D Fructose
D-fructose is a simple sugar, also known as a monosaccharide, that is commonly found in fruits, honey, and root vegetables. It is a key component of many biomolecules and plays a crucial role in energy metabolism. Structurally, it is a ketohexose, meaning it has six carbon atoms and contains a ketone functional group.
6 Key excerpts on "D Fructose"
eBook - ePub- James N. BeMiller(Author)
- 2018(Publication Date)
...55% of a common commercial high-fructose syrup (Chapter 7) used in soft drinks. About 40% of the carbohydrates of honey are D -fructose. D -Fructose is the principal commercial ketose and the only one of importance in foods. (In the past, D -fructose was called both levulose and fruit sugar, but these designations are rarely used today.) D -Fructose has only three chiral carbon atoms (C3, C4, and C5). Thus, there are only 2 3 or 8 ketohexoses. The various ketotetroses, -pentoses, and -hexoses are related to nonchiral dihydroxyacetone. The suffix designating a ketose in systematic carbohydrate nomenclature is – ulose (Table 1.1). In systematic nomenclature, D -fructose is D - arabino -hexulose because its three chiral carbon atoms have the same configuration as those in D -arabinose. The Rosanoff projection of a ketopentose (pentulose) with the D- threo configuration (that is the configuration of the two chiral carbon atoms in D -threose) is given in Fig. 1.3 as another demonstration of the nomenclature principle. Figure 1.3 Rosanoff projection of a ketopentose (D- threo -pentulose, “D -xylulose”) showing the configurations of the two chiral carbon atoms. Isomerization Simple aldoses and ketoses containing the same number of carbon atoms are isomers of each other (that is, a hexose and a hexulose both have the empirical formula C 6 H 12 O 6). Isomerization 5 of monosaccharides involves both the carbonyl group and the adjacent hydroxyl group. By isomerization, an aldose is converted into another aldose (with the opposite configuration of C2) and the corresponding ketose, and a ketose is converted into the corresponding two aldoses (Fig. 1.4). Therefore, by isomerization, D -glucose, D -mannose, and D -fructose can be interconverted (Fig. 1.5)...
eBook - ePub- Jose Perez-Castineira(Author)
- 2020(Publication Date)
- De Gruyter(Publisher)
...Most naturally occurring sugars are D (Figure 3.2, Table 3.1). The classical D-L terminology for isomerism preceding the trivial names of monosaccharides (and aminoacids, as we shall see in Chapter 4) is preferred by biochemists over the Cahn–Ingold–Prelog rules [ 8 ]. The latter is more systematic, but rather cumbersome for these compounds, thus, the IUPAC systematic name for D-glucose would be (2 R,3 S,4 R,5 R)-2,3,4,5,6-pentahydroxyhexanal. Table 3.1: Some monosaccharides of nutritional interest. Sources Pentoses L-Arabinose Plant exudates, hemicelluloses, pectines (dietary fiber) D-Xylose Hemicelluloses (dietary fiber) 2-deoxy-D-ribose DNA D-ribose RNA Aldohexoses L-Fucose (6-deoxy-L-galactose) Human milk, plant exudates, and mucous membranes D-Galactose Milk (as lactose), oligo- and polysaccharides, cerebrosides D-Glucose Frequent and ubiquitous (sugar, milk, starch, cellulose …) D-Mannose Homo- or heteropolysaccharides, glycoconjugates Ketohexoses (or hexuloses) D-Fructose Fruits, honey, sacarose The most abundant in human nutrition are underlined. 3.2.2 Cyclic forms of monosaccharides Monosaccharides are readily soluble in water due to the presence of hydroxyl groups that form hydrogen bonds with the surrounding water molecules. In aqueous solutions, monosaccharides exist as an equilibrium mixture of acyclic and cyclic forms. In the latter, one of the hydroxyl groups reacts with the carbonyl group producing cyclic hemiacetals (Figure 3.3). Five- and six-membered rings are structurally favoured, the former being named furanoses and the latter pyranoses...
