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What Converts Galactose And Fructose To Glucose?

What Is Galactose?

What Is Galactose?

Galactose is a simple sugar, which belongs to simple carbohydrates. Galactose is composed of the same elements as glucose, but has a different arrangement of atoms. Name origin: From the Greek gala = milk, and -ose, which denotes sugar. Galactose Formula Picture 1. Galactose vs glucose structure Nutrition Facts for Galactose Calories per gram = 4.1 Glycemic index (GI) = ? Sweetness relative to sucrose = 30% Net carbohydrates = 100% Is galactose an essential nutrient? Galactose is not an essential nutrient, which means you do not need to get it from food to be healthy; galactose can be synthesized in the human body from glucose. Galactose Functions in the Human Body In the human body, most of the ingested galactose is converted to glucose, which can provide 4.1 kilocalories per gram of energy, which is about the same as sucrose [1]. Galactose can bind to glucose to make lactose (in breast milk), to lipids to make glycolipids (for example, molecules that constitute blood groups A, B and AB), or to proteins to make glycoproteins (for example, in cell membranes). Galactose Sources The main dietary source of galactose is lactose from milk and yogurt, which is digested to galactose and glucose [2,3]. Foods containing small amounts of free galactose include low-lactose or lactose-free milk, certain yogurts, cheeses, creams, ice creams and other foods artificially sweetened with galactose [4]. Plain natural foods (fruits, vegetables, nuts, grains, fresh meats, eggs, milk) usually contain less than 0.3 g galactose per serving [4]. Certain medications may contain galactose as a filler. Galactose Absorption Galactose is absorbed in the small intestine by the same mechanism as glucose, that is by the help of SGLT-1 and GLUT-2 transport proteins in the small intestinal lining [6]. I Continue reading >>

Carbohydrates

Carbohydrates

Carbohydrates (also called saccharides) are molecular compounds made from just three elements: carbon, hydrogen and oxygen. Monosaccharides (e.g. glucose) and disaccharides (e.g. sucrose) are relatively small molecules. They are often called sugars. Other carbohydrate molecules are very large (polysaccharides such as starch and cellulose). Carbohydrates are: a source of energy for the body e.g. glucose and a store of energy, e.g. starch in plants building blocks for polysaccharides (giant carbohydrates), e.g. cellulose in plants and glycogen in the human body components of other molecules eg DNA, RNA, glycolipids, glycoproteins, ATP Monosaccharides Monosaccharides are the simplest carbohydrates and are often called single sugars. They are the building blocks from which all bigger carbohydrates are made. Monosaccharides have the general molecular formula (CH2O)n, where n can be 3, 5 or 6. They can be classified according to the number of carbon atoms in a molecule: n = 3 trioses, e.g. glyceraldehyde n = 5 pentoses, e.g. ribose and deoxyribose ('pent' indicates 5) n = 6 hexoses, e.g. fructose, glucose and galactose ('hex' indicates 6) There is more than one molecule with the molecular formula C5H10O5 and more than one with the molecular formula C6H12O6. Molecules that have the same molecular formula but different structural formulae are called structural isomers. Glyceraldehyde's molecular formula is C3H6O3. Its structural formula shows it contains an aldehyde group (-CHO) and two hydroxyl groups (-OH). The presence of an aldehyde group means that glyceraldehyde can also be classified as an aldose. It is a reducing sugar and gives a positive test with Benedict's reagent. CH2OHCH(OH)CHO is oxidised by Benedict's reagent to CH2OHCH(OH)COOH; the aldehyde group is oxidised to Continue reading >>

