D Glucose Structure
D-glucose is a six-carbon sugar molecule with the molecular formula C6H12O6. It is a key source of energy in living organisms and is a fundamental building block of carbohydrates. The structure of D-glucose consists of a six-membered ring formed by five carbon atoms and one oxygen atom, with a hydroxyl group attached to each carbon atom.
4 Key excerpts on "D Glucose Structure"
eBook - ePub- James N. BeMiller(Author)
- 2018(Publication Date)
...(Note that L -glucose is the complete molecular mirror image of D -glucose and not the substance with the opposite configuration of just C5. If only the configuration of C5 is changed, the product is L -idose [see below].) The structure of D -glucose is shown in its open-chain (acyclic) form (called the Fischer projection) with the carbon atoms numbered in the conventional manner. As is customary, the horizontal lines indicating the covalent chemical bonds to the hydrogen atoms and hydroxyl groups are omitted in the structure on the right. Because the lowermost carbon atom (C6 in the case of D -glucose) is not chiral, the relative positions of the atoms and groups attached to it need not be designated, and it is written as –CH 2 OH. The great majority of carbohydrates found in foods are composed mostly of aldohexoses. Shown below is the aldopentose arabinose in both the D and L forms, both of which occur in nature. Glucose is found only in the form of D -glucose. An organic chemist say that D -glucose and all other carbohydrate molecules as highly functionalized because there is a functional group 3 on each carbon atom. The complete functionalization of the backbone carbon atom structure with hydroxyl groups, a carbonyl oxygen atom (in the case of the simple sugars), and a high percentage of chiral carbon atoms are distinguishing features of carbohydrates. D -Glucose, as its O6 phosphate ester 4 (D -glucose 6-phosphate), is the first sugar of photosynthesis. D -Glucose 6-phosphate (Chapter 2) is present in only small amounts because it is rapidly converted into sucrose (Chapter 3) for transport to various parts of the plant where it is used for synthesis of other substances...
eBook - ePubBiochemistry Explained
A Practical Guide to Learning Biochemistry
- Thomas Millar(Author)
- 2018(Publication Date)
- CRC Press(Publisher)
...(1972) The Carbohydrates. New York: Academic Press. Roehrig, K.L. (1984) Carbohydrate Biochemistry and Metabolism. Westport, CT: AVI Publishing Company. Q&A Answers 1 L-glucose is the mirror image of D-glucose. Note that C1 and C6 have not been rotated because these are not chiral carbons. If these (C1 and C6) had been drawn in their rotated forms, it is exactly the same structure. The temptation is to simply switch the hydroxyl group on C5 from the right to the left. If you did this, this is not the answer. Remember, L-glucose is the mirror image of D-glucose. 2. No, you cannot predict which way D-glucose will rotate polarised light. The designation of D or L is structural for all molecules except for glyceraldehyde. The D designation for glucose is based on the D structural form of glyceraldehyde. In fact, it does rotate light to the right and to signify this it is given a + designation and hence is written as (+)-D-glucose. 3. The structure on the right is α-D-glucopyranose. It is glucose in the pyran form and the hydroxyl (-OH) group on C1 is below the plain of the ring, hence it is the α form. 4. 5. A is α-D-fructofuranose and the name of B is β-D-fructofuranose. A B 6. The structure of α-D- N -acetylgalactosamine is illustrated below. Its abbreviation is GalNAc. 7. The phosphorylation of fructose-6-phosphate by phos-phofructokinase gives fructose-1,6-bisphosphate. 8. 9. lactose (β-D-galactopyranosyl-(1→4)-D-glucopyranoside) sucrose (Ot-D-glucopyranosyl-(1→2)-β-D-fructofuranoside). 10. 11. N -acetylgalactosamine is attached to serine by an O -glycosidic bond. 12....
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- Raymond S. Ochs(Author)
- 2021(Publication Date)
- CRC Press(Publisher)
...In the linear form of a sugar, this is a carbonyl. However, in the ring form, it is an alcohol and a new chiral center. As expected with a chiral carbon, there are two stereochemical forms of the molecule, each in equilibrium with the straight-chain form (Figure 4.7). We need a designation for this new form of stereochemistry. Consider the position of the hydroxyl group at the anomeric carbon (for glucose, carbon 1). If this hydroxyl group is on the opposite side of the ring from the carbon substitution determining the d -form of the sugar, it is the alpha form. The top ring form sugar of Figure 4.7 is therefore designated formally as α- d -glucose. In the other ring form, the two groups – the connections to C1 and C5 – are on the same side; this is the beta form. As a quick check, with the ring oriented as in Figure 4.7, the newly appearing hydroxyl group is below the ring in the α-anomer and above the ring in the β-anomer. Notice that each form is in equilibrium with the open-chain form so that it is possible to convert the α form to the β form by going through the open-chain intermediate. At equilibrium, less than one percent of all the glucose in solution is in the open-chain form. The distribution of ring forms is about 36% alpha and 64% beta. This preference stems in part from the axial position of the –OH group in the alpha form and its equatorial position in the beta form. Equatorial substitutions on six-membered rings have less steric hindrance and are thus more stable than axial substitutions. A more complete explanation for the preference for beta substitutions is presented in Box 4.2. FIGURE 4.7 Multiple forms of glucose...
