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Describe The Fate Of Glucose In The Glucose Fructose Sucrose System Shown Above

Lecture 4a: Carbohydrates

Lecture 4a: Carbohydrates

Policy about returning exams: To prevent exams from being in circulation (which would decrease their reliability as an assessment tool), you're not able to see graded exams online. Students in campus sections are also not allowed to keep their exams. Those of you in this area are welcome to come see me during my office hours and you can see your exam then. I also posted your grade as of Exam 1, it will show you your total points earned plus a percentage of total points. See syllabus for details on how this percentage translates into a letter grade. The second EXAM isWeek 5 on carbohydrates. It will be available to take on Tuesday of Week 5, but is due THURSDAY of Week 5. What did you learn in this chapter that made you think differently about carbohydrates? How will this impact your food choices? As you're looking at this lecture, have in front of you your lecture outline for Ch. 4- Part 2 to fill in the blanks and to answer the questions. The Lecture Outline in your packet begins by asking this question: If someone told you "My carbohydrate intake is too high", what would you assume about what they're eating? When I've asked this question in class, the two most common things people say are: BOTH of these kinds of foods are high in carbohydrates, but the kinds of carbohydrates are different, Bread is high in the carbohydrate starch and sweets are high in sugar. A third type of carbohydrate is fiber and it's the one that sometimes people don't think of as a carbohydrate. which include SIMPLE and COMPLEX Carbohydrates. SIMPLECarbohydrate and starch and fiber are both III Digestion & Absorption of Carbohydrates Notice that BOTH monosaccharides and disaccharides are SIMPLE CARBOHYRATES. Glucose, fructose and galactose are MONOsaccharides and maltose, sucrose and lactose ar Continue reading >>

Fructose

Fructose

Fructose, or fruit sugar, is a simple ketonic monosaccharide found in many plants, where it is often bonded to glucose to form the disaccharide, sucrose. It is one of the three dietary monosaccharides, along with glucose and galactose, that are absorbed directly into blood during digestion. Fructose was discovered by French chemist Augustin-Pierre Dubrunfaut in 1847.[4][5] The name “fructose” was coined in 1857 by the English chemist, William Allen Miller.[6] Pure, dry fructose is a sweet, white, odorless, crystalline solid, and is the most water-soluble of all the sugars.[7] Fructose is found in honey, tree and vine fruits, flowers, berries, and most root vegetables. Commercially, fructose is derived from sugar cane, sugar beets, and maize. Crystalline fructose is the monosaccharide, dried, ground, and of high purity. High-fructose corn syrup is a mixture of glucose and fructose as monosaccharides. Sucrose is a compound with one molecule of glucose covalently linked to one molecule of fructose. All forms of fructose, including fruits and juices, are commonly added to foods and drinks for palatability and taste enhancement, and for browning of some foods, such as baked goods. About 240,000 tonnes of crystalline fructose are produced annually.[8] As for any sugar, excessive consumption of fructose may contribute to insulin resistance, obesity,[9] elevated LDL cholesterol and triglycerides, leading to metabolic syndrome,[10][11][12] type 2 diabetes and cardiovascular disease.[13] The European Food Safety Authority stated that fructose is preferable over sucrose and glucose in sugar-sweetened foods and beverages because of its lower effect on postprandial blood sugar levels, and also noted that “high intakes of fructose may lead to metabolic complications such as dys Continue reading >>

Fructose Metabolism And Relation To Atherosclerosis, Type 2 Diabetes, And Obesity

Fructose Metabolism And Relation To Atherosclerosis, Type 2 Diabetes, And Obesity

Journal of Nutrition and Metabolism Volume 2015 (2015), Article ID 823081, 12 pages 1Faculty of Public Health, Hedmark University College, P.O. Box 400, 2418 Elverum, Norway 2Norwegian University of Life Sciences, P.O. Box 5003, 1432 Aas, Norway Academic Editor: Michael B. Zemel Copyright © 2015 Astrid Kolderup and Birger Svihus. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. A high intake of sugars has been linked to diet-induced health problems. The fructose content in sugars consumed may also affect health, although the extent to which fructose has a particularly significant negative impact on health remains controversial. The aim of this narrative review is to describe the body’s fructose management and to discuss the role of fructose as a risk factor for atherosclerosis, type 2 diabetes, and obesity. Despite some positive effects of fructose, such as high relative sweetness, high thermogenic effect, and low glycaemic index, a high intake of fructose, particularly when combined with glucose, can, to a larger extent than a similar glucose intake, lead to metabolic changes in the liver. Increased de novo lipogenesis (DNL), and thus altered blood lipid profile, seems to be the most prominent change. More studies with realistic consumption levels of fructose are needed, but current literature does not indicate that a normal consumption of fructose (approximately 50–60 g/day) increases the risk of atherosclerosis, type 2 diabetes, or obesity more than consumption of other sugars. However, a high intake of fructose, particularly if combined with a high energy intake in the form of glucose/starch, ma Continue reading >>

