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Where Is Glucose Converted Into Glycogen?

How Insulin And Glucagon Work

How Insulin And Glucagon Work

Insulin and glucagon are hormones that help regulate the levels of blood glucose, or sugar, in your body. Glucose, which comes from the food you eat, moves through your bloodstream to help fuel your body. Insulin and glucagon work together to balance your blood sugar levels, keeping them in the narrow range that your body requires. These hormones are like the yin and yang of blood glucose maintenance. Read on to learn more about how they function and what can happen when they don’t work well. Insulin and glucagon work in what’s called a negative feedback loop. During this process, one event triggers another, which triggers another, and so on, to keep your blood sugar levels balanced. How insulin works During digestion, foods that contain carbohydrates are converted into glucose. Most of this glucose is sent into your bloodstream, causing a rise in blood glucose levels. This increase in blood glucose signals your pancreas to produce insulin. The insulin tells cells throughout your body to take in glucose from your bloodstream. As the glucose moves into your cells, your blood glucose levels go down. Some cells use the glucose as energy. Other cells, such as in your liver and muscles, store any excess glucose as a substance called glycogen. Your body uses glycogen for fuel between meals. Read more: Simple vs. complex carbs » How glucagon works Glucagon works to counterbalance the actions of insulin. About four to six hours after you eat, the glucose levels in your blood decrease, triggering your pancreas to produce glucagon. This hormone signals your liver and muscle cells to change the stored glycogen back into glucose. These cells then release the glucose into your bloodstream so your other cells can use it for energy. This whole feedback loop with insulin and gluca Continue reading >>

Blood Glucose Regulation

Blood Glucose Regulation

Glucose is needed by cells for respiration. It is important that the concentration of glucose in the blood is maintained at a constant level. Insulin is a hormone produced by the pancreas that regulates glucose levels in the blood. How glucose is regulated Glucose level Effect on pancreas Effect on liver Effect on glucose level too high insulin secreted into the blood liver converts glucose into glycogen goes down too low insulin not secreted into the blood liver does not convert glucose into glycogen goes up Use the animation to make sure you understand how this works. You have an old or no version of flash - you need to upgrade to view this funky content! Go to the WebWise Flash install guide Glucagon – Higher tier The pancreas releases another hormone, glucagon, when the blood sugar levels fall. This causes the cells in the liver to turn glycogen back into glucose which can then be released into the blood. The blood sugar levels will then rise. Now try a Test Bite- Higher tier. Diabetes is a disorder in which the blood glucose levels remain too high. It can be treated by injecting insulin. The extra insulin allows the glucose to be taken up by the liver and other tissues, so cells get the glucose they need and blood-sugar levels stay normal. There are two types of diabetes. Type 1 diabetes Type 1 diabetes is caused by a lack of insulin. It can be controlled by: monitoring the diet injecting insulin People with type 1 diabetes have to monitor their blood sugar levels throughout the day as the level of physical activity and diet affect the amount of insulin required. Type 2 diabetes Type 2 diabetes is caused by a person becoming resistant to insulin. It can be controlled by diet and exercise. There is a link between rising levels of obesity (chronic overweight) and i Continue reading >>

Glycogenolysis And Glycogenesis

Glycogenolysis And Glycogenesis

Structure of glycogen Figure 1. Glycogen structure (Click for enlarged view). Panel A. Schematic two-dimensional cross-sectional view of glycogen: A core protein of glycogenin is surrounded by branches of glucose units. The entire globular granule may contain around 30,000 glucose units. [Source: Mikael Häggström[2], . Panel B. Schematic of glycogen structure showing the glucose units in each chain linked together linearly by α(1→4 glycosidic bonds. Branches are linked to the chains from which they are branching off by α(1→6) glycosidic bonds between the first glucose of the new branch and a glucose on the stem chain.Glycogen is a multi-branched polysaccharide of glucose that serves as an energy store primarily in muscle and liver. It is stored in the form of granules in the cytoplasm of the cell and is the main storage form of glucose in the body. The concentration of glycogen in muscle is low (1-2% fresh weight) compared to the levels stored in the liver (up to 8% fresh weight)[1]. Glycogen is an energy reserve that can be quickly mobilized to meet a sudden need for glucose. The significance of the multi-branched structure is that multiple glucose units, rather than a single glucose can be mobilized from any glycogen molecule when glycogenolysis is initiated. The structure of glycogen is summarized in Figure 1[2]. Enzymes involved in glycogenolysis The process of glycogenolysis involves the sequential removal of glucose monomers by phosphorolysis, a reaction catalysed by the phosphorylated (active) ‘a’ form of the enzyme glycogen phosphorylase[3]. This enzyme cleaves the glycosidic bond linking a terminal glucose to a glycogen branch by substituting a phosphoryl group for the α[1→4] linkage producing glucose-1-phosphate and glycogen that contains one le Continue reading >>

