D Glucose

8 Key excerpts on "D Glucose"

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  eBook - PDF

  Organic and Biological Chemistry

  • H. Stephen Stoker(Author)
  • 2015(Publication Date)
  • Cengage Learning EMEA

    (Publisher)

  ▶ It is often useful to have the structures of the six monosac-charides considered in this section memorized. 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. 264 CHAPTER 7 Carbohydrates d-Glucose Of all monosaccharides, D -glucose is the most abundant in nature and the most important from a human nutritional standpoint. Its Fischer projection formula is 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 Ripe fruits, particularly ripe grapes (20%–30% glucose by mass), are a good source of glucose, which is often referred to as grape sugar. Two other names for D -glucose are dextrose and blood sugar. The name dextrose draws attention to the fact that the optically active D -glucose, in aqueous solution, rotates plane-polarized light to the right. ◀ The term blood sugar draws attention to the fact that blood contains dissolveD Glucose. The normal concentration of glucose in human blood is in the range of 70–100 mg/dL (1 dL = 100 mL). The actual glucose concentration in blood is depend-ent on the time that has elapsed since the last meal was eaten. A concentration of about 130 mg/dL occurs in the first hour after eating, and then the concentration decreases over the next 2–3 hours back to the normal range. Cells use glucose as a primary source of energy (Figure 7-16). Two hormones, insulin and glucagon (Section 13-9), have important roles in keeping glucose blood concentrations within the normal range, which is required for normal body function.

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  Dietary Sugars

  Chemistry, Analysis, Function and Effects

  • Victor R Preedy(Author)
  • 2012(Publication Date)
  • Royal Society of Chemistry

    (Publisher)

  This molecular group can be defined as polyhydroxy aldehydes and polyhydroxy ketones or as substances that can release these compounds when they are hydrolysed. Their general chemical formula is [C(H 2 O)] n , where n Z 3. However, even though the majority of the saccharides present this empirical formula, some carbohydrates can include nitrogen, phosphorus or sulphur in their structures. The simplest carbohydrates, which cannot be hydrolysed into smaller sub-units, are known as monosaccharides. Monosaccharides can be one unit polyhydroxy aldehydes or polyhydroxy ketones. D-glucose is the most Food and Nutritional Components in Focus No. 3 Dietary Sugars: Chemistry, Analysis, Function and Effects Edited by Victor R Preedy r The Royal Society of Chemistry 2012 Published by the Royal Society of Chemistry, www.rsc.org 86 abundant of the monosaccharides and has a fundamental role in the energetic metabolism of living organisms. Another important monosaccharide is D-galactose. This sugar contains six carbons (hexose) and is frequently observed associated with glucose in the disaccharide lactose (Figure 6.1), which is present in the milk of mammals. D-galactose, like D-glucose, is an energetic source in cell metabolism. Information on galactose metabolism will be discussed in other chapters of this book. Briefly, in this biochemical process, D-galactose is converted into galactose-6-phosphate by the action of the enzyme galactokinase (GALK) through the consumption of ATP. After this reaction, UDP-galactose is obtained through the action of the enzyme galactose-1-phosphate uridyl-transferase (GALT). The enzyme UDP-galactose 4-epimerase catalyses the regeneration of UDP-glucose in the final step of normal galactose metabolism (Holden et al . 2003). After these reactions, glucose-6-phosphate is obtained through the action of a transferase and the enzyme phosphoglucomutase. Glucose-6-phosphate is then able to enter into the glycolysis pathway.

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  Introduction to General, Organic, and Biochemistry

  • 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.

