D Glucose
D-glucose is a simple sugar and a fundamental building block of carbohydrates. It is a hexose sugar, meaning it contains six carbon atoms. In its cyclic form, D-glucose is the most abundant monosaccharide and serves as a primary source of energy in living organisms.
6 Key excerpts on "D Glucose"
- Kim S Suvarna, Christopher Layton, John D. Bancroft(Authors)
- 2018(Publication Date)
- Elsevier(Publisher)
...Typical monosaccharides have the empirical formula (CH 2 O) n, where n is a value between 3 and 9. Glucose (Fig. 13.1) is a six-carbon simple carbohydrate which is not charged or ionized and referred to as a neutral sugar. Other neutral sugars include mannose, galactose and fructose. Monosaccharides contain asymmetric carbons referred to as chiral centers and the letters D or L at the beginning of a name refer to the structure of one of the chiral carbons within the molecule. D -Monosaccharides predominate in nature. The high numbers of hydroxyl (OH) groups present in the monosaccharide make most of them extremely water soluble. The majority of monosaccharides within a tissue specimen are lost during fixation and tissue processing due to their small size and water solubility and, as a result are not easily demonstrated by most histochemical techniques. The basic monosaccharide structure however, represents the building blocks of larger, more complex carbohydrates. The chemical and physical properties of the polysaccharides and glycoconjugates are largely determined by the types of monosaccharide which make up these molecules and the various reactive groups within them. Polysaccharides These are large macromolecules composed of multiple monosaccharides joined by covalent bonds known as glycosidic linkages. Fig. 13.2 demonstrates an α1–4 glycosidic linkage connecting two units of glucose which is the predominant linkage in the polysaccharides starch and glycogen. Additionally, some of the glucose units of these polysaccharides may have more than one glycosidic linkage, forming a branching structure resembling a tree. Starch and glycogen are large macromolecules with molecular weights exceeding 1 x 10 6 Daltons...
eBook - ePub- K. B. Sherrington, P. M. Gaman(Authors)
- 2010(Publication Date)
- Routledge(Publisher)
...5 Carbohydrates Carbohydrates are a group of nutrients important in the diet as a source of energy. They contain the elements carbon, hydrogen and oxygen and are produced in plants by the process of photosynthesis, which may be represented by the following equation: Chlorophyll is a green pigment which absorbs energy from sunlight and enables plants to build up carbohydrates from carbon dioxide and water. There are various different carbohydrates but they may be divided into three main groups according to the size of their molecules: Sugars 1 Monosaccharides The monosaccharide sugars commonly found in food contain six carbon atoms and have the general formula C 6 H 12 O 6. The three most important members of this group are: (A) Glucose (Dextrose) The structure of a molecule of glucose is shown in Figure 5.1. In the conventional representation the carbon atoms in the ring are omitted. Figure 5.1 Structure of glucose. Glucose is found in varying amounts in fruits and vegetables. Large amounts are found in fruits such as grapes and smaller quantities in vegetables such as young peas and carrots. It is also found in the blood of animals. Glucose syrup or commercial glucose is not pure glucose but a mixture of glucose, other carbohydrates and water (see page 65). (B) Fructose (Laevulose) This is chemically similar to glucose except that the arrangement of the atoms within the molecule is slightly different. Fructose is found, together with glucose, in many fruits and in honey. (C) Galactose This is also chemically similar to glucose. It does not exist as such in foods but is produced when lactose, a disaccharide, is broken down during digestion. 2 Disaccharides These sugars have the general formula C 12 H 22 C 11. They are formed when two monosaccharide molecules combine with the elimination of a water molecule. This is an example of a condensation reaction, i.e...
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 - ePubBiochemistry Explained
A Practical Guide to Learning Biochemistry
- Thomas Millar(Author)
- 2018(Publication Date)
- CRC Press(Publisher)
...3 Sugars In this chapter you will learn: the structure of monosaccharides, disacharides, polysaccharides and oligosaccharides the structure of glycerol, glyceraldehyde, glucose, mannose and galactose, glucosamine and galactosamine, N -acetylgalactosamine and N -acetylglucosamine, fructose, ribose and deoxyribose, AMP to recognise the importance of poly hydroxyl groups in sugars to understand the meaning of D-isomers and L-isomers the functional groups aldehyde and ketone about a chiral carbon how mutarotation forms an anomeric carbon and the à and á designation for sugars the basic structures of DNA and RNA the importance of the formation of an ester bond with phosphate and with sulphate the function of kinases O -glycosidic bonds and N -glycosidic bonds the structure and nomenclature of sugar acids. General structure of sugars Sugars, or saccharides, come under the more general name of carbohydrate. As the word carbohydrate suggests, they are hydrated carbon, or carbon with water added to it. As may be expected, carbohydrates have the general formulae (CH 2 O) n, where n is an integer of 3 or greater. The simplest carbohydrates are the sugars (monosaccharides) which have 3 to 9 carbon (C) elements. Structurally, sugars have two important features: more than one hydroxyl (OH) group (polyhydroxyl); and a carbonyl group (C = O) as either an aldehyde group (-CHO) or a ketone group (-CO-). The first of these points is important because sugars can be phosphorylated via an ester bond between one or more of the hydroxyl groups and phosphoric acid, or two sugars can be linked together by an ether bond. Aldoses The most commonly known sugar is the monosaccharide glucose. We understand its structure by perceiving it as a variation of glycerol. The aldehyde of glycerol is glyceraldehyde. Glucose is glyceraldehyde with an extra 3 carbons and an extra 3 hydroxyl groups (or another glycerol group)...
eBook - ePubBiermann's Handbook of Pulp and Paper
Volume 2: Paper and Board Making
- Pratima Bajpai(Author)
- 2018(Publication Date)
- Elsevier(Publisher)
...Some interesting facts regarding carbohydrates only hint at their remarkable properties. 1. Cellulose is the most abundant organic chemical on the face of the earth. 2. Some 400 billion tons of carbohydrates are produced annually by photosynthesis. 3. The typical diet consists of more than 60% (dry weight) of carbohydrates. 4. The major blood group types are determined by sequences and branching of carbohydrates. 5. Clearance of erythrocytes from the blood stream by the spleen is determined by the structure of oligosaccharides on the erythrocyte membrane. Generally, carbohydrates may be defined as polyhydroxy aldehydes or polyhydroxy ketones, occurring in their open chain forms or in their heterocyclic ring forms (the acetal or ketal forms). The simplest types of carbohydrates are called neutral sugars. Sugars may be chemically modified to form derivatives. Some examples include reduction of the carbonyl group to give alditols and oxidation of either terminal carbon to form sugar acids, acetylation or methylation of hydroxy 1 groups. The chemistry of carbohydrates is presented here to the extent that it is of importance to the understanding of cellulose and hemicelluloses during pulping and papermaking. For further information, introductory biochemistry, wood chemistry, and organic chemistry texts should be consulted. Many of these texts contain chapters devoted to carbohydrate chemistry. 17.2. Nomenclature The monosaccharides, simple sugars that cannot be easily hydrolyzed into smaller units, are classified according to the number of carbon atoms in the molecule. 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)...
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...