eBook - ePub- Antonio Blanco, Gustavo Blanco(Authors)
- 2017(Publication Date)
- Academic Press(Publisher)
...Chapter 4 Carbohydrates Abstract Carbohydrates are polyhydroxyaldehydes (aldoses) or polyhydroxyketones (ketoses) composed of C, H, and O. They are classified into monosaccharides, oligosaccharides, and polysaccharides. Monosaccharides can be trioses, tetroses, pentoses, etc. depending on the number of carbon atoms in the molecule. They present optical isomerism due to the presence of an asymmetric or chiral C. In animals, most carbohydrates in humans are D isomers. Glucose is an aldohexose and the most important monosaccharide in humans, used as fuel by cells. Other aldohexoses are galactose and mannose, which form part of complex molecules. Fructose is a ketohexose, while ribose is the most important aldopentose and a component of RNA. These molecules usually form a cyclic structure, which could be pyran or furan and they present isomers α and β. There are monosaccharide derivatives which include the following: (1) glycosides, in which the aldehyde or the ketone group react with other molecule; (2) polyalcohols, which are obtained by reduction of the aldehyde or ketone group; (3) deoxysugars, which are produced by loss of oxygen from the alcohol group of a monosaccharide; (4) aldonic, aldaric, and uronic acids, which result from oxidation of the C1 or C6 of aldoses; (5) phosphate esters, which are produced by phosphorylation and are commonly found as monosaccharide metabolic products; (6) amino sugars, which generally have an amine group attached to C2 (glucosamine and galactosamine). Other nitrogenous derivatives are neuraminic and muramic acids. Disaccharides include maltose, composed of two D -glucoses linked by a α-glycosidic bond from the C1 of one to the OH at C4 of the other glucose (α-1→4 glycosidic bond). Lactose is the milk sugar, formed by D -galactose and D -glucose bound via β glycosidic bound from C1 of galactose to C4 of D -glucose (β-1→4 glycosidic bond)...
eBook - ePub- B.K. Dwivedi(Author)
- 2018(Publication Date)
- CRC Press(Publisher)
...This misses the point — the typical dieting person wishes to reduce caloric intake by an effective regime demanding least restriction of former eating pleasures. Consequently, when selecting a sweetening system for dietetic or reduced-calorie products, it is important to choose those ingredients providing maximum sweetness for a given caloric expenditure. TABLE 6.1 Anomers of Fructose II. PHYSICAL AND CHEMICAL PROPERTIES OF FRUCTOSE Fructose is a highly reactive keto-hexose with the typical monosaccharide C 6 H 12 O 6 empirical formula. It crystallizes as anhydrous prisms of (β -D-fructopyranose and has a melting point of 102 to 104°C. In solution, an equilibrium is established among the anomers. The much sweeter pyranose form dominates (67 to 31%) the furanose structure (Table 1). The open-chain keto configuration is present to a very small degree. However, in some reactions, this form manifests its presence, particularly during the heating of fructose solutions. 6 Fructose is the most water-soluble of all sugars, a property advantageously utilized in dry mixes that must be rapidly dissolved in limited volumes of cold water prior to consumption. Table 2 shows a comparison of fructose solubility and that of sucrose and dextrose. A typical assay for food-grade crystalline fructose that conforms to the Codex Alimentarius Draft International Standard (Alinorm 76/27) for fructose is III. SWEETNESS OF FRUCTOSE For processors of reduced calorie foods, undoubtedly the most interesting attribute of fructose is that it is the sweetest of the natural sugars (Table 3). Recent investigations show that under optimum conditions the relative sweetness of crystalline fructose is 170 compared to 100 for sucrose. 22, 32 Thus, many full calorie products can be converted to their reduced calories-from-sugar counterparts by replacing each 100 lb of sucrose with approximately 60 lb of fructose...
