diabetestalk.net

Which Metabolic Process Refers To The Breakdown Of Glycogen To Glucose

Metabolism And Energetics

Metabolism And Energetics

Metabolism basically refers to all the chemical reactions within the body used to produce energy. This involves a complex set of processes that convert fuels into specialised compounds loaded with energy. In the body, the primary final agent to produce energy is called adenosine triphosphate (ATP) . When ATP is broken down or used by cells huge amounts of energy is released. This energy is essential for cells to grow and divide, synthesise important compounds, for muscles to contract and numerous other important functions. Metabolism therefore produces energy to perform all the functions of different tissues within the body. Metabolism works by breaking down foods in the diet or compounds in the body into their smaller components. These can then enter into special reactions to produce ATP. The left over components are recycled by the body and used to regenerate the original compounds. The body has three main types of molecules it uses for energy: Carbohydrates: These are the sugar type compounds in the body. Carbohydrates come from foods such as bread, cereal, potatoes, fruits and sugar-containing foods or bevarages. When carbohydrates are digested in the gastrointestinal system they are broken down into smaller molecules such as glucose (a simple sugar). The main storage sites for carbohydrates in the body are the liver and muscles. Lipids: This basically refers to fats (such as cholesterol) from the diet or stored in adipose tissue (in other words the body fat). Lipids are broken down into smaller components called fatty acids for energy. Therefore lipids are really just chains of fatty acids joined together. Proteins: These make up nearly three quarters of all the solid materials in the body. Proteins are thus the basic structural components in the body. They are ma Continue reading >>

Glycogenolysis | Biochemistry | Britannica.com

Glycogenolysis | Biochemistry | Britannica.com

Glycogenolysis, process by which glycogen , the primary carbohydrate stored in the liver and muscle cells of animals, is broken down into glucose to provide immediate energy and to maintain blood glucose levels during fasting . Glycogenolysis occurs primarily in the liver and is stimulated by the hormones glucagon and epinephrine (adrenaline). Various enzyme defects can prevent the release of energy by the normal breakdown of glycogen in muscles. Enzymes in which defects may occur include glucose-6-phosphatase (I); lysosomal x-1,4-glucosidase (II); debranching enzyme (III); branching enzyme (IV); muscle phosphorylase (V); liver phosphorylase (VI, VIII, IX, X); and muscle phosphofructokinase (VII). Enzyme defects that can give rise to other carbohydrate diseases include galactokinase (A1); galactose 1-phosphate UDP transferase (A2); fructokinase (B); aldolase (C); fructose 1,6-diphosphatase deficiency (D); pyruvate dehydrogenase complex (E); and pyruvate carboxylase (F). When blood glucose levels fall, as during fasting, there is an increase in glucagon secretion from the pancreas . That increase is accompanied by a concomitant decrease in insulin secretion, because the actions of insulin, which are aimed at increasing the storage of glucose in the form of glycogen in cells, oppose the actions of glucagon. Following secretion, glucagon travels to the liver, where it stimulates glycogenolysis. The vast majority of glucose that is released from glycogen comes from glucose-1-phosphate, which is formed when the enzyme glycogen phosphorylase catalyzes the breakdown of the glycogen polymer . In the liver, kidneys , and intestines , glucose-1-phosphate is converted (reversibly) to glucose-6-phosphate by the enzyme phosphoglucomutase. Those tissues also house the enzyme glucose Continue reading >>

Metabolic States Of The Body

Metabolic States Of The Body

The Absorptive State The absorptive state, or the fed state, occurs after a meal when your body is digesting the food and absorbing the nutrients (catabolism exceeds anabolism). Digestion begins the moment you put food into your mouth, as the food is broken down into its constituent parts to be absorbed through the intestine. The digestion of carbohydrates begins in the mouth, whereas the digestion of proteins and fats begins in the stomach and small intestine. The constituent parts of these carbohydrates, fats, and proteins are transported across the intestinal wall and enter the bloodstream (sugars and amino acids) or the lymphatic system (fats). From the intestines, these systems transport them to the liver, adipose tissue, or muscle cells that will process and use, or store, the energy. Depending on the amounts and types of nutrients ingested, the absorptive state can linger for up to 4 hours. The ingestion of food and the rise of glucose concentrations in the bloodstream stimulate pancreatic beta cells to release insulin into the bloodstream, where it initiates the absorption of blood glucose by liver hepatocytes, and by adipose and muscle cells. Once inside these cells, glucose is immediately converted into glucose-6-phosphate. By doing this, a concentration gradient is established where glucose levels are higher in the blood than in the cells. This allows for glucose to continue moving from the blood to the cells where it is needed. Insulin also stimulates the storage of glucose as glycogen in the liver and muscle cells where it can be used for later energy needs of the body. Insulin also promotes the synthesis of protein in muscle. As you will see, muscle protein can be catabolized and used as fuel in times of starvation. If energy is exerted shortly after eatin Continue reading >>

Which Metabolic Process Refers To The Breakdown Of Glycogen To Glucose?

