View source for Glucose

{{Short description|Naturally produced monosaccharide}}
{{Use dmy dates|date=June 2024}}
{{cs1 config |name-list-style=vanc |display-authors=6}}

{{Chembox
| verifiedrevid  = 818842877
| Name           = {{sm|d}}-Glucose
| ImageFile      = D-glucose lineal.svg
| ImageClass     = skin-invert-image
| ImageCaption   = [[Skeletal formula]] of {{sm|d}}-glucose
| pronounce      = {{IPAc-en|ˈ|ɡ|l|uː|k|oʊ|z}}, {{IPAc-en||ɡ|l|uː|k|oʊ|s}}
| ImageFile2     = Alpha-D-Glucopyranose.svg
| ImageSize2     = 120
| ImageCaption2  = [[Haworth projection]] of α-{{sm|d}}-glucopyranose
| ImageClass2    = skin-invert-image
| ImageFile3     = D-glucose chain (Fischer).svg
| ImageSize3     = 100
| ImageCaption3  = [[Fischer projection]] of {{sm|d}}-glucose
| ImageClass3    = skin-invert-image
| PIN            = 
| SystematicName = (2''R'',3''S'',4''R'',5''R'')-2,3,4,5,6-Pentahydroxyhexanal <small>'''(linear form)'''</small><br>
(3''R'',4''S'',5''S'',6''R'')-6-(hydroxymethyl)oxane-2,3,4,5-tetrol <small>'''(cyclic form)'''</small>
| OtherNames     = Blood sugars<br>Dextrose<br>Corn sugar<br>{{sm|d}}-Glucose<br>Grape sugar
| IUPACName      = {{sm|d}}-Glucose<br>
ᴅ-''gluco''-Hexose<ref>[https://iupac.qmul.ac.uk/2carb/02.html Nomenclature of Carbohydrates (Recommendations 1996) {{!}} 2-Carb-2] {{Webarchive|url=https://web.archive.org/web/20230827082825/https://iupac.qmul.ac.uk/2carb/02.html |date=27 August 2023 }}. ''iupac.qmul.ac.uk''.</ref>
| Section1       = {{Chembox Identifiers
| IUPHAR_ligand = 4536
| Abbreviations = Glc
| CASNo = 50-99-7
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo1 = 492-62-6
| CASNo1_Ref = {{cascite|correct|CAS}}
| CASNo1_Comment = (α-{{sm|d}}-glucopyranose)
| PubChem = 5793
| ChemSpiderID = 5589
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| UNII = 5SL0G7R0OK
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII1_Ref = {{fdacite|correct|FDA}}
| UNII1 = 5J5I9EB41E
| UNII1_Comment = (α-{{sm|d}}-glucopyranose)
| ChEMBL_Ref = {{ebicite|correct|EBI}}
| ChEMBL = 1222250
| EINECS = 200-075-1
| MeSHName = Glucose
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 4167
| KEGG_Ref = {{keggcite|correct|kegg}}
| KEGG = C00031
| RTECS = LZ6600000
| SMILES_Comment = α-{{sm|d}}-glucopyranose
| SMILES = C([C@@H]1[C@H]([C@@H]([C@H]([C@H](O1)O)O)O)O)O
| SMILES1_Comment = β-{{sm|d}}-glucopyranose
| SMILES1 = OC[C@H]1OC(O)[C@H](O)[C@@H](O)[C@@H]1O
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| 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
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = WQZGKKKJIJFFOK-GASJEMHNSA-N
| Beilstein = 1281604
| Gmelin = 83256
| 3DMet = B01203
}}
| Section2       = {{Chembox Properties
| C=6 | H=12 | O=6 
| MolarMassUnit = g/mol
| Appearance = White powder
| MeltingPt = α-{{sm|d}}-Glucose:
| MeltingPtC = 146
| MeltingPt_notes = β-{{sm|d}}-Glucose: 150&nbsp;°C (302&nbsp;°F; 423&nbsp;K)
| Density = 1.54&nbsp;g/cm<sup>3</sup>
| Solubility = 909&nbsp;g/L ({{convert|25|C}})
| Dipole = 10.5674
| MagSus = −101.5×10<sup>−6</sup>&nbsp;cm<sup>3</sup>/mol
}}
| Section3       = 
| Section4       = 
| Section5       = {{Chembox Thermochemistry
| DeltaHf = −1271&nbsp;kJ/mol<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}}</ref>
| HHV = {{cvt|2805|kJ/mol|kcal/mol}}
| Entropy = 209.2&nbsp;J/(K·mol)<ref name="Boerio-Goates 1991 403–9">{{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. Thermodyn. | year = 1991 | volume = 23 | issue = 5 | pages = 403–09 | doi = 10.1016/S0021-9614(05)80128-4| bibcode = 1991JChTh..23..403B }}</ref>
| HeatCapacity = 218.6&nbsp;J/(K·mol)<ref name="Boerio-Goates 1991 403–9"/>
}}
| Section6       = {{Chembox Pharmacology
| Pharmacology_ref = 
| ATCCode_prefix = B05
| ATCCode_suffix = CX01
| ATC_Supplemental = {{ATC|V04|CA02}}, {{ATC|V06|DC01}}
| ATCvet = 
| Licence_EU = 
| INN = 
| INN_EMA = 
| Licence_US = 
| Legal_status = 
| Legal_AU = 
| Legal_AU_comment = 
| Legal_CA = 
| Legal_CA_comment = 
| Legal_NZ = 
| Legal_NZ_comment = 
| Legal_UK = 
| Legal_UK_comment = 
| Legal_US = 
| Legal_US_comment = 
| Legal_EU = 
| Legal_EU_comment = 
| Legal_UN = 
| Legal_UN_comment = 
| Pregnancy_category = 
| Pregnancy_AU = 
| Pregnancy_AU_comment = 
| Dependence_liability = 
| AdminRoutes = 
| Bioavail = 
| ProteinBound = 
| Metabolism = 
| Metabolites = 
| OnsetOfAction = 
| HalfLife = 
| DurationOfAction = 
| Excretion = 
}}
| Section7       = {{Chembox Hazards
| ExternalSDS = [http://www.inchem.org/documents/icsc/icsc/eics0865.htm ICSC 08655]
| NFPA-H = 0
| NFPA-F = 1
| NFPA-R = 0
}}
}}

'''Glucose''' is a [[sugar]] with the [[Chemical formula#Molecular formula|molecular formula]] {{chem2|auto=1|C6H12O6}}. It is the most abundant [[monosaccharide]],<ref name="DombKost1998">{{Cite book |url=https://books.google.com/books?id=iLjhl6AvfIsC&pg=PA275 |isbn=978-1-4200-4936-7 |page=275|title=Handbook of Biodegradable Polymers |last1=Domb |first1=Abraham J. |last2=Kost |first2=Joseph |last3=Wiseman |first3=David |date=4 February 1998 |publisher=CRC Press }}</ref> a subcategory of [[carbohydrate]]s. It is made from water and carbon dioxide during [[photosynthesis]] by [[plants]] and most [[algae]]. It is used by plants to make [[cellulose]], the most abundant carbohydrate in the world, for use in [[cell wall]]s, and by all living [[organism]]s to make [[adenosine triphosphate]] (ATP), which is used by the cell as energy.<ref name="froms">{{cite web | url=https://drugs.ncats.io/drug/IY9XDZ35W2 | title=NCATS Inxight Drugs — DEXTROSE, UNSPECIFIED FORM | access-date=18 March 2024 | archive-date=11 December 2023 | archive-url=https://web.archive.org/web/20231211224631/https://drugs.ncats.io/drug/IY9XDZ35W2 | url-status=live }}</ref><ref>{{cite book |last1=Kamide |first1=Kenji |title=Cellulose products and Cellulose Derivatives: Molecular Characterization and its Applications |date=2005 |publisher=Elsevier |location=Amsterdam |isbn=978-0-08-045444-3 |page=1 |edition=1st |url=https://books.google.com/books?id=28Vx9OkEtQcC&pg=PA1 |access-date=13 May 2021}}</ref><ref name="r2"/>  Glucose is often abbreviated as '''Glc'''.<ref>{{Cite web |title=2-Carb-2 |url=https://iupac.qmul.ac.uk/2carb/02.html |access-date=2025-02-10 |website=iupac.qmul.ac.uk}}</ref>

In [[energy metabolism]], glucose is the most important source of energy in all [[organism]]s. Glucose for metabolism is stored as a [[polymer]], in plants mainly as [[amylose]] and [[amylopectin]], and in animals as [[glycogen]]. Glucose circulates in the blood of animals as [[blood sugar]].<ref name="froms"/><ref name="r2"/> The naturally occurring form is {{sm|d}}-glucose, while its [[Stereoisomerism|stereoisomer]] [[L-glucose|{{sm|l}}-glucose]] is produced synthetically in comparatively small amounts and is less biologically active.<ref name="r2">{{Cite web |date=7 October 2019 |title=L-glucose |url=https://www.biologyonline.com/dictionary/l-glucose |access-date=6 May 2022 |website=Biology Articles, Tutorials & Dictionary Online |language=en-US |archive-date=25 May 2022 |archive-url=https://web.archive.org/web/20220525135220/https://www.biologyonline.com/dictionary/l-glucose |url-status=live }}</ref> Glucose is a monosaccharide containing six carbon atoms and an [[aldehyde]] group, and is therefore an [[aldohexose]]. The glucose molecule can exist in an open-chain (acyclic) as well as ring (cyclic) form. Glucose is naturally occurring and is found in its free state in fruits and other parts of plants. In animals, it is released from the breakdown of glycogen in a process known as [[glycogenolysis]].

Glucose, as [[intravenous sugar solution]], is on the [[World Health Organization's List of Essential Medicines]].<ref name="WHO21st">{{cite book | vauthors = ((World Health Organization)) | title = World Health Organization model list of essential medicines: 21st list 2019 | year = 2019 | hdl = 10665/325771 | author-link = World Health Organization | publisher = World Health Organization | location = Geneva | id = WHO/MVP/EMP/IAU/2019.06. License: CC BY-NC-SA 3.0 IGO | hdl-access=free }}</ref> It is also on the list in combination with [[sodium chloride]] (table salt).<ref name="WHO21st" />

The name glucose is derived from [[Ancient Greek]] {{lang|grc|γλεῦκος}} ({{transliteration|grc|gleûkos}}) 'wine, must', from {{lang|grc|γλυκύς}} ({{transliteration|grc|glykýs}}) 'sweet'.<ref>{{cite web |url=http://www.etymonline.com/index.php?term=glucose |title=Online Etymology Dictionary |website=Etymonline.com |access-date=25 November 2016 |url-status=live |archive-url= https://web.archive.org/web/20161126065057/http://www.etymonline.com/index.php?term=glucose |archive-date=26 November 2016 }}</ref><ref>Thénard, Gay-Lussac, Biot, and Dumas (1838) [http://gallica.bnf.fr/ark:/12148/bpt6k29662/f106.langEN "Rapport sur un mémoire de M. Péligiot, intitulé: Recherches sur la nature et les propriétés chimiques des sucres"]. {{webarchive|url= https://web.archive.org/web/20151206043449/http://gallica.bnf.fr/ark:/12148/bpt6k29662/f106.langEN |date=6 December 2015 }} (Report on a memoir of Mr. Péligiot, titled: Investigations on the nature and chemical properties of sugars), ''Comptes rendus'', '''7''' : 106–113.  [http://gallica.bnf.fr/ark:/12148/bpt6k29662/f109.langEN From page 109]. {{webarchive|url=https://web.archive.org/web/20151206050123/http://gallica.bnf.fr/ark:/12148/bpt6k29662/f109.langEN |date=6 December 2015 }}: "Il résulte des comparaisons faites par M. Péligot, que le sucre de raisin, celui d'amidon, celui de diabètes et celui de miel ont parfaitement la même composition et les mêmes propriétés, et constituent un seul corps que nous proposons d'appeler {{em|Glucose}} (1). ... (1) γλευχος, moût, vin doux." It follows from the comparisons made by Mr. Péligot, that the sugar from grapes, that from starch, that from diabetes and that from honey have exactly the same composition and the same properties, and constitute a single substance that we propose to call ''glucose'' (1) ... (1) γλευχος, must, sweet wine.</ref> The suffix ''[[-ose]]'' is a chemical classifier denoting a sugar.

==History== <!-- Dextrose redirects here -->
Glucose was first isolated from [[raisin]]s in 1747 by the German chemist [[Andreas Sigismund Marggraf|Andreas Marggraf]].<ref name="Encyclopedia of Food and Health">{{cite book|title=Encyclopedia of Food and Health|date=2015|publisher=Academic Press|isbn=978-0-12-384953-3|page=239|url=https://books.google.com/books?id=O-t9BAAAQBAJ&pg=RA2-PA239|language=en|url-status=live|archive-url=https://web.archive.org/web/20180223145046/https://books.google.com/books?id=O-t9BAAAQBAJ&pg=RA2-PA239|archive-date=23 February 2018}}</ref><ref>Marggraf (1747) [https://books.google.com/books?id=lJQDAAAAMAAJ&pg=PA79 "Experiences chimiques faites dans le dessein de tirer un veritable sucre de diverses plantes, qui croissent dans nos contrées"] {{webarchive|url=https://web.archive.org/web/20160624083152/https://books.google.com/books?id=lJQDAAAAMAAJ&pg=PA79 |date=24 June 2016 }} [Chemical experiments made with the intention of extracting real sugar from diverse plants that grow in our lands], ''Histoire de l'académie royale des sciences et belles-lettres de Berlin'', pp. 79–90.  [https://archive.org/details/bub_gb_lJQDAAAAMAAJ/page/n114 From page 90:] {{webarchive|url=https://web.archive.org/web/20141027011957/http://books.google.com/books?id=lJQDAAAAMAAJ&pg=PA90 |date=27 October 2014 }}  "Les raisins secs, etant humectés d'une petite quantité d'eau, de maniere qu'ils mollissent, peuvent alors etre pilés, & le suc qu'on en exprime, etant depuré & épaissi, fournira une espece de Sucre." ("Raisins, being moistened with a small quantity of water, in a way that they soften, can be then pressed, and the juice that is squeezed out, [after] being purified and thickened, will provide a sort of sugar.")</ref> Glucose was discovered in grapes by another German chemist, [[Johann Tobias Lowitz]], in 1792, and distinguished as being different from cane sugar ([[sucrose]]). Glucose is the term coined by [[Jean-Baptiste Dumas]] in 1838, which has prevailed in the chemical literature. [[August Kekulé|Friedrich August Kekulé]] proposed the term '''dextrose''' (from the [[Latin]] {{lang|la|dexter}}, meaning "right"), because in aqueous solutions of glucose, the plane of linearly polarized light is turned to the right. In contrast, [[l-fructose]] (usually referred to as {{sm|d}}-fructose) (a ketohexose) and l-glucose ({{sm|l}}-glucose) turn linearly [[Polarization (waves)|polarized]] light to the left. The earlier notation according to the rotation of the plane of linearly polarized light (''d'' and ''l''-nomenclature) was later abandoned in favor of the [[optical rotation#Chirality prefixes|{{sm|d}}- and {{sm|l}}-notation]], which refers to the absolute configuration of the asymmetric center furthest from the carbonyl group, and in concordance with the configuration of {{sm|d}}- or {{sm|l}}-glyceraldehyde.<ref name="Robyt 7">John F. Robyt: ''Essentials of Carbohydrate Chemistry''. Springer Science & Business Media, 2012, {{ISBN|978-1-461-21622-3}}. p. 7.</ref><ref name="Rosanoff">{{Cite journal|doi=10.1021/ja01967a014|title=On Fischer's Classification of Stereo-Isomers.1|journal=Journal of the American Chemical Society|volume=28|pages=114–121|year=1906|last1=Rosanoff|first1=M. A.|issue=1 |bibcode=1906JAChS..28..114R |url=https://zenodo.org/record/1428874|access-date=1 July 2019|archive-date=17 December 2019|archive-url=https://web.archive.org/web/20191217170142/https://zenodo.org/record/1428874|url-status=live}}</ref>

Since 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|Hermann Emil Fischer]], a German chemist who received the 1902 [[Nobel Prize in Chemistry]] for his findings.<ref>{{citation | title = Emil Fischer | url = http://nobelprize.org/nobel_prizes/chemistry/laureates/1902/fischer-bio.html | publisher = Nobel Foundation | access-date = 2 September 2009 | url-status = live | archive-url = https://web.archive.org/web/20090903164859/http://nobelprize.org/nobel_prizes/chemistry/laureates/1902/fischer-bio.html | archive-date = 3 September 2009 }}</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 equation]] of asymmetrical carbon atoms. The names initially referred to the natural substances. Their [[enantiomer]]s were given the same name with the introduction of systematic nomenclatures, taking into account absolute stereochemistry (e.g. [[Fischer projection|Fischer nomenclature]], {{sm|d}}/{{sm|l}} nomenclature).

