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In chemistry, a Haworth projection is a common way of writing a structural formula to represent the cyclic structure of monosaccharides with a simple three-dimensional perspective. Haworth projection approximate the shapes of the actual molecules better for furanoses —which are in reality nearly planar—than for pyranoses that exist in ...
The stereochemical structure of a cyclic monosaccharide can be represented in a Haworth projection. In this diagram, the α-isomer for the pyranose form of a D -aldohexose has the −OH of the anomeric carbon below the plane of the carbon atoms, while the β-isomer has the −OH of the anomeric carbon above the plane.
Fructose exists in foods either as a monosaccharide (free fructose) or as a unit of a disaccharide (sucrose). Free fructose is a ketonic simple sugar and one of the three dietary monosaccharides absorbed directly by the intestine. When fructose is consumed in the form of sucrose, it is digested (broken down) and then absorbed as free fructose.
In solution, reducing monosaccharides exist in equilibrium between their acyclic and cyclic forms with less than 1% in the acyclic form. The open chain form can close to give the pyranose and furanose with both the α- and β-anomers present for each. The equilibrium population of conformers depends on their relative energies which can be ...
Allulose, also known by its systematic name D-ribo-2-hexulose as well as by the name D-psicose, is a monosaccharide and a ketohexose. [ 2 ] [ 11 ] It is a C3 epimer of fructose . [ 2 ] Fructose can be converted to allulose by the enzymes D -tagatose 3-epimerase ( EC 5.1.3.31 ) and/or D -psicose 3-epimerase ( EC 5.1.3.30 ), which has allowed for ...
The conventional numbering of the carbons in the closed form is the same as in the open-chain form. If the sugar is an aldohexose, with the carbonyl in position 1, the reaction may involve the hydroxyl on carbon 4 or carbon 5, creating a hemiacetal with five- or six-membered ring, respectively.
Fischer projection of D-glyceraldehyde. Like most carbohydrates, simple aldoses have the general chemical formula C n (H 2 O) n.Because formaldehyde (n=1) and glycolaldehyde (n=2) are not generally considered to be carbohydrates, [1] the simplest possible aldose is the triose glyceraldehyde, which only contains three carbon atoms.
Haworth Projection of β-D-glucopyranose. Hermann Emil Fischer won the Nobel Prize in Chemistry (1902) for his work in determining the structure of the D-aldohexoses. [1] However, the linear, free-aldehyde structures that Fischer proposed represent a very minor percentage of the forms that hexose sugars adopt in solution.