Which Metabolic Process Refers To The Breakdown Of Glycogen To Glucose?

Which metabolic process refers to the breakdown of glycogen to glucose? Which metabolic process refers to the breakdown of glycogen to glucose? [center][color=gray]Please [b]login or register[/b] to leave a reply[/color][/center] Biology Forums - Study Force is the leading provider of online homework help for college and high school students. Get homework help and answers to your toughest questions in biology, chemistry, physics, math, calculus, engineering, accounting, English, writing help, business, humanities, and more. Master your assignments with step-by-step solutions to countless homework questions asked and answered by our members. If we don't have your question, dont worry. You can ask any homework question and get expert homework help in as little as two hours. Our extensive online study community is made up of college and high school students, teachers, professors, parents and subject enthusiasts who contribute to our vast collection of study resources: textbook solutions, study guides, practice tests, practice problems, lecture notes, equation sheets and more. With our help, your homework will never be the same! Continue reading >>

A General Overview Of The Major Metabolic Pathways

A General Overview Of The Major Metabolic Pathways

A general overview of the major metabolic pathways Assistant Professor, Universidade FernandoPessoa Metabolism is the set of chemical rections that occur in a cell, which enable it to keep living, growing and dividing.Metabolic processes are usually classified as: catabolism - obtaining energy and reducing power from nutrients. anabolism - production of new cell components, usually through processes that require energy and reducing power obtained from nutrient catabolism. There is a very large number of metabolic pathways. In humans, the most important metabolic pathways are: glycolysis - glucose oxidation in order to obtain ATP citric acid cycle (Krebs' cycle) - acetyl-CoA oxidation in order to obtain GTP and valuable intermediates. oxidative phosphorylation - disposal of the electrons released by glycolysis and citric acid cycle. Much of the energy released in this process can be stored as ATP. pentose phosphate pathway - synthesis of pentoses and release of the reducing power needed for anabolic reactions. urea cycle - disposal of NH4+ in less toxic forms fatty acid -oxidation - fatty acids breakdown into acetyl-CoA, to be used by the Krebs' cycle. gluconeogenesis - glucose synthesis from smaller percursors, to be used by the brain. Click on the picture to get information on each pathway Metabolic pathways interact in a complex way in order to allow an adequate regulation. This interaction includes the enzymatic control of each pathway, each organ's metabolic profile and hormone control . Flow is regulated in the gluconeogenesis-specific reactions. Pyruvate carboxilase is activated by acetyl-CoA, which signals the abundance of citric acid cycle intermediates, i.e., a decreased need of glucose. The citric acid cycle is regulated mostly by substrate availability, prod 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 >>

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 >>

Carbohydrate Metabolism

Carbohydrate Metabolism

Carbohydrate metabolism denotes the various biochemical processes responsible for the formation, breakdown, and interconversion of carbohydrates in living organisms. Carbohydrates are central to many essential metabolic pathways.[1] Plants synthesize carbohydrates from carbon dioxide and water through photosynthesis, allowing them to store energy absorbed from sunlight internally.[2] When animals and fungi consume plants, they use cellular respiration to break down these stored carbohydrates to make energy available to cells.[2] Both animals and plants temporarily store the released energy in the form of high energy molecules, such as ATP, for use in various cellular processes.[3] Although humans consume a variety of carbohydrates, digestion breaks down complex carbohydrates into a few simple monomers for metabolism: glucose, fructose, and galactose.[4] Glucose constitutes about 80% of the products, and is the primary structure that is distributed to cells in the tissues, where it is broken down or stored as glycogen.[3][4] In aerobic respiration, the main form of cellular respiration used by humans, glucose and oxygen are metabolized to release energy, with carbon dioxide and water as byproducts.[2] Most of the fructose and galactose travel to the liver, where they can be converted to glucose.[4] Some simple carbohydrates have their own enzymatic oxidation pathways, as do only a few of the more complex carbohydrates. The disaccharide lactose, for instance, requires the enzyme lactase to be broken into its monosaccharide components, glucose and galactose.[5] Metabolic pathways[edit] Overview of connections between metabolic processes. Glycolysis[edit] Glycolysis is the process of breaking down a glucose molecule into two pyruvate molecules, while storing energy released Continue reading >>