Health Implications Of Fructose Consumption: A Review Of Recent Data

Health Implications Of Fructose Consumption: A Review Of Recent Data

Health implications of fructose consumption: A review of recent data 1INSERM, U872, quipe 7 Nutriomique, Universit Pierre et Marie Curie-Paris 6, Centre de Recherche des Cordeliers, UMR S 872, Paris, 75006 France 2Centre de Recherche Nutrition Humaine, Ile de France, Assistance Publique-Hpitaux de Paris, Hpital Piti-Salptrire, Dpartement de Nutrition et d'Endocrinologie, Paris, 75013 France 1INSERM, U872, quipe 7 Nutriomique, Universit Pierre et Marie Curie-Paris 6, Centre de Recherche des Cordeliers, UMR S 872, Paris, 75006 France 2Centre de Recherche Nutrition Humaine, Ile de France, Assistance Publique-Hpitaux de Paris, Hpital Piti-Salptrire, Dpartement de Nutrition et d'Endocrinologie, Paris, 75013 France Received 2010 Feb 12; Accepted 2010 Nov 4. Copyright 2010 Rizkalla; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( ), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. This article has been cited by other articles in PMC. This paper reviews evidence in the context of current research linking dietary fructose to health risk markers. Fructose intake has recently received considerable media attention, most of which has been negative. The assertion has been that dietary fructose is less satiating and more lipogenic than other sugars. However, no fully relevant data have been presented to account for a direct link between dietary fructose intake and health risk markers such as obesity, triglyceride accumulation and insulin resistance in humans. First: a re-evaluation of published epidemiological studies concerning the consumption of dietary fructose or mainly high fructose corn syrup shows that most of such stu Continue reading >>

Sugars: The Difference Between Fructose, Glucose And Sucrose

Sugars: The Difference Between Fructose, Glucose And Sucrose

29/06/2016 7:43 AM AEST | Updated 15/07/2016 12:56 PM AEST Sugars: The Difference Between Fructose, Glucose And Sucrose We're not just confused, we're also misinformed. "Fructose is the worst for you." "No way, sucrose is the devil." "I don't eat any sugar." Sugar is confusing. While some people only use certain types of sugars, others dismiss them completely. But is this necessary, or even grounded? To help settle the confusion, we spoke to Alan Barclay -- accredited practising dietitian, spokesperson for the Dietitians Association of Australia and Chief Scientific Officer at the Glycemic Index Foundation . "All the sugars are used as a source of fuel, but there are subtle differences in the way they are digested and absorbed," Barclay said. "In foods in Australia, the most common sugars are monosaccharides (glucose, fructose and galactose), but mostly these are occurring as disaccharides (which are sucrose, lactose and maltose)." Monosaccharides and disaccharides are two kinds of simple sugars, which are a form of carbohydrate. Oligosaccharides and polysaccharides, on the other hand, contain more sugar combinations and are known as complex carbohydrates -- for example, whole grain breads, brown rice and sweet potatoes. Monosaccharides require the least effort by the body to break down, meaning they are available for energy more quickly than disaccharides. "Monosaccharides don't require any digestion and can be absorbed into the mouth," Barclay said. "The problem there is they can cause dental caries which is one of the primary reasons why we need to be careful of how much added sugar we're consuming." Glucose -- the body's main source of energy and is found in fruit such as pasta, whole grain bread, legumes and a range of vegetables. Fructose -- this 'fruit sugar' fo Continue reading >>

