Chemistry
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.
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11 Key excerpts on "D Glucose Structure"
eBook - PDF- Allan Blackman, Steven E. Bottle, Siegbert Schmid, Mauro Mocerino, Uta Wille(Authors)
- 2022(Publication Date)
- Wiley(Publisher)
Almost all monosaccharides in the biological world belong to the d series, and the majority of them are either hexoses or pentoses. Figure 22.7 shows the names and Fischer projections for all d-aldo trioses, tetroses, pentoses and hexoses. Each name consists of three parts. The letter d specifies the configuration at the stereocentre furthest from the carbonyl group. Prefixes, such as rib-, arabin- and gluc-, specify the configurations of all other stereocentres relative to one another. The suffix -ose shows that the compound is a carbohydrate. 1154 Chemistry FIGURE 22.7 Configurational relationships among the isomeric D-aldotetroses, D-aldopentoses and D-aldohexoses. The configuration of the reference OH on the penultimate carbon atom is shown in blue. D-glyceraldehyde D-erythrose D-threose aldotetrose CH 2 OH CHO H OH H OH CH 2 OH CHO HO H H OH HO H HO H CH 2 OH CHO H OH H OH HO H CH 2 OH CHO H OH HO H H OH CH 2 OH CHO H OH aldopentose H OH H OH CH 2 OH CHO H OH D-ribose D-arabinose D-xylose D-lyxose H OH CHO CH 2 OH aldohexose H OH H OH H OH CH 2 OH CHO H OH HO H H OH H OH CH 2 OH CHO H OH D-allose D-altrose H OH HO H H OH CH 2 OH CHO H OH HO H HO H H OH CH 2 OH CHO H OH D-glucose D-mannose H OH H OH HO H CH 2 OH CHO H OH HO H H OH HO H CH 2 OH CHO H OH D-gulose D-idose H OH HO H HO H CH 2 OH CHO H OH HO H HO H HO H CH 2 OH CHO H OH D-galactose D-talose aldotriose The three most abundant hexoses in the biological world are d-glucose, d-galactose and d-fructose. The first two (see figure 22.7) are d-aldohexoses while the third, fructose (figure 22.8), is a d-2-ketohexose. Glucose, by far the most abundant of the three, is also known as dextrose because it is dextrorotatory. Other names for this monosaccharide include grape sugar and blood sugar. Human blood normally contains 65–110 mg of glucose/100 mL of blood. d-fructose is one of the two monosaccharide building blocks of sucrose (table sugar, section 22.5).
- Morris Hein, Scott Pattison, Susan Arena, Leo R. Best(Authors)
- 2014(Publication Date)
- Wiley(Publisher)
706 CHAPTER 27 • Carbohydrates compromise in portraying the three-dimensional configuration of such molecules. Structural models are much more effective, especially if constructed by the student. The two cyclic forms of D-glucose differ only in the relative positions of the i H and i OH groups attached to carbon 1. Yet this seemingly minor structural difference has important bio- chemical consequences because the physical shape of a molecule often determines its biological use. For example, the fundamental structural difference between starch and cellulose is that starch is a polymer of a-D-glucopyranose, whereas cellulose is a polymer of b-D-glucopyranose. As a consequence, starch is easily digested by humans, but we are totally unable to digest cellulose. Galactose, like glucose, is an aldohexose and differs structurally from glucose only in the configuration of the i H and i OH group on carbon 4. Galactose is an epimer of glucose and vice versa. H O C CH 2 OH OH H H HO H HO OH H 1 2 3 4 5 6 D-galactose differs from D-glucose here H O C CH 2 OH OH H H HO OH H OH H 1 2 3 4 5 6 D-glucose Galactose, like glucose, also exists primarily in two cyclic pyranose forms that have hemiacetal structures and undergo mutarotation: CH 2 OH OH OH O 5 6 4 1 3 2 5 CH 2 OH OH OH O 6 4 1 3 2 �-D-galactopyranose �-D-galactopyranose OH OH OH OH � � Fructose is a ketohexose. The open-chain form may be represented in a Fischer projection formula: CH 2 OH CH 2 OH H HO OH H OH H 1 2 3 4 5 6 D-fructose This portion has the same configuration as D-glucose. O C keto group H H H O O H H H H O O O H H H H H O (a) Ball-and-stick model (b) Spacefilling model Figure 27.4 Three-dimensional representations of the chair form of a-D-glucopyranose. To identify anomers in the Haworth formula, focus on carbon 1 for aldoses and carbon 2 for ketoses.