Glycolysis Is An Energy-conversion Pathway In Many Organisms

Glycolysis Is An Energy-conversion Pathway In Many Organisms

We now start our consideration of the glycolytic pathway. This pathway is common to virtually all cells, both prokaryotic and eukaryotic. In eukaryotic cells, glycolysis takes place in the cytosol. This pathway can be thought of as comprising three stages (Figure 16.3). Stage 1, which is the conversion of glucose into fructose 1,6-bisphosphate, consists of three steps: a phosphorylation, an isomerization, and a second phosphorylation reaction. The strategy of these initial steps in glycolysis is to trap the glucose in the cell and form a compound that can be readily cleaved into phosphorylated three-carbon units. Stage 2 is the cleavage of the fructose 1,6-bisphosphate into two three-carbon fragments. These resulting three-carbon units are readily interconvertible. In stage 3, ATP is harvested when the three-carbon fragments are oxidized to pyruvate. Go to: 16.1.1. Hexokinase Traps Glucose in the Cell and Begins Glycolysis Glucose enters cells through specific transport proteins (Section 16.2.4) and has one principal fate: it is phosphorylated by ATP to form glucose 6-phosphate. This step is notable for two reasons: (1) glucose 6-phosphate cannot diffuse through the membrane, because of its negative charges, and (2) the addition of the phosphoryl group begins to destabilize glucose, thus facilitating its further metabolism. The transfer of the phosphoryl group from ATP to the hydroxyl group on carbon 6 of glucose is catalyzed by hexokinase. Phosphoryl transfer is a fundamental reaction in biochemistry and is one that was discussed in mechanistic and structural detail earlier (Section 9.4). Kinases are enzymes that catalyze the transfer of a phosphoryl group from ATP to an acceptor. Hexokinase, then, catalyzes the transfer of a phosphoryl group from ATP to a variety of s Continue reading >>

How Food Works

How Food Works

You have probably heard of "carbohydrates" and "complex carbohydrates." Carbohydrates provide your body with its basic fuel. Your body thinks about carbohydrates like a car engine thinks about gasoline. The simplest carbohydrate is glucose. Glucose, also called "blood sugar" and "dextrose," flows in the bloodstream so that it is available to every cell in your body. Your cells absorb glucose and convert it into energy to drive the cell. Specifically, a set of chemical reactions on glucose creates ATP (adenosine triphosphate), and a phosphate bond in ATP powers most of the machinery in any human cell. If you drink a solution of water and glucose, the glucose passes directly from your digestive system into the bloodstream. The word "carbohydrate" comes from the fact that glucose is made up of carbon and water. The chemical formula for glucose is: You can see that glucose is made of six carbon atoms (carbo...) and the elements of six water molecules (...hydrate). Glucose is a simple sugar, meaning that to our tongues it tastes sweet. There are other simple sugars that you have probably heard of. Fructose is the main sugar in fruits. Fructose has the same chemical formula as glucose (C6H12O6), but the atoms are arranged slightly differently. The liver converts fructose to glucose. Sucrose, also known as "white sugar" or "table sugar," is made of one glucose and one fructose molecule bonded together. Lactose (the sugar found in milk) is made of one glucose and one galactose molecule bonded together. Galactose, like fructose, has the same chemical components as glucose but the atoms are arranged differently. The liver also converts galactose to glucose. Maltose, the sugar found in malt, is made from two glucose atoms bonded together. Glucose, fructose and galactose are monosa Continue reading >>

Galactose - An Overview | Sciencedirect Topics

Galactose - An Overview | Sciencedirect Topics

Galactose is a naturally occurring monosaccharide that is found at high levels in milk and dairy products, and at low levels in many other foods. C.A. Williams, in Encyclopedia of Food Sciences and Nutrition (Second Edition) , 2003 Galactose is a monosaccharide and has the same chemical formula as glucose, i.e., C6H12O6. It is similar to glucose in its structure, differing only in the position of one hydroxyl group. This difference, however, gives galactose different chemical and biochemical properties to glucose. The major dietary source of galactose is lactose, a disaccharide formed from one molecule of glucose plus one of galactose. Lactose is found only in milk; after weaning, significant quantities of dietary lactose are found only in dairy products (Table 1). Lactose levels are lower than expected in some dairy products, where it has been used by the microbes involved in processing the food. Lactose, a byproduct of the dairy industry, can be hydrolyzed to produce lactose hydrolysate syrup, which contains lactose, galactose, and glucose. This syrup is used as a sweetener in biscuits, confectionery, and some dairy desserts. Thus, small amounts of lactose and galactose can appear in nondairy foods. (See Lactose.) Apart from its presence in lactose hydrolysate syrup, the monosaccharide galactose is seldom found in the diet, although it has been identified as a trace component of some seeds and pulses. Larry R. Engelking, in Textbook of Veterinary Physiological Chemistry (Third Edition) , 2015 Galactose, derived from dietary sources, is largely removed from the portal circulation by the liver and converted in a series of reactions to glucose 1-phosphate (Glc-1-P), and then to glucose 6-phosphate (Glc-6-P). The ability of the liver to accomplish this conversion forms t Continue reading >>