eBook - ePubBiermann's Handbook of Pulp and Paper
Volume 2: Paper and Board Making
- Pratima Bajpai(Author)
- 2018(Publication Date)
- Elsevier(Publisher)
...This classification is used for carbohydrates with three to seven carbon atoms; that is, with trioses, tetroses, pentoses, hexoses, and heptoses. Aldoses are monosaccharides that have an aldehyde when in the acyclic form (in the absence of the hemiacetal form); ketoses are monosaccharides with a ketone when in the acyclic form (absence of the hemiketal bond). Glucose is an example of an aldohexose, anD Fructose is an example of a ketohexose or hexulose, a six-carbon ketose, as shown in Fig. 17.1. If the terminal R CH 2 OH (at the C 6 position) of an aldose is oxidized to a carboxylic acid, then the monosaccharide is known as an uronic acid ; if the aldehyde is oxidized to a carboxylic acid, the compound is referred to as an aldonic acid; and if both terminal carbon atoms are oxidized to carboxylic acids, the compound is referred to as an aldaric acid. Monosaccharide constituents of particular importance in woody plant cell wall polysaccharides are the pentoses arabinose and xylose; the hexoses glucose, mannose, and galactose; and the uronic acid (4- O -methyl) glucuronic acid; these structures are shown with the hemicelluloses in Chapter 2, Volume 1. 17.3. Forms of Monosaccharides Monosaccharides may be represented, as in Fig. 17.1, by the Fischer projection, introduced by Emil Fischer in the late 19th century. The Fischer projection and the ball-and-stick model of D -glucose are presented in Fig. 17.2, as well as the Fischer projection of L -glucose. Horizontal lines of the Fischer projection represent H and OH groups coming toward the viewer. Vertical lines represent bonds going into the plane of the paper. Although these models force the carbon backbone to be curved, it is projected onto the plane of the paper as flat. Carbon atoms are numbered consecutively from the top to the bottom. When n is the number of carbon atoms, aldoses have n minus 2 and ketoses have n minus 3 chiral (asymmetric) substituted carbon atoms...
eBook - ePub- Raymond S. Ochs(Author)
- 2021(Publication Date)
- CRC Press(Publisher)
...All remaining carbons have an attached hydroxyl group. There are two classes of monosaccharides: aldoses and ketoses. Aldoses (aldehydes) have the carbonyl at carbon one, whereas ketoses (ketones) have the carbonyl at carbon two. The “-ose” suffix (as in aldose and ketose) usually indicates that a compound is a sugar. The general category name for sugars is shown in Table 4.1, starting with the smallest, the triose. Exceptions to this naming rule occur in the simplest monosaccharides: dihydroxyacetone and glyceraldehyde. Table 4.1 General Nomenclature of Sugars Carbons Category Name 3 Triose 4 Tetrose 5 Pentose 6 Hexose 7 Heptose 8 Octose Dihydroxyacetone is a symmetrical molecule because a plane of symmetry can be drawn through its center. However, glyceraldehyde is asymmetric: there are two distinct arrangements of the four groups attached to its central carbon. These forms are illustrated in Figure 4.1 using a Fischer projection to represent three-dimensional molecules in a plane. The two-dimensional Fischer projection convention is that the horizontal attachments project above the plane, and the vertical attachments project behind the plane. A further requirement is that the first carbon – the most oxidized – is shown on top. Another representation of the central carbon and its attached groups is a virtual tetrahedron, as shown in Figure 4.2. FIGURE 4.1 d -and l -glyceraldehyde. These mirror images are shown as Fischer projections and three-dimensional views. Asterisks indicate chiral carbons. FIGURE 4.2 Tetrahedral carbon. The four groups attached to the central carbon are as far apart from one another as possible, forming a tetrahedron in space. The two forms of glyceraldehyde are called stereoisomers, and molecules that display this form of stereoisomerism are known as enantiomers. The central carbon to which the four distinct groups are attached is the chiral carbon ; any molecule containing such a carbon is known as a chiral molecule...