Module 6: Glucose Flashcards | Quizlet

Module 6: Glucose Flashcards | Quizlet

transfers electrons from a two-electron carrier to a one-electron carrier. Electron flow down the electron-transport chain leads to: the transport of protons across the inner mitochondrial membrane from inside the matrix to the intermembrane space. the transport of protons across the inner mitochondrial membrane from the intermembrane space into the matrix. a dangerous imbalance of K+ ions across the mitochondrial membrane. the transport of protons across the inner mitochondrial membrane from inside the matrix to the intermembrane space. ROS are feedback inhibitors of the ET chain Formation of water necessary for cell metabolism Is prevented Enzymes that reduce ROS make toxic molecules that damage DNA, proteins, and lipids The presence of ROS induces proteins to be made that damage cells What is the name given to the hypothesis proposed by Peter Mitchell to explain how ATP synthesis is coupled to electron transport. How does the rotation of the c ring lead to ATP synthesis? The c ring is linked tightly to the gamma and epsilon subunits in the stalk of F1. The c ring interacts with the beta subunit. The gamma subunit rotates with proton gradient formation, inducing the binding-change mechanism. Why is it more sensible for phosphofructokinase, rather than hexokinase, to be an important control step? Phosphofructokinase is involved with the committed step, the conversion of fructose 6-phosphate and ATP to fructose 1,6-bisphosphate and ADP in the glycolysis. Because it's a committing step, its an important allosteric regulatory control mechanism. It can increase or decrease the rate of glycolysis in response to the cell's energy requirements. In contrast, production of glucose 6-phosphate is the first step in many different paths. Thus, glycolytic control would not be main Continue reading >>

Connections Of Carbohydrate, Protein, And Lipid Metabolic Pathways

Connections Of Carbohydrate, Protein, And Lipid Metabolic Pathways

Connecting Other Sugars to Glucose Metabolism Sugars, such as galactose, fructose, and glycogen, are catabolized into new products in order to enter the glycolytic pathway. Learning Objectives Identify the types of sugars involved in glucose metabolism Key Takeaways When blood sugar levels drop, glycogen is broken down into glucose -1-phosphate, which is then converted to glucose-6-phosphate and enters glycolysis for ATP production. In the liver, galactose is converted to glucose-6-phosphate in order to enter the glycolytic pathway. Fructose is converted into glycogen in the liver and then follows the same pathway as glycogen to enter glycolysis. Sucrose is broken down into glucose and fructose; glucose enters the pathway directly while fructose is converted to glycogen. disaccharide: A sugar, such as sucrose, maltose, or lactose, consisting of two monosaccharides combined together. glycogen: A polysaccharide that is the main form of carbohydrate storage in animals; converted to glucose as needed. monosaccharide: A simple sugar such as glucose, fructose, or deoxyribose that has a single ring. You have learned about the catabolism of glucose, which provides energy to living cells. But living things consume more than glucose for food. How does a turkey sandwich end up as ATP in your cells? This happens because all of the catabolic pathways for carbohydrates, proteins, and lipids eventually connect into glycolysis and the citric acid cycle pathways. Metabolic pathways should be thought of as porous; that is, substances enter from other pathways, and intermediates leave for other pathways. These pathways are not closed systems. Many of the substrates, intermediates, and products in a particular pathway are reactants in other pathways. Like sugars and amino acids, the catabo Continue reading >>

The Difference In How Fructose And Glucose Affect Your Body

The Difference In How Fructose And Glucose Affect Your Body

My regular readers know that I consider agave to be a BIG enemy to health and beauty- which is very high in fructose (up to 97% fructose). It truly irks me that sly marketing makes the general public think agave is a “healthy” sweetener, and that it continues to be used in “health” products purported to be better than regular baked or other goods, as well as in many restaurants. It is not. There is a myth that exists that fructose is a “healthy” sugar while glucose is bad stuff. In fact, in recent years, there has been a rise in sweeteners that contain this “healthy” sugar, such as the dreaded agave nectar. I sincerely hope that this information (please help spread it!) makes more people aware of the differences in sugar types, and makes more people know to avoid agave at all costs. S.O.S: Save Our Skin!!! Fructose Fructose is one type of sugar molecule. It occurs naturally in fresh fruits, giving them their sweetness. Because of this, many people consider fructose “natural,” and assume that all fructose products are healthier than other types of sugar. Likewise, fructose has a low glycemic index, meaning it has minimal impact on blood glucose levels. This has made it a popular sweetener with people on low-carbohydrate and low-glycemic diets, which aim to minimize blood glucose levels in order to minimize insulin release. But the glycemic index is not the sole determining factor in whether a sweetener is “healthy” or desirable to use. Because fructose is very sweet, fruit contains relatively small amounts, providing your body with just a little bit of the sugar, which is very easily handled. If people continued to eat fructose only in fruit and occasionally honey as our ancestors did, the body would easily process it without any problems. Unfortu Continue reading >>

What Is The Difference Between Sucrose, Glucose & Fructose?

What Is The Difference Between Sucrose, Glucose & Fructose?