Catabolism Of Sugars Other Than Glucose

Catabolism Of Sugars Other Than Glucose

Catabolism of sugars other than glucose Starch is the most abundant carbohydrate in our diet, which makes glucose the most important dietary monosaccharide. However, our diet contains several other sugars in significant amounts. The guiding motif in the metabolism of these sugars is economy: instead of completely separate degradative pathways, there are short adapter pathways which merge into the main pathway of carbohydrate degradation, that is, glycolysis. Lactose and sucrose are disaccharides. Degradation of both sugars begins with hydrolytic cleavage, which releases glucose and galactose or glucose and fructose, respectively. Fructose is also found in the diet as a monosaccharide. We already know how glucose is degraded, so we here only need to concern ourselves with the remaining monosaccharides. The degradation of sorbitol will be discussed as well, whereas ribose and deoxyribose will be covered in later chapters. Sucrose is produced from sugar cane and sugar beet, which contain it in high concentrations (1520%). In a typical Western diet, it may amount to as much as 20% of the total carbohydrate intake. Sucrose consists of glucose and fructose joined by a -glycosidic bond between the carbon 1 of glucose and carbon 2 of fructose. The hydrolytic cleavage of sucrose, like that of of maltose, occurs at the surface of the intestinal epithelial cells. The enzyme responsible is -fructosidase, also named sucrase. Both sugars are then taken up by specific transport: Glucose by the SGLT1 transporter, and fructose by the GLUT5 transporter, which is named after glucose but actually transports fructose more effectively than glucose. Fructose degradation, also called fructolysis, runs mostly in the liver. In the first step, fructose is phosphorylated by fructokinase (1), whic Continue reading >>

Do All Sugars Transported To The Liver Convert To Glucose?

Do All Sugars Transported To The Liver Convert To Glucose?

Sugar can come from natural sources, such as fruits, honey and maple syrup, or added sugars, such as table sugar or high-fructose corn syrup. The way sugar is processed by your body does not depend on what food it is found in but rather on the nature of the sugar molecules. Some sugars need to be transported directly to the liver in order to be metabolized or processed by your body, while others can also be used directly by your muscles and brain. Fructose is transported to your liver to be converted to glucose or fat, while glucose can be burned for energy as is anywhere in your body. Types of Sugars Glucose is one of the main sugar molecules found in various types of sugar. The sucrose found in table sugar and maple sugar is actually half glucose. Dextrose is 100 percent glucose. Although fructose is usually thought to be the main sugar in fruits, all fruits also contain varying proportion of glucose and sucrose. Both fructose and glucose are also found in high-fructose corn syrup, agave syrup and other sweeteners. Glucose Metabolism Once absorbed into your bloodstream, glucose does not necessarily have to be transported to your liver. Almost all of your cells, including the cells of your liver, muscles, brain and fat, can take some of the glucose circulating in your blood. Glucose can be used as a form of energy by most of your cells and converted to glycogen by your liver or muscles or converted to fat in your fat cells. Fructose Metabolism Fructose can only be processed by your liver. After absorbing fructose from fruits or a food sweetened with sugar, agave syrup or high-fructose corn syrup, fructose enters your bloodstream to be transported right to your liver. Part of this fructose can be converted into glucose by the liver to be stored as glycogen, and the rema Continue reading >>

Hnf Midterm Exam Flashcards | Quizlet

Hnf Midterm Exam Flashcards | Quizlet

Some public health nutritionists are ineligible to take the Academy of Nutrition and Dietetics exam. Which food is commonly included in Indian meals? Which of the following are not macronutrients? Which of the following is not a proposed focus of Healthy People 2020? Support food industry efforts to obtain favorable health claims on nutrition labels. Minerals are inorganic because they do not contain carbon. research that involves looking at factors in two or more groups of subjects to see if there is a relationship to certain outcomes. Which nutrient class is used to build body tissues and make enzymes Mutton is a staple in the diet of which ethnic group? Over 65 percent of American adults are overweight and of those, approximately 50 percent are considered obese. What percentage of American adults are considered obese? A well-balanced diet includes all of the following except A regular magazine is just as credible as a peer-reviewed journal. A research journal in which fellow scientists review studies to assess if they are accurate before they are published is known as a peer-reviewed journal. Only the energy nutrient carbohydrate contains the element nitrogen. Which is the correct definition of the term organic? According to Healthy People 2020, Americans' body weights are decreasing. All of the following are correct about the typical American diet except that it is Which of the following is not a function of water in the body? Which of the following is not true about phytochemicals? The reference values for the essential nutrients needed to maintain good health, to prevent chronic diseases, and to avoid excesses are known as the A food is considered high in a nutrient if it provides If one cup of reduced-fat milk provides 8 percent of your Daily Value for fat, this Continue reading >>