For the discovery of the metabolism of glucose [[Otto Fritz Meyerhof]] received the [[Nobel Prize in Physiology or Medicine]] in 1922.<ref>[https://www.nobelprize.org/nobel_prizes/medicine/laureates/1922/meyerhof-facts.html "Otto Meyerhof - Facts - NobelPrize.org"] {{Webarchive|url=https://web.archive.org/web/20180715011915/https://www.nobelprize.org/nobel_prizes/medicine/laureates/1922/meyerhof-facts.html |date=15 July 2018 }}. ''NobelPrize.org''. Retrieved on 5 September 2018.</ref> [[Hans von Euler-Chelpin]] was awarded the Nobel Prize in Chemistry along with [[Arthur Harden]] in 1929 for their "research on the [[fermentation]] of sugar and their share of enzymes in this process".<ref>[https://www.nobelprize.org/prizes/chemistry/1929/euler-chelpin/facts/ "Hans von Euler-Chelpin - Facts - NobelPrize.org"] {{Webarchive|url=https://web.archive.org/web/20180903153041/https://www.nobelprize.org/prizes/chemistry/1929/euler-chelpin/facts/ |date=3 September 2018 }}. ''NobelPrize.org''. Retrieved on 5 September 2018.</ref><ref>[https://www.nobelprize.org/prizes/chemistry/1929/harden/facts/ "Arthur Harden - Facts - NobelPrize.org"] {{Webarchive|url=https://web.archive.org/web/20180903151549/https://www.nobelprize.org/prizes/chemistry/1929/harden/facts/ |date=3 September 2018 }}. ''NobelPrize.org''. Retrieved on 5 September 2018.</ref> In 1947, [[Bernardo Houssay]] (for his discovery of the role of the [[pituitary gland]] in the metabolism of glucose and the derived carbohydrates) as well as [[Carl Ferdinand Cori|Carl]] and [[Gerty Cori]] (for their discovery of the conversion of glycogen from glucose) received the Nobel Prize in Physiology or Medicine.<ref>[https://www.nobelprize.org/nobel_prizes/medicine/laureates/1947/houssay-facts.html "Bernardo Houssay - Facts - NobelPrize.org"] {{Webarchive|url=https://web.archive.org/web/20180715011905/https://www.nobelprize.org/nobel_prizes/medicine/laureates/1947/houssay-facts.html |date=15 July 2018 }}. ''NobelPrize.org''. Retrieved on 5 September 2018.</ref><ref>[https://www.nobelprize.org/nobel_prizes/medicine/laureates/1947/cori-cf-facts.html "Carl Cori - Facts - NobelPrize.org"] {{Webarchive|url=https://web.archive.org/web/20180715035943/https://www.nobelprize.org/nobel_prizes/medicine/laureates/1947/cori-cf-facts.html |date=15 July 2018 }}. ''NobelPrize.org''. Retrieved on 5 September 2018.</ref><ref>[https://www.nobelprize.org/nobel_prizes/medicine/laureates/1947/cori-gt-facts.html "Gerty Cori - Facts - NobelPrize.org"] {{Webarchive|url=https://web.archive.org/web/20180715011845/https://www.nobelprize.org/nobel_prizes/medicine/laureates/1947/cori-gt-facts.html |date=15 July 2018 }}. ''NobelPrize.org''. Retrieved on 5 September 2018.</ref> In 1970, [[Luis Federico Leloir|Luis Leloir]] was awarded the Nobel Prize in Chemistry for the discovery of glucose-derived sugar nucleotides in the biosynthesis of carbohydrates.<ref>[https://www.nobelprize.org/nobel_prizes/chemistry/laureates/1970/leloir-facts.html "Luis Leloir - Facts - NobelPrize.org"] {{Webarchive|url=https://web.archive.org/web/20180715035858/https://www.nobelprize.org/nobel_prizes/chemistry/laureates/1970/leloir-facts.html |date=15 July 2018 }}. ''NobelPrize.org''. Retrieved on 5 September 2018.</ref>

== Chemical and physical properties ==
Glucose forms white or colorless solids that are highly [[soluble]] in water and [[acetic acid]] but poorly soluble in [[methanol]] and [[ethanol]]. They melt at {{convert|146|C|F}} (''α'') and {{convert|150|C|F}} (''beta''),  [[Chemical decomposition|decompose]] starting at {{convert|188|C|F}} with release of various volatile products, ultimately leaving a residue of [[carbon]].<ref name=kang2020>{{cite journal | doi = 10.3390/catal10050502| doi-access = free| date = 2020| volume = 10| issue = 5| title = Selective Production of Acetic Acid via Catalytic Fast Pyrolysis of Hexoses over Potassium Salts| journal = Catalysts| vauthors = Kang W, Zhang Z | page = 502}}</ref> Glucose has a [[acid strength|pKa value]] of 12.16 at {{cvt|25|C}} in water.<ref>{{cite journal |last1=Bosch |first1=L.I. |last2=Fyles |first2=T.M. |last3=James |first3=T.D. |title=Binary and ternary phenylboronic acid complexes with saccharides and Lewis bases |journal=Tetrahedron |date=November 2004 |volume=60 |issue=49 |pages=11175–11190 |doi=10.1016/j.tet.2004.08.046 }}</ref>

With six carbon atoms, it is classed as a [[hexose]], a subcategory of the [[monosaccharide]]s. {{sm|d}}-Glucose is one of the sixteen [[aldohexose]] [[stereoisomer]]s. The {{sm|d}}-[[isomer]], {{sm|d}}-glucose, also known as dextrose, occurs widely in nature, but the {{sm|l}}-isomer, [[L-glucose|{{sm|l}}-glucose]], does not. Glucose can be obtained by [[hydrolysis]] of carbohydrates such as milk sugar ([[lactose]]), cane sugar (sucrose), [[maltose]], [[cellulose]], [[glycogen]], etc. Dextrose is commonly commercially manufactured from [[starch]]es, such as [[corn starch]] in the US and Japan, from potato and wheat starch in Europe, and from [[tapioca starch]] in tropical areas.<ref>{{Citation|last=Yebra-Biurrun|first=M.C.|title=Sweeteners|date=2005|encyclopedia=Encyclopedia of Analytical Science|pages=562–572|publisher=Elsevier|language=en|doi=10.1016/b0-12-369397-7/00610-5|isbn=978-0-12-369397-6}}</ref> The manufacturing process uses hydrolysis via pressurized steaming at controlled [[pH]] in a jet followed by further enzymatic depolymerization.<ref>"glucose." The Columbia Encyclopedia, 6th ed.. 2015. Encyclopedia.com. 17 November 2015 http://www.encyclopedia.com {{webarchive|url=https://web.archive.org/web/20090426025317/http://www.encyclopedia.com/ |date=26 April 2009 }}.</ref> Unbonded glucose is one of the main ingredients of [[honey]].<ref>{{cite journal | doi=10.1002/efd2.71 | title=Comprehensive review on functional and nutraceutical properties of honey | date=2023 | journal=Efood | volume=4 | issue=2 | vauthors = Aga MB, Sharma V, Dar AH, Dash KK, Singh A, Shams R, Khan SA | article-number=e71 | doi-access=free }}</ref><ref>{{cite journal | doi=10.1155/2018/4757893 | title=Honey and Diabetes: The Importance of Natural Simple Sugars in Diet for Preventing and Treating Different Type of Diabetes | date=2018 | journal=Oxidative Medicine and Cellular Longevity | volume=2018 | pages=1–12 | pmid=29507651 | pmc=5817209 | vauthors = Bobiş O, Dezmirean DS, Moise AR | issue=1 | article-number=4757893 | doi-access=free }}</ref><ref>{{cite book |doi=10.1007/978-981-15-7305-7_9 |chapter=Scope of Honey in Diabetes and Metabolic Disorders |title=Therapeutic Applications of Honey and its Phytochemicals |date=2020 |pages=195–217 |isbn=978-981-15-7304-0 | vauthors = Wani HA, Majid S, Khan MS, Bhat AA, Wani RA, Bhat SA, Ali S, Rehman MU |publisher=Springer |location=Singapore }}</ref><ref>{{cite journal |doi=10.1007/s12349-009-0051-6 |title=Contribution of honey in nutrition and human health: A review |date=2010 |journal=Mediterranean Journal of Nutrition and Metabolism |volume=3 |pages=15–23 | vauthors = Alvarez-Suarez JM, Tulipani S, Romandini S, Bertoli E, Battino M |issue=1 }}</ref><ref>{{cite journal |last1=Ischayek |first1=Jennifer Ilana |last2=Kern |first2=Mark |title=US Honeys Varying in Glucose and Fructose Content Elicit Similar Glycemic Indexes |journal=Journal of the American Dietetic Association |date=August 2006 |volume=106 |issue=8 |pages=1260–1262 |doi=10.1016/j.jada.2006.05.003 |pmid=16863724 }}</ref>

The term ''dextrose'' is often used in a clinical (related to patient's health status) or nutritional context (related to dietary intake, such as food labels or dietary guidelines), while "glucose" is used in a biological or physiological context (chemical processes and molecular interactions),<ref>{{Cite journal |url=https://diabetesjournals.org/care/article/28/4/981/23717/Potentially-Important-Contribution-of-Dextrose |title=Potentially Important Contribution of Dextrose Used as Diluent to Hyperglycemia in Hospitalized Patients &#124; Diabetes Care &#124; American Diabetes Association |date=2005 |volume=28 |issue=4 |doi=10.2337/diacare.28.4.981 |access-date=18 March 2024 |archive-date=29 May 2022 |archive-url=https://web.archive.org/web/20220529014858/https://diabetesjournals.org/care/article/28/4/981/23717/Potentially-Important-Contribution-of-Dextrose |url-status=live |journal=Diabetes Care |pages=981–982 |pmid=15793213 | vauthors = Krajicek BJ, Kudva YC, Hurley HA }}</ref><ref>{{cite web | url=https://www.medicalnewstoday.com/articles/322243 | title=Dextrose: Why is it in food and medicine? | date=24 June 2018 | access-date=18 March 2024 | archive-date=13 February 2024 | archive-url=https://web.archive.org/web/20240213110503/https://www.medicalnewstoday.com/articles/322243 | url-status=live }}</ref><ref name="wid">{{cite web | url=https://thenutritioninsider.com/wellness/what-is-dextrose/ | title=What is Dextrose, How is It Used, and is It Healthy? - the Nutrition Insider | date=27 October 2023 | access-date=18 March 2024 | archive-date=14 February 2024 | archive-url=https://web.archive.org/web/20240214235338/https://thenutritioninsider.com/wellness/what-is-dextrose/ | url-status=live }}</ref><ref>{{cite web | url=https://www.livestrong.com/article/534228-glucose-vs-dextrose/ | title=Dextrose vs. Glucose: Are These Sugars Equal? | access-date=18 March 2024 | archive-date=29 September 2023 | archive-url=https://web.archive.org/web/20230929231815/https://www.livestrong.com/article/534228-glucose-vs-dextrose/ | url-status=live }}</ref> but both terms refer to the same molecule, specifically D-glucose.<ref name="wid"/><ref name="pmid938892">{{cite journal | pmid=938892 | date=1976 | last1=Baron | first1=D. N. | last2=McIntyre | first2=N. | title=Letter: Glucose is dextrose is glucose | journal=British Medical Journal | volume=2 | issue=6026 | pages=41–42 | doi=10.1136/bmj.2.6026.41-c | pmc=1687736 }}</ref>

''Dextrose monohydrate'' is the hydrated form of D-glucose, meaning that it is a glucose molecule with an additional water molecule attached.<ref name="chem"/> Its chemical formula is {{chem2|C6H12O6}}&nbsp;·&nbsp;{{chem2|H2O}}.<ref name="chem"/><ref name="api110617">{{cite web | url=https://www.cdek.liu.edu/api/110617/ | title=API &#124; glucose monohydrate | access-date=18 March 2024 | archive-date=24 March 2023 | archive-url=https://web.archive.org/web/20230324200604/https://www.cdek.liu.edu/api/110617/ | url-status=live }}</ref> Dextrose monohydrate is also called ''hydrated D-glucose'', and commonly manufactured from plant starches.<ref name="chem">{{cite web | url=https://www.pciplindia.com/product-detail/Dextrose-Monohydrate- | title=Prakash Chemicals International | access-date=18 March 2024 | archive-date=6 June 2023 | archive-url=https://web.archive.org/web/20230606204745/https://www.pciplindia.com/product-detail/Dextrose-Monohydrate- | url-status=live }}</ref><ref name="diff">{{cite web | url=https://gtspfood.com/en/the-difference-between-dextrose-anhydrous-and-dextrose-monohydrate/ | title=The difference between dextrose anhydrous and dextrose monohydrate | date=28 December 2022 | access-date=18 March 2024 | archive-date=18 March 2024 | archive-url=https://web.archive.org/web/20240318213001/https://gtspfood.com/en/the-difference-between-dextrose-anhydrous-and-dextrose-monohydrate/ | url-status=live }}</ref> Dextrose monohydrate is utilized as the predominant type of dextrose in food applications, such as beverage mixes—it is a common form of glucose widely used as a nutrition supplement in production of foodstuffs. Dextrose monohydrate is primarily consumed in North America as a [[corn syrup]] or [[high-fructose corn syrup]].<ref name="wid" />

''Anhydrous dextrose'', on the other hand, is glucose that does not have any water molecules attached to it.<ref name="diff"/><ref name="ahn1">{{Cite web|url=https://www.chembk.com/en/chem/Dextrose%20anhydrous|title=Dextrose anhydrous|access-date=18 March 2024|archive-date=18 March 2024|archive-url=https://web.archive.org/web/20240318212942/https://www.chembk.com/en/chem/Dextrose%20anhydrous|url-status=live}}</ref> Anhydrous chemical substances are commonly produced by eliminating water from a hydrated substance through methods such as heating or drying up (desiccation).<ref>{{cite journal |last1=Khvorova |first1=L. S. |last2=Andreev |first2=N. R. |last3=Lukin |first3=N. D. |title=Study of Conditions for Applying Surfactants in Crystalline Glucose Production |journal=Russian Agricultural Sciences |date=January 2020 |volume=46 |issue=1 |pages=90–93 |doi=10.3103/S1068367420010048 |bibcode=2020RuAgS..46...90K }}</ref><ref name="a2">{{cite web | url=https://topic.echemi.com/a/what-is-the-difference-between-anhydrous-glucose-and-glucose_176447.html | title=What is the difference between anhydrous glucose and glucose | access-date=18 March 2024 | archive-date=18 March 2024 | archive-url=https://web.archive.org/web/20240318212829/https://topic.echemi.com/a/what-is-the-difference-between-anhydrous-glucose-and-glucose_176447.html | url-status=live }}</ref><ref>{{cite web | url=https://thisvsthat.io/anhydrous-vs-monohydrate | title=Anhydrous vs. Monohydrate - What's the Difference? | access-date=18 March 2024 | archive-date=18 March 2024 | archive-url=https://web.archive.org/web/20240318215004/https://thisvsthat.io/anhydrous-vs-monohydrate | url-status=live }}</ref> Dextrose monohydrate can be dehydrated to anhydrous dextrose in industrial setting.<ref>{{cite journal |last1=Trasi |first1=Niraj S. |last2=Boerrigter |first2=Stephan X.M. |last3=Byrn |first3=Stephen R. |last4=Carvajal |first4=Teresa M. |title=Investigating the effect of dehydration conditions on the compactability of glucose |journal=International Journal of Pharmaceutics |date=15 March 2011 |volume=406 |issue=1–2 |pages=55–61 |doi=10.1016/j.ijpharm.2010.12.042 |pmid=21232587 }}</ref><ref>{{cite journal |last1=Mitra |first1=Biplob |last2=Wolfe |first2=Chad |last3=Wu |first3=Sy-Juen |title=Dextrose monohydrate as a non-animal sourced alternative diluent in high shear wet granulation tablet formulations |journal=Drug Development and Industrial Pharmacy |date=4 May 2018 |volume=44 |issue=5 |pages=817–828 |doi=10.1080/03639045.2017.1414231 |pmid=29300107 }}</ref> Dextrose monohydrate is composed of approximately 9.5% water by mass; through the process of dehydration, this water content is eliminated to yield anhydrous (dry) dextrose.<ref name="diff"/>

Anhydrous dextrose has the chemical formula {{chem2|C6H12O6}}, without any water molecule attached which is the same as glucose.<ref name="chem"/> Anhydrous dextrose on open air tends to absorb moisture and transform to the monohydrate, and it is more expensive to produce.<ref name="diff"/> Anhydrous dextrose (anhydrous D-glucose) has increased stability and increased shelf life,<ref name="a2"/> has medical applications, such as in oral [[glucose tolerance test]].<ref>{{cite web | url=https://www.niddk.nih.gov/health-information/professionals/clinical-tools-patient-management/diabetes/diabetes-prediabetes | title=Diabetes & Prediabetes Tests - NIDDK | access-date=18 March 2024 | archive-date=16 December 2023 | archive-url=https://web.archive.org/web/20231216120841/https://www.niddk.nih.gov/health-information/professionals/clinical-tools-patient-management/diabetes/diabetes-prediabetes | url-status=live }}</ref>