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  Food Carbohydrates

  Chemistry, Physical Properties, and Applications

  • Steve W. Cui(Author)
  • 2005(Publication Date)
  • CRC Press

    (Publisher)

  While the pyranose forms dominate in aqueous solution of most monosaccharides, it is quite common to find furanose form when the sugar is incorporated into a biomolecule. The popular names of sugars often indicate their principal sources and their optical rotary properties. Synonyms for D -glucose are dextrose, grape sugar, and starch sugar. Synonyms for fructose are levulose, honey sugar, fruit sugar. FIGURE 1.16 Anomeric effect. O O O O β -anomer (less stable) α -anomer (more stable) 22 Food Carbohydrates: Chemistry, Physical Properties, and Applications 1.3 Oligosaccharides 1.3.1 Formation of Glycosidic Linkage The hemiacetal form of sugars can react with alcohol to produce a full acetal 4,12,13 according to the following reaction (Figure 1.17). The two products are more commonly referred to as glycosides — more specifically, as methyl α - and β -D -glucopyranosides. The carbohydrate ( glycon ) portion of the molecule is distinguished from the noncarbohydrate aglycon . The acetal linkage is formed from a glycosyl donor and a glycosyl acceptor. 1.3.2 Disaccharides Because carbohydrates are polyalcohols with primary and secondary alcohol groups, their alcohol groups can react with a hemiacetal hydroxyl group of another carbohydrate and form a glycoside between two carbohydrate units (Figure 1.18). Disaccharides are therefore glycosides in which the aglycon constitutes another monosaccharide unit. Taking D -glucose as a starting point, one can form 11 different disaccha-rides. α -D -Glucose can react with the alcohol group at C-2, C-3, C-4, and C-6 of another glucose unit to give four reducing disaccharides (Figure 1.19). β -D -Glucose can also react with the same alcohol group at C-2, C-3, C-4, and C-6 to give another four possible reducing disaccharides (Figure 1.20).

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  Textbook on Food Science and Human Nutrition

  • Sharma, Dipiti(Authors)
  • 2021(Publication Date)
  • Daya Publishing House

    (Publisher)

  Cannot be resold/distributed. 4.1.1.1. Monosaccharides These are simple sugars containing short chains of carbon atoms with one aldehydic or ketonic group (carbonyl group), each of remaining carbons bear a hydroxyl group. Polyhydroxy aldehydes or ketones that can’t easily be further hydrolyzed are “Simple sugars”. The simplest sugars are glyceraldehyde and dihydroxyacetone. Depending on the total no. of carbon atoms present in the monosaccharide molecule, they are designated as below: Number of Carbons Name Example 3 Trioses Glyceraldehyde 4 Tetroses Erythrose 5 Pentoses Ribose 6 Hexoses Glucose, Fructose 7 Heptoses Sedoheptulose 9 Nonoses Neuraminic acid Individual Monosaccharides are discussed below: 1. Glucose = Dextrose = Blood Sugar The parent monosacharide from which others are obtained and is also the basic building block of the most abundant polysaccharides-starch and cellulose. It is the most common carbohydrate. This is the main source of energy, most quickly absorbed by the human body. Glucose is the primary source of energy for brain. Glucose exists in the ring form, the body can metabolize only the D-isomer of glucose, the L isomer might be useful as an alternative sweetener. Relative sweetness of glucose is 0.7. This is found in ripe fruits, flowers, beetroot, honey etc. 2. Fructose = Levulose = Fruit Sugar It is a structural isomer of glucose. Although it is a hexose, but can form either a five or six member ring. Natural sources of fructose include fruits, some vegetables, honey (half fructose and half glucose), sugar cane and sugar beets. This is absorbed much slower than glucose. After absorption by the small intestine and transport to the liver, fructose is almost all metabolized to glucose. However some fructose is converted to glycogen, lactic acid, or This ebook is exclusively for this university only. Cannot be resold/distributed. glucose depending on the metabolic state of the individual.