Galactose

Galactose

For the EP by The Sweet Science, see Galactose (EP). Galactose (galacto- + -ose, "milk sugar"), sometimes abbreviated Gal, is a monosaccharide sugar that is about as sweet as glucose, and about 65% as sweet as sucrose.[1] It is a C-4 epimer of glucose.[2] Galactan is a polymeric form of galactose found in hemicellulose, and forming the core of the galactans, a class of natural polymeric carbohydrates.[3] Etymology[edit] The word "Galactose" is coined by Charles Weissman[4]in mid 19th century from Greek galaktos("milk") and the generic chemical suffix for sugars -ose.[5] Structure and isomerism[edit] Galactose exists in both open-chain and cyclic form. The open-chain form has a carbonyl at the end of the chain. Four isomers are cyclic, two of them with a pyranose (six-membered) ring, two with a furanose (five-membered) ring. Galactofuranose occurs in bacteria, fungi and protozoa ,[6] and is recognized by a putative chordate immune lectin intelectin through its exocyclic 1,2-diol. In the cyclic form there are two anomers, named alpha and beta, since the transition from the open-chain form to the cyclic form involves the creation of a new stereocenter at the site of the open-chain carbonyl. In the beta form, the alcohol group is in the equatorial position, whereas in the alpha form, the alcohol group is in the axial position.[7] Cyclic forms of galactose Relationship to lactose[edit] Galactose is a monosaccharide. When combined with glucose (monosaccharide), through a condensation reaction, the result is the disaccharide lactose. The hydrolysis of lactose to glucose and galactose is catalyzed by the enzymes lactase and β-galactosidase. The latter is produced by the lac operon in Escherichia coli. In nature, lactose is found primarily in milk and milk products. Consequentl Continue reading >>

Digestion, Absorption And Transport Of Carbohydrates

Digestion, Absorption And Transport Of Carbohydrates

Sign up to our newsletter Receive the latest newsletter with research on sugar. Plus insights from scientific experts. Carbohydrates are broken down to provide glucose for energy Digestion predominantly occurs via enzymes lining the wall of the small intestine Once absorbed, galactose and fructose are metabolised further by the liver to produce glucose and minimal amounts of other metabolites ___________________ The metabolism of carbohydrates is the process of getting the carbohydrates in the foods we eat into the right format to provide fuel to our body's cells. This process involves digestion, absorption and transportation. Most commonly, carbohydrate metabolism results in the production of glucose molecules which are the most efficient source of energy (ATP) for our muscles and our brains. Energy or fuel from our food is used for cell growth, repair and normal cell functioning. Digestion Carbohydrates are most commonly consumed as polysaccharides (e.g. starch, fibre or cellulose) or disaccharides (e.g. lactose, sucrose, galactose) and therefore need to be broken down into their simpler monosaccharide forms which the body can utilise. The digestion process of polysaccharides such as starch will begin in the mouth where it is hydrolysed by salivary amylase. The amount of starch hydrolysed in this environment is often quite small as most food does not stay in the mouth long. Once the food bolus reaches the stomach the salivary enzymes are denatured. As a result, digestion predominantly occurs in the small intestine with pancreatic amylase hydrolysing the starch to dextrin and maltose. Enzymes classed as glucosidases on the brush border of the small intestine break down the dextrin and maltase, lactase and sucrase convert the other disaccharides into their two monosacch Continue reading >>

