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Can Glucose Make Fatty Acids

Fatty Acids -- Overview: Reaction Sum

Fatty Acids -- Overview: Reaction Sum

8 acetyl CoA + 7 ATP + 14 (NADPH + H+) -> palmitate (16:0) + 8 CoA + 7 (ADP + Pi) + 14 NADP+ +6 H2O This is the overall process for fatty acid synthesis. Acetyl CoA for fatty acid synthesis comes mostly from glycolytic breakdown of glucose. Glucose is first degraded to pyruvate by aerobic glycolysis in thecytoplasm. Pyruvate is then transported into the mitochondria, where pyruvate dehydrogenase oxidatively decarboxylates pyruvate, forming acetyl CoA and otherproducts. Acetyl CoA can then serve as a substrate for citratesynthesis. Citrate, in turn, can be transported out of the mitochondria to the cytoplasm (where fatty acid synthesis occurs), and there split to generate cytoplasmic acetyl CoA for fatty acid synthesis. Citrate can also be oxidized by the tricarboxylic acid cycle in the mitochondria to yield energy. Notice that the need first to form citrate, then to transport it to the cytoplasm and then split it in order to get acetyl CoA for fatty acid synthesis provides several points at which control over acetyl CoA availability can be exerted. Continue reading >>

Gluconeogenesis

Gluconeogenesis

Not to be confused with Glycogenesis or Glyceroneogenesis. Simplified Gluconeogenesis Pathway Gluconeogenesis (GNG) is a metabolic pathway that results in the generation of glucose from certain non-carbohydrate carbon substrates. From breakdown of proteins, these substrates include glucogenic amino acids (although not ketogenic amino acids); from breakdown of lipids (such as triglycerides), they include glycerol (although not fatty acids); and from other steps in metabolism they include pyruvate and lactate. Gluconeogenesis is one of several main mechanisms used by humans and many other animals to maintain blood glucose levels, avoiding low levels (hypoglycemia). Other means include the degradation of glycogen (glycogenolysis)[1] and fatty acid catabolism. Gluconeogenesis is a ubiquitous process, present in plants, animals, fungi, bacteria, and other microorganisms.[2] In vertebrates, gluconeogenesis takes place mainly in the liver and, to a lesser extent, in the cortex of the kidneys. In ruminants, this tends to be a continuous process.[3] In many other animals, the process occurs during periods of fasting, starvation, low-carbohydrate diets, or intense exercise. The process is highly endergonic until it is coupled to the hydrolysis of ATP or GTP, effectively making the process exergonic. For example, the pathway leading from pyruvate to glucose-6-phosphate requires 4 molecules of ATP and 2 molecules of GTP to proceed spontaneously. Gluconeogenesis is often associated with ketosis. Gluconeogenesis is also a target of therapy for type 2 diabetes, such as the antidiabetic drug, metformin, which inhibits glucose formation and stimulates glucose uptake by cells.[4] In ruminants, because dietary carbohydrates tend to be metabolized by rumen organisms, gluconeogenesis occurs Continue reading >>

The Science Behind Fat Metabolism

The Science Behind Fat Metabolism

Per the usual disclaimer, always consult with your doctor before experimenting with your diet (seriously, go see a doctor, get data from blood tests, etc.). Please feel free to comment below if you’re aware of anything that should be updated; I’d appreciate knowing and I’ll update the content quickly. My goal here is to help a scientifically curious audience know the basic story and where to dive in for further study. If I’m successful, the pros will say “duh”, and everyone else will be better informed about how this all works. [UPDATE: based on a ton a helpful feedback and questions on the content below, I’ve written up a separate article summarizing the science behind ketogenic (low-carb) diets. Check it out. Also, the below content has been updated and is still very much applicable to fat metabolism on various kinds of diets. Thanks, everyone!] tl;dr The concentration of glucose in your blood is the critical upstream switch that places your body into a “fat-storing” or “fat-burning” state. The metabolic efficiency of either state — and the time it takes to get into one from the other — depends on a large variety of factors such as food and drink volume and composition, vitamin and mineral balances, stress, hydration, liver and pancreas function, insulin sensitivity, exercise, mental health, and sleep. Carbohydrates you eat, with the exception of indigestible forms like most fibers, eventually become glucose in your blood. Assuming your metabolism is functioning normally, if the switch is on you will store fat. If the switch is off, you will burn fat. Therefore, all things being equal, “diets” are just ways of hacking your body into a sufficiently low-glycemic state to trigger the release of a variety of hormones that, in turn, result in 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 >>

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 >>

Can Fats Be Turned Into Glycogen For Muscle?

Can Fats Be Turned Into Glycogen For Muscle?

Can Fats Be Turned Into Glycogen for Muscle? Glycogen is stored energy that muscles use to function. 4 What Are the Metabolic Pathways to Metabolize Fats? 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. 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. 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. Once glucose has been obtained Continue reading >>

How Fat Cells Work

How Fat Cells Work

When you are not eating, your body is not absorbing food. If your body is not absorbing food, there is little insulin in the blood. However, your body is always using energy; and if you're not absorbing food, this energy must come from internal stores of complex carbohydrates, fats and proteins. Under these conditions, various organs in your body secrete hormones: pancreas - glucagon pituitary gland - growth hormone pituitary gland - ACTH (adrenocorticotropic hormone) adrenal gland - epinephrine (adrenaline) thyroid gland - thyroid hormone These hormones act on