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  Biochemistry

  An Integrative Approach

  • John T. Tansey(Author)
  • 2019(Publication Date)
  • Wiley

    (Publisher)

  Likewise, reactions that have ΔG° values close to zero can be tipped to move in either direction by changing the concentrations of substrates or products. • The synthesis of glucose and the degradation of monosaccharides use similar reactions but different pathways. Key steps are different, and compartmentalization is important. A similar theme is seen in fatty acid metabolism. DYNAMIC FIGURE 6.1 Carbohydrates can be simply classified as monosaccharides (single building blocks) or polysaccharides (polymers of monosaccharides). Polysaccharides can serve structural roles or can serve as a stored form of energy. Monosaccharides can be catabolized into pyruvate. Likewise, pyruvate can be used to synthesize new glucose through gluconeogenesis. 6.1 Properties, Nomenclature, and Biological Functions of Monosaccharides 163 6.1 Properties, Nomenclature, and Biological Functions of Monosaccharides Carbohydrates are a group of biological molecules with the basic formula C x (H 2 O) x , hence the name “carbo-hydrate.” At their most basic level, carbohydrates have the equivalent of one molecule of water for every carbon atom. This means that carbohydrates are polyhydroxy aldehydes or polyhydroxy ketones, that is, molecules in which one carbon bears a carbonyl group (CO) and the others all carry hydroxyls (OH). They also contain at least three carbons. We will first discuss the basic structures of carbohydrates and different ways we can represent these molecules on paper, and then we will move into modifications of these molecules. H C OH H C OH H C OH C CH 2 OH CH 2 OH O Generic formula Bond-angle depiction of a carbohydrate Fischer projection of a carbohydrate C x (H 2 O) x Formula of a carbohydrate C 6 H 12 O 6 O OH OH OH OH OH 6.1.1 Monosaccharides are the simplest carbohydrates This section focuses on the simplest carbohydrates, the monosaccharides. Monosaccharides can be linked together to form more complex carbohydrates.

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  Asymmetric Synthesis of Natural Products

  • 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).

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  The Components of Life

  From Nucleic Acids to Carbohydrates

  • Britannica Educational Publishing, Kara Rogers(Authors)
  • 2010(Publication Date)
  • Britannica Educational Publishing

    (Publisher)

  The generic nomenclature ending for the monosaccharides is -ose. Thus, the term pentose (pent = five) is used for monosaccharides containing five carbon atoms, and hexose (hex = six) is used for those containing six. In addition, because the monosaccharides contain a chemically reactive group that is either an aldehyde group or a keto group, they are frequently referred to as aldopentoses or ketopentoses or aldohexoses or ketohexoses. In the examples that follow, the aldehyde group is at position 1 of the aldopentose, and the keto group is at position 2 of the ketohexose. Glucose is an aldohexose—it contains six carbon atoms, and the chemically reactive group is an aldehyde group.

  BIOLOGICAL SIGNIFICANCE

  The importance of carbohydrates to living things can hardly be overemphasized. The energy stores of most animals and plants are both carbohydrate and lipid in nature. Carbohydrates are generally available as an immediate energy source, whereas lipids act as a long-term energy resource and tend to be utilized at a slower rate. Glucose, the prevalent uncombined, or free, sugar circulating in the blood of higher animals, is essential to cell function. The proper regulation of glucose metabolism is of paramount importance to survival.

  Sugar Beet

  The sugar beet (Beta vulgaris ) is a biennial plant of the Amaranthaceae family. It is cultivated for its juice, from which sugar is processed. The sugar beet is second only to sugarcane as the major source of the world’s sugar.

  Sugar was produced experimentally from beets in Germany in 1747 by the chemist Andreas Marggraf, but the first beet-sugar factory was built in Silesia in 1802. Napoleon became interested in the process in 1811 because the British blockade had cut off the French Empire’s raw sugar supply from the West Indies, and under his influence 40 factories to process beet sugar were established in France. The industry temporarily collapsed after Napoleon’s fall but recovered in the 1840s. Beet-sugar production then increased rapidly throughout Europe, and by 1880 the tonnage had overtaken that of cane sugar. Beet sugar now accounts for almost all sugar production in continental Europe and for almost one-third of total world production. The top 12 sugar-beet producing countries are France, the United States, Russia, Germany, Ukraine, Turkey, Poland, China, Belgium, Egypt, the Netherlands, and Iran.

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