Whereas molecular weight (molar mass) for D-glucose monohydrate is 198.17 g/mol,<ref>{{cite web | url=https://pubchem.ncbi.nlm.nih.gov/compound/22814120 | title=Dextrose Monohydrate | access-date=18 March 2024 | archive-date=2 December 2023 | archive-url=https://web.archive.org/web/20231202032815/https://pubchem.ncbi.nlm.nih.gov/compound/22814120 | url-status=live }}</ref><ref>{{Cite web |url=https://www.sigmaaldrich.com/MD/en/product/mm/108342 |title=D-(+)-glucose monohydrate |access-date=18 March 2024 |archive-date=18 March 2024 |archive-url=https://web.archive.org/web/20240318213348/https://www.sigmaaldrich.com/US/en/product/mm/108342 |url-status=live }}</ref> that for anhydrous D-glucose is 180.16 g/mol<ref>{{cite web | url=https://pubchem.ncbi.nlm.nih.gov/compound/5793 | title=D-Glucose | access-date=18 March 2024 | archive-date=15 December 2023 | archive-url=https://web.archive.org/web/20231215173911/https://pubchem.ncbi.nlm.nih.gov/compound/5793 | url-status=live }}</ref><ref>{{Cite web |url=https://www.sigmaaldrich.com/MD/en/product/mm/137048 |title=D-(+)-Glucose |access-date=18 March 2024 |archive-date=18 March 2024 |archive-url=https://web.archive.org/web/20240318213459/https://www.sigmaaldrich.com/US/en/product/mm/137048 |url-status=live }}</ref><ref>{{Cite web |url=https://www.sigmaaldrich.com/MD/en/product/mm/108337 |title=D-(+)-Glucose |access-date=18 March 2024 |archive-date=18 March 2024 |archive-url=https://web.archive.org/web/20240318213357/https://www.sigmaaldrich.com/US/en/product/mm/108337 |url-status=live }}</ref> The density of these two forms of glucose is also different.{{specify|date=March 2024}}

In terms of chemical structure, glucose is a monosaccharide, that is, a simple sugar. Glucose contains six carbon atoms and an [[aldehyde group]], and is therefore an [[aldohexose]]. The glucose molecule can exist in an [[Open-chain compound|open-chain]] (acyclic) as well as ring (cyclic) form—due to the presence of [[Alcohol (chemistry)|alcohol]] and [[aldehyde]] or [[ketone]] functional groups, the form having the straight chain can easily convert into a chair-like [[hemiacetal]] ring structure commonly found in carbohydrates.<ref name="chem2">{{cite web | url=https://chem.libretexts.org/Bookshelves/Biological_Chemistry/Supplemental_Modules_%28Biological_Chemistry%29/Carbohydrates/Monosaccharides/Glucose_%28Dextrose%29 | title=Glucose (Dextrose) | date=2 October 2013 | access-date=18 March 2024 | archive-date=21 December 2023 | archive-url=https://web.archive.org/web/20231221223258/https://chem.libretexts.org/Bookshelves/Biological_Chemistry/Supplemental_Modules_(Biological_Chemistry)/Carbohydrates/Monosaccharides/Glucose_(Dextrose) | url-status=live }}</ref>

===Structure and nomenclature===
Glucose is present in solid form as a [[monohydrate]] with a closed [[pyran]] ring (α-D-glucopyranose monohydrate, sometimes known less precisely by dextrose hydrate). In aqueous solution, on the other hand, a small proportion of glucose can be found in an open-chain configuration while remaining predominantly as α- or β-[[pyranose]], which interconvert. From aqueous solutions, the three known forms can be crystallized: α-glucopyranose, β-glucopyranose and α-glucopyranose monohydrate.<ref name="Ullmann">{{Cite book |doi=10.1002/14356007.a12_457.pub2 |chapter=Glucose and Glucose-Containing Syrups |title=Ullmann's Encyclopedia of Industrial Chemistry |year=2006 |last1=Schenck |first1=Fred W. |publisher=Wiley |isbn=978-3-527-30673-2}}</ref> Glucose is a building block of the disaccharides lactose and sucrose (cane or beet sugar), of [[oligosaccharide]]s such as [[raffinose]] and of [[polysaccharide]]s such as [[starch]], [[amylopectin]], [[glycogen]], and [[cellulose]].<ref name="r2"/><ref name="pf"/> The [[glass transition temperature]] of glucose is {{cvt|31|C}} and the Gordon–Taylor constant (an experimentally determined constant for the prediction of the glass transition temperature for different mass fractions of a mixture of two substances)<ref name="pf">Patrick F. Fox: ''Advanced Dairy Chemistry Volume 3: Lactose, water, salts and vitamins'', Springer, 1992. Volume 3, {{ISBN|9780412630200}}. p. 316.</ref> is 4.5.<ref name="Caballero 1 76">Benjamin Caballero, Paul Finglas, Fidel Toldrá: ''Encyclopedia of Food and Health''. Academic Press (2016). {{ISBN|9780123849533}}, Volume 1, p. 76.</ref>

{| class="wikitable centered"
|- style="background:#FFDEAD;"
! colspan="3"| Forms and projections of {{sm|d}}-glucose in comparison
|- class="background color5"
! [[Natta projection]]
! colspan="2"| [[Haworth projection]]
|- class="background color2"
| align="center" rowspan="2" | [[File:D-Glucose Keilstrich.svg|100px|class=skin-invert-image]]
| align="center" | [[File:Alpha-D-Glucofuranose.svg|120px|class=skin-invert-image]]{{pb}}α-{{sm|d}}-glucofuranose
| align="center" | [[File:Beta-D-Glucofuranose.svg|120px|class=skin-invert-image]]{{pb}}β-{{sm|d}}-glucofuranose
|- class="background color2"
| align="center" | [[File:Alpha-D-Glucopyranose.svg|100px|class=skin-invert-image]]{{pb}}α-{{sm|d}}-glucopyranose
| align="center" | [[File:Beta-D-Glucopyranose.svg|100px|class=skin-invert-image]]{{pb}}β-{{sm|d}}-glucopyranose
|- class="background color5"
! colspan="3"| α-{{sm|d}}-Glucopyranose in (1) [[Fischer projection|Tollens/Fischer]] (2) Haworth projection (3) chair conformation (4) Mills projection
|- class="background color2"
| align="center" colspan="3" | [[File:Alpha glucose views.svg|500px|class=skin-invert-image]]
|}

===Open-chain form===
An open-chain form of glucose makes up less than 0.02% of the glucose molecules in an aqueous solution at equilibrium.<ref>{{Cite web |date=18 July 2014 |title=16.4: Cyclic Structures of Monosaccharides |url=https://chem.libretexts.org/Bookshelves/Introductory_Chemistry/Basics_of_General_Organic_and_Biological_Chemistry_(Ball_et_al.)/16%3A_Carbohydrates/16.04%3A_Cyclic_Structures_of_Monosaccharides |access-date=17 April 2023 |website=Chemistry LibreTexts |language=en |archive-date=17 April 2023 |archive-url=https://web.archive.org/web/20230417213903/https://chem.libretexts.org/Bookshelves/Introductory_Chemistry/Basics_of_General_Organic_and_Biological_Chemistry_(Ball_et_al.)/16:_Carbohydrates/16.04:_Cyclic_Structures_of_Monosaccharides |url-status=live }}</ref> The rest is one of two cyclic hemiacetal forms. In its [[open-chain]] form, the glucose molecule has an open (as opposed to [[cyclic compound|cyclic]]) unbranched backbone of six carbon atoms, where C-1 is part of an [[aldehyde group]] {{chem2|H(C\dO)\s}}. Therefore, glucose is also classified as an [[aldose]], or an [[aldohexose]]. The aldehyde group makes glucose a [[reducing sugar]] giving a positive reaction with the [[Fehling test]].

===Cyclic forms===
{{multiple image
| align = right
| direction = horizontal
| total_width = 600
| image_style = border:none; background-color:light-dark(white,black);
| perrow = 4
| image1 = Alpha-D-Glucopyranose.svg | width1 = 157 | height1 = 170 
| class1 = skin-invert
| class2 = bg-transparent
| class3 = skin-invert
| class4 = bg-transparent
| class5 = skin-invert
| class7 = skin-invert
| image2 = Alpha-D-glucose-from-xtal-1979-3D-balls.png | width2 = 1014 | height2 = 1100
| image3 = Beta-D-Glucopyranose.svg | width3 = 157 | height3 = 170
| image4 = Beta-D-glucose-from-xtal-3D-balls.png | width4 = 1034 | height4 = 1100
| image5 = Alpha-D-Glucofuranose.svg | width5 = 173 | height5 = 187
| image6 = Alpha-D-Glucofuranose Molekülbaukasten 9134 (crop).jpg | width6 = 3073 | height6 = 3074
| image7 = Beta-D-Glucofuranose.svg | width7 = 173 | height7 = 187
| image8 = Beta-D-Glucofuranose Molekülbaukasten 9136 (crop).jpg | width8 = 3089 | height8 = 2873
| header = Cyclic forms of glucose
| footer = From left to right: [[Haworth projection]]s and [[ball-and-stick model|ball-and-stick]] structures of the α- and β- [[anomer]]s of {{small|D}}-glucopyranose (top row) and {{small|D}}-glucofuranose (bottom row)
}}
In solutions, the open-chain form of glucose (either "{{small|D}}-" or "{{small|L}}-") exists in equilibrium with several [[Carbohydrate#Ring-straight chain isomerism|cyclic isomers]], each containing a ring of carbons closed by one oxygen atom. In aqueous solution, however, more than 99% of glucose molecules exist as [[pyranose]] forms. The open-chain form is limited to about 0.25%, and [[furanose]] forms exist in negligible amounts. The terms "glucose" and "{{small|D}}-glucose" are generally used for these cyclic forms as well. The ring arises from the open-chain form by an intramolecular [[nucleophilic addition]] reaction between the aldehyde group (at C-1) and either the C-4 or C-5 hydroxyl group, forming a [[hemiacetal]] linkage, {{chem2|\sC(OH)H\sO\s}}.

The reaction between C-1 and C-5 yields a six-membered [[heterocycle|heterocyclic]] system called a pyranose, which is a monosaccharide sugar (hence "-ose") containing a derivatised [[pyran]] skeleton. The (much rarer) reaction between C-1 and C-4 yields a five-membered furanose ring, named after the cyclic ether [[furan]]. In either case, each carbon in the ring has one hydrogen and one hydroxyl attached, except for the last carbon (C-4 or C-5) where the hydroxyl is replaced by the remainder of the open molecule (which is {{chem2|\s(C(CH2OH)HOH)\sH}} or {{chem2|\s(CHOH)\sH}} respectively).

The ring-closing reaction can give two products, denoted "α-" and "β-". When a glucopyranose molecule is drawn in the [[Haworth projection]], the designation "α-" means that the hydroxyl group attached to C-1 and the {{chem2|\sCH2OH}} group at C-5 lies on opposite sides of the ring's plane (a[[cis–trans isomerism|'' trans'']] arrangement), while "β-" means that they are on the same side of the plane (a[[cis–trans isomerism|'' cis'']] arrangement). Therefore, the open-chain isomer {{small|D}}-glucose gives rise to four distinct cyclic isomers: α-{{small|D}}-glucopyranose, β-{{small|D}}-glucopyranose, α-{{small|D}}-glucofuranose, and β-{{small|D}}-glucofuranose. These five structures exist in equilibrium and interconvert, and the interconversion is much more rapid with acid [[catalysis]].

[[File:Alpha-D-glucose and beta-D-glucose acid-catalyzed mechanism.svg|centre|500px|class=skin-invert-image|Widely proposed arrow-pushing mechanism for acid-catalyzed dynamic equilibrium between the α- and β- [[anomer]]s of D-glucopyranose]]
{{multiple image
| align = right
| direction = horizontal
| total_width = 400
| image_style = border:none; background-color:light-dark(white,black);
| image1 = ALPHA-D-Glucopyranose V.1.png | width1 = 2240 | height1 = 1662
| class1 = skin-invert
| class2 = skin-invert
| image2 = BETA-D-Glucopyranose V.1.png | width2 = 2608| height2 = 1420
| footer = [[Chair conformation]]s of α- (left) and β- (right) {{small|D}}-glucopyranose
}}
The other open-chain isomer {{small|L}}-glucose similarly gives rise to four distinct cyclic forms of {{small|L}}-glucose, each the mirror image of the corresponding {{small|D}}-glucose.

The glucopyranose ring (α or β) can assume several non-planar shapes, analogous to the "chair" and "boat" conformations of [[cyclohexane]]. Similarly, the glucofuranose ring may assume several shapes, analogous to the "envelope" conformations of [[cyclopentane]].

In the solid state, only the glucopyranose forms are observed.

Some derivatives of glucofuranose, such as [[1,2-O-isopropylidene-D-glucofuranose|1,2-''O''-isopropylidene-{{sc|D}}-glucofuranose]] are stable and can be obtained pure as crystalline solids.<ref name=taka1979>{{cite journal | last1 = Takagi | first1 = S. | last2 = Jeffrey | first2 = G. A. | year = 1979 | title = 1,2-O-isopropylidene-D-glucofuranose | journal = Acta Crystallographica Section B | volume = B35 | issue = 6| pages = 1522–1525 | doi = 10.1107/S0567740879006968 | bibcode = 1979AcCrB..35.1522T }}</ref><ref name=biel1999>{{cite journal | last1 = Bielecki | first1 = Mia | last2 = Eggert | first2 = Hanne | last3 = Christian Norrild | first3 = Jens | year = 1999 | title = A fluorescent glucose sensor binding covalently to all five hydroxy groups of α-D-glucofuranose. A reinvestigation | journal = Journal of the Chemical Society, Perkin Transactions | volume = 2 | issue = 3 | pages = 449–456 | doi = 10.1039/A808896I }}</ref> For example, reaction of α-D-glucose with [[p-tolylboronic acid|''para''-tolylboronic acid]] {{chem2|H3C\s(C6H4)\sB(OH)2}} reforms the normal pyranose ring to yield the 4-fold ester α-D-glucofuranose-1,2:3,5-bis(''p''-tolylboronate).<ref name=chan2006>{{cite journal | last1 = Chandran | first1 = Sreekanth K. | last2 = Nangia | first2 = Ashwini | year = 2006 | title = Modulated crystal structure (Z{{prime}} = 2) of α-d-glucofuranose-1,2:3,5-bis(p-tolyl)boronate | journal = CrystEngComm | volume = 8 | issue = 8| pages = 581–585 | doi = 10.1039/B608029D }}</ref>

===Mutarotation===
{{See also|Mutarotation}}
[[File:Mutarotation D-Glucose V.1.png|thumb|upright=2|class=skin-invert-image|Mutarotation: {{sm|d}}-glucose molecules exist as cyclic hemiacetals that are epimeric (= diastereomeric) to each other. The epimeric ratio α:β is 36:64. In the α-D-glucopyranose (left), the blue-labelled hydroxy group is in the axial position at the anomeric centre, whereas in the β-D-glucopyranose (right) the blue-labelled hydroxy group is in equatorial position at the anomeric centre.]]
Mutarotation consists of a temporary reversal of the ring-forming reaction, resulting in the open-chain form, followed by a reforming of the ring. The ring closure step may use a different {{chem2|\sOH}} group than the one recreated by the opening step (thus switching between pyranose and furanose forms), or the new hemiacetal group created on C-1 may have the same or opposite handedness as the original one (thus switching between the α and β forms). Thus, though the open-chain form is barely detectable in solution, it is an essential component of the equilibrium.

The open-chain form is [[Chemical stability|thermodynamically unstable]], and it spontaneously [[isomer]]izes to the cyclic forms. (Although the ring closure reaction could in theory create four- or three-atom rings, these would be highly strained, and are not observed in practice.) In solutions at [[room temperature]], the four cyclic isomers interconvert over a time scale of hours, in a process called [[mutarotation]].<ref>{{McMurry2nd | page = 866}}.</ref> Starting from any proportions, the mixture converges to a stable ratio of α:β 36:64.<!--AT ANY TEMPERATURE?--> 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 = 978-0-8493-8941-2}}</ref> Mutarotation is considerably slower at temperatures close to {{convert|0|C}}.

===Optical activity===
Whether in water or the solid form, {{sm|d}}-(+)-glucose is [[Dextrorotation and levorotation|dextrorotatory]], meaning it will rotate the direction of [[polarized light]] clockwise as seen looking toward the light source. The effect is due to the [[chirality]] of the molecules, and indeed the mirror-image isomer, {{sm|l}}-(−)-glucose, is [[Dextrorotation and levorotation|levorotatory]] (rotates polarized light counterclockwise) by the same amount. The strength of the effect is different for each of the five [[tautomer]]s.