Why Is Ribose Not A Dietary Consideration

Why Is Ribose Not A Dietary Consideration

Carbohydrates Structures and Function Simple sugars: monosaccharides, disaccharides, oligosaccharides) Complex sugar: polysaccharides (starch and fiber) Monosaccharides (glucose, fructose, and galactose – isomers of each other) Glucose (also called dextrose and blood sugar) has a six carbon (hexose) ring structure Fructose (also called levulose) has a six carbon ring structure Found in fruit, honey, and corn syrup used in soft drink and food production 8 to 10% of our energy intake Metabolized into glucose in the liver Converted into glycogen, lactic acid, or fat if consumption is high Galactose has a six carbon ring structure Not usually found in nature but exists mostly as a unit of the disaccharide lactose which is found in nature Converted to glucose in the liver or stored as glycogen Ribose has a five carbon ring structure and used in genetic material (?) Oligosaccharides Raffinose (trisaccharide - made up of glucose, fructose, and galactose) Stachyose (tetrasaccharide - made up of a glucose, fructose, and two galactose) Bacteria in the large intestines break apart these oligosaccharides, producing gas and other byproducts Complex Cabohydrates (Digestible starch and glycogen and indigestible fiber) Starch Amylose is a straight chain polymer Amylopectin is a branched chain polymer Amylopectin raises blood sugar levels quicker because of the branched configuration which enables more digestive capabilities Fiber Dietary fibers also composed of the non-carbohydrate called lignin All dietary fibers come from plants and are not digested in the stomach But fibers can be soluble and insoluble in water Those that are soluble include pectins, gums, and mucilages and are metabolized by bacteria in the intestines Carbohydrate Digestion and Absorption Begins in the mouth (sal Continue reading >>

Human Nutrition Ch 4

Human Nutrition Ch 4

In what form glucose stored in plants? In the human body? How are the bonds in most fibers different from starch? What foods are rich in soluble fiber? What part of grain is rich in soluble fiber? Why is carbohydrate the preferred source? They aren't expensive, and the brain prefers them for fuel over protein and fats What is the main source of energy for nerve cells? What is the minimum amount of CHO per day? What percent of our total calories should come from CHO? How much fiber is recommended for young men? Young women? What are the main actions of soluble fiber in the body? Insoluble fiber? Soluble: lowers blood cholesterol and helps to control blood glucose Insoluble: ease elimination in the digestive system What disease or conditions may be reduced by the inclusion of fiber in the diet? What type of fiber is most likely to lower blood cholesterol? What are diverticula? What factor in the diet may decrease their presence? They are abnormally bulging pockets in the colon wall How does the average intake of fiber compare with the suggested intake? Suggested fiber intake is 2x higher than the average Comment on the fiber content of meats and dairy products. In dairy and meat products there is no fiber Why may a very high fiber diet be potentially harmful? Blockage in the intestines, replace other needed nutrients, prevent nutrient absorption in the binding process In what part of the body does starch digestion begin? CHO is broken down into _____ before it is absorbed? What three parts of a wheat kernel are removed in the refinement process? How does the definition of wheat flour differ from whole wheat flour? White flour has been refined and bleached, whole wheat flour is made from whole wheat kernels Is unbleached flour more similar to white or whole wheat flour in Continue reading >>

Carbohydrate Chapter 4

Carbohydrate Chapter 4

what are the six major classes of nutrients vitamins, water minerals carbs fats and proteins break up the six classes of nutrients into organic and inorganic categories organic-carbs, fat protein vitaminsinorganic-minerals and water the study of the nutrients and other substances in foods and the bodies handling of them what are the foundation sciences of nutrition identify methods for assessing nutrient status historical info, anthropometric measurements, physical exam and lab tests what are the ten leading causes of death in the US heart disease, cancer, stroke, chronic lung disease, accidents, diabetes mellitus, pneumonia/influenza, alzeimers disease, kidney disease, and blood infections what are the diet planning principles as they as apply to food selections adequacy, balance, kcalorie (energy)control, nutrient desity, moderation, variety what are the ten dietary guidelines for americans aim for a healthy weight, be physically active every day, let the pyramid guide your food choices, choose a variety of grains daily, choose a variety of fruits and vegetables daily, keep foods safe to eat, low in cholesterol and moderate in total fat, intake of sugar, less salt, alcoholic beverages to a minimum what is the main goal for healthy people 2010 focus on improving the quality of life and eliminating disparity in health among racial and ethnic groups daily food guide, notable nutrients, miscellaneous foods, mixtures of foods, nutrient density, recommended servings, serving sizes, food guide pyramid, vegetarian food guide, ethnic food choices, and perceptions vs actual intakes help in achieving kcal control and moderation (originally for diabetics) what are the four components of the food label ingredients, serving sizes, nutrition facts and daily values what is the diffe Continue reading >>