The Liver And Blood Glucose Levels

The Liver And Blood Glucose Levels

Tweet Glucose is the key source of energy for the human body. Supply of this vital nutrient is carried through the bloodstream to many of the body’s cells. The liver produces, stores and releases glucose depending on the body’s need for glucose, a monosaccharide. This is primarily indicated by the hormones insulin - the main regulator of sugar in the blood - and glucagon. In fact, the liver acts as the body’s glucose reservoir and helps to keep your circulating blood sugar levels and other body fuels steady and constant. How the liver regulates blood glucose During absorption and digestion, the carbohydrates in the food you eat are reduced to their simplest form, glucose. Excess glucose is then removed from the blood, with the majority of it being converted into glycogen, the storage form of glucose, by the liver’s hepatic cells via a process called glycogenesis. Glycogenolysis When blood glucose concentration declines, the liver initiates glycogenolysis. The hepatic cells reconvert their glycogen stores into glucose, and continually release them into the blood until levels approach normal range. However, when blood glucose levels fall during a long fast, the body’s glycogen stores dwindle and additional sources of blood sugar are required. To help make up this shortfall, the liver, along with the kidneys, uses amino acids, lactic acid and glycerol to produce glucose. This process is known as gluconeogenesis. The liver may also convert other sugars such as sucrose, fructose, and galactose into glucose if your body’s glucose needs not being met by your diet. Ketones Ketones are alternative fuels that are produced by the liver from fats when sugar is in short supply. When your body’s glycogen storage runs low, the body starts conserving the sugar supplies fo Continue reading >>

Glucose

Glucose

Physiology • Glucose in the blood is derived from three main sources: ○ ▪ Glucose is the end-product of carbohydrate digestion, absorbed by enterocytes. ▪ Increased blood glucose concentrations occur 2 to 4 hours after a meal in simple-stomached animals. ○ Hepatic production ▪ Gluconeogenesis and glycogenolysis within hepatic cells produce glucose when metabolically necessary. □ Gluconeogenesis converts noncarbohydrate sources, primarily amino acids (from protein) and glycerol (from fat), in simple-stomached animals. □ Glycogenolysis converts glycogen (poly-glucose) stored in hepatocytes to glucose through hydrolysis. ▪ Gluconeogenesis and glycogenolysis within hepatic cells produce glucose when metabolically necessary. □ Gluconeogenesis converts noncarbohydrate sources, primarily amino acids (from protein) and glycerol (from fat), in simple-stomached animals. □ Glycogenolysis converts glycogen (poly-glucose) stored in hepatocytes to glucose through hydrolysis. ○ ▪ Gluconeogenesis and glycogenolysis within renal epithelial cells can result in the formation of glucose when metabolically necessary. • The plasma concentration of glucose is controlled by a number of hormones, in particular, insulin and glucagon. The physiology of glucose homeostasis is controlled primarily by insulin release in response to elevated glucose levels (postprandial), although in birds, glucagon appears to serve as the primary regulator. Significant species variations in glucose levels have been noted. In general, levels are lowest in reptiles (60 to 100 mg/dL) and highest in birds (200 to 500 mg/dL), with mammals in between (100 to 200 mg/dL). Glucose that is not needed for energy is stored in the form of glycogen as a source of potential energy, readily available whe Continue reading >>