eBook - PDFThe Carbohydrates Volume 1A
Chemistry and Biochemistry
- W.W. Pigman(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
1. INTRODUCTION: STRUCTURE AND STEREOCHEMISTRY OF THE MONOSACCHARIDES WARD PIGMAN AND DEREK HORTON I. General Relations 1 II. Some Definitions 2 III. Nomenclature 6 IV. Development of Carbohydrate Chemistry . . . 6 V. Structures of D-Glucose and D-Fructose . . . 8 VI. Stereochemistry 9 A. General Principles 9 B. Establishment of the Configuration of D-Glucose and Some Other Sugars 14 C. D and L Nomenclature 22 D. Conformational Representation of Acyclic Sugar Derivatives 30 VII. Ring Structures of the Sugars 33 A. Necessity for Ring Structures . . . . 3 3 B. Proof of Ring Structure 35 C. Configuration at the Anomeric Carbon Atom . 39 D. Depiction of the Ring Structures of the Sugars . 40 E. Nomenclature of Anomers (α,β Nomenclature) . 45 VIII. Homomorphous Sugars 47 A. Homomorphology 47 B. Nomenclature for Higher Sugars and for Com-pounds Having Numerous Asymmetric Atoms in a Carbon Chain 52 IX. Conformational Representation of Cyclic Sugars . 55 References . . . . . . . . 65 I. GENERAL RELATIONS The carbohydrates comprise one of the major groups of naturally occurring organic materials. They are the basis of many important industries or segments of industries, including manufacture of sugar and sugar products, D-glucose and starch products, paper and wood pulp, textile fibers, plastics, foods and food processing, fermentation, and, to a less-developed extent, pharma-ceuticals, drugs, vitamins, and specialty chemicals. 1 2 W. PIGMAN AND D. HORTON They are of special significance in plants, the dry substance of which is usually composed of 50 to 80% of carbohydrates. For plants, the structural material is mainly cellulose and the related hemicelluloses, accompanied by smaller proportions of a phenolic polymer (lignin). Lower but important proportions of starch, pectins, and sugars, especially sucrose and D-glucose, are also constituents and are obtained commercially from plants.
eBook - PDF- H. Stephen Stoker(Author)
- 2015(Publication Date)
- Cengage Learning EMEA(Publisher)
From the third to the sixth carbon, the structure of D -fructose is identical to that of D -glucose. Differences at carbons 1 and 2 are related to the presence of a ketone group in fructose and of an aldehyde group in glucose. CHO A A A A A A O O OO O O CH 2 OH OH H A A OO OH OH H HO H H D -Glucose A A A A A A OO O O CH 2 OH CH 2 OH HO OH H H A A O O OH H C P O D -Fructose Same structure d-Ribose D -Glucose, D -galactose, and D -fructose are all hexoses. D -Ribose is a pentose. If car-bon 3 and its accompanying ! H and ! OH groups were eliminated from the struc-ture of D -glucose, the remaining structure would be that of D -ribose. CHO A A A A O O OO O O CH 2 OH OH H A A A A OO OH OH H HO H H D -Glucose CHO A A A A A A A A O O O O CH 2 OH OH OO OH OH H H H D -Ribose D -Ribose is a component of a variety of complex molecules, including ribo-nucleic acids (RNAs) and energy-rich compounds such as adenosine triphosphate (ATP). The compound 2-deoxy-D -ribose is also important in nucleic acid chemistry. This monosaccharide is a component of DNA molecules. The prefix deoxy - means “minus an oxygen”; the structures of ribose and 2-deoxyribose differ in that the latter compound lacks an oxygen atom at carbon 2. CHO A A A A A O O O O CH 2 OH OH A A A OO OH OH H H H D -Ribose CHO A A A A A A O O O O CH 2 OH H OO OH OH H H H C 2-Deoxy-D -ribose Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 266 CHAPTER 7 Carbohydrates 7-10 Cyclic Forms of Monosaccharides L E A R N I N G F O C U S Be able to use Haworth projection formulas to denote the cyclic forms of monosaccharides.