The {{sm|d}}- prefix does not refer directly to the optical properties of the compound. It indicates that the C-5 chiral centre has the same handedness as that of [[glyceraldehyde|{{sm|d}}-glyceraldehyde]] (which was so labelled because it is dextrorotatory). The fact that {{sm|d}}-glucose is dextrorotatory is a combined effect of its four chiral centres, not just of C-5; some of the other {{sm|d}}-aldohexoses are levorotatory.<!--CHECK-->

The conversion between the two anomers can be observed in a [[polarimeter]] since pure α-{{sm|d}}-glucose has a specific rotation angle of +112.2° mL/(dm·g), pure β-{{sm|d}}-glucose of +17.5° mL/(dm·g).<ref name=" Hesse">Manfred Hesse, Herbert Meier, Bernd Zeeh, Stefan Bienz, Laurent Bigler, Thomas Fox: ''Spektroskopische Methoden in der organischen Chemie''. 8th revised Edition. Georg Thieme, 2011, {{ISBN|978-3-13-160038-7}}, p. 34 (in German).</ref> When equilibrium has been reached after a certain time due to mutarotation, the angle of rotation is +52.7° mL/(dm·g).<ref name="Hesse" /> By adding acid or base, this transformation is much accelerated. The equilibration takes place via the open-chain aldehyde form.

===Isomerisation===
In dilute [[sodium hydroxide]] or other dilute bases, the monosaccharides [[mannose]], glucose, and [[fructose]] interconvert (via a [[Lobry de Bruyn–Van Ekenstein transformation|Lobry de Bruyn–Alberda–Van Ekenstein transformation]]), so that a balance between these isomers is formed. This reaction proceeds via an [[enediol]]:

[[File:Glucose Fructose Mannose Gleichgewicht.png|frameless|upright=2.0|class=skin-invert-image|Glucose-Fructose-Mannose-isomerisation]]

==Biochemical properties==
{| class="toccolours collapsible collapsed"  style="width:100%; text-align:left;"
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! Metabolism of common [[monosaccharide]]s and some biochemical reactions of glucose
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|[[File:Metabolism of common monosaccharides, and related reactions.png|none|1000px|class=skin-invert-image]]
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Glucose is the most abundant monosaccharide. Glucose is also the most widely used aldohexose in most living organisms. One possible explanation for this is that glucose has a lower tendency than other aldohexoses to react nonspecifically with the [[amine]] groups of [[protein]]s.<ref name=Higgins>{{cite journal|last1=Bunn|first1=H. F.|last2=Higgins|first2=P. J.|title=Reaction of monosaccharides with proteins: possible evolutionary significance |journal=Science|date=1981|volume=213 |issue=4504|pages=222–24|doi=10.1126/science.12192669|pmid=12192669| bibcode=1981Sci...213..222B}}<!--|access-date=13 May 2015--></ref> This reaction—[[glycation]]—impairs or destroys the function of many proteins,<ref name=Higgins/> e.g. in [[glycated hemoglobin]]. Glucose's low rate of glycation can be attributed to its having a more stable [[#Cyclic forms|cyclic form]] compared to other aldohexoses, which means it spends less time than they do in its reactive [[#Open-chain form|open-chain form]].<ref name=Higgins/> The reason for glucose having the most stable cyclic form of all the aldohexoses is that its [[hydroxy group]]s (with the exception of the hydroxy group on the anomeric carbon of {{sm|d}}-glucose) are in the [[Cyclohexane conformation|equatorial position]]. Presumably, glucose is the most abundant natural monosaccharide because it is less glycated with proteins than other monosaccharides.<ref name=Higgins /><ref name="Stryer 531">Jeremy M. Berg: ''Stryer Biochemie'' {{In lang|de}}. Springer-Verlag, 2017, {{ISBN|978-3-662-54620-8}}, p.&nbsp;531.</ref> Another hypothesis is that glucose, being the only {{sm|d}}-aldohexose that has all five hydroxy substituents in the [[Equatorial bond|equatorial]] position in the form of β-{{sm|d}}-glucose, is more readily accessible to chemical reactions,<ref name="Garrett">{{cite book |last1=Garrett |first1=Reginald H. |title=Biochemistry |date=2013 |publisher=Brooks/Cole, Cengage Learning |location=Belmont, CA |isbn=978-1-133-10629-6 |edition=5th}}</ref>{{rp|194, 199}} for example, for [[esterification]]<ref name=Voet>{{cite book |last1=Voet |first1=Donald |last2=Voet |first2=Judith G. |title=Biochemistry |date=2011 |publisher=John Wiley & Sons |location=Hoboken, NJ |isbn=978-0-470-57095-1 |edition=4th}}</ref>{{rp|363}} or [[acetal]] formation.<ref>Albert L. Lehninger, ''Biochemistry, 6th printing'', Worth Publishers Inc. 1972, {{ISBN|0-87901-009-6}} p. 228.</ref> For this reason, {{sm|d}}-glucose is also a highly preferred building block in natural polysaccharides (glycans). Polysaccharides that are composed solely of glucose are termed [[glucan]]s.

Glucose is produced by plants through photosynthesis using sunlight,<ref name="photo"/><ref name="Löffler/Petrides 195"/> water, and carbon dioxide and can be used by all living organisms as an energy and carbon source. However, most glucose does not occur in its free form, but in the form of its polymers, i.e. lactose, sucrose, starch, and others which are energy reserve substances, and cellulose and [[chitin]], which are components of the cell wall in plants or [[fungi]] and [[arthropod]]s, respectively. These polymers, when consumed by animals, fungi, and bacteria, are degraded to glucose using enzymes. All animals are also able to produce glucose themselves from certain precursors as the need arises. [[Neuron]]s, cells of the [[renal medulla]], and [[erythrocytes]] depend on glucose for their energy production.<ref name="Löffler/Petrides 195">Peter C. Heinrich: ''Löffler/Petrides Biochemie und Pathobiochemie'' {{In lang|de}}.. Springer-Verlag, 2014, {{ISBN|978-3-642-17972-3}}, p.&nbsp;195.</ref> In adult humans, there is about {{cvt|18|g}} of glucose,<ref name="Satyanarayana">U. Satyanarayana: ''Biochemistry''. Elsevier Health Sciences, 2014, {{ISBN|978-8-131-23713-7}}. p. 674.</ref> of which about {{cvt|4|g}} is present in the blood.<ref>{{Cite journal |doi=10.1152/ajpendo.90563.2008 |pmc=2636990 |pmid=18840763|year=2009 |last1=Wasserman |first1=D. H. |title=Four grams of glucose |journal=American Journal of Physiology. Endocrinology and Metabolism |volume=296 |issue=1 |pages=E11–21 }}</ref> Approximately {{cvt|180-220|g}} of glucose is produced in the liver of an adult in 24 hours.<ref name="Satyanarayana" />

Many of the long-term complications of [[diabetes]] (e.g., [[Visual impairment|blindness]], [[kidney failure]], and [[peripheral neuropathy]]) are probably due to the glycation of proteins or [[lipid]]s.<ref>{{citation | title = High Blood Glucose and Diabetes Complications: The buildup of molecules known as AGEs may be the key link | journal = Diabetes Forecast | url = http://forecast.diabetes.org/magazine/features/high-blood-glucose-and-diabetes-complications | year = 2010 | publisher = American Diabetes Association | issn = 0095-8301 | access-date = 20 May 2010 | archive-url = https://web.archive.org/web/20131014173838/http://forecast.diabetes.org/magazine/features/high-blood-glucose-and-diabetes-complications | archive-date = 14 October 2013 | url-status = dead }}</ref> In contrast, [[enzyme]]-regulated addition of sugars to protein is called [[glycosylation]] and is essential for the function of many proteins.<ref name="varki">{{Cite book|edition = 2nd|publisher = Cold Spring Harbor Laboratories Press|isbn = 978-0-87969-770-9| editor-first= Ajit |editor-last=Varki |title = Essentials of Glycobiology|url = https://www.ncbi.nlm.nih.gov/books/NBK1908/|url-status = live|archive-url = https://web.archive.org/web/20161206081633/https://www.ncbi.nlm.nih.gov/books/NBK1908/|archive-date = 6 December 2016|year = 2009| pmid=20301239 | last1=Varki | first1=A. | last2=Cummings | first2=R. D. | last3=Esko | first3=J. D. | last4=Freeze | first4=H. H. | last5=Stanley | first5=P. | last6=Bertozzi | first6=C. R. | last7=Hart | first7=G. W. | last8=Etzler | first8=M. E. }}</ref>

===Uptake===
Ingested glucose initially binds to the receptor for sweet taste on the tongue in humans. This complex of the proteins [[T1R2]] and [[T1R3]] makes it possible to identify glucose-containing food sources.<ref name="fca">{{cite web | url=https://foodb.ca/compounds/FDB012530 | title=Showing Compound D-Glucose (FDB012530) - FooDB | access-date=18 March 2024 | archive-date=6 December 2022 | archive-url=https://web.archive.org/web/20221206084746/https://www.foodb.ca/compounds/FDB012530 | url-status=live }}</ref><ref name="Löffler/Petrides 404"/> Glucose mainly comes from food—about {{cvt|300|g}} per day is produced by conversion of food,<ref name="Löffler/Petrides 404">Peter C. Heinrich: ''Löffler/Petrides Biochemie und Pathobiochemie''. Springer-Verlag, 2014, {{ISBN|978-3-642-17972-3}}, p.&nbsp;404.</ref> but it is also synthesized from other metabolites in the body's cells. In humans, the breakdown of glucose-containing polysaccharides happens in part already during [[chewing]] by means of [[amylase]], which is contained in [[saliva]], as well as by [[maltase]], [[lactase]], and [[sucrase]] on the [[brush border]] of the [[small intestine]]. Glucose is a building block of many carbohydrates and can be split off from them using certain enzymes. [[Glucosidases]], a subgroup of the glycosidases, first catalyze the hydrolysis of long-chain glucose-containing polysaccharides, removing terminal glucose. In turn, disaccharides are mostly degraded by specific glycosidases to glucose. The names of the degrading enzymes are often derived from the particular poly- and disaccharide; inter alia, for the degradation of polysaccharide chains there are amylases (named after amylose, a component of starch), cellulases (named after cellulose), chitinases (named after chitin), and more. Furthermore, for the cleavage of disaccharides, there are maltase, lactase, sucrase, [[trehalase]], and others. In humans, about 70 genes are known that code for glycosidases. They have functions in the digestion and degradation of glycogen, [[sphingolipid]]s, [[mucopolysaccharides]], and poly([[Adenosine diphosphate ribose|ADP-ribose]]). Humans do not produce cellulases, chitinases, or trehalases, but the bacteria in the [[gut microbiota]] do.

In order to get into or out of cell membranes of cells and membranes of cell compartments, glucose requires special transport proteins from the [[major facilitator superfamily]]. In the small intestine (more precisely, in the [[jejunum]]),<ref name="Harper 641">Harold A. Harper: ''Medizinische Biochemie'' {{In lang|de}}. Springer-Verlag, 2013, {{ISBN|978-3-662-22150-1}}, p.&nbsp;641.</ref> glucose is taken up into the intestinal [[epithelium]] with the help of [[glucose transporter]]s<ref>{{Cite journal |doi=10.1007/s12551-015-0186-2 |pmc=5425736 |pmid=28510148|year=2016 |last1=Navale |first1=A. M. |title=Glucose transporters: Physiological and pathological roles |journal=Biophysical Reviews |volume=8 |issue=1 |pages=5–9 |last2=Paranjape |first2=A. N. }}</ref> via a [[secondary active transport]] mechanism called sodium ion-glucose [[symport]] via [[sodium/glucose cotransporter 1]] (SGLT1).<ref name="Löffler/Petrides 199" /> Further transfer occurs on the [[basolateral]] side of the intestinal epithelial cells via the glucose transporter [[GLUT2]],<ref name="Löffler/Petrides 199" /> as well uptake into [[hepatocyte|liver cells]], kidney cells, cells of the [[Pancreatic islets|islets of Langerhans]], [[neuron]]s, [[astrocyte]]s, and [[tanycyte]]s.<ref>{{Cite journal|doi=10.1007/s00125-014-3451-1|pmid=25421524|year=2015|last1=Thorens|first1=B.|title=GLUT2, glucose sensing and glucose homeostasis|journal=Diabetologia|volume=58|issue=2|pages=221–32|doi-access=free|url=http://doc.rero.ch/record/331705/files/125_2014_Article_3451.pdf|access-date=18 March 2024|archive-date=2 December 2023|archive-url=https://web.archive.org/web/20231202190651/http://doc.rero.ch/record/331705/files/125_2014_Article_3451.pdf|url-status=live}}</ref> Glucose enters the liver via the [[portal vein]] and is stored there as a cellular glycogen.<ref name="Löffler/Petrides 214" /> In the liver cell, it is [[Phosphorylation|phosphorylated]] by [[glucokinase]] at position 6 to form [[glucose 6-phosphate]], which cannot leave the cell. [[Glucose 6-phosphatase]] can convert glucose 6-phosphate back into glucose exclusively in the liver, so the body can maintain a sufficient blood glucose concentration. In other cells, uptake happens by passive transport through one of the 14 GLUT proteins.<ref name="Löffler/Petrides 199" /> In the other cell types, phosphorylation occurs through a [[hexokinase]], whereupon glucose can no longer diffuse out of the cell.

The glucose transporter [[GLUT1]] is produced by most cell types and is of particular importance for nerve cells and pancreatic [[Beta cell|β-cell]]s.<ref name="Löffler/Petrides 199" /> [[GLUT3]] is highly expressed in nerve cells.<ref name="Löffler/Petrides 199" /> Glucose from the bloodstream is taken up by [[GLUT4]] from [[muscle cell]]s (of the [[skeletal muscle]]<ref>{{Cite journal |doi=10.1016/j.cmet.2007.03.006 |pmid=17403369|year=2007|last1=Huang| first1=S.|title=The GLUT4 glucose transporter|journal=Cell Metabolism|volume=5|issue=4|pages=237–52|last2=Czech|first2=M. P.|doi-access=free}}</ref> and [[heart muscle]]) and [[fat cell]]s.<ref>{{Cite book |pmid=25344989|date=2014| last1=Govers|first1=R.|title=Cellular regulation of glucose uptake by glucose transporter GLUT4|series=Advances in Clinical Chemistry|volume=66|pages=173–240|publisher=Elsevier |doi=10.1016/B978-0-12-801401-1.00006-2|isbn=978-0-12-801401-1}}</ref> [[GLUT14]] is expressed exclusively in [[testicle]]s.<ref>{{cite journal |last1=Wu |first1=Xiaohua |last2=Freeze |first2=Hudson H. |title=GLUT14, a Duplicon of GLUT3, is Specifically Expressed in Testis as Alternative Splice Forms |journal=Genomics |date=December 2002 |volume=80 |issue=6 |pages=553–7 |doi=10.1006/geno.2002.7010 |pmid=12504846}}</ref> Excess glucose is broken down and converted into fatty acids, which are stored as [[triglyceride]]s. In the [[kidney]]s, glucose in the urine is absorbed via SGLT1 and [[SGLT2]] in the apical cell membranes and transmitted via GLUT2 in the basolateral cell membranes.<ref>{{Cite journal |doi=10.1007/s00125-018-4656-5 |pmid=30132032|pmc=6133168|year=2018|last1=Ghezzi|first1=C.|title=Physiology of renal glucose handling via SGLT1, SGLT2, and GLUT2|journal=Diabetologia|volume=61|issue=10|pages=2087–2097|author2=Loo DDF|last3=Wright|first3=E. M.}}</ref> About 90% of kidney glucose reabsorption is via SGLT2 and about 3% via SGLT1.<ref>{{Cite journal |doi=10.1097/MNH.0000000000000152 |pmc=5364028 |pmid=26125647|year=2015 |last1=Poulsen |first1=S. B. |title=Sodium-glucose cotransport |journal=Current Opinion in Nephrology and Hypertension |volume=24 |issue=5 |pages=463–9 |last2=Fenton |first2=R. A. |last3=Rieg |first3=T. }}</ref>

===Biosynthesis===
{{main|Gluconeogenesis|Glycogenolysis}}
In plants and some [[prokaryote]]s, glucose is a product of [[photosynthesis]].<ref name="photo">{{Cite web|url=http://www.rsc.org/Education/Teachers/Resources/cfb/Photosynthesis.htm|title=Chemistry for Biologists: Photosynthesis|website=www.rsc.org|access-date=5 February 2018|url-status=live|archive-url=https://web.archive.org/web/20160804060610/http://www.rsc.org/Education/Teachers/Resources/cfb/Photosynthesis.htm|archive-date=4 August 2016}}</ref> Glucose is also formed by the breakdown of polymeric forms of glucose like [[glycogen]] (in animals and [[mushroom]]s) or starch (in plants). The cleavage of glycogen is termed glycogenolysis, the cleavage of starch is called starch degradation.<ref>{{cite journal |last1= Smith, Alison M. |last2=Zeeman, Samuel C. |last3= Smith, Steven M. |year= 2005 |title= Starch Degradation |journal= Annu. Rev. Plant Biol. |volume= 56 |issue=1 |pages= 73–98 |doi= 10.1146/annurev.arplant.56.032604.144257 |pmid=15862090 |bibcode=2005AnRPB..56...73S }}</ref>

The metabolic pathway that begins with molecules containing two to four carbon atoms (C) and ends in the glucose molecule containing six carbon atoms is called gluconeogenesis and occurs in all living organisms. The smaller starting materials are the result of other metabolic pathways. Ultimately almost all [[biomolecule]]s come from the assimilation of carbon dioxide in plants and microbes during photosynthesis.<ref name=Voet/>{{rp|359}} The free energy of formation of α-{{sm|d}}-glucose is 917.2 kilojoules per mole.<ref name=Voet/>{{rp|59}} In humans, gluconeogenesis occurs in the liver and kidney,<ref name="Szablewski">Leszek Szablewski: ''Glucose Homeostasis and Insulin Resistance''. Bentham Science Publishers, 2011, {{ISBN|978-1-608-05189-2}}, p.&nbsp;46.</ref> but also in other cell types. In the liver about {{cvt|150|g}} of glycogen are stored, in skeletal muscle about {{cvt|250|g}}.<ref name="Löffler/Petrides 389">Peter C. Heinrich: ''Löffler/Petrides Biochemie und Pathobiochemie'' {{In lang|de}}. Springer-Verlag, 2014, {{ISBN|978-3-642-17972-3}}, p.&nbsp;389.</ref> However, the glucose released in muscle cells upon cleavage of the glycogen can not be delivered to the circulation because glucose is phosphorylated by the hexokinase, and a glucose-6-phosphatase is not expressed to remove the phosphate group. Unlike for glucose, there is no transport protein for [[Glucose-6-phosphate dehydrogenase (coenzyme-F420)|glucose-6-phosphate]]. Gluconeogenesis allows the organism to build up glucose from other metabolites, including [[lactic acid|lactate]] or certain [[amino acid]]s, while consuming energy. The renal [[tubular cell]]s can also produce glucose.