Glycogen Metabolism

Glycogen Metabolism

Glycogen is a readily mobilized storage form of glucose. It is a very large, branched polymer of glucose residues (Figure 21.1) that can be broken down to yield glucose molecules when energy is needed. Most of the glucose residues in glycogen are linked by α-1,4-glycosidic bonds. Branches at about every tenth residue are created by α-1,6-glycosidic bonds. Recall that α-glycosidic linkages form open helical polymers, whereas β linkages produce nearly straight strands that form structural fibrils, as in cellulose (Section 11.2.3). Glycogen is not as reduced as fatty acids are and consequently not as energy rich. Why do animals store any energy as glycogen? Why not convert all excess fuel into fatty acids? Glycogen is an important fuel reserve for several reasons. The controlled breakdown of glycogen and release of glucose increase the amount of glucose that is available between meals. Hence, glycogen serves as a buffer to maintain blood-glucose levels. Glycogen's role in maintaining blood-glucose levels is especially important because glucose is virtually the only fuel used by the brain, except during prolonged starvation. Moreover, the glucose from glycogen is readily mobilized and is therefore a good source of energy for sudden, strenuous activity. Unlike fatty acids, the released glucose can provide energy in the absence of oxygen and can thus supply energy for anaerobic activity. The two major sites of glycogen storage are the liver and skeletal muscle. The concentration of glycogen is higher in the liver than in muscle (10% versus 2% by weight), but more glycogen is stored in skeletal muscle overall because of its much greater mass. Glycogen is present in the cytosol in the form of granules ranging in diameter from 10 to 40 nm (Figure 21.2). In the liver, glycoge Continue reading >>

Glycogen And Glucose

Glycogen And Glucose

Glycogen and Glucose are the two forms of sugar that your body employs to store and use as energy . Glucose is the sugar your body converts into energy. Glycogen is the sugar your body stores in both your liver and muscle cells. Your body can't use glycogen directly as a source of energy, and cannot store glucose. When you eat a well-balanced meal with both carbohydrates and protein, your body converts and absorbs the carbohydrates and part of the protein into glucose. It then attempts to maintain an even blood glucose level. When your blood glucose is too high, your pancreas produces insulin to convert some of that glucose into glycogen and then stores it for later use. When it is running low, it produces glucagon, a hormone secreted by the pancreas which stimulates your liver to convert some glycogen into glucose. Once converted, the glucose can be released into your blood stream. (The glycogen stored in your muscles can't be converted back into sugar, so it can only be used by your muscles.) Your liver can only store 90 to 110 grams of glycogen (the equivalent of about three to four hours of normal activity). When your glycogen reserves are full, and you still have glucose in your blood or glucose being absorbed into your bloodstream from a meal, your liver then starts to convert glucose into fat. That is actually a normal process because with a regular size meal, you will invariably fill up your glycogen reserves. Therefore it is customary to store some fat when you eat. If you don't eat between meals, after around three hours your liver glycogen will be running low and your body will start converting that fat into energy until you eat your next meal. Overall, this is a healthy, natural process of filling up your glycogen supply, storing some fat, and then accessing Continue reading >>

How Our Bodies Turn Food Into Energy

How Our Bodies Turn Food Into Energy

All parts of the body (muscles, brain, heart, and liver) need energy to work. This energy comes from the food we eat. Our bodies digest the food we eat by mixing it with fluids (acids and enzymes) in the stomach. When the stomach digests food, the carbohydrate (sugars and starches) in the food breaks down into another type of sugar, called glucose. The stomach and small intestines absorb the glucose and then release it into the bloodstream. Once in the bloodstream, glucose can be used immediately for energy or stored in our bodies, to be used later. However, our bodies need insulin in order to use or store glucose for energy. Without insulin, glucose stays in the bloodstream, keeping blood sugar levels high. Insulin is a hormone made by beta cells in the pancreas. Beta cells are very sensitive to the amount of glucose in the bloodstream. Normally beta cells check the blood's glucose level every few seconds and sense when they need to speed up or slow down the amount of insulin they're making and releasing. When someone eats something high in carbohydrates, like a piece of bread, the glucose level in the blood rises and the beta cells trigger the pancreas to release more insulin into the bloodstream. When insulin is released from the pancreas, it travels through the bloodstream to the body's cells and tells the cell doors to open up to let the glucose in. Once inside, the cells convert glucose into energy to use right then or store it to use later. As glucose moves from the bloodstream into the cells, blood sugar levels start to drop. The beta cells in the pancreas can tell this is happening, so they slow down the amount of insulin they're making. At the same time, the pancreas slows down the amount of insulin that it's releasing into the bloodstream. When this happens, Continue reading >>