Sucrose, glucose and fructose are important carbohydrates, commonly referred to as simple sugars. Sugar is found naturally in whole foods and is often added to processed foods to sweeten them and increase flavor. Your tongue can't quite distinguish between these sugars, but your body can tell the difference. They all provide the same amount of energy per gram, but are processed and used differently throughout the body. Structure Simple carbohydrates are classified as either monosaccharides or disaccharides. Monosaccharides are the simplest, most basic units of carbohydrates and are made up of only one sugar unit. Glucose and fructose are monosaccharides and are the building blocks of sucrose, a disaccharide. Thus, disaccharides are just a pair of linked sugar molecules. They are formed when two monosaccharides are joined together and a molecule of water is removed -- a dehydration reaction. The most important monosaccharide is glucose, the body’s preferred energy source. Glucose is also called blood sugar, as it circulates in the blood, and relies on the enzymes glucokinase or hexokinase to initiate metabolism. Your body processes most carbohydrates you eat into glucose, either to be used immediately for energy or to be stored in muscle cells or the liver as glycogen for later use. Unlike fructose, insulin is secreted primarily in response to elevated blood concentrations of glucose, and insulin facilitates the entry of glucose into cells. Fructose is a sugar found naturally in many fruits and vegetables, and added to various beverages such as soda and fruit-flavored drinks. However, it is very different from other sugars because it has a different metabolic pathway and is not the preferred energy source for muscles or the brain. Fructose is only metabolized in the li Continue reading >>

Carbohydrate Metabolism

Carbohydrate Metabolism

The metabolism of the sugars found in our food is discussed in all textbooks and I will not take up all of the details here. The points I do wish to discuss are concerned with maintenance of blood sugar levels under differing physiological conditions. How do we start up storage of glucose after a meal? How do we preserve blood glucose levels between meals? What are the differences in metabolism of common sugars in various organs? Transport of Glucose in and out of the Liver The whole thing begins with transport of sugars over tissue membranes. These "small" sugars (glucose, fructose and galactose) are so large that they cannot cross cell membranes without "carriers". Sugar carriers are proteins embedded in the cell's outer membrane that provide transport systems for monosaccharides. The glucose transport protein family (called GLUT) is discussed elsewhere in MedBio. Click here for more information . The point to note now is that these carriers are bidirectional; they can transport glucose both into and out of cells. The direction of movement is determined by the concentrations of glucose in and outside of the liver cell. This is illustrated in the figure to the left. Drawing "1" shows the situation when the portal blood and the liver cell have equal concentrations of glucose; sugar moves in both directions simultaneously. This may seem to be wasteful, but gears the system to react to small changes in glucose concentration. The second drawing shows what happens when blood glucose tends to fall. Glucose production in the liver accelerates and the net flow of glucose is outward, stabilizing the blood sugar level. This is extremely important. The total amount of sugar present in the blood can support resting activity for about 40 minutes. Just walking increases glucose use Continue reading >>

Connections Between Cellular Respiration And Other Pathways

Connections Between Cellular Respiration And Other Pathways

So far, we’ve spent a lot of time describing the pathways used to break down glucose. When you sit down for lunch, you might have a turkey sandwich, a veggie burger, or a salad, but you’re probably not going to dig in to a bowl of pure glucose. How, then, are the other components of food – such as proteins, lipids, and non-glucose carbohydrates – broken down to generate ATP? As it turns out, the cellular respiration pathways we’ve already seen are central to the extraction of energy from all these different molecules. Amino acids, lipids, and other carbohydrates can be converted to various intermediates of glycolysis and the citric acid cycle, allowing them to slip into the cellular respiration pathway through a multitude of side doors. Once these molecules enter the pathway, it makes no difference where they came from: they’ll simply go through the remaining steps, yielding NADH, FADH​, and ATP. Simplified image of cellular respiration pathways, showing the different stages at which various types of molecules can enter. Glycolysis: Sugars, glycerol from fats, and some types of amino acids can enter cellular respiration during glycolysis. Pyruvate oxidation: Some types of amino acids can enter as pyruvate. Citric acid cycle: Fatty acids from fats and certain types of amino acids can enter as acetyl CoA, and other types of amino acids can enter as citric acid cycle intermediates. In addition, not every molecule that enters cellular respiration will complete the entire pathway. Just as various types of molecules can feed into cellular respiration through different intermediates, so intermediates of glycolysis and the citric acid cycle may be removed at various stages and used to make other molecules. For instance, many intermediates of glycolysis and the cit Continue reading >>