Glucose also can be found outside of living organisms in the ambient environment. Glucose concentrations in the atmosphere are detected via collection of samples by aircraft and are known to vary from location to location. For example, glucose concentrations in atmospheric air from inland China range from 0.8 to 20.1 pg/L, whereas east coastal China glucose concentrations range from 10.3 to 142 pg/L.<ref>{{cite journal |last1=Wang |first1=Gehui |last2=Kawamura |first2=Kimitaka |last3=Hatakeyama |first3=Shiro |last4=Takami |first4=Akinori |last5=Li |first5=Hong |last6=Wang |first6=Wei |title=Aircraft Measurement of Organic Aerosols over China |journal=Environmental Science & Technology |date=May 2007 |volume=41 |issue=9 |pages=3115–3120 |doi=10.1021/es062601h |pmid=17539513 |bibcode=2007EnST...41.3115W }}</ref>

===Glucose degradation===
{{Main|Glycolysis|Pentose phosphate pathway}}
[[File:Glucose metabolism.svg|thumb|Glucose metabolism and various forms of it in the process.{{pb}}Glucose-containing compounds and [[isomer]]ic forms are digested and taken up by the body in the intestines, including [[starch]], [[glycogen]], [[disaccharide]]s, and [[monosaccharide]]s.{{pb}}Glucose is stored in mainly the liver and muscles as glycogen. It is distributed and used in tissues as free glucose.]]

In humans, glucose is metabolized by glycolysis<ref>{{Cite journal |doi=10.1042/BSR20160385 |pmc=5293555 |pmid=27707936|year=2016 |last1=Adeva-Andany |first1=M. M. |title=Liver glucose metabolism in humans |journal=Bioscience Reports |volume=36 |issue=6 |pages=e00416 |last2=Pérez-Felpete |first2=N. |last3=Fernández-Fernández |first3=C. |last4=Donapetry-García |first4=C. |last5=Pazos-García |first5=C. }}</ref> and the pentose phosphate pathway.<ref name="Horton">H. Robert Horton, [[Laurence A. Moran]], K. Gray Scrimgeour, Marc D. Perry, J. David Rawn: ''Biochemie'' {{In lang|de}}. Pearson Studium; 4. aktualisierte Auflage 2008; {{ISBN|978-3-8273-7312-0}}; pp. 490–496.</ref> Glycolysis is used by all living organisms,<ref name="Garrett"/>{{rp|551}}<ref name="Hall">Brian K. Hall: ''Strickberger's Evolution''. Jones & Bartlett Publishers, 2013, {{ISBN|978-1-449-61484-3}}, p.&nbsp;164.</ref> with small variations, and all organisms generate energy from the breakdown of monosaccharides.<ref name="Hall" /> In the further course of the metabolism, it can be completely degraded via [[oxidative decarboxylation]], the [[citric acid cycle]] (synonym ''Krebs cycle'') and the [[respiratory chain]] to water and carbon dioxide. If there is not enough oxygen available for this, the glucose degradation in animals occurs anaerobic to lactate via lactic acid fermentation and releases much less energy. Muscular lactate enters the liver through the bloodstream in mammals, where gluconeogenesis occurs ([[Cori cycle]]). With a high supply of glucose, the metabolite [[acetyl-CoA]] from the Krebs cycle can also be used for [[fatty acid synthesis]].<ref>{{Cite journal |doi=10.1007/s00125-016-3940-5|pmid=27048250|year=2016|last1=Jones|first1=J. G.|title=Hepatic glucose and lipid metabolism|journal=Diabetologia|volume=59|issue=6|pages=1098–103|doi-access=free}}</ref> Glucose is also used to replenish the body's glycogen stores, which are mainly found in liver and skeletal muscle. These processes are [[Hormone|hormonally]] regulated.

In other living organisms, other forms of fermentation can occur. The bacterium ''[[Escherichia coli]]'' can grow on nutrient media containing glucose as the sole carbon source.<ref name=Voet/>{{rp|59}} In some bacteria and, in modified form, also in archaea, glucose is degraded via the [[Entner-Doudoroff pathway]].<ref>{{cite journal | last1 = Entner | first1 = N. | last2 = Doudoroff | first2 = M. | year = 1952 | title = Glucose and gluconic acid oxidation of Pseudomonas saccharophila | journal = [[J Biol Chem]] | volume = 196 | issue = 2| pages = 853–862 | doi = 10.1016/S0021-9258(19)52415-2 | pmid = 12981024 | doi-access = free }}</ref> With glucose, a mechanism for [[gene regulation]] was discovered in ''E. coli'', the [[catabolite repression]] (formerly known as ''glucose effect'').<ref name="PMID29330542">{{cite journal | vauthors = Ammar EM, Wang X, Rao CV | title = Regulation of metabolism in Escherichia coli during growth on mixtures of the non-glucose sugars: arabinose, lactose, and xylose | journal = Scientific Reports | volume = 8 | issue = 1 | article-number = 609 | date = January 2018 | pmid = 29330542 | pmc = 5766520 | doi = 10.1038/s41598-017-18704-0 | bibcode = 2018NatSR...8..609A | url = | issn = }}</ref>

Use of glucose as an energy source in cells is by either aerobic respiration, anaerobic respiration, or fermentation.<ref name="sil"/> The first step of glycolysis is the [[phosphorylation]] of glucose by a [[hexokinase]] to form [[glucose 6-phosphate]]. The main reason for the immediate phosphorylation of glucose is to prevent its diffusion out of the cell as the charged [[phosphate]] group prevents glucose 6-phosphate from easily crossing the [[cell membrane]].<ref name="sil">{{cite journal|last1=Bonadonna|first1=Riccardo C|last2=Bonora|first2=Enzo|last3=Del Prato|first3=Stefano|last4=Saccomani|first4=Maria|last5=Cobelli|first5=Claudio|last6=Natali|first6=Andrea|last7=Frascerra|first7=Silvia|last8=Pecori|first8=Neda|last9=Ferrannini|first9=Eleuterio|last10=Bier|first10=Dennis|last11=DeFronzo|first11=Ralph A|last12=Gulli|first12=Giovanni|title=Roles of glucose transport and glucose phosphorylation in muscle insulin resistance of NIDDM|journal=Diabetes|date=July 1996|volume=45|issue=7|pages=915–25|doi=10.2337/diab.45.7.915|pmid=8666143|s2cid=219249555|url=http://diabetes.diabetesjournals.org/content/45/7/915.full-text.pdf |archive-url=https://web.archive.org/web/20170306131309/http://diabetes.diabetesjournals.org/content/45/7/915.full-text.pdf |archive-date=6 March 2017 |url-status=live|access-date=5 March 2017}}</ref> Furthermore, addition of the high-energy phosphate group [[Activation#Biochemistry|activates]] glucose for subsequent breakdown in later steps of glycolysis.<ref>{{cite web | url=https://go.drugbank.com/drugs/DB09341 | title=Glucose | access-date=18 March 2024 | archive-date=5 December 2023 | archive-url=https://web.archive.org/web/20231205120936/https://go.drugbank.com/drugs/DB09341 | url-status=live }}</ref>

In anaerobic respiration, one glucose molecule produces a net gain of two ATP molecules (four ATP molecules are produced during glycolysis through substrate-level phosphorylation, but two are required by enzymes used during the process).<ref>{{citation | title = Medical Biochemistry at a Glance @Google books | url = https://books.google.com/books?id=9BtxCWxrWRoC&pg=PA52 | year = 2006 | page = 52 | publisher = Blackwell Publishing | isbn = 978-1-4051-1322-9 | url-status = live | archive-url = https://web.archive.org/web/20180223145046/https://books.google.com/books?id=9BtxCWxrWRoC&pg=PA52 | archive-date = 23 February 2018 }}</ref> In aerobic respiration, a molecule of glucose is much more profitable in that a maximum net production of 30 or 32 ATP molecules (depending on the organism) is generated.<ref>{{citation|title=Medical Biochemistry at a Glance @Google books|url=https://books.google.com/books?id=9BtxCWxrWRoC&pg=PA50|page=50|year=2006|archive-url=https://web.archive.org/web/20180223145046/https://books.google.com/books?id=9BtxCWxrWRoC&pg=PA50|publisher=Blackwell Publishing|isbn=978-1-4051-1322-9|archive-date=23 February 2018|url-status=live}}</ref>

{{GlycolysisGluconeogenesis_WP534|highlight=Glucose}}

[[Tumor]] cells often grow comparatively quickly and consume an above-average amount of glucose by glycolysis,<ref>{{Cite journal |doi=10.1097/MCO.0b013e32833a5577 |pmid=20473153|year=2010|last1=Annibaldi|first1=A.|title=Glucose metabolism in cancer cells|journal=Current Opinion in Clinical Nutrition and Metabolic Care|volume=13|issue=4|pages=466–70|last2=Widmann|first2=C.|s2cid=205782021}}</ref> which leads to the formation of lactate, the end product of fermentation in mammals, even in the presence of oxygen. This is called the [[Warburg effect (oncology)|Warburg effect]]. For the increased uptake of glucose in tumors various SGLT and GLUT are overly produced.<ref>{{Cite journal |doi=10.1016/j.bbcan.2012.12.004|pmid=23266512|year=2013|last1=Szablewski|first1=L.|title=Expression of glucose transporters in cancers|journal=Biochimica et Biophysica Acta (BBA) - Reviews on Cancer|volume=1835|issue=2|pages=164–9}}</ref><ref>{{Cite journal |doi=10.1097/CCO.0b013e328356da72 |pmid=22913968|year=2012|last1=Adekola|first1=K.|title=Glucose transporters in cancer metabolism|journal=Current Opinion in Oncology|volume=24|issue=6|pages=650–4|last2=Rosen|first2=S. T.|last3=Shanmugam|first3=M.|pmc=6392426}}</ref>

In [[yeast]], ethanol is fermented at high glucose concentrations, even in the presence of oxygen (which normally leads to respiration rather than fermentation). This is called the [[Crabtree effect]].

Glucose can also degrade to form carbon dioxide through abiotic means. This has been demonstrated to occur experimentally via oxidation and hydrolysis at 22&nbsp;°C and a pH of 2.5.<ref>{{cite journal |last1=Schümann |first1=U. |last2=Gründler |first2=P. |title=Electrochemical degradation of organic substances at PbO2 anodes: Monitoring by continuous CO2 measurements |journal=Water Research |date=September 1998 |volume=32 |issue=9 |pages=2835–2842 |doi=10.1016/s0043-1354(98)00046-3 }}</ref>

===Energy source===
[[File:Glucose catabolism intermediates de.png|thumb|upright=1.2|class=skin-invert-image|Diagram showing the possible intermediates in glucose degradation; Metabolic pathways orange: glycolysis, green: Entner-Doudoroff pathway, phosphorylating, yellow: Entner-Doudoroff pathway, non-phosphorylating]]
Glucose is a ubiquitous fuel in [[biology]]. It is used as an energy source in organisms, from bacteria to humans, through either [[aerobic respiration]], [[anaerobic respiration]] (in bacteria), or [[Fermentation (biochemistry)|fermentation]]. Glucose is the human body's key source of energy, through aerobic respiration, providing about 3.75&nbsp;[[kilocalorie]]s (16&nbsp;[[kilojoule]]s) of [[food energy]] per gram.<ref>{{citation | title = Food energy&nbsp;– methods of analysis and conversion factors | chapter-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 = 978-92-5-105014-9 | url-status = live | archive-url = https://web.archive.org/web/20100524003622/http://www.fao.org/DOCREP/006/Y5022E/y5022e04.htm | archive-date = 24 May 2010 }}</ref> Breakdown of carbohydrates (e.g., starch) yields mono- and [[disaccharide]]s, most of which is glucose. Through [[glycolysis]] and later in the reactions of the [[citric acid cycle]] and [[oxidative phosphorylation]], glucose is [[oxidize]]d to eventually form [[carbon dioxide]] and water, yielding energy mostly in the form of [[adenosine triphosphate]] (ATP). The insulin reaction, and other mechanisms, regulate the concentration of glucose in the blood. The physiological caloric value of glucose, depending on the source, is 16.2 kilojoules per gram<ref name="Schwedt">Georg Schwedt: ''Zuckersüße Chemie'' {{In lang|de}}. John Wiley & Sons, 2012, {{ISBN|978-3-527-66001-8}}, p.&nbsp;100.</ref> or 15.7 kJ/g (3.74 kcal/g).<ref>Schmidt, Lang: ''Physiologie des Menschen'', 30. Auflage. Springer Verlag, 2007, p.&nbsp;907 {{in lang|de}}.</ref> The high availability of carbohydrates from plant biomass has led to a variety of methods during evolution, especially in microorganisms, to utilize glucose for energy and carbon storage. Differences exist in which end product can no longer be used for energy production. The presence of individual genes, and their gene products, the enzymes, determine which reactions are possible. The metabolic pathway of glycolysis is used by almost all living beings. An essential difference in the use of glycolysis is the recovery of [[NADPH]] as a reductant for [[anabolism]] that would otherwise have to be generated indirectly.<ref>{{Cite journal |pmc=1220531 |pmid=10493919 |year=1999 |last1=Dandekar |first1=T. |title=Pathway alignment: Application to the comparative analysis of glycolytic enzymes |journal=The Biochemical Journal |volume=343 |pages=115–124 |last2=Schuster |first2=S. |last3=Snel |first3=B. |last4=Huynen |first4=M. |last5=Bork |first5=P. |doi=10.1042/bj3430115 |issue=1}}</ref>

Glucose and oxygen supply almost all the energy for the [[brain]],<ref>{{cite web |first = Pramod|last = Dash |url =http://neuroscience.uth.tmc.edu/s4/chapter11.html |title=Blood Brain Barrier and Cerebral Metabolism (Section 4, Chapter 11) |work =Neuroscience Online: An Electronic Textbook for the Neurosciences |publisher =Department of Neurobiology and Anatomy – The University of Texas Medical School at Houston  |url-status=dead |archive-url=https://web.archive.org/web/20161117104126/http://neuroscience.uth.tmc.edu/s4/chapter11.html |archive-date=17 November 2016 }}</ref> so 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 | s2cid = 44500072 | title = A metabolic measure of mental effort | journal = Biol. Psychol.  | year = 2004 | volume = 66 | issue = 2 | pages = 177–190 | 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. Pers. Soc. Psychol. | year = 2007 | volume = 92 | issue = 2 | pages = 325–336 | pmid = 17279852 | doi = 10.1037/0022-3514.92.2.325 | url = http://www.uky.edu/~njdewa2/gailliotetal07JPSP.pdf | url-status = live | archive-url = https://web.archive.org/web/20170818111037/http://www.uky.edu/~njdewa2/gailliotetal07JPSP.pdf | archive-date = 18 August 2017 | citeseerx = 10.1.1.337.3766 | s2cid = 7496171 }}</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 = 303–327 | doi = 10.1177/1088868307303030 | pmid = 18453466 | citeseerx = 10.1.1.475.9484 | s2cid = 14380313 }}</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 | pmid = 18315798| s2cid = 38596025 }}</ref> In the brain, which is dependent on glucose and oxygen as the major source of energy, the glucose concentration is usually 4 to 6&nbsp;mM (5&nbsp;mM equals 90&nbsp;mg/dL),<ref name="Satyanarayana" /> but decreases to 2 to 3&nbsp;mM when fasting.<ref name="Dwyer" /> [[Confusion]] occurs below 1&nbsp;mM and [[coma]] at lower levels.<ref name="Dwyer" />