Storage Of Glucose As Glycogen

Storage Of Glucose As Glycogen

The liver secretes glucose into the bloodstream as an essential mechanism to keep blood glucose levels constant. Liver, muscle, and other tissues also store glucose as glycogen, a high‐molecular‐weight, branched polymer of glucose. Glycogen synthesis begins with glucose‐1‐phosphate, which can be synthesized from glucose‐6‐ phosphate by the action of phosphoglucomutase (an isomerase). Glucose‐1‐phosphate is also the product of glycogen breakdown by phosphorylase: The K eq of the phosphorylase reaction lies in the direction of breakdown. In general, a biochemical pathway can't be used efficiently in both the synthetic and the catabolic direction. This limitation implies that there must be another step in glycogen synthesis that involves the input of extra energy to the reaction. The extra energy is supplied by the formation of the intermediate UDP‐glucose. This is the same compound found in galactose metabolism. It is formed along with inorganic pyrophosphate from glucose‐1‐phosphate and UTP. The inorganic pyrophosphate is then hydrolyzed to two phosphate ions; this step pulls the equilibrium of the reaction in the direction of UDP‐glucose synthesis (see Figure 1). Figure 1 Glycogen synthase transfers the glucose of UDP‐glucose to the nonreducing end (the one with a free Carbon‐4 of glucose) of a preexisting glycogen molecule (another enzyme starts the glycogen molecule), making an A, 1‐4 linkage and releasing UDP (see Figure 2 ). This reaction is exergonic, though not as much as the synthesis of UDP‐ glucose is. Figure 2 Summing up, the synthesis of glycogen from glucose‐1‐phosphate requires the consumption of a single high‐energy phosphate bond and releases pyrophosphate (converted to phosphates) and UDP. Overall, the reaction is: G Continue reading >>

Glycogen

Glycogen

Schematic two-dimensional cross-sectional view of glycogen: A core protein of glycogenin is surrounded by branches of glucose units. The entire globular granule may contain around 30,000 glucose units.[1] A view of the atomic structure of a single branched strand of glucose units in a glycogen molecule. Glycogen (black granules) in spermatozoa of a flatworm; transmission electron microscopy, scale: 0.3 µm Glycogen is a multibranched polysaccharide of glucose that serves as a form of energy storage in humans,[2] animals,[3] fungi, and bacteria. The polysaccharide structure represents the main storage form of glucose in the body. Glycogen functions as one of two forms of long-term energy reserves, with the other form being triglyceride stores in adipose tissue (i.e., body fat). In humans, glycogen is made and stored primarily in the cells of the liver and skeletal muscle.[2][4] In the liver, glycogen can make up from 5–6% of the organ's fresh weight and the liver of an adult weighing 70 kg can store roughly 100–120 grams of glycogen.[2][5] In skeletal muscle, Glycogen is found in a low concentration (1–2% of the muscle mass) and the skeletal muscle of an adult weighing 70 kg can store roughly 400 grams of glycogen.[2] The amount of glycogen stored in the body—particularly within the muscles and liver—mostly depends on physical training, basal metabolic rate, and eating habits. Small amounts of glycogen are also found in other tissues and cells, including the kidneys, red blood cells,[6][7][8] white blood cells,[medical citation needed] and glial cells in the brain.[9] The uterus also stores glycogen during pregnancy to nourish the embryo.[10] Approximately 4 grams of glucose are present in the blood of humans at all times;[2] in fasted individuals, blood glucos Continue reading >>

Can Fats Be Turned Into Glycogen For Muscle?