Insights Into The Hexose Liver Metabolismglucose Versus Fructose

Insights Into The Hexose Liver Metabolismglucose Versus Fructose

Insights into the Hexose Liver MetabolismGlucose versus Fructose Division of Endocrinology, Diabetes, and Clinical Nutrition, University Hospital Zurich, 8091 Zurich, Switzerland; [email protected] *Correspondence: [email protected] ; Tel.: +41-44-255-3620 Received 2017 Jul 21; Accepted 2017 Sep 11. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ( ). High-fructose intake in healthy men is associated with characteristics of metabolic syndrome. Extensive knowledge exists about the differences between hepatic fructose and glucose metabolism and fructose-specific mechanisms favoring the development of metabolic disturbances. Nevertheless, the causal relationship between fructose consumption and metabolic alterations is still debated. Multiple effects of fructose on hepatic metabolism are attributed to the fact that the liver represents the major sink of fructose. Fructose, as a lipogenic substrate and potent inducer of lipogenic enzyme expression, enhances fatty acid synthesis. Consequently, increased hepatic diacylglycerols (DAG) are thought to directly interfere with insulin signaling. However, independently of this effect, fructose may also counteract insulin-mediated effects on liver metabolism by a range of mechanisms. It may drive gluconeogenesis not only as a gluconeogenic substrate, but also as a potent inducer of carbohydrate responsive element binding protein (ChREBP), which induces the expression of lipogenic enzymes as well as gluconeogenic enzymes. It remains a challenge to determine the relative contributions of the impact of fructose on hepatic transcriptome, proteome and allosterome changes and consequently on the regulation of pl Continue reading >>

Chapter 5. Carbohydrates 1/

Chapter 5. Carbohydrates 1/

Carbohydrates represent a broad group of substances which include the sugars, starches, gums and celluloses. The common attributes of carbohydrates are that they contain only the elements carbon, hydrogen and oxygen, and that their combustion will yield carbon dioxide plus one or more molecules of Water. The simplest carbohydrates are the three-carbon sugars which figure importantly in intermediary metabolism and the most complex are the naturally occurring polysaccharides, primarily of plant, origin. In the diet of animals and fish, two classes of polysaccharides are significant: (a) structural polysaccharides which are digestible by herbivorous species -cellulose, lignin, dextrans, mannans, inulin, pentosans, pectic acids, algic acids, agar and chitin; and (b) universally digestible polysaccharides - principally starch. Carbohydrates make up three-fourths of the biomass of plants but are present only in small quantities in the animal body as glycogen, sugars and their derivatives. Glycogen is often referred to as animal starch because it is not present in plants. Derived mono-saccharides such as the sugar acids, amino sugars and the deoxysugars are constituents of all living organisms. Carbohydrates are classified generally according to their degree of complexity. Hence, the free sugars such as glucose and fructose are termed monosaccharides; sucrose and maltose, disaccharides; and the starches and celluloses, polysaccharides. Carbohydrates of short chain lengths such as raffinose, stachyose and verbascose, which are three, four and five sugar polymers respectively, are classified as oligosaccharides. Pentoses are five-carbon sugars seldom found in the free state in nature. In plants they occur in polymeric forms and are collectively known as pentosans. Thus, xylose Continue reading >>

Structural Biochemistry/carbohydrates

Structural Biochemistry/carbohydrates

Carbohydrates are important macromolecules that consist of carbon, hydrogen, and oxygen. They are organic compounds organized in the form of aldehydes or ketones with multiple hydroxyl groups coming off the carbon chain. Carbohydrates are the most abundant organic compounds in living organisms and account for one of the four major biomolecular classes including proteins, lipids, and nucleic acids. They originate as products from carbon dioxide and water by photosynthesis, (+ reducing agents and energy from photon [sunlight]) where ADP (Adenosine diphosphate) is a product that can be synthesized to form ATP (Adenosine-5'-triphosphate) - a form of chemical energy used in cells which acts as a fuel of metabolism in plants and animals - through aerobic cellular respiration, (+ oxidizing agent and energy from photon [through electrochemical gradient]) Carbohydrates play a variety of extensive roles in all forms of life: The general empirical structure for carbohydrates is (CH2O)n. Monosaccharides, which are simple sugars that serve as fuel molecules as well as fundamental constituents of living organisms, are the simplest carbohydrates, and are required as energy sources. The most commonly known ones are perhaps glucose and fructose. Carbohydrates exist in a variety of isomers forms. Those that differ in arrangements of atoms are known as constitutional isomers, such as glyceradehyde and dihydroxyacetone. Stereoisomers have the same attachments of the atoms, but different in spatial arrangements, which can be further separated into two types: diastereoisomers and enantiomers. Diastereoisomers are the molecules that are not mirror images of each other and enantiomers exists as nonsuperimposable mirror images. The fact that monosacharides can possess up to three different asy 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 >>

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