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Aldose
An aldose is a monosaccharide (a simple sugar) with a carbon backbone chain with a carbonyl group on the endmost carbon atom, making it an aldehyde, and hydroxyl groups connected to all the other carbon atoms. Aldoses can be distinguished from ketoses, which have the carbonyl group away from the end of the molecule, and are therefore ketones. Structure Like most carbohydrates, simple aldoses have the general chemical formula C''n''(H2O)''n''. Because formaldehyde (n=1) and glycolaldehyde (n=2) are not generally considered to be carbohydrates, the simplest possible aldose is the triose glyceraldehyde, which only contains three carbon atoms. Because they have at least one asymmetric carbon center, all aldoses exhibit stereoisomerism. Aldoses can exist in either a - form or - form. The determination is made based on the chirality of the asymmetric carbon furthest from the aldehyde end, namely the second-last carbon in the chain. Aldoses with alcohol groups on the right of the Fische ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Monosaccharide
Monosaccharides (from Greek ''monos'': single, '' sacchar'': sugar), also called simple sugars, are the simplest forms of sugar and the most basic units (monomers) from which all carbohydrates are built. They are usually colorless, water-soluble, and crystalline solids. Contrary to their name (sugars), only some monosaccharides have a sweet taste. Most monosaccharides have the formula (though not all molecules with this formula are monosaccharides). Examples of monosaccharides include glucose (dextrose), fructose (levulose), and galactose. Monosaccharides are the building blocks of disaccharides (such as sucrose and lactose) and polysaccharides (such as cellulose and starch). The table sugar used in everyday vernacular is itself a disaccharide sucrose comprising one molecule of each of the two monosaccharides D-glucose and D-fructose. Each carbon atom that supports a hydroxyl group is chiral, except those at the end of the chain. This gives rise to a number of isomeric ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ketose
A ketose is a monosaccharide containing one ketone group per molecule. The simplest ketose is dihydroxyacetone, which has only three carbon atoms. It is the only ketose with no optical activity. All monosaccharide ketoses are reducing sugars, because they can tautomerize into aldoses via an enediol intermediate, and the resulting aldehyde group can be oxidised, for example in the Tollens' test or Benedict's test. Ketoses that are bound into glycosides, for example in the case of the fructose moiety of sucrose, are nonreducing sugars. Examples of ketoses All ketoses listed here are 2-ketoses, in other words, the carbonyl group is on the second carbon atom from the end: * Trioses: dihydroxyacetone * Tetroses: erythrulose * Pentoses: ribulose, xylulose * Hexoses: fructose, psicose, sorbose, tagatose * Heptoses: sedoheptulose * Octoses: D-''manno''-octulose (the basis for KDO) * Nonoses: D-''glycero''-D-''galacto''-nonulose (the basis for neuraminic acid) Chemistry Ketoses an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seliwanoff's Test
Seliwanoff’s test is a chemical test which distinguishes between aldose and ketose sugars. If the sugar contains a ketone group, it is a ketose. If a sugar contains an aldehyde group, it is an aldose. This test relies on the principle that, when heated, ketoses are more rapidly dehydrated than aldoses. It is named after Theodor Seliwanoff, the chemist that devised the test. When added to a solution containing ketoses, a red color is formed rapidly indicating a positive test. When added to a solution containing aldoses, a slower forming light pink is observed instead. The reagents consist of resorcinol and concentrated hydrochloric acid: * The acid hydrolysis of polysaccharide and oligosaccharide ketoses yields simpler sugars followed by furfural.Abramoff, Peter; Thomson, Robert (1966). An experimental approach to biology. WH Freeman & Company, San Francisco. p. 47. * The dehydrated ketose then reacts with two equivalents of resorcinol in a series of condensation reactions ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Triose
A triose is a monosaccharide, or simple sugar, containing three carbon atoms. There are only three possible trioses (including dihydroxyacetone): L-glyceraldehyde and D-glyceraldehyde, the two enantiomers of glyceraldehyde, which are aldotrioses because the carbonyl group is at the end of the chain, and dihydroxyacetone, the only ketotriose, which is symmetrical and therefore has no enantiomers. Trioses are important in cellular respiration. During glycolysis, fructose-1,6-bisphosphate is broken down into glyceraldehyde-3-phosphate and dihydroxyacetone phosphate. Lactic acid Lactic acid is an organic acid. It has a molecular formula . It is white in the solid state and it is miscible with water. When in the dissolved state, it forms a colorless solution. Production includes both artificial synthesis as well as natu ... and pyruvic acid are later derived from these molecules. References Trioses {{Biochem-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aldehyde
In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl group. Aldehydes are common and play important roles in the technology and biological spheres. Structure and bonding Aldehydes feature a carbon center that is connected by a double bond to oxygen and a single bond to hydrogen and single bond to a third substituent, which is carbon or, in the case of formaldehyde, hydrogen. The central carbon is often described as being sp2- hybridized. The aldehyde group is somewhat polar. The C=O bond length is about 120-122 picometers. Physical properties and characterization Aldehydes have properties that are diverse and that depend on the remainder of the molecule. Smaller aldehydes are more soluble in water, formaldehyde and acetaldehyde completely so. The volatile aldehydes have pungent odors. Al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Triose