Can Fats Be Turned Into Glycogen For Muscle?

The amount of fat in the average diet and the amount of stored fat in the average body make the notion of converting that fat into usable energy appealing. Glycogen, a form of energy stored in muscles for quick use, is what the body draws on first to perform movements, and higher glycogen levels result in higher usable energy. It is not possible for fats to be converted directly into glycogen because they are not made up glucose, but it is possible for fats to be indirectly broken down into glucose, which can be used to create glycogen. Relationship Between Fats and Glycogen Fats are a nutrient found in food and a compound used for long-term energy storage in the body, while glycogen is a chain of glucose molecules created by the body from glucose for short-term energy storage and utilization. Dietary fats are used for a number of functions in the body, including maintaining cell membranes, but they are not used primarily as a source of fast energy. Instead, for energy the body relies mostly on carbohydrates, which are converted into glucose that is then used to form glycogen. Turning Fats Into Glucose Excess glucose in the body is converted into stored fat under certain conditions, so it seems logical that glucose could be derived from fats. This process is called gluconeogenesis, and there are multiple pathways the body can use to achieve this conversion. Gluconeogenesis generally occurs only when the body cannot produce sufficient glucose from carbohydrates, such as during starvation or on a low-carbohydrate diet. This is less efficient than producing glucose through the metabolizing of carbohydrates, but it is possible under the right conditions. Turning Glucose Into Glycogen Once glucose has been obtained from fats, your body easily converts it into glycogen. In gl Continue reading >>

Does Carbohydrate Become Body Fat?

Does Carbohydrate Become Body Fat?

Dear Reader, Ah, poor carbohydrates, maligned by diets such as Atkins’ and the ketogenic diet. However, carbohydrates are your body’s main source of energy — in fact your muscles and brain cells prefer carbs more than other sources of energy (triglycerides and fat, for example). To answer your question: research completed over the last several decades suggests that if you are eating a diet that is appropriate for your levels of daily activity, little to no carbohydrate is converted to fat in your body. For most people (unless you have a metabolic disorder) when you eat carbs they are digested, broken down to glucose, and then transported to all the cells in your body. They are then metabolized and used to support cellular processes. If you’re active and eating appropriately for your activity level, most of the carbs you consume are more or less burned immediately. There are two caveats here: first, if you’re eating a lot more calories per day than you are burning, then yes, your liver will convert excess calories from carbohydrate into fats; second, not all carbs are created equal. If you consume too many calories from simple sugars like sucrose and fructose (think sugary sodas sweetened by sugar and high fructose corn syrup) then your body will more readily take some of those sugars and turn them into triglycerides (fat) in your liver. What happens to excess calories that come from carbs? The answer depends on several things: what kind of carbs you consumed, your genetics, as well as how many extra calories we’re talking about. For those who eat a well-balanced diet and have no metabolic disorders, excess dietary carbohydrates are converted by the liver into complex chains of glucose called glycogen. Glycogen is stored in liver and muscle cells and is a sec Continue reading >>

How Is Excess Glucose Stored?

How Is Excess Glucose Stored?

The human body has an efficient and complex system of storing and preserving energy. Glucose is a type of sugar that the body uses for energy. Glucose is the product of breaking down carbohydrates into their simplest form. Carbohydrates should make up approximately 45 to 65 percent of your daily caloric intake, according to MayoClinic.com. Video of the Day Glucose is a simple sugar found in carbohydrates. When more complex carbohydrates such as polysaccharides and disaccharides are broken down in the stomach, they break down into the monosaccharide glucose. Carbohydrates serve as the primary energy source for working muscles, help brain and nervous system functioning and help the body use fat more efficiently. Function of Glucose Once carbohydrates are absorbed from food, they are carried to the liver for processing. In the liver, fructose and galactose, the other forms of sugar, are converted into glucose. Some glucose gets sent to the bloodstream while the rest is stored for later energy use. Once glucose is inside the liver, glucose is phosphorylated into glucose-6-phosphate, or G6P. G6P is further metabolized into triglycerides, fatty acids, glycogen or energy. Glycogen is the form in which the body stores glucose. The liver can only store about 100 g of glucose in the form of glycogen. The muscles also store glycogen. Muscles can store approximately 500 g of glycogen. Because of the limited storage areas, any carbohydrates that are consumed beyond the storage capacity are converted to and stored as fat. There is practically no limit on how many calories the body can store as fat. The glucose stored in the liver serves as a buffer for blood glucose levels. Therefore, if the blood glucose levels start to get low because you have not consumed food for a period of time Continue reading >>