eBook - PDF- David Ucko(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
T h e two possible arrangements in space, or configurations, of glyceralde-hyde are called D and L . Other molecules are labeled b y comparing their configuration around the chiral carbon atom with D-glyceraldehyde and L-glyceraldehyde. T h e configuration for monosaccharides is based on the chiral carbon atom farthest from the carbonyl group. If the hydroxyl group is on the right side in the open-chain form with the carbonyl group at the t o p , the configuration is D . All of the monosaccharides in nature exist in the Ό form. Thus, glucose should b e written D-glucose. Light interacts with enantiomers in a special way. You can think of ordinary light in terms of vibrating waves; polarized light, produced w h e n light passes through Polaroid sunglasses, for example, consists of waves vibrating in only one plane, such as just up and d o w n . Enantiomers have the property of being able to rotate this plane of polarized light; they are called optically active. Those substances that rotate the plane in a clockwise direction are dextrorota-tory, symbolized + , while those that cause rotation in a counterclockwise manner are levorotatory, symbolized —. (A solution containing equal parts of these two forms shows no optical rotation and is called a racemic mixture.) E v e n though all natural monosaccharides have the D configuration, some cause clockwise rotation of the plane of polarized light, symbolized D ( + ), and some cause a counterclockwise rotation, symbolized D ( — ) . Whether a molecule is in the D or L configuration has great biological im-portance. As you will see in a later chapter, the enzymes of your b o d y are very specific; they recognize only one enantiomer of a molecule. Thus, the form of the optical isomer determines the effect that a chiral molecule has on the body. A drug, for example, must have the proper configuration to b e able to carry out its designed role. Su ar SU Carbohydrates are one o f your major sources of energy.
eBook - PDF- Martha Bruch(Author)
- 1996(Publication Date)
- CRC Press(Publisher)
Monosaccharides are optically ac tive, with both d and l stereochemistry possible. However, as with amino acids, biology has selected exclusively one type of stereochemistry, and only d mono saccharides are found in nature. In all subsequent discussions, the stereochem istry is assumed to be d unless otherwise specified. The structure of sugars is further complicated by the fact that two possible anomers exist for an individual monosaccharide, called a and β. These anomers differ in the relative sterochemistry about carbon 1. In the β anomer of glucose, for example, both the Η 1 and H2 protons are in the axial positions, with the cor responding hydroxyl groups equatorial, whereas the HI proton is equatorial in the a anomer, as shown in Fig. 6.27. The two anomers of other monosaccharides are defined in a similar manner. Because of the existence of a and β anomers, the HI proton is generally referred to as the anomeric proton. When two pyranosides are connected through a glycosidic linkage, the OH group of carbon 1 of one monosaccharide and the OH group of any of the carbons on the other monosaccharide are replaced by a single oxygen connecting the two sugar rings, as shown in Fig. 6.28. The structure is specified by the anomeric con figuration of the first sugar, a or β, and the carbon number for the attachment site on the second sugar. For example, the disaccharide maltose, which consists of an a l->4 linkage of two glucose units, is named 4-<9-(a-D-glucopyranosyl)-D- glucopyranose and is described by the shorthand notation Glu (a l->4)-Glu Structure of Biological Macromolecules 373 Figure 6.27 Structures of some common monosaccharides: (a) α-D-glucose (or a-D-glucopyranose), (b) β-D-mannose (or β-D-mannopyranose), (c) α-D-galactose (or a-D-galactopyranose), (d) β-D-fructose (or β-D-fructofuranose). a b c d 374 Rizo and Bruch (Fig. 6.28). For more complex oligosaccharides, the shorthand notation is used almost exclusively.