The glucose in the blood is called [[blood sugar]]. Blood sugar levels are regulated by glucose-binding nerve cells in the [[hypothalamus]].<ref name="Koekkoek">{{Cite journal |doi=10.3389/fnins.2017.00716 |pmc=5742113 |pmid=29311793|year=2017 |last1=Koekkoek |first1=L. L. |title=Glucose-Sensing in the Reward System |journal=Frontiers in Neuroscience |volume=11 |article-number=716 |last2=Mul |first2=J. D. |last3=La Fleur |first3=S. E. |doi-access=free }}</ref> In addition, glucose in the brain binds to glucose receptors of the [[reward system]] in the [[nucleus accumbens]].<ref name="Koekkoek" /> The binding of glucose to the sweet receptor on the tongue induces a release of various hormones of energy metabolism, either through glucose or through other sugars, leading to an increased cellular uptake and lower blood sugar levels.<ref name="Tucker">{{Cite journal |doi=10.1016/j.physbeh.2017.09.016 |pmid=28939430 |year=2017 |last1=Tucker |first1=R. M. |title=Do non-nutritive sweeteners influence acute glucose homeostasis in humans? A systematic review |journal=Physiology & Behavior |volume=182 |pages=17–26 |last2=Tan |first2=S. Y. |s2cid=38764657 |url=https://ap01.alma.exlibrisgroup.com/view/delivery/61USOUTHAUS_INST/12149779800001831 |access-date=7 June 2020 |archive-date=29 July 2020 |archive-url=https://web.archive.org/web/20200729195754/https://ap01.alma.exlibrisgroup.com/view/delivery/61USOUTHAUS_INST/12149779800001831 |url-status=dead |url-access=subscription }}</ref> [[Artificial sweetener]]s do not lower blood sugar levels.<ref name="Tucker" />

The blood sugar content of a healthy person in the short-time fasting state, e.g. after overnight fasting, is about 70 to 100&nbsp;mg/dL of blood (4 to 5.5&nbsp;mM). In [[blood plasma]], the measured values are about 10–15% higher. In addition, the values in the [[artery|arterial]] blood are higher than the concentrations in the [[vein|venous]] blood since glucose is absorbed into the tissue during the passage of the [[capillary bed]]. Also in the capillary blood, which is often used for blood sugar determination, the values are sometimes higher than in the venous blood. The glucose content of the blood is regulated by the hormones [[insulin]], [[incretin]], and [[glucagon]].<ref name="Koekkoek" /><ref>{{Cite book |doi=10.1016/B978-0-444-53480-4.00026-6 |pmid=25410233 |year=2014 |last1=La Fleur |first1=S. E. |series=Handbook of Clinical Neurology |volume=126 |pages=341–351 |last2=Fliers |first2=E. |last3=Kalsbeek |first3=A. |title=Diabetes and the Nervous System |chapter=Neuroscience of glucose homeostasis |isbn=978-0-444-53480-4}}.</ref> Insulin lowers the glucose level, glucagon increases it.<ref name="Satyanarayana" /> Furthermore, the hormones [[adrenaline]], [[thyroxine]], [[glucocorticoid]]s, [[somatotropin]], and [[adrenocorticotropin]] lead to an increase in the glucose level.<ref name="Satyanarayana" /> There is also a hormone-independent regulation, which is referred to as [[glucose autoregulation]].<ref>{{Cite journal |doi=10.1002/cphy.c140009 |pmid=25589267 |year=2015 |last1=Bisschop |first1=P. H. |title=Autonomic regulation of hepatic glucose production |journal=Comprehensive Physiology |volume=5 |issue=1 |pages=147–165 |last2=Fliers |first2=E. |last3=Kalsbeek |first3=A.}}</ref> After food intake the blood sugar concentration increases. Values over 180&nbsp;mg/dL in venous whole blood are pathological and are termed [[hyperglycemia]], values below 40&nbsp;mg/dL are termed [[hypoglycaemia]].<ref>W. A. Scherbaum, B. M. Lobnig<!--: ''Abschnittstitel''.-->, In: Hans-Peter Wolff, Thomas R. Weihrauch: ''Internistische Therapie 2006, 2007''. 16th Edition. Elsevier, 2006, {{ISBN|3-437-23182-0}}, p.&nbsp;927, 985 {{in lang|de}}.</ref> When needed, glucose is released into the bloodstream by glucose-6-phosphatase from glucose-6-phosphate originating from liver and kidney glycogen, thereby regulating the [[homeostasis]] of blood glucose concentration.<ref name="Szablewski" /><ref name="Löffler/Petrides 195" /> In [[ruminant]]s, the blood glucose concentration is lower (60&nbsp;mg/dL in [[cattle]] and 40&nbsp;mg/dL in [[sheep]]), because the carbohydrates are converted more by their gut microbiota into [[short-chain fatty acid]]s.<ref name="Harper">Harold A. Harper: ''Medizinische Biochemie''. Springer-Verlag, 2013, {{ISBN|978-3-662-22150-1}}, p.&nbsp;294.</ref>

Some glucose is converted to [[lactic acid]] by [[astrocyte]]s, which is then utilized as an energy source by [[brain cells]]; some glucose is used by intestinal cells and [[red blood cell]]s, 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 [[Adipocyte|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.

As a result of its importance in human health, glucose is an analyte in [[glucose test]]s that are common medical [[blood test]]s.<ref>{{Cite journal |pmid=22872934 |year=2012 |last1=Clarke |first1=S. F. |title=A history of blood glucose meters and their role in self-monitoring of diabetes mellitus |journal=British Journal of Biomedical Science |volume=69 |issue=2 |pages=83–93 |last2=Foster |first2=J. R. |citeseerx=10.1.1.468.2196 |doi=10.1080/09674845.2012.12002443|s2cid=34263228 }}</ref> Eating or fasting prior to taking a blood sample has an effect on analyses for glucose in the blood; a high fasting glucose blood sugar level may be a sign of [[prediabetes]] or [[diabetes mellitus]].<ref>{{Cite web |url=http://www.diabetes.org/diabetes-basics/diagnosis/ |title=Diagnosing Diabetes and Learning About Prediabetes |website=American Diabetes Association |language=en |access-date=20 February 2018 |url-status=live |archive-url=https://web.archive.org/web/20170728020224/http://www.diabetes.org/diabetes-basics/diagnosis/ |archive-date=28 July 2017}}</ref>

The [[glycemic index]] is an indicator of the speed of resorption and conversion to blood glucose levels from ingested carbohydrates, measured as the [[area under a curve|area under the curve]] of blood glucose levels after consumption in comparison to glucose (glucose is defined as 100).<ref name="Harvey 366">Richard A. Harvey, Denise R. Ferrier: ''Biochemistry''. 5th Edition, Lippincott Williams & Wilkins, 2011, {{ISBN|978-1-608-31412-6}}, p.&nbsp;366.</ref> The clinical importance of the glycemic index is controversial,<ref name="Harvey 366" /><ref name="Satyarayana 508">U Satyanarayana: ''Biochemistry''. Elsevier Health Sciences, 2014, {{ISBN|978-8-131-23713-7}}, p.&nbsp;508.</ref> as foods with high fat contents slow the resorption of carbohydrates and lower the glycemic index, e.g. ice cream.<ref name="Satyarayana 508" /> An alternative indicator is the [[insulin index]],<ref>{{Cite journal |doi=10.1093/ajcn/66.5.1264 |pmid=9356547 |year=1997 |last1=Holt |first1=S. H. |title=An insulin index of foods: The insulin demand generated by 1000-kJ portions of common foods |journal=The American Journal of Clinical Nutrition |volume=66 |issue=5 |pages=1264–1276 |last2=Miller |first2=J. C. |last3=Petocz |first3=P. |doi-access=free}}</ref> measured as the impact of carbohydrate consumption on the blood insulin levels. The [[glycemic load]] is an indicator for the amount of glucose added to blood glucose levels after consumption, based on the glycemic index and the amount of consumed food.

===Precursor===
Organisms use glucose as a precursor for the synthesis of several important substances. Starch, [[cellulose]], and glycogen ("animal starch") are common glucose [[polymer]]s (polysaccharides). Some of these polymers (starch or glycogen) serve as energy stores, while others (cellulose and [[chitin]], which is made from a derivative of glucose) have structural roles. Oligosaccharides of glucose combined with other sugars serve as important energy stores. These include lactose, the predominant sugar in milk, which is a glucose-galactose disaccharide, and sucrose, another disaccharide which is composed of glucose and fructose. Glucose is also added onto certain proteins and [[lipid]]s in a process called [[glycosylation]]. This is often critical for their functioning. The enzymes that join glucose to other molecules usually use [[phosphorylation|phosphorylated]] glucose to power the formation of the new bond by coupling it with the breaking of the glucose-phosphate bond.

Other than its direct use as a monomer, glucose can be broken down to synthesize a wide variety of other biomolecules. This is important, as glucose serves both as a primary store of energy and as a source of organic carbon. Glucose can be broken down and converted into lipids. It is also a precursor for the synthesis of other important molecules such as [[vitamin C]] (ascorbic acid). In living organisms, glucose is converted to several other chemical compounds that are the starting material for various [[metabolic pathway]]s. Among them, all other monosaccharides<ref name="Löffler/Petrides 27">Peter C. Heinrich: ''Löffler/Petrides Biochemie und Pathobiochemie'' {{In lang|de}}. Springer-Verlag, 2014, {{ISBN|978-3-642-17972-3}}, p.&nbsp;27.</ref> such as fructose (via the [[polyol pathway]]),<ref name="Löffler/Petrides 199">Peter C. Heinrich: ''Löffler/Petrides Biochemie und Pathobiochemie'' {{In lang|de}}. Springer-Verlag, 2014, {{ISBN|978-3-642-17972-3}}, p.&nbsp;199, 200.</ref> mannose (the epimer of glucose at position 2), galactose (the epimer at position 4), fucose, various [[uronic acids]], and the [[amino sugar]]s are produced from glucose.<ref name="Löffler/Petrides 214">Peter C. Heinrich: ''Löffler/Petrides Biochemie und Pathobiochemie'' {{In lang|de}}. Springer-Verlag, 2014, {{ISBN|978-3-642-17972-3}}, p.&nbsp;214.</ref> In addition to the phosphorylation to glucose-6-phosphate, which is part of the glycolysis, glucose can be oxidized during its degradation to [[glucono-1,5-lactone]]. Glucose is used in some bacteria as a building block in the [[trehalose]] or the [[dextran]] biosynthesis and in animals as a building block of glycogen. Glucose can also be converted from bacterial [[xylose isomerase]] to fructose. In addition, glucose [[metabolite]]s produce all nonessential amino acids, [[sugar alcohol]]s such as [[mannitol]] and [[sorbitol]], [[fatty acid]]s, [[cholesterol]], and [[nucleic acid]]s.<ref name="Löffler/Petrides 27" /> Finally, glucose is used as a building block in the [[glycosylation]] of proteins to [[glycoprotein]]s, [[glycolipid]]s, [[peptidoglycan]]s, [[glycoside]]s, and other substances (catalyzed by [[glycosyltransferase]]s) and can be cleaved from them by [[glycosidase]]s.

=== Regulatory role in cell differentiation ===
In addition to its well-known function as a cellular energy source, glucose has been identified as a master regulator of tissue maturation.<ref>{{Cite web |title=Study reveals glucose's surprising role as master manipulator of tissue maturation |url=https://news.stanford.edu/stories/2025/03/glucose-tissue-regeneration-study-diabetes-cancer |access-date=2025-04-01 |website=news.stanford.edu |language=en}}</ref> A 2025 study by Stanford Medicine uncovered that glucose, in its intact (non-metabolized) form, can bind to various regulatory proteins involved in gene expression. One such protein is IRF6, which alters its conformation upon glucose binding, thereby influencing the expression of genes associated with stem cell differentiation. This regulatory role is independent of glucose's catabolic function and has been observed across multiple tissue types, including skin, bone, fat, and white blood cells. The research demonstrated that even glucose analogs incapable of metabolism could promote differentiation, suggesting a signaling function for glucose. These findings have potential implications in understanding and treating diseases characterized by impaired differentiation, such as diabetes and certain cancers.<ref>{{cite journal |last1=Lopez-Pajares |first1=Vanessa |last2=Khavari |first2=Paul A. |date=2025-03-21 |title=Glucose is a global regulator of tissue maturation independent of its metabolic role |url=https://med.stanford.edu/news/all-news/2025/03/glucose-tissue-regeneration.html |journal=Cell Stem Cell |publisher=Stanford University School of Medicine}}</ref>

==Pathology==
===Diabetes===
[[Diabetes]] is a metabolic disorder where the body is unable to regulate [[Blood sugar|levels of glucose in the blood]] either because of a lack of insulin in the body or the failure, by cells in the body, to respond properly to insulin. Each of these situations can be caused by persistently high elevations of blood glucose levels, through pancreatic burnout and [[insulin resistance]]. The [[pancreas]] is the organ responsible for the secretion of the hormones insulin and glucagon.<ref>{{cite journal | vauthors = Röder PV, Wu B, Liu Y, Han W | title = Pancreatic Regulation of Glucose Homeostasis | journal = Exp. Mol. Med. | volume = 48 | issue = 3, March  | pages = e219– | year = 2016 | pmid =  26964835| doi = 10.1038/emm.2016.6 | pmc = 4892884 }}</ref> Insulin is a hormone that regulates glucose levels, allowing the body's cells to absorb and use glucose. Without it, glucose cannot enter the cell and therefore cannot be used as fuel for the body's functions.<ref>Estela, Carlos (2011) "Blood Glucose Levels," Undergraduate Journal of Mathematical Modeling: One + Two: Vol. 3: Iss. 2, Article 12.</ref> If the pancreas is exposed to persistently high elevations of blood glucose levels, the [[beta cell|insulin-producing cells]] in the pancreas could be damaged, causing a lack of insulin in the body. Insulin resistance occurs when the pancreas tries to produce more and more insulin in response to persistently elevated blood glucose levels. Eventually, the rest of the body becomes resistant to the insulin that the pancreas is producing, thereby requiring more insulin to achieve the same blood glucose-lowering effect, and forcing the pancreas to produce even more insulin to compete with the resistance. This negative spiral contributes to pancreatic burnout, and the disease progression of diabetes.

To monitor the body's response to blood glucose-lowering therapy, glucose levels can be measured. [[Blood glucose monitoring]] can be performed by multiple methods, such as the fasting glucose test which measures the level of glucose in the blood after 8 hours of fasting. Another test is the 2-hour glucose tolerance test (GTT){{Snd}}for this test, the person has a fasting glucose test done, then drinks a 75-gram glucose drink and is retested. This test measures the ability of the person's body to process glucose. Over time the blood glucose levels should decrease as insulin allows it to be taken up by cells and exit the blood stream.

===Hypoglycemia management===
[[File:Soluţie glucoză 5%.jpg|thumb|right|220px|Glucose, 5% solution for [[Infusion therapy|infusion]]s]]
Individuals with diabetes or other conditions that result in [[hypoglycemia|low blood sugar]] often carry small amounts of sugar in various forms. One sugar commonly used is glucose, often in the form of glucose tablets (glucose pressed into a tablet shape sometimes with one or more other ingredients as a binder), [[hard candy]], or [[sugar packet]].