Glycogenesis, Glycogenolysis,

Glycogenesis, Glycogenolysis,

Biosynthesis of Glycogen: The goal of glycolysis, glycogenolysis, and the citric acid cycle is to conserve energy as ATP from the catabolism of carbohydrates. If the cells have sufficient supplies of ATP, then these pathways and cycles are inhibited. Under these conditions of excess ATP, the liver will attempt to convert a variety of excess molecules into glucose and/or glycogen. Glycogenesis: Glycogenesis is the formation of glycogen from glucose. Glycogen is synthesized depending on the demand for glucose and ATP (energy). If both are present in relatively high amounts, then the excess of insulin promotes the glucose conversion into glycogen for storage in liver and muscle cells. In the synthesis of glycogen, one ATP is required per glucose incorporated into the polymeric branched structure of glycogen. actually, glucose-6-phosphate is the cross-roads compound. Glucose-6-phosphate is synthesized directly from glucose or as the end product of gluconeogenesis. Link to: Interactive Glycogenesis (move cursor over arrows) Jim Hardy, Professor of Chemistry, The University of Akron. Glycogenolysis: In glycogenolysis, glycogen stored in the liver and muscles, is converted first to glucose-1- phosphate and then into glucose-6-phosphate. Two hormones which control glycogenolysis are a peptide, glucagon from the pancreas and epinephrine from the adrenal glands. Glucagon is released from the pancreas in response to low blood glucose and epinephrine is released in response to a threat or stress. Both hormones act upon enzymes to stimulate glycogen phosphorylase to begin glycogenolysis and inhibit glycogen synthetase (to stop glycogenesis). Glycogen is a highly branched polymeric structure containing glucose as the basic monomer. First individual glucose molecules are hydrolyzed fr Continue reading >>

Glycogenesis

Glycogenesis

Not to be confused with Gluconeogenesis or Glycogenolysis. Glycogenesis is the process of glycogen synthesis, in which glucose molecules are added to chains of glycogen for storage. This process is activated during rest periods following the Cori cycle, in the liver, and also activated by insulin in response to high glucose levels, for example after a carbohydrate-containing sweetie. Steps[edit] Glucose is converted into glucose-6-phosphate by the action of glucokinase or hexokinase.with conversion of ATP to ADP Glucose-6-phosphate is converted into glucose-1-phosphate by the action of phosphoglucomutase, passing through the obligatory intermediate glucose-1,6-bisphosphate. Glucose-1-phosphate is converted into UDP-glucose by the action of the enzyme UDP-glucose pyrophosphorylase. Pyrophosphate is formed, which is later hydrolysed by pyrophosphatase into two phosphate molecules. The enzyme glycogenin is needed to create initial short glycogen chains, which are then lengthened and branched by the other enzymes of glycogenesis. Glycogenin, a homodimer, has a tyrosine residue on each subunit that serves as the anchor for the reducing end of glycogen. Initially, about eight UDP-glucose molecules are added to each tyrosine residue by glycogenin, forming α(1→4) bonds. Once a chain of eight glucose monomers is formed, glycogen synthase binds to the growing glycogen chain and adds UDP-glucose to the 4-hydroxyl group of the glucosyl residue on the non-reducing end of the glycogen chain, forming more α(1→4) bonds in the process. Branches are made by glycogen branching enzyme (also known as amylo-α(1:4)→α(1:6)transglycosylase), which transfers the end of the chain onto an earlier part via α-1:6 glycosidic bond, forming branches, which further grow by addition of more α Continue reading >>

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