A triose is a monosaccharide, or simple sugar, containing three carbon atoms. There are only three possible trioses (including dihydroxyacetone): L-glyceraldehyde and D-glyceraldehyde, the two enantiomers of glyceraldehyde, which are aldotrioses because the carbonyl group is at the end of the chain, and dihydroxyacetone, the only ketotriose, which is symmetrical and therefore has no enantiomers. Trioses are important in cellular respiration. During glycolysis, fructose-1,6-bisphosphate is broken down into glyceraldehyde-3-phosphate and dihydroxyacetone phosphate. Lactic acid Lactic acid is an organic acid. It has a molecular formula . It is white in the solid state and it is miscible with water. When in the dissolved state, it forms a colorless solution. Production includes both artificial synthesis as well as natu ... and pyruvic acid are later derived from these molecules. References Trioses {{Biochem-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glucose
Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, using energy from sunlight, where it is used to make cellulose in cell walls, the most abundant carbohydrate in the world. In energy metabolism, glucose is the most important source of energy in all organisms. Glucose for metabolism is stored as a polymer, in plants mainly as starch and amylopectin, and in animals as glycogen. Glucose circulates in the blood of animals as blood sugar. The naturally occurring form of glucose is -glucose, while -glucose is produced synthetically in comparatively small amounts and is less biologically active. 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. Gluco ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pentose
In chemistry, a pentose is a monosaccharide (simple sugar) with five carbon atoms. The chemical formula of many pentoses is , and their molecular weight is 150.13 g/mol.-Ribose . PubChem compound webpage, accessed on 2010-02-06. Pentoses are very important in . is a constituent of , and the related molecule, , is a constituent of [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Threose
Threose is a four-carbon monosaccharide with molecular formula C4H8O4. It has a terminal aldehyde group rather than a ketone in its linear chain, and so is considered part of the aldose family of monosaccharides. The threose name can be used to refer to both the D- and L-stereoisomers, and more generally to the racemic mixture (D/L-, equal parts D- and L-) as well as to the more generic threose structure (absolute stereochemistry unspecified). The prefix "threo" which derives from threose (and "erythro" from a corresponding diastereomer erythrose) offer a useful way to describe general organic structures with adjacent chiral centers, where "the prefixes... designate the relative configuration of the centers".Formulas Using Other Configurational Notations W. Rausch, accessed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fischer Projection
In chemistry, the Fischer projection, devised by Emil Fischer in 1891, is a two-dimensional representation of a three-dimensional organic molecule by projection. Fischer projections were originally proposed for the depiction of carbohydrates and used by chemists, particularly in organic chemistry and biochemistry. The use of Fischer projections in non-carbohydrates is discouraged, as such drawings are ambiguous and easily confused with other types of drawing. The main purpose of Fischer projections is to show the chirality of a molecule and to distinguish between a pair of enantiomers. Some notable uses include drawing sugars and depicting isomers. Conventions All bonds are depicted as horizontal or vertical lines. The carbon chain is depicted vertically, with carbon atoms sometimes not shown and represented by the center of crossing lines (see figure below). The orientation of the carbon chain is so that the first carbon (C1) is at the top. In an aldose, C1 is the carbon o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Erythrose
Erythrose is a tetrose saccharide with the chemical formula C4H8O4. It has one aldehyde group, and is thus part of the aldose family. The natural isomer is D-erythrose; it is a diastereomer of D -threose. Erythrose was first isolated in 1849 from rhubarb by the French pharmacist Louis Feux Joseph Garot (1798-1869), and was named as such because of its red hue in the presence of alkali metals (ἐρυθρός, "red"). Erythrose 4-phosphate is an intermediate in the pentose phosphate pathway and the Calvin cycle. Oxidative bacteria can be made to use erythrose as its sole energy source. See also * Erythritol Erythritol is an organic compound, a four-carbon sugar alcohol (or polyol) with no optical activity, used as a food additive and sugar substitute. It is naturally occurring. It can be made from corn using enzymes and fermentation. Its formula i ... References {{Carbohydrates Aldotetroses ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glyceraldehyde
Glyceraldehyde (glyceral) is a triose monosaccharide with chemical formula C3 H6 O3. It is the simplest of all common aldoses. It is a sweet, colorless, crystalline solid that is an intermediate compound in carbohydrate metabolism. The word comes from combining glycerol and aldehyde, as glyceraldehyde is glycerol with one alcohol group oxidized to an aldehyde. Structure Glyceraldehyde has one chiral center and therefore exists as two different enantiomers with opposite optical rotation: * In the nomenclature, either from Latin ''Dexter'' meaning "right", or from Latin ''Laevo'' meaning "left" * In the R/S nomenclature, either R from Latin ''Rectus'' meaning "right", or S from Latin ''Sinister'' meaning "left" While the optical rotation of glyceraldehyde is (+) for ''R'' and (−) for ''S'', this is not true for all monosaccharides. The stereochemical configuration can only be determined from the chemical structure, whereas the optical rotation can only be determined em ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