2.4.4. Fructose And Galactose Metabolism And Pentose Pathway Flashcards Preview

2.4.4. Fructose And Galactose Metabolism And Pentose Pathway Flashcards Preview

hepatic fructokinase cant convert Fructose to Fructose-1-phosphate What symptoms do we see with Essential Fructosemia? symptoms: fructosemia (relatively mild), fructosuria after fructose injection. It ismostly a benign condition becausefructose is slowly phosphorylated by hexokinase in OTHER tissues and still metabolized via glycolysis. Hereditary pattern and defect associated with Hereditary Fructose Intolerance? Defect:aldolase B is defective (liver) andcant create glyceraldehyde and dihydroxyacetone phosphate (DHAP) from F1P.Ultimately, F1P accumulates and inhibits glucose production, causing severe hypoglycemia if any more fructose is ingested Effect of Hereditary Fructose Intolerence on Glycolysis as compared to fructose metabolism? Aldolase B can function just fine in GLYCOLYSIS (on F-1,6-BP), BUT NOT in fructose metabolism, since this enzyme is the sole metabolizer of Fructose-1-phosphate How does Hereditary Fructose Intolerance cause fasting hypoglycemia? F1P is a competitive inhibitor of glycogen phosphorylase (allows glycogen to be catabolized into glucose) and if F1P accumulates, ATP and Pi are depleted Where does the defect for galactosemia typically present itself? Where else can it present itself in a less common way? Classic - Defect in the enzyme Galactose-1-phosphate uridylyltransferase that turns Galactose 1-phosphate into glucose1-phosphate. It can also present itself in the first,irreversible, step of this process just before the classic route with a bad galactokinase enzyme that turns Galactose into Galactose 1-Phosphate Describe Galactose metabolism and indicate where galactosemia typically presents itself. May initially present as failure to track objects or to develop a social smile Effect of eating a meal and fasting on the conversion of galact Continue reading >>

Contribution Of Galactose And Fructose To Glucose Homeostasis

Contribution Of Galactose And Fructose To Glucose Homeostasis

Contribution of Galactose and Fructose to Glucose Homeostasis Jorge A. Coss-Bu , Agneta L. Sunehag , and Morey W. Haymond Department of Pediatrics, Childrens Nutrition Research Center, U.S. Department of Agriculture/Agricultural Research Service, Baylor College of Medicine, Houston, Texas 77030 Corresponding Author, Morey W. Haymond, M.D., Childrens Nutrition Research Center, 1100 Bates St., Houston, TX 77030-2600, E-mail: ude.cmt.mcb @ dnomyahm The publisher's final edited version of this article is available at Metabolism See other articles in PMC that cite the published article. To determine the contributions of galactose and fructose to glucose formation, six subjects (262 y; BMI 22.40.2 kg/m2) (MeanSE) were studied during fasting conditions. Three subjects received a primed constant intravenous infusion of [6,6-2H2]glucose for 3 h followed by oral bolus ingestion of galactose labeled to 2% with [U-13C]galactose (0.72 gm/kg); the other three subjects received a primed constant intravenous infusion of [6,6-2H2]glucose followed by either a bolus ingestion of fructose alone (0.72 gm/kg) (labeled to 2% with [U-13C]fructose) or co-ingestion of fructose (labeled with [U-13C]fructose) (0.72 gm/kg) and unlabeled glucose (0.72 gm/kg). Four hours after ingestion, subjects received 1 mg of glucagon intravenously to stimulate glycogenolysis. When galactose was ingested alone, the area under the curve (AUC) of [13C6] glucose and [13C3] glucose were 7.28 0.39 and 3.52 0.05 mMole/l per 4 h respectively. When [U-13C] fructose was ingested with unlabeled fructose or unlabeled fructose plus glucose, no [13C6] glucose was detected in plasma. The AUC of [13C3] glucose after fructose and fructose plus glucose ingestion were 20.21 2.41 and 6.25 0.34 mMol/l per 4h respectively. Comparing Continue reading >>

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