Bicarbonate
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| Names | |
|---|---|
| IUPAC name
Hydrogencarbonate
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| Systematic IUPAC name
Hydroxidodioxidocarbonate(1−)[1] | |
Other names
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| Identifiers | |
3D model (JSmol)
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| 3DMet | |
| 3903504 | |
| ChEBI | |
| ChEMBL | |
| ChemSpider | |
| 49249 | |
| KEGG | |
PubChemCID
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| UNII | |
CompTox Dashboard(EPA)
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| Properties | |
| HCO− 3 | |
| Molar mass | 61.0168 g mol−1 |
| logP | −0.82 |
| Acidity(pKa) | 10.3 |
| Basicity(pKb) | 7.7 |
| Conjugate acid | Carbonic acid |
| Conjugate base | Carbonate |
Except where otherwise noted, data are given for materials in theirstandard state(at 25 °C [77 °F], 100 kPa).
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Ininorganic chemistry,bicarbonate(IUPAC-recommended nomenclature:hydrogencarbonate[2]) is an intermediate form in thedeprotonationofcarbonic acid.It is apolyatomicanionwith the chemical formulaHCO−
3.
Bicarbonate serves a crucial biochemical role in the physiologicalpHbufferingsystem.[3]
The term "bicarbonate" wascoinedin 1814 by the English chemistWilliam Hyde Wollaston.[4][5]The name lives on as atrivial name.
Chemical properties
[edit]The bicarbonate ion (hydrogencarbonate ion) is ananionwith theempirical formulaHCO−
3and a molecular mass of 61.01daltons;it consists of one central carbonatomsurrounded by three oxygen atoms in atrigonal planararrangement, with a hydrogen atom attached to one of the oxygens. It isisoelectronicwithnitric acidHNO
3.The bicarbonate ion carries a negative oneformal chargeand is anamphiproticspecies which has both acidic and basic properties. It is both theconjugate baseofcarbonic acidH
2CO
3;and theconjugate acidofCO2−
3,thecarbonateion, as shown by theseequilibriumreactions:
- CO2−
3+ 2 H2O ⇌HCO−
3+ H2O + OH−⇌ H2CO3+ 2 OH−
- H2CO3+ 2 H2O ⇌HCO−
3+ H3O++ H2O ⇌CO2−
3+ 2 H3O+.
A bicarbonate salt forms when apositively charged ionattaches to the negatively charged oxygen atoms of the ion, forming anionic compound.Many bicarbonates aresolubleinwateratstandard temperature and pressure;in particular, sodium bicarbonate contributes tototal dissolved solids,a common parameter for assessingwater quality.[6]
Physiological role
[edit]
Bicarbonate (HCO−
3) is a vital component of thepHbuffering system[3]of the human body (maintainingacid–base homeostasis). 70%–75% of CO2in the body is converted intocarbonic acid(H2CO3), which is theconjugate acidofHCO−
3and can quickly turn into it.[citation needed]
With carbonic acid as thecentral intermediatespecies,bicarbonate – in conjunction with water,hydrogen ions,andcarbon dioxide– forms this buffering system, which is maintained at the volatile equilibrium[3]required to provide prompt resistance to pH changes in both the acidic andbasicdirections. This is especially important for protectingtissuesof thecentral nervous system,where pH changes too far outside of the normal range in either direction could prove disastrous (seeacidosisoralkalosis). Recently it has been also demonstrated that cellular bicarbonate metabolism can be regulated by mTORC1 signaling.[7]
Additionally, bicarbonate plays a key role in the digestive system. It raises the internal pH of the stomach, after highly acidic digestive juices have finished in their digestion of food. Bicarbonate also acts to regulate pH in the small intestine. It is released from thepancreasin response to the hormonesecretinto neutralize the acidicchymeentering theduodenumfrom the stomach.[8]
Bicarbonate in the environment
[edit]Bicarbonate is the dominant form ofdissolved inorganic carbonin sea water,[9]and in most fresh waters. As such it is an important sink in thecarbon cycle.
Some plants likeCharautilize carbonate and produce calcium carbonate (CaCO3) as result of biological metabolism.[10]
In freshwater ecology, strongphotosyntheticactivity by freshwater plants in daylight releases gaseousoxygeninto the water and at the same time produces bicarbonate ions. These shift the pH upward until in certain circumstances the degree of alkalinity can become toxic to some organisms or can make other chemical constituents such asammoniatoxic. In darkness, when no photosynthesis occurs, respiration processes release carbon dioxide, and no new bicarbonate ions are produced, resulting in a rapid fall in pH.[citation needed]
The flow of bicarbonate ions from rocks weathered by the carbonic acid in rainwater is an important part of thecarbon cycle.
