compound|C00668}} {{KEGG reaction|R01786}}
|}

Use of glucose as an energy source in cells is via aerobic or anaerobic respiration. Both of these start with the early steps of the [[glycolysis]] [[metabolic pathway]]. The first step of this is the [[phosphorylation]] of glucose by [[hexokinase]] to prepare it for later breakdown to provide energy.

The major reason for the immediate phosphorylation of glucose by a [[hexokinase]] is to prevent diffusion out of the cell. The phosphorylation adds a charged [[phosphate]] group so the [[glucose 6-phosphate]] cannot easily cross the [[cell membrane]]. Irreversible first steps of a metabolic pathway are common for regulatory purposes.

===As a precursor ===
Glucose is critical in the production of [[protein]]s and in [[lipid]] metabolism. In plants and most animals, it is also a [[precursor (chemistry)|precursor]] for [[vitamin C]] ([[ascorbic acid]]) production. It is modified for use in these processes by the glycolysis pathway.

Glucose is used as a precursor for the synthesis of several important substances. Starch, [[cellulose]], and [[glycogen]] ("animal starch") are common glucose [[polymer]]s ([[polysaccharide]]s). [[Lactose]], the predominant sugar in milk, is a glucose-galactose disaccharide. In [[sucrose]], another important [[disaccharide]], glucose is joined to fructose. These synthesis processes also rely on the phosphorylation of glucose through the first step of glycolysis. 

====Industrial use====
In the industry glucose is used as a precursor to make vitamin C in the [[Reichstein process]], to make [[citric acid]], [[gluconic acid]], bio-[[ethanol]], [[polylactic acid]], [[sorbitol]].

==Sources and absorption==
Most dietary carbohydrates contain glucose, either as their only building block, as in starch and [[glycogen]], or together with another monosaccharide, as in sucrose and lactose. [[Crystalline fructose]], for example, does not contain glucose and is about ninety-eight percent fructose.  In the lumen of the duodenum and small intestine, the glucose oligo- and polysaccharides are broken down to monosaccharides by the pancreatic and intestinal glycosidases. Other polysaccarhides cannot be processed by the human intestine and require assistance by intestinal flora if they are to be broken down; the most notable exceptions are [[sucrose]] ([[fructose]]-glucose) and [[lactose]] ([[galactose]]-glucose). Glucose is then transported across the apical membrane of the [[enterocyte]]s by [[SLC5A1]], and later across their basal membrane by [[SLC2A2]].<ref>{{citation | last = Ferraris | first = Ronaldo P. | year = 2001 | title = Dietary and developmental regulation of intestinal sugar transport | journal = Biochem. J. | volume = 360 | pages = 265–76 | url = http://www.biochemj.org/bj/360/0265/bj3600265.htm | doi = 10.1042/0264-6021:3600265}}.</ref> Some of the glucose is directly utilized as an energy source by [[brain cells]], intestinal cells and [[erythrocytes|red blood cells]], while the rest reaches the [[liver]], [[adipose tissue]] and [[muscle]] cells, where it is absorbed and stored as glycogen (under the influence of [[insulin]]). Liver cell glycogen can be converted to glucose and returned to the blood when insulin is low or absent; muscle cell glycogen is not returned to the blood because of a lack of enzymes. In fat cells, glucose is used to power reactions that synthesize some [[fat]] types and have other purposes. Glycogen is the body's 'glucose energy storage' mechanism because it is much more 'space efficient' and less reactive than glucose itself.

==History==
Because glucose is a basic necessity of many organisms, a correct understanding of its chemical makeup and structure contributed greatly to a general advancement in organic chemistry.  This understanding occurred largely as a result of the investigations of [[Emil Fischer]], a German chemist who received the 1902 [[Nobel Prize]] in [[Chemistry]] as a result of his findings.<ref>{{citation | title = Emil Fischer | url = http://nobelprize.org/nobel_prizes/chemistry/laureates/1902/fischer-bio.html | publisher = Nobel Foundation | accessdate = 2009-09-02}}.</ref>  The synthesis of glucose established the structure of organic material and consequently formed the first definitive validation of [[Jacobus Henricus van't Hoff]]'s theories of chemical kinetics and the arrangements of chemical bonds in carbon-bearing molecules.<ref>{{citation | title = van't Hoff's Glucose | first = Bert | last = Fraser-Reid | journal = Chem. Eng. News | volume = 77 | issue = 39 | page = 8}}.</ref>  Between 1891 and 1894, Fischer established the stereochemical configuration of all the known sugars and correctly predicted the possible [[isomer]]s, applying van't Hoff's theory of asymmetrical carbon atoms.

==See also==
* [[Blood glucose]] or Blood sugar
* [[HbA1c]]
* [[2,5-Dimethylfuran|DMF]] (potential glucose-based [[biofuel]])
* [[Glycation]]
* [[Glycosylation]]
* [[Photosynthesis]]
* [[Fructose]]
* [[Beriberi]] - vitamin deficiency affecting ability to convert [[carbohydrates]] into glucose
* [[Sugars in wine]]
* [[Trinder glucose activity test]]
* [[Glucose transporter]] ([[GLUT]]): [[GLUT1]], [[GLUT2]]

{{Glycolysis}}

==References==
{{reflist}}

==External links  ==
{{commons|Glucose}}
*{{ICSC|0865}}
* [http://www.compchemwiki.org/index.php?title=Glucose Computational Chemistry Wiki]
* [http://www.dex4.ca/main_about_glucose.asp What is Glucose]

{{Carbohydrates}}

[[Category:Monosaccharides]]
[[Category:Sweeteners]]

{{Imported from Wikipedia|name=Glucose|id=311529759}}