==Sources==
[[File:Glucose 2.jpg|thumb|Glucose tablets]]
Most dietary carbohydrates contain glucose, either as their only building block (as in the polysaccharides starch and glycogen), or together with another monosaccharide (as in the hetero-polysaccharides sucrose and lactose).<ref>{{Cite news|url=https://www.hsph.harvard.edu/nutritionsource/carbohydrates/carbohydrates-and-blood-sugar/|title=Carbohydrates and Blood Sugar|date=5 August 2013|newspaper=The Nutrition Source|language=en-US|access-date=30 January 2017|via=Harvard T.H. Chan School of Public Health|url-status=live|archive-url=https://web.archive.org/web/20170130010758/https://www.hsph.harvard.edu/nutritionsource/carbohydrates/carbohydrates-and-blood-sugar/|archive-date=30 January 2017}}</ref> Unbound glucose is one of the main ingredients of honey. Glucose is extremely abundant and has been isolated from a variety of natural sources across the world, including male cones of the coniferous tree ''Wollemia nobilis'' in Rome,<ref>{{cite journal |last1=Venditti |first1=Alessandro |last2=Frezza |first2=Claudio |last3=Vincenti |first3=Flaminia |last4=Brodella |first4=Antonia |last5=Sciubba |first5=Fabio |last6=Montesano |first6=Camilla |last7=Franceschin |first7=Marco |last8=Sergi |first8=Manuel |last9=Foddai |first9=Sebastiano |last10=Di Cocco |first10=Maria Enrica |last11=Curini |first11=Roberta |last12=Delfini |first12=Maurizio |last13=Bianco |first13=Armandodoriano |last14=Serafini |first14=Mauro |title=A syn-ent-labdadiene derivative with a rare spiro-β-lactone function from the male cones of Wollemia nobilis |journal=Phytochemistry |date=February 2019 |volume=158 |pages=91–95 |doi=10.1016/j.phytochem.2018.11.012 |pmid=30481664 |bibcode=2019PChem.158...91V }}</ref> the roots of ''Ilex asprella'' plants in China,<ref>{{cite journal |last1=Lei |first1=Yu |last2=Shi |first2=She-Po |last3=Song |first3=Yue-Lin |last4=Bi |first4=Dan |last5=Tu |first5=Peng-Fei |title=Triterpene Saponins from the Roots of Ilex asprella |journal=Chemistry & Biodiversity |date=May 2014 |volume=11 |issue=5 |pages=767–775 |doi=10.1002/cbdv.201300155 |pmid=24827686 }}</ref> and straws from rice in California.<ref>{{cite book |doi=10.1007/978-1-60761-214-8_5 |chapter=Lignocellulosic Biomass Pretreatment Using AFEX |title=Biofuels |series=Methods in Molecular Biology |date=2009 |volume=581 |pages=61–77 |pmid=19768616 |isbn=978-1-60761-213-1 | vauthors = Balan V, Bals B, Chundawat SP, Marshall D, Dale BE |publisher=Humana Press |location=Totowa, NJ }}</ref>

{|class="wikitable sortable" style="text-align:center; margin:auto"
|+ Sugar content of selected common plant foods (in grams per 100&nbsp;g)<ref name="www.nal.usda.gov">{{Cite web|url=https://fdc.nal.usda.gov/index.html|title=FoodData Central|website=fdc.nal.usda.gov|access-date=18 March 2024|archive-date=3 December 2019|archive-url=https://web.archive.org/web/20191203185131/https://fdc.nal.usda.gov/index.html|url-status=live}}</ref>
|-
! Food <br />item
! Carbohydrate, <br />total,{{efn|The carbohydrate value is calculated in the USDA database and does not always correspond to the sum of the sugars, the starch, and the "dietary fiber".}} including <br />[[dietary fiber]]
! Total <br />sugars
! Free <br />fructose
! Free <br />glucose
! Sucrose
! Ratio of <br />fructose/<br />glucose
! Sucrose as <br />proportion of <br />total sugars (%)
|-
!colspan=8 style="text-align:left"| Fruits
|-
| style="text-align:left;" | [[Apple]] || 13.8|| 10.4|| 5.9|| 2.4|| 2.1|| 2.0|| 19.9
|-
| style="text-align:left;" | [[Apricot]]|| 11.1|| 9.2|| 0.9|| 2.4|| 5.9|| 0.7|| 63.5
|-
| style="text-align:left;" | [[Banana]]|| 22.8|| 12.2|| 4.9|| 5.0|| 2.4|| 1.0|| 20.0
|-
| style="text-align:left;" | [[Ficus|Fig]], dried|| 63.9|| 47.9|| 22.9|| 24.8|| 0.9|| 0.93|| 0.15
|-
| style="text-align:left;" | [[Grape]]s|| 18.1|| 15.5|| 8.1|| 7.2|| 0.2|| 1.1|| 1
|-
| style="text-align:left;" | [[Navel orange]]|| 12.5|| 8.5|| 2.25|| 2.0|| 4.3|| 1.1|| 50.4
|-
| style="text-align:left;" | [[Peach]]|| 9.5|| 8.4|| 1.5|| 2.0|| 4.8|| 0.9|| 56.7
|-
| style="text-align:left;" | [[Pear]]|| 15.5|| 9.8|| 6.2|| 2.8|| 0.8|| 2.1|| 8.0
|-
| style="text-align:left;" | [[Pineapple]]|| 13.1|| 9.9|| 2.1|| 1.7|| 6.0|| 1.1|| 60.8
|-
| style="text-align:left;" | [[Plum]]|| 11.4|| 9.9|| 3.1|| 5.1|| 1.6|| 0.66|| 16.2
|-
!colspan=8 style="text-align:left"| Vegetables
|-
| style="text-align:left;" | [[Beet]], red|| 9.6|| 6.8|| 0.1|| 0.1|| 6.5||1.0|| 96.2
|-
| style="text-align:left;" | [[Carrot]]|| 9.6|| 4.7|| 0.6|| 0.6|| 3.6|| 1.0|| 77
|-
| style="text-align:left;" | [[Chili pepper|Red pepper]], sweet|| 6.0|| 4.2|| 2.3|| 1.9|| 0.0|| 1.2|| 0.0
|-
| style="text-align:left;" | [[Onion]], sweet|| 7.6|| 5.0|| 2.0|| 2.3|| 0.7|| 0.9|| 14.3
|-
| style="text-align:left;" | [[Sweet potato]]||20.1|| 4.2|| 0.7|| 1.0|| 2.5|| 0.9|| 60.3
|-
| style="text-align:left;" | [[Yam (vegetable)|Yam]]|| 27.9|| 0.5|| {{n/a|Traces}}|| {{n/a|Traces}}|| {{n/a|Traces}}|| {{n/a}}|| {{n/a|Traces}}
|-
| style="text-align:left;" | [[Sugar cane]]|| || 13–18|| 0.2–1.0|| 0.2–1.0|| 11–16|| 1.0|| high
|-
| style="text-align:left;" | [[Sugar beet]]|| || 17–18|| 0.1–0.5|| 0.1–0.5|| 16–17|| 1.0|| high
|-
!colspan=8 style="text-align:left"| Grains
|-
| style="text-align:left;" | [[Maize|Corn]], sweet|| 19.0|| 6.2|| 1.9|| 3.4|| 0.9|| 0.61|| 15.0
|}
{{notelist}}

==Commercial production==
[[File:Ministry of Information First World War Official Collection Q28219.jpg|thumb|Glucose production from starch, 1918]]
Glucose is produced industrially from starch by [[enzyme|enzymatic]] [[hydrolysis]] using [[glucose amylase]] or by the use of [[acids]]. Enzymatic hydrolysis has largely displaced acid-catalyzed hydrolysis reactions.<ref name="Fellows">P. J. Fellows: ''Food Processing Technology. Woodhead Publishing'', 2016, {{ISBN|978-0-081-00523-1}}, p. 197.</ref> The result is glucose syrup (enzymatically with more than 90% glucose in the dry matter)<ref name="Fellows" /> with an annual worldwide production volume of 20 million tonnes (as of 2011).<ref name="Ullmann 48">Thomas Becker, Dietmar Breithaupt, Horst Werner Doelle, Armin Fiechter, Günther Schlegel, Sakayu Shimizu, Hideaki Yamada: ''Biotechnology'', in: ''Ullmann's Encyclopedia of Industrial Chemistry'', 7th Edition, Wiley-VCH, 2011. {{ISBN|978-3-527-32943-4}}. Volume 6, p. 48.</ref> This is the reason for the former common name "starch sugar". The amylases most often come from ''[[Bacillus licheniformis]]''<ref name="ResSoc">The Amylase Research Society of Japan: ''Handbook of Amylases and Related Enzymes''. Elsevier, 2014, {{ISBN|978-1-483-29939-6}}, p.&nbsp;195.</ref> or ''[[Bacillus subtilis]]'' (strain MN-385),<ref name="ResSoc" /> which are more thermostable than the originally used enzymes.<ref name="ResSoc" /><ref name="Madsen">{{Cite journal |doi=10.1002/star.19730250906 |title=A New, Heat Stable Bacterial Amylase and its Use in High Temperature Liquefaction |journal=Starch - Stärke |volume=25 |issue=9 |pages=304–308 |year=1973 |last1=Madsen |first1=G. B. |last2=Norman |first2=B. E. |last3=Slott |first3=S.}}</ref> Starting in 1982, [[pullulanase]]s from ''[[Aspergillus niger]]'' were used in the production of glucose syrup to convert amylopectin to starch (amylose), thereby increasing the yield of glucose.<ref name="Norman">{{Cite journal |doi=10.1002/star.19820341005 |title=A Novel Debranching Enzyme for Application in the Glucose Syrup Industry |journal=Starch - Stärke |volume=34 |issue=10 |pages=340–346 |year=1982 |last1=Norman |first1=B. E.}}</ref> The reaction is carried out at a pH = 4.6–5.2 and a temperature of 55–60&nbsp;°C.<ref name="Encyclopedia of Food and Health" /> [[Corn syrup]] has between 20% and 95% glucose in the dry matter.<ref>{{cite book | author = James N. BeMiller, Roy L. Whistler | year = 2009 | title = Starch: Chemistry and Technology | series = Food Science and Technology | edition = 3rd | location = New York | publisher = Academic Press | isbn = 978-0-08-092655-1 | url = https://books.google.com/books?isbn=008092655X }}</ref><ref>{{cite book |editor= BeMiller, James N. |editor2=Whistler, Roy L. | year = 2009 | title = Starch: Chemistry and Technology | series = Food Science and Technology | edition = 3rd | location = New York | publisher = Academic Press | isbn = 978-0-08-092655-1 | url = https://books.google.com/books?isbn=008092655X | access-date = 25 November 2016 }}</ref> The Japanese form of the glucose syrup, [[Mizuame]], is made from [[sweet potato]] or [[rice]] starch.<ref>Alan Davidson: ''Oxford Companion to Food'' (1999). "Mizuame", p.&nbsp;510 {{ISBN|0-19-211579-0}}.</ref>

Many crops can be used as the source of starch. [[Maize]],<ref name="Fellows" /> rice,<ref name="Fellows" /> [[wheat]],<ref name="Fellows" /> [[cassava]],<ref name="Fellows" /> [[potato]],<ref name="Fellows" /> [[barley]],<ref name="Fellows" /> sweet potato,<ref name="Davidson">Alan Davidson: ''The Oxford Companion to Food''. OUP Oxford, 2014, {{ISBN|978-0-191-04072-6}}, p.&nbsp;527.</ref> [[corn husk]] and [[sago]] are all used in various parts of the world. In the [[United States]], [[corn starch]] (from maize) is used almost exclusively. Some commercial glucose occurs as a component of [[invert sugar]], a roughly 1:1 mixture of glucose and fructose that is produced from sucrose. In principle, cellulose could be hydrolyzed to glucose, but this process is not yet commercially practical.<ref name="Ullmann" />

===Conversion to fructose===
{{main|isoglucose}}
In the US, almost exclusively corn{{citation needed|date=August 2025}} (more precisely, corn syrup) is used as glucose source for the production of [[isoglucose]], which is a mixture of glucose and fructose, since fructose has a higher sweetening power{{Snd}}with same physiological calorific value of 374 kilocalories per 100 g.{{citation needed|date=August 2025}} The annual world production of isoglucose is 8 million tonnes (as of 2011).<ref name="Ullmann 48" /> When made from corn syrup, the final product is [[high-fructose corn syrup]] (HFCS).

==Commercial usage==
[[File:Relativesweetness.svg|thumb|class=skin-invert-image|Relative sweetness of various sugars in comparison with sucrose<ref>{{cite web
| url = http://food.oregonstate.edu/learn/sugar.html
| url-status = dead
| access-date = 28 June 2018
| archive-date = 18 July 2011
| archive-url = https://web.archive.org/web/20110718233541/http://food.oregonstate.edu/learn/sugar.html
| website = food.oregonstate.edu
| title = Sugar
| department = Learning, Food Resources
| publisher = [[Oregon State University]], Corvallis, OR
| date = 23 May 2012
}}</ref>]]
Glucose is mainly used for the production of fructose and of glucose-containing foods. In foods, it is used as a sweetener, [[humectant]], to increase the [[volume]] and to create a softer [[mouthfeel]].<ref name="Fellows" /> Various sources of glucose, such as grape juice (for wine) or malt (for beer), are used for fermentation to ethanol during the production of [[alcoholic beverage]]s. Most soft drinks in the US use HFCS-55 (with a fructose content of 55% in the dry mass), while most other HFCS-sweetened foods in the US use HFCS-42 (with a fructose content of 42% in the dry mass).<ref name="fda2014">{{cite web |url=https://www.fda.gov/food/food-additives-petitions/high-fructose-corn-syrup-questions-and-answers |title=High Fructose Corn Syrup: Questions and Answers |publisher=US Food and Drug Administration |date=5 November 2014 |access-date=18 December 2017 |url-status=live |archive-url=https://web.archive.org/web/20180125013538/https://www.fda.gov/Food/IngredientsPackagingLabeling/FoodAdditivesIngredients/ucm324856.htm |archive-date=25 January 2018}}</ref> In Mexico, on the other hand, soft drinks are sweetened by cane sugar, which has a higher sweetening power.<ref>Kevin Pang: "[https://web.archive.org/web/20110629002034/http://seattletimes.nwsource.com/html/nationworld/2002076071_coke29.html Mexican Coke a Hit in U.S.]" In: ''[[Seattle Times]]'', 29 October 2004.</ref> In addition, glucose syrup is used, inter alia, in the production of [[confectionery]] such as [[candy|candies]], [[toffee]], and [[fondant icing|fondant]].<ref name="Beckett">Steve T. Beckett: ''Beckett's Industrial Chocolate Manufacture and Use''. John Wiley & Sons, 2017, {{ISBN|978-1-118-78014-5}}, p.&nbsp;82.</ref> Typical chemical reactions of glucose when heated under water-free conditions are [[caramelization]] and, in presence of amino acids, the [[Maillard reaction]].

In addition, various organic acids can be biotechnologically produced from glucose, for example by fermentation with ''[[Clostridium thermoaceticum]]'' to produce [[acetic acid]], with ''[[Penicillium notatum]]'' for the production of [[araboascorbic acid]], with ''[[Rhizopus delemar]]'' for the production of [[fumaric acid]], with ''[[Aspergillus niger]]'' for the production of [[gluconic acid]], with ''[[Candida brumptii]]'' to produce [[isocitric acid]], with ''[[Aspergillus terreus]]'' for the production of [[itaconic acid]], with ''[[Pseudomonas fluorescens]]'' for the production of [[2-ketogluconic acid]], with ''[[Gluconobacter suboxydans]]'' for the production of [[5-ketogluconic acid]], with ''[[Aspergillus oryzae]]'' for the production of [[kojic acid]], with ''[[Lactobacillus delbrueckii]]'' for the production of [[lactic acid]], with ''[[Lactobacillus brevis]]'' for the production of [[malic acid]], with ''[[Propionibacter shermanii]]'' for the production of [[propionic acid]], with ''[[Pseudomonas aeruginosa]]'' for the production of [[pyruvic acid]] and with ''[[Gluconobacter suboxydans]]'' for the production of [[tartaric acid]].<ref name="Kent">James A. Kent: ''Riegel's Handbook of Industrial Chemistry''. Springer Science & Business Media, 2013, {{ISBN|978-1-475-76431-4}}, p.&nbsp;938.</ref>{{additional citation needed|date=April 2022}} Potent, bioactive natural products like triptolide that inhibit mammalian transcription via inhibition of the XPB subunit of the general transcription factor TFIIH has been recently reported as a glucose conjugate for targeting hypoxic cancer cells with increased glucose transporter expression.<ref>{{cite journal | journal = iScience | title = A Glucose-Triptolide Conjugate Selectively Targets Cancer Cells under Hypoxia | volume = 23 | issue = 9 | year = 2020 |vauthors=Datan E, Minn I, Peng X, He QL, Ahn H, Yu B, Pomper MG, Liu JO | article-number = 101536 | pmid = 33083765 | doi=10.1016/j.isci.2020.101536| pmc = 7509213 | bibcode = 2020iSci...23j1536D }}</ref> Recently, glucose has been gaining commercial use as a key component of "kits" containing lactic acid and insulin intended to induce hypoglycemia and hyperlactatemia to combat different cancers and infections.<ref>{{Cite journal|last1=Goodwin|first1=Matthew L.|last2=Gladden|first2=L. Bruce|last3=Nijsten|first3=Maarten W. N.|date=3 September 2020|title=Lactate-Protected Hypoglycemia (LPH)|journal=Frontiers in Neuroscience|volume=14|article-number=920|doi=10.3389/fnins.2020.00920|pmid=33013305|pmc=7497796|issn=1662-453X|doi-access=free}}</ref>

==Analysis==
When a glucose molecule is to be detected at a certain position in a larger molecule, [[nuclear magnetic resonance spectroscopy]], [[X-ray crystallography]] analysis or [[lectin]] [[immunostaining]] is performed with [[concanavalin A]] reporter enzyme conjugate, which binds only glucose or mannose.