Blood Proteins - Albumen, Clotting Proteins

Blood Proteins - Albumen, Clotting Proteins

Liver Pathology Functions of the liver: Manufacture - blood proteins - albumen, clotting proteins urea - nitrogenous waste from amino acid metabolism bile - excretory for the bile pigments, emulsification of fats by bile salts Storage - glycogen - carbohydrate fuel iron - as hemosiderin and ferritin fat soluble vitamins A, D, E, K Detoxification - alcohol drugs and medicines environmental toxins Protein metabolism - (See Figure 25.15) transamination - removing the amine from one amino acid and using it to produce a different amino acid. The body can produce all but the essential amino acids; these must be included in the diet. (See Figure 25.3) deamination - removal of the amine group in order to catabolize the remaining keto acid. The amine group enters the blood as urea which is excreted through the kidneys. Glycemic Regulation - the management of blood glucose. glycogenesis - the conversion of glucose into glycogen. glycogenolysis - the breakdown of glycogen into glucose. gluconeogenesis - the manufacture of glucose from non carbohydrate sources, mostly protein. See Disorders below. See [Liver Pathology] Structure of the liver - (See Figure 24.24) The liver is composed mostly of cells known as hepatocytes which perform the functions listed above. They have the ability to shift functions so their efforts can be directed at what is most needed. They can also divide to repair and replace tissue. Cirrhosis is a condition which can occur in the liver and other organs in which the cells are damaged as a result of toxins, pathogenic organisms, etc. Cirrhosis causes thickening and fibrosis and can progressively damage the liver to the point it can no longer recover by replacing its cells. Other functions also suffer as more hepatocytes become committed to detoxification. The Continue reading >>

Principles Of Biochemistry/gluconeogenesis And Glycogenesis

Principles Of Biochemistry/gluconeogenesis And Glycogenesis

Gluconeogenesis (abbreviated GNG) is a metabolic pathway that results in the generation of glucose from non-carbohydrate carbon substrates such as lactate, glycerol, and glucogenic amino acids. It is one of the two main mechanisms humans and many other animals use to keep blood glucose levels from dropping too low (hypoglycemia). The other means of maintaining blood glucose levels is through the degradation of glycogen (glycogenolysis). Gluconeogenesis is a ubiquitous process, present in plants, animals, fungi, bacteria, and other microorganisms. In animals, gluconeogenesis takes place mainly in the liver and, to a lesser extent, in the cortex of kidneys. This process occurs during periods of fasting, starvation, low-carbohydrate diets, or intense exercise and is highly endergonic. For example, the pathway leading from phosphoenolpyruvate to glucose-6-phosphate requires 6 molecules of ATP. Gluconeogenesis is often associated with ketosis. Gluconeogenesis is also a target of therapy for type II diabetes, such as metformin, which inhibits glucose formation and stimulates glucose uptake by cells. Lactate is transported back to the liver where it is converted into pyruvate by the Cori cycle using the enzyme lactate dehydrogenase. Pyruvate, the first designated substrate of the gluconeogenic pathway, can then be used to generate glucose. All citric acid cycle intermediates, through conversion to oxaloacetate, amino acids other than lysine or leucine, and glycerol can also function as substrates for gluconeogenesis.Transamination or deamination of amino acids facilitates entering of their carbon skeleton into the cycle directly (as pyruvate or oxaloacetate), or indirectly via the citric acid cycle. Whether fatty acids can be converted into glucose in animals has been a longst Continue reading >>

Muscle Metabolism

Muscle Metabolism

Online Quizzes for CliffsNotes Anatomy and Physiology QuickReview, 2nd Edition In order for muscles to contract, ATP must be available in the muscle fiber. ATP is available from the following sources: Within the muscle fiber. ATP available within the muscle fiber can maintain muscle contraction for several seconds. Creatine phosphate. Creatine phosphate, a highenergy molecule stored in muscle cells, transfers its highenergy phosphate group to ADP to form ATP. The creatine phosphate in muscle cells is able to generate enough ATP to maintain muscle contraction for about 15 seconds. Glucose stored within the cell. Glucose within the cell is stored in the carbohydrate glycogen. Through the metabolic process of glycogenolysis, glycogen is broken down to release glucose. ATP is then generated from glucose by cellular respiration. Glucose and fatty acids obtained from the bloodstream. When energy requirements are high, glucose from glycogen stored in the liver and fatty acids from fat stored in adipose cells and the liver are released into the bloodstream. Glucose and fatty acids are then absorbed from the bloodstream by muscle cells. ATP is then generated from these energyrich molecules by cellular respiration. Cellular respiration is the process by which ATP is obtained from energyrich molecules. Several major metabolic pathways are involved, some of which require the presence of oxygen. Here's a summary of the important pathways: In glycolysis, glucose is broken down to pyruvic acid, and two ATP molecules are generated even though oxygen is not present. The production of ATP without the use of oxygen is called anaerobic respiration, and, because no oxygen is used during the various metabolic steps of this pathway, glycolysis is called an anaerobic process. During anaerobic Continue reading >>

