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Aconitic Acid
Aconitic acid is an organic acid. The two isomers are ''cis''-aconitic acid and ''trans''-aconitic acid. The conjugate base of ''cis''-aconitic acid, ''cis''-aconitate is an intermediate in the isomerization of citrate to isocitrate in the citric acid cycle. It is acted upon by the enzyme aconitase. Aconitic acid can be synthesized by dehydration of citric acid using sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular formu ...: :(HO2CCH2)2C(OH)CO2H → HO2CCH=C(CO2H)CH2CO2H + H2O A mixture of isomers are generated in this way. It was first prepared by thermal dehydration. References {{Citric acid cycle Tricarboxylic acids Enoic acids ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PubChem
PubChem is a database of chemical molecules and their activities against biological assays. The system is maintained by the National Center for Biotechnology Information (NCBI), a component of the National Library of Medicine, which is part of the United States National Institutes of Health (NIH). PubChem can be accessed for free through a web user interface. Millions of compound structures and descriptive datasets can be freely downloaded via FTP. PubChem contains multiple substance descriptions and small molecules with fewer than 100 atoms and 1,000 bonds. More than 80 database vendors contribute to the growing PubChem database. History PubChem was released in 2004 as a component of the Molecular Libraries Program (MLP) of the NIH. As of November 2015, PubChem contains more than 150 million depositor-provided substance descriptions, 60 million unique chemical structures, and 225 million biological activity test results (from over 1 million assay experiments performed on more t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Conjugate Base
A conjugate acid, within the Brønsted–Lowry acid–base theory, is a chemical compound formed when an acid donates a proton () to a base—in other words, it is a base with a hydrogen ion added to it, as in the reverse reaction it loses a hydrogen ion. On the other hand, a conjugate base is what is left over after an acid has donated a proton during a chemical reaction. Hence, a conjugate base is a species formed by the removal of a proton from an acid, as in the reverse reaction it is able to gain a hydrogen ion. Because some acids are capable of releasing multiple protons, the conjugate base of an acid may itself be acidic. In summary, this can be represented as the following chemical reaction: :acid + base conjugate\ base + conjugate\ acid Johannes Nicolaus Brønsted and Martin Lowry introduced the Brønsted–Lowry theory, which proposed that any compound that can transfer a proton to any other compound is an acid, and the compound that accepts the proton is a b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isomer
In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers. Isomers do not necessarily share similar chemical or physical properties. Two main forms of isomerism are structural or constitutional isomerism, in which ''bonds'' between the atoms differ; and stereoisomerism or spatial isomerism, in which the bonds are the same but the ''relative positions'' of the atoms differ. Isomeric relationships form a hierarchy. Two chemicals might be the same constitutional isomer, but upon deeper analysis be stereoisomers of each other. Two molecules that are the same stereoisomer as each other might be in different conformational forms or be different isotopologues. The depth of analysis depends on the field of study or the chemical and physical properties of interest. The English word "isomer" () is a back-for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Citrate
Citric acid is an organic compound with the chemical formula HOC(CO2H)(CH2CO2H)2. It is a colorless weak organic acid. It occurs naturally in citrus fruits. In biochemistry, it is an intermediate in the citric acid cycle, which occurs in the metabolism of all aerobic organisms. More than two million tons of citric acid are manufactured every year. It is used widely as an acidifier, as a flavoring, and a chelating agent. A citrate is a derivative of citric acid; that is, the salts, esters, and the polyatomic anion found in solution. An example of the former, a salt is trisodium citrate; an ester is triethyl citrate. When part of a salt, the formula of the citrate anion is written as or . Natural occurrence and industrial production Citric acid occurs in a variety of fruits and vegetables, most notably citrus fruits. Lemons and limes have particularly high concentrations of the acid; it can constitute as much as 8% of the dry weight of these fruits (about 47 g/L in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isocitrate
Isocitric acid is a structural isomer of citric acid. Since citric acid and isocitric acid are structural isomers, they share similar physical and chemical properties. Due to these similar properties, it is difficult to separate the isomers. Salts and esters of isocitric acid are known as isocitrates. The isocitrate anion is a substrate of the citric acid cycle. Isocitrate is formed from citrate with the help of the enzyme aconitase Aconitase (aconitate hydratase; ) is an enzyme that catalyses the stereo-specific isomerization of citrate to isocitrate via ''cis''- aconitate in the tricarboxylic acid cycle, a non-redox-active process. Image:Citrate wpmp.png, Image:Cis- ..., and is acted upon by isocitrate dehydrogenase. Isocitric acid is commonly used as a marker to detect the authenticity and quality of fruit products, most often citrus juices. In authentic orange juice, for example, the ratio of citric acid to D-isocitric acid is usually less than 130. An isocitr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Citric Acid Cycle