===Classical qualitative detection reactions===
These reactions have only historical significance:

====Fehling test====
The [[Fehling test]] is a classic method for the detection of aldoses.<ref name="Fehling-Harn">H. Fehling: ''Quantitative Bestimmung des Zuckers im Harn''. In: ''[[Archiv für physiologische Heilkunde]]'' (1848), volume 7, p.&nbsp;64–73 (in German).</ref> Due to mutarotation, glucose is always present to a small extent as an open-chain aldehyde. By adding the Fehling reagents (Fehling (I) solution and Fehling (II) solution), the aldehyde group is oxidized to a [[carboxylic acid]], while the Cu<sup>2+</sup> tartrate complex is reduced to Cu<sup>+</sup> and forms a brick red precipitate (Cu<sub>2</sub>O).

====Tollens test====
In the [[Tollens test]], after addition of ammoniacal [[Silver nitrate|AgNO<sub>3</sub>]] to the sample solution, glucose reduces Ag<sup>+</sup> to elemental [[silver]].<ref>B. Tollens: [https://babel.hathitrust.org/cgi/pt?id=uiug.30112025692838;view=1up;seq=535 ''Über ammon-alkalische Silberlösung als Reagens auf Aldehyd''] {{Webarchive|url=https://web.archive.org/web/20220219063751/https://babel.hathitrust.org/cgi/pt?id=uiug.30112025692838;view=1up;seq=535 |date=19 February 2022 }}. In ''[[Berichte der Deutschen Chemischen Gesellschaft]]'' (1882), volume 15, p. 1635–1639 (in German).</ref>

====Barfoed test====
In [[Barfoed's test]],<ref name="barfoed">{{Cite journal |doi=10.1007/BF01462957 |title=Ueber die Nachweisung des Traubenzuckers neben Dextrin und verwandten Körpern |language=de |journal=Zeitschrift für Analytische Chemie |volume=12 |pages=27–32 |year=1873 |last1=Barfoed |first1=C. |issue=1 |s2cid=95749674 |url=https://zenodo.org/record/1594255 |access-date=1 July 2019 |archive-date=29 July 2020 |archive-url=https://web.archive.org/web/20200729234027/https://zenodo.org/record/1594255 |url-status=live }}</ref> a solution of dissolved [[copper acetate]], [[sodium acetate]], and acetic acid is added to the solution of the sugar to be tested and subsequently heated in a water bath for a few minutes. Glucose and other monosaccharides rapidly produce a reddish color and reddish brown [[copper(I) oxide]] (Cu<sub>2</sub>O).

====Nylander's test====
As a reducing sugar, glucose reacts in the [[Nylander's test]].<ref>Emil Nylander: ''Über alkalische Wismuthlösung als Reagens auf Traubenzucker im Harne'', [[Zeitschrift für physiologische Chemie]]. Volume 8, Issue 3, 1884, p.&nbsp;175–185 [http://www.degruyter.com/dg/viewarticle/j$002fbchm1.1884.8.issue-3$002fbchm1.1884.8.3.175$002fbchm1.1884.8.3.175.xml Abstract]. {{Webarchive|url=https://web.archive.org/web/20150923213720/http://www.degruyter.com/dg/viewarticle/j$002fbchm1.1884.8.issue-3$002fbchm1.1884.8.3.175$002fbchm1.1884.8.3.175.xml |date=23 September 2015 }} (in German).</ref>

====Other tests====
{{See also|Maillard reaction|Lye roll}}
Upon heating a dilute [[potassium hydroxide]] solution with glucose to 100&nbsp;°C, a strong reddish browning and a caramel-like odor develops.<ref name="Schwedt 102">Georg Schwedt: ''Zuckersüße Chemie''. John Wiley & Sons, 2012, {{ISBN|978-3-527-66001-8}}, p.&nbsp;102 (in German).</ref> Concentrated [[sulfuric acid]] dissolves dry glucose without blackening at room temperature forming sugar sulfuric acid.<ref name="Schwedt 102" />{{Verify source|date=April 2022}} In a yeast solution, alcoholic fermentation produces carbon dioxide in the ratio of 2.0454 molecules of glucose to one molecule of [[Carbon dioxide|CO<sub>2</sub>]].<ref name="Schwedt 102" /> Glucose forms a black mass with [[stannous chloride]].<ref name="Schwedt 102" /> In an ammoniacal silver solution, glucose (as well as lactose and dextrin) leads to the deposition of silver. In an ammoniacal [[lead acetate]] solution, white [[lead glycoside]] is formed in the presence of glucose, which becomes less soluble on cooking and turns brown.<ref name="Schwedt 102" /> In an ammoniacal copper solution, yellow [[copper oxide]] hydrate is formed with glucose at room temperature, while red copper oxide is formed during boiling (same with dextrin, except for with an ammoniacal copper acetate solution).<ref name="Schwedt 102" /> With [[Picric acid|Hager's reagent]], glucose forms [[mercury oxide]] during boiling.<ref name="Schwedt 102" /> An alkaline [[bismuth]] solution is used to precipitate elemental, black-brown bismuth with glucose.<ref name="Schwedt 102" /> Glucose boiled in an [[ammonium molybdate]] solution turns the solution blue. A solution with [[indigo carmine]] and [[sodium carbonate]] destains when boiled with glucose.<ref name="Schwedt 102" />

===Instrumental quantification===
====Refractometry and polarimetry====
In concentrated solutions of glucose with a low proportion of other carbohydrates, its concentration can be determined with a polarimeter. For sugar mixtures, the concentration can be determined with a [[refractometer]], for example in the [[Oechsle scale|Oechsle]] determination in the course of the production of wine.

====Photometric enzymatic methods in solution====
{{main|Glucose oxidation reaction}}
The enzyme glucose oxidase (GOx) converts glucose into gluconic acid and hydrogen peroxide while consuming oxygen. Another enzyme, peroxidase, catalyzes a chromogenic reaction (Trinder reaction)<ref>{{Cite journal |doi=10.1177/000456326900600108 |title=Determination of Glucose in Blood Using Glucose Oxidase with an Alternative Oxygen Acceptor |journal=Annals of Clinical Biochemistry |volume=6 |pages=24–27 |year=1969 |last1=Trinder |first1=P. |issue=1 |s2cid=58131350 |doi-access=free }}</ref> of [[phenol]] with [[4-Aminoantipyrine|4-aminoantipyrine]] to a purple dye.<ref name="purpuled">{{cite book |doi=10.1016/bs.pmbts.2019.01.004 |chapter=Fasting blood glucose levels in patients with different types of diseases |title=Glycans and Glycosaminoglycans as Clinical Biomarkers and Therapeutics - Part A |series=Progress in Molecular Biology and Translational Science |date=2019 |volume=162 |pages=277–292 |isbn=978-0-12-817738-9 | vauthors = Zhang Q, Zhao G, Yang N, Zhang L |publisher=Elsevier |pmid=30905457 }}</ref>

====Photometric test-strip method====
The test-strip method employs the above-mentioned enzymatic conversion of glucose to gluconic acid to form hydrogen peroxide. The reagents are immobilised on a polymer matrix, the so-called test strip, which assumes a more or less intense color. This can be measured reflectometrically at 510&nbsp;nm with the aid of an LED-based handheld photometer. This allows routine blood sugar determination by nonscientists. In addition to the reaction of phenol with 4-aminoantipyrine, new chromogenic reactions have been developed that allow photometry at higher wavelengths (550&nbsp;nm, 750&nbsp;nm).<ref name="purpuled"/><ref>{{Cite journal |doi=10.1039/A709038B |title=Water-soluble chromogenic reagent for colorimetric detection of hydrogen peroxide—an alternative to 4-aminoantipyrine working at a long wavelength |journal=Analytical Communications |volume=35 |issue=2 |pages=71–74 |year=1998 |last1=Mizoguchi |first1=Makoto |last2=Ishiyama |first2=Munetaka |last3=Shiga |first3=Masanobu}}</ref>

====Amperometric glucose sensor====
The electroanalysis of glucose is also based on the enzymatic reaction mentioned above. The produced hydrogen peroxide can be amperometrically quantified by anodic oxidation at a potential of 600 mV.<ref>{{Cite journal |pmid=18154363 |year=2008 |last1=Wang |first1=J. |title=Electrochemical glucose biosensors |journal=Chemical Reviews |volume=108 |issue=2 |pages=814–825 |doi=10.1021/cr068123a}}.</ref> The GOx is immobilized on the electrode surface or in a membrane placed close to the electrode. Precious metals such as platinum or gold are used in electrodes, as well as carbon nanotube electrodes, which e.g. are doped with boron.<ref>{{Cite journal |doi=10.1016/j.talanta.2008.04.023 |pmid=18656655 |year=2008 |last1=Chen |first1=X. |title=Amperometric glucose biosensor based on boron-doped carbon nanotubes modified electrode |journal=Talanta |volume=76 |issue=4 |pages=763–767 |last2=Chen |first2=J. |last3=Deng |first3=C. |last4=Xiao |first4=C. |last5=Yang |first5=Y. |last6=Nie |first6=Z. |last7=Yao |first7=S.}}</ref> Cu–CuO nanowires are also used as enzyme-free amperometric electrodes, reaching a detection limit of 50&nbsp;μmol/L.<ref>{{Cite journal |doi=10.1007/s00604-009-0260-1 |title=Enzyme-free amperometric sensing of glucose using Cu-CuO nanowire composites |journal=Microchimica Acta |volume=168 |issue=1–2 |pages=87–92 |year=2010 |last1=Wang |first1=Guangfeng |last2=Wei |first2=Yan |last3=Zhang |first3=Wei |last4=Zhang |first4=Xiaojun |last5=Fang |first5=Bin |last6=Wang |first6=Lun |s2cid=98567636 }}</ref> A particularly promising method is the so-called "enzyme wiring", where the electron flowing during the oxidation is transferred via a molecular wire directly from the enzyme to the electrode.<ref>{{Cite journal |doi=10.1021/ac00087a008 |pmid=8092486 |year=1994 |last1=Ohara |first1=T. J. |title="Wired" enzyme electrodes for amperometric determination of glucose or lactate in the presence of interfering substances |journal=Analytical Chemistry |volume=66 |issue=15 |pages=2451–2457 |last2=Rajagopalan |first2=R. |last3=Heller |first3=A. |bibcode=1994AnaCh..66.2451O }}</ref>

====Other sensory methods====
There are a variety of other chemical sensors for measuring glucose.<ref name="Borisov">{{Cite journal |doi=10.1021/cr068105t |pmid=18229952 |year=2008 |last1=Borisov |first1=S. M. |title=Optical biosensors |journal=Chemical Reviews |volume=108 |issue=2 |pages=423–461 |last2=Wolfbeis |first2=O. S.}}</ref><ref>{{Cite journal |doi=10.1177/193229681100500507 |pmc=3208862 |pmid=22027299 |year=2011 |last1=Ferri |first1=S. |title=Review of glucose oxidases and glucose dehydrogenases: A bird's eye view of glucose sensing enzymes |journal=Journal of Diabetes Science and Technology |volume=5 |issue=5 |pages=1068–76 |last2=Kojima |first2=K. |last3=Sode |first3=K. }}</ref> Given the importance of glucose analysis in the life sciences, numerous optical probes have also been developed for saccharides based on the use of boronic acids,<ref>{{Cite journal |doi=10.1007/s00604-008-0947-8 |title=Boronic acid based probes for microdetermination of saccharides and glycosylated biomolecules |journal=Microchimica Acta |volume=162 |issue=1–2 |pages=1–34 |year=2008 |last1=Mader |first1=Heike S. |last2=Wolfbeis |first2=Otto S. |s2cid=96768832 }}</ref> which are particularly useful for intracellular sensory applications where other (optical) methods are not or only conditionally usable. In addition to the organic boronic acid derivatives, which often bind highly specifically to the 1,2-diol groups of sugars, there are also other probe concepts classified by functional mechanisms which use selective glucose-binding proteins (e.g. concanavalin A) as a receptor. Furthermore, methods were developed which indirectly detect the glucose concentration via the concentration of metabolized products, e.g. by the consumption of oxygen using fluorescence-optical sensors.<ref>{{Cite journal |doi=10.1016/S0956-5663(99)00073-1 |pmid=10826645 |title=Sol–gel based glucose biosensors employing optical oxygen transducers, and a method for compensating for variable oxygen background |journal=Biosensors and Bioelectronics |volume=15 |issue=1–2 |pages=69–76 |year=2000 |last1=Wolfbeis |first1=Otto S. |last2=Oehme |first2=Ines |last3=Papkovskaya |first3=Natalya |last4=Klimant |first4=Ingo}}</ref> Finally, there are enzyme-based concepts that use the intrinsic absorbance or fluorescence of (fluorescence-labeled) enzymes as reporters.<ref name="Borisov" />

====Copper iodometry====
Glucose can be quantified by copper iodometry.<ref name="Galant">{{Cite journal |doi=10.1016/j.foodchem.2015.04.071 |pmid=26041177 |year=2015 |last1=Galant |first1=A. L. |title=Glucose: Detection and analysis |journal=Food Chemistry |volume=188 |pages=149–160 |last2=Kaufman |first2=R. C. |last3=Wilson |first3=J. D.}}</ref>

===Chromatographic methods===
In particular, for the analysis of complex mixtures containing glucose, e.g. in honey, chromatographic methods such as [[high performance liquid chromatography]] and [[gas chromatography]]<ref name="Galant" /> are often used in combination with [[mass spectrometry]].<ref>{{cite journal | last1 = Sanz | first1 = M. L. | last2 = Sanz | first2 = J. | last3 = Martínez-Castro | first3 = I. | year = 2004| title = Gas chromatographic-mass spectrometric method for the qualitative and quantitative determination of disaccharides and trisaccharides in honey. | journal = [[Journal of Chromatography A]] | volume = 1059 | issue = 1–2| pages = 143–148 | pmid = 15628134 | doi = 10.1016/j.chroma.2004.09.095 }}</ref><ref name="mpg-210190">{{cite web|title=Glucose mass spectrum|periodical=Golm Metabolome Database|url=http://gmd.mpimp-golm.mpg.de/Spectrums/8dee81a1-8d98-4a73-b55d-9de42f10e190.aspx|access-date=4 June 2018|last=[[Max Planck Institute of Molecular Plant Physiology]] in Golm Database|date=19 July 2007|archive-url=https://web.archive.org/web/20180909000409/http://gmd.mpimp-golm.mpg.de/Spectrums/8dee81a1-8d98-4a73-b55d-9de42f10e190.aspx|archive-date=9 September 2018|url-status=live}}</ref> Taking into account the isotope ratios, it is also possible to reliably detect honey adulteration by added sugars with these methods.<ref>{{cite journal | last1 = Cabañero | first1 = A. I. | last2 = Recio | first2 = J. L. | last3 = Rupérez | first3 = M. | year = 2006| title = Liquid chromatography coupled to isotope ratio mass spectrometry: a new perspective on honey adulteration detection. | journal = [[J Agric Food Chem]] | volume = 54 | issue = 26| pages = 9719–9727 | pmid = 17177492 | doi = 10.1021/jf062067x | bibcode = 2006JAFC...54.9719C }}</ref> Derivatization using silylation reagents is commonly used.<ref>{{Cite journal |pmid=24054643|year=2013|last1=Becker|first1=M.|title=Ethoximation-silylation approach for mono- and disaccharide analysis and characterization of their identification parameters by GC/MS|journal=Talanta|volume=115|pages=642–51|last2=Liebner|first2=F.|last3=Rosenau|first3=T.|last4=Potthast|first4=A.|doi=10.1016/j.talanta.2013.05.052}}</ref> Also, the proportions of di- and trisaccharides can be quantified.

====In vivo analysis====
Glucose uptake in cells of organisms is measured with [[2-deoxy-D-glucose]] or [[fluorodeoxyglucose]].<ref name="Dwyer">Donard Dwyer: ''Glucose Metabolism in the Brain''. Academic Press, 2002, {{ISBN|978-0-123-66852-3}}, p.&nbsp;XIII.</ref> (<sup>18</sup>F)fluorodeoxyglucose is used as a tracer in [[positron emission tomography]] in oncology and neurology,<ref name="gdch">[[Gesellschaft Deutscher Chemiker]]: [http://www.gdch.de/strukturen/fg/nuklear/posi2.pdf wayback=20100331071121 ''Anlagen zum Positionspapier der Fachgruppe Nuklearchemie''] {{Webarchive|url=https://web.archive.org/web/20100331071121/http://www.gdch.de/strukturen/fg/nuklear/posi2.pdf |date=31 March 2010 }}, February 2000.</ref> where it is by far the most commonly used diagnostic agent.<ref>{{Cite journal |doi=10.1155/2014/214748 |pmc=4058687 |pmid=24991541|year=2014 |last1=Maschauer |first1=S. |title=Sweetening pharmaceutical radiochemistry by (18)f-fluoroglycosylation: A short review |journal=BioMed Research International |volume=2014 |pages=1–16 |last2=Prante |first2=O. |doi-access=free }}</ref>

==References==
{{Reflist}}

== External links ==
* {{Commons category-inline|Glucose}}

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