Other uses
[edit]The most common salt of the bicarbonate ion issodium bicarbonate,NaHCO3,which is commonly known asbaking soda.When heated or exposed to anacidsuch asacetic acid(vinegar), sodium bicarbonate releasescarbon dioxide.This is used as aleavening agentinbaking.[citation needed]
Ammonium bicarbonateis used indigestive biscuitmanufacture.[citation needed]
Diagnostics
[edit]Indiagnostic medicine,theblood valueof bicarbonate is one of several indicators of the state ofacid–base physiologyin the body. It is measured, along withchloride,potassium,andsodium,to assesselectrolytelevels in anelectrolyte paneltest (which hasCurrent Procedural Terminology,CPT, code 80051).[citation needed]
The parameterstandard bicarbonate concentration(SBCe) is the bicarbonate concentration in the blood at aPaCO2of 40 mmHg (5.33 kPa), full oxygen saturation and 36 °C.[11]
Bicarbonate compounds
[edit]- Sodium bicarbonate
- Potassium bicarbonate
- Caesium bicarbonate
- Magnesium bicarbonate
- Calcium bicarbonate
- Ammonium bicarbonate
- Carbonic acid
See also
[edit]References
[edit]- ^ab"hydrogencarbonate (CHEBI:17544)".Chemical Entities of Biological Interest (ChEBI).UK: European Institute of Bioinformatics. IUPAC Names.Archivedfrom the original on 7 June 2015.
- ^Nomenclature of Inorganic Chemistry IUPAC Recommendations 2005(PDF),IUPAC, p. 137
- ^abc"Clinical correlates of pH levels: bicarbonate as a buffer".Biology.arizona.edu. October 2006.Archivedfrom the original on 31 May 2015.
- ^William Hyde Wollaston (1814) "A synoptic scale of chemical equivalents",Philosophical Transactions of the Royal Society,104:1-22.On page 11,Wollaston coins the term "bicarbonate": "The next question that occurs relates to the composition of this crystallized carbonate of potash, which I am induced to call bi-carbonate of potash, for the purpose of marking more decidedly the distinction between this salt and that which is commonly called a subcarbonate, and in order to refer at once to the double dose of carbonic acid contained in it."
- ^"Baking Soda".Newton – Ask a Scientist.Argonne National Laboratory.Archived fromthe originalon 26 February 2015.Retrieved2 May2018.
- ^Geor, Raymond J.; Coenen, Manfred; Harris, Pat (31 January 2013).Equine Applied and Clinical Nutrition: Health, Welfare and Performance.Elsevier Health Sciences. p. 90.ISBN978-0-7020-5418-1.
The most common indicator of water quality is the concentration of total dissolved solids (TDS)
- ^Ali E, Liponska A, O'Hara B, Amici D, Torno M, Gao P, Asara J, Yap M-N F, Mendillo M, Ben-Sahra I (June 2022)."The mTORC1-SLC4A7 axis stimulates bicarbonate import to enhance de novo nucleotide synthesis".Molecular Cell.82(1): 3284–3298.e7.doi:10.1016/j.molcel.2022.06.008.PMC9444906.PMID35772404.
- ^Berne & Levy,Principles of Physiology
- ^"The chemistry of ocean acidification: OCB-OA".www.whoi.edu.Woods Hole Oceanographic Institution. 24 September 2012.Archivedfrom the original on 19 May 2017.Retrieved17 May2017.
- ^Pełechaty, Mariusz; Pukacz, Andrzej; Apolinarska, Karina; Pełechata, Aleksandra; Siepak, Marcin (June 2013). Porta, Giovanna Della (ed.)."The significance of Chara vegetation in the precipitation of lacustrine calcium carbonate".Sedimentology.60(4): 1017–1035.Bibcode:2013Sedim..60.1017P.doi:10.1111/sed.12020.S2CID128758128.
- ^Acid Base Balance (page 3)Archived2002-06-13 at theWayback Machine
External links
[edit]
- Bicarbonatesat the U.S. National Library of MedicineMedical Subject Headings(MeSH)