Metabolic Functions Of The Liver

Metabolic Functions Of The Liver

Hepatocytes are metabolic overachievers in the body. They play critical roles in synthesizing molecules that are utilized elsewhere to support homeostasis, in converting molecules of one type to another, and in regulating energy balances. If you have taken a course in biochemistry, you probably spent most of that class studying metabolic pathways of the liver. At the risk of damning by faint praise, the major metabolic functions of the liver can be summarized into several major categories: Carbohydrate Metabolism It is critical for all animals to maintain concentrations of glucose in blood within a narrow, normal range. Maintainance of normal blood glucose levels over both short (hours) and long (days to weeks) periods of time is one particularly important function of the liver. Hepatocytes house many different metabolic pathways and employ dozens of enzymes that are alternatively turned on or off depending on whether blood levels of glucose are rising or falling out of the normal range. Two important examples of these abilities are: Excess glucose entering the blood after a meal is rapidly taken up by the liver and sequestered as the large polymer, glycogen (a process called glycogenesis). Later, when blood concentrations of glucose begin to decline, the liver activates other pathways which lead to depolymerization of glycogen (glycogenolysis) and export of glucose back into the blood for transport to all other tissues. When hepatic glycogen reserves become exhaused, as occurs when an animal has not eaten for several hours, do the hepatocytes give up? No! They recognize the problem and activate additional groups of enzymes that begin synthesizing glucose out of such things as amino acids and non-hexose carbohydrates (gluconeogenesis). The ability of the liver to synthe 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 >>

Glycogen Biosynthesis; Glycogen Breakdown

Glycogen Biosynthesis; Glycogen Breakdown

Glycogen is a polymer of glucose (up to 120,000 glucose residues) and is a primary carbohydrate storage form in animals. The polymer is composed of units of glucose linked alpha(1-4) with branches occurring alpha(1-6) approximately every 8-12 residues. The end of the molecule containing a free carbon number one on glucose is called a reducing end. The other ends are all called non-reducing ends. Related polymers in plants include starch (alpha(1-4) polymers only) and amylopectin (alpha (1-6) branches every 24-30 residues). Glycogen provides an additional source of glucose besides that produced via gluconeogenesis. Because glycogen contains so many glucoses, it acts like a battery backup for the body, providing a quick source of glucose when needed and providing a place to store excess glucose when glucose concentrations in the blood rise. The branching of glycogen is an important feature of the molecule metabolically as well. Since glycogen is broken down from the "ends" of the molecule, more branches translate to more ends, and more glucose that can be released at once. Liver and skeletal muscle are primary sites in the body where glycogen is found. The primary advantagesof storage carbohydrates in animals are that 1) energy is not released from fat (other majorenergy storage form in animals) as fast as from glycogen; 2) glycolysis provides a mechanism of anaerobic metabolism (importantin muscle cells that cannot get oxygen as fast as needed); and 3) glycogen provides a means of maintaining glucose levels thatcannot be provided by fat. Breakdown of glycogen involves 1) release of glucose-1-phosphate (G1P), 2) rearranging the remaining glycogen (as necessary) to permit continued breakdown, and 3) conversion of G1P to G6P for further metabolism. Remember that G6P can be Continue reading >>

Fshn 265- Exam 3 Flashcards | Quizlet

Fshn 265- Exam 3 Flashcards | Quizlet

Which metabolic process refers to the breakdown of glycogen to glucose Excess carbohydrates in the diet are first stored as Fatty acids are cleaved from the glycerol backbone during digestion to yield free fatty acids in a process called The formation of glucose from noncarbohydrate sources, such as glucogenic amino acids, is called The process of converting excess glucose to glycogen in the liver and muscle is referred to as The process in which glucose is broken down to produce energy is called is the process that converts excess glucose or amino acids into fatty acids to be stored as triglycerides in the adipose cells. carbohydrate metabolism during the postabsorptive state Muscle glycogen stores are depleted early in the postabsorptive state. Glycogen stores are used during short periods of fasting overnight or between meals. These stores are depleted early when fasting becomes prolonged. protein metabolism during the postabsorptive state Amino acids are used to produce glucose through gluconeogenesis during the postabsorptive state. lipid metabolism during the postabsorptive state F.A. rapidly broken down from adipose tissues and converted to ketone bodies glycolosis-acetyl coa-TCA cycle-Electron Transport Chain-Oxidative Phosporylation benefit endurance athletes. replaces water and electrolytes. Glucose facilitates electrolyte absorption. not idea! does not restore electrolytes and glycogen stores measure calories in foods in terms of heat. burn hotter=more calories what keeps us alive, and heart pumping. depends on many factors; age, gender, body size, genes, ethnicity, nutritional state energy to digest food. protein has highest thermic effect because it require ATP to get absorbed. Obese individuals have a lower thermic effect due to less muscle mass. thermal Continue reading >>

More in diabetes