eBook - ePub- Ronald E. Wrolstad(Author)
- 2011(Publication Date)
- Wiley-Blackwell(Publisher)
C-1 for aldoses and C-2 for ketoses are the reactive centers for these molecules and are known as the anomeric carbon atoms. Figure 1.1 shows the structure for D-glucose, D-fructose, and, in addition, D-arabinose. Sugars have common or trivial names with historical origins from chemistry, medicine, and industry. There is also a systematic procedure for naming sugars (some examples are shown in Table 1.1). Glucose is also commonly known as dextrose. In systematic nomenclature, its suffix is hexose, indicating a 6-carbon aldose sugar, and the prefix is gluco-, which shows the orientation of the hydroxyl groups around carbons 2–5. The symbol D refers to the orientation of the hydroxyl group on C-5, the highest numbered asymmetric carbon atom, also known as the reference carbon atom. Since fructose (also known as levulose) has just three asymmetric carbon atoms, its configurational prefix is the same as that for the pentose sugar arabinose. Thus, the systematic name for glucose is D- gluco -hexose and fructose is D- arabino -hexulose. Table 1.1 Trivial and Systematic Names of Selected Sugars Trivial (or. Common) Systematic a D-Erythrose D- erythro -tetrose D-Threose D- threo -tetrose D-Arabinose D- arabino -pentose D-Lyxose D- lyxo -pentose D-Ribose D- ribo -pentose D-Xylose D- xylo -pentose D-Allose D- allo -hexose D-Altrose D- altro -hexose D-Galactose D- galacto -hexose D-Glucose D- gluco -hexose D-Gulose D- gulo -hexose D-Idose D- ido -hexose D-Mannose D- manno -hexose D-Talose D- talo -hexose a In the systematic name, the configurational prefix is italicized, and the stem name indicates the number of carbon atoms in the molecule. Configurations of Aldose Sugars Figure
eBook - ePubThe Components of Life
From Nucleic Acids to Carbohydrates
- Britannica Educational Publishing, Kara Rogers(Authors)
- 2010(Publication Date)
- Britannica Educational Publishing(Publisher)
6 ), but because their atoms have different structural arrangements, the sugars have different characteristics (i.e., they are isomers). Slight changes in structural arrangements are detectable by living things and influence the biological significance of isomeric compounds. It is known, for example, that the degree of sweetness of various sugars differs according to the arrangement of the hydroxyl groups (-OH) that compose part of the molecular structure. A direct correlation that may exist between taste and any specific structural arrangement, however, has not yet been established—it is not yet possible to predict the taste of a sugar by knowing its specific structural arrangement. The energy in the chemical bonds of glucose indirectly supplies most living things with a major part of the energy that is necessary for them to carry on their activities. Galactose, which is rarely found as a simple sugar, is usually combined with other simple sugars in order to form larger molecules.Two molecules of a simple sugar that are linked to each other form a disaccharide, or double sugar. The disaccharide sucrose, or table sugar, consists of one molecule of glucose and one molecule of fructose; the most familiar sources of sucrose are sugar beets and cane sugar. Milk sugar, or lactose, and maltose are also disaccharides. Before the energy in disaccharides can be utilized by living things, the molecules must be broken down into their respective monosaccharides.Oligosaccharides, which consist of three to six monosaccharide units, are rather infrequently found in natural sources, although a few plant derivatives have been identified. Polysaccharides (the term means many sugars) represent most of the structural and energy-reserve carbohydrates found in nature. Large molecules that may consist of as many as 10,000 monosaccharide units linked together, polysaccharides vary considerably in size, in structural complexity, and in sugar content. Several hundred distinct types have thus far been identified. Cellulose, the principal structural component of plants, is a complex polysaccharide comprising many glucose units linked together. Cellulose is the most common polysaccharide. The starch found in plants and the glycogen found in animals also are complex glucose polysaccharides. Starch (from the old English word stercan