The citric acid cycle (CAC)—also known as the Krebs cycle or the TCA cycle (tricarboxylic acid cycle)—is a series of chemical reactions to release stored energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins. The Krebs cycle is used by organisms that respire (as opposed to organisms that ferment) to generate energy, either by anaerobic respiration or aerobic respiration. In addition, the cycle provides precursors of certain amino acids, as well as the reducing agent NADH, that are used in numerous other reactions. Its central importance to many biochemical pathways suggests that it was one of the earliest components of metabolism and may have originated abiogenically. Even though it is branded as a 'cycle', it is not necessary for metabolites to follow only one specific route; at least three alternative segments of the citric acid cycle have been recognized. The name of this metabolic pathway is derived from the citric acid (a tricarboxy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aconitase
Aconitase (aconitate hydratase; ) is an enzyme that catalyses the stereo-specific isomerization of citrate to isocitrate via ''cis''- aconitate in the tricarboxylic acid cycle, a non-redox-active process. Image:Citrate wpmp.png, Image:Cis-Aconitate wpmp.png, Image:isocitric acid.svg, Structure Aconitase, displayed in the structures in the right margin of this page, has two slightly different structures, depending on whether it is activated or inactivated. In the inactive form, its structure is divided into four domains. Counting from the N-terminus, only the first three of these domains are involved in close interactions with the Fe-4Scluster, but the active site consists of residues from all four domains, including the larger C-terminal domain. The Fe-S cluster and a anion also reside in the active site. When the enzyme is activated, it gains an additional iron atom, creating a Fe-4Scluster. However, the structure of the rest of the enzyme is nearly unchanged; the c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Citric Acid
Citric acid is an organic compound with the chemical formula HOC(CO2H)(CH2CO2H)2. It is a colorless weak organic acid. It occurs naturally in citrus fruits. In biochemistry, it is an intermediate in the citric acid cycle, which occurs in the metabolism of all aerobic organisms. More than two million tons of citric acid are manufactured every year. It is used widely as an acidifier, as a flavoring, and a chelating agent. A citrate is a derivative of citric acid; that is, the salts, esters, and the polyatomic anion found in solution. An example of the former, a salt is trisodium citrate; an ester is triethyl citrate. When part of a salt, the formula of the citrate anion is written as or . Natural occurrence and industrial production Citric acid occurs in a variety of fruits and vegetables, most notably citrus fruits. Lemons and limes have particularly high concentrations of the acid; it can constitute as much as 8% of the dry weight of these fruits (about 47 g/L in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sulfuric Acid
Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular formula . It is a colorless, odorless and viscous liquid that is miscible with water. Pure sulfuric acid does not exist naturally on Earth due to its strong affinity to water vapor; it is hygroscopic and readily absorbs water vapor from the air. Concentrated sulfuric acid is highly corrosive towards other materials, from rocks to metals, since it is an oxidant with powerful dehydrating properties. Phosphorus pentoxide is a notable exception in that it is not dehydrated by sulfuric acid, but to the contrary dehydrates sulfuric acid to sulfur trioxide. Upon addition of sulfuric acid to water, a considerable amount of heat is released; thus the reverse procedure of adding water to the acid should not be performed since the heat released may boi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tricarboxylic Acids
A tricarboxylic acid is an organic carboxylic acid whose chemical structure contains three carboxyl functional groups (-COOH). The best-known example of a tricarboxylic acid is citric acid. Uses Citric acid cycle Citric acid, a type of tricarboxylic acid, is used in the citric acid cycle – also known as tricarboxylic acid (TCA) cycle or Krebs cycle – which is fundamental to all aerobic organisms. Examples See also * Citric acid cycle (tricarboxylic acid cycle) * Dicarboxylic acid * Mellitic acid Mellitic acid, also called graphitic acid or benzenehexacarboxylic acid, is an acid first discovered in 1799 by Martin Heinrich Klaproth in the mineral mellite (honeystone), which is the aluminium salt of the acid. It crystallizes in fine silky ne ... Literature *{{cite journal , title = The Tricarboxylic Acid Cycle, an Ancient Metabolic Network with a Novel Twist. , author = Ryan J. Mailloux, Robin Bériault, Joseph Lemire, Ranji Singh, Daniel R. Chénier, Robert D. Hamel, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