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
eBook - PDF- Ari M. P. Koskinen(Author)
- 2022(Publication Date)
- Wiley(Publisher)
4 Sugars New conceptual approaches to glycosylation and novel strategies for the construction of complex oligosaccharides and glycoconjugates are … welcome to meet the intrinsic structural diversity of carbohydrates. R.R. Schmidt, 2009 In the early nineteenth century, individual sugars were often named after their source, e.g. grape sugar (Traubenzucker) for glucose and cane sugar (Rohrzucker) for saccharose (the name sucrose was coined much later). Cellulose (from French ‘cellule’ for cell and ending ‘-ose’ to refer to sugars) was isolated and its overall composition elucidated in 1838 by the French chemist Anselme Payen (1795–1878). Its chemical formula was confirmed to be the same as that of dextrin (starch) [1]. The term ‘carbohydrate’ (French ‘hydrate de carbone’) was applied originally to monosaccha- rides, in recognition of the fact that their empirical composition can be expressed as C n (H 2 O) n . Although misleading, the term persists in general use in a wider sense, including monosaccharides, oligosaccharides (oligomers with a few monosaccharides), and polysaccharides (glycans consisting of a large number of monosaccharide units), as well as sub- stances derived from monosaccharides by reduction, oxidation, or by replacement of one or more hydroxy group(s) by heteroatomic groups. We prefer the term ‘sugar,’ which is frequently applied to monosaccharides and lower oligosac- charides. Strictly speaking, cyclitols (Section 4.6) are generally not regarded as carbohydrates, but are sugars. In a common parlance, sugars are often associated with a sweet taste. If we compare the sweetness of sugars to that of sucrose, the common sugar, which is a disaccharide formed of glucose and fructose, we observe that most of the sugars are only fairly sweet. Lactose, the milk sugar, a disaccharide of galactose and glucose, and maltose, the malt sugar, a disaccharide of two glucoses, are really not sweet at all (Table 4.1).
- Hari G. Garg, Mary K. Cowman, Charles A. Hales(Authors)
- 2011(Publication Date)
- Elsevier Science(Publisher)
A key crystallographic study on a small sugar molecule was that performed by Cox and Jeffrey (104) on a -D -glucosamine hydro-bromide, undertaken to settle the controversy as to the orientation of the amino group at C-2. Not only was this point resolved, but the three-dimensional architec-ture of the nonhydrogen atoms in the unit cell clearly demonstrated the familiar 4 C 1 chair conformation of the pyranose ring and the axial orientation of the hydroxyl group at C-1, long before the advent of NMR spectroscopy. The computa-tional burden of manually resolving the diffraction data was enormous in early work, but the introduction of digital computers has greatly facilitated the task to the point that the three-dimensional structure of most sugar derivatives for which a small single crystal is available can be obtained rapidly and routinely, greatly reducing the need for traditional degradative methods for structure determination. Since that pioneering 1939 crystallographic study on glucosamine, Jeffrey and Sundaralingam have compiled critical reviews of all published crystal structures dealing with sugars, nucleosides, and nucleotides (105) up through 1980, correcting where necessary the authors’ original interpretations and rendering the structures in familiar conformational depictions. It should be noted that most crystal-structure determinations do not differentiate between enantiomers, and require reference to a known center of chirality in the molecule. In addition to presenting the generalized chair conformations of the pyranose ring system, precise angular devia-tions from the ideal chair are represented as Cremer–Pople (106) puckering para-meters. The large volume of subsequent crystal structure data on sugars is accessible in the Cambridge Crystallographic Data Bank (107), and the 16 D. Horton Glycoscience database (108) provides a comprehensive resource on a wide range of structural data on carbohydrates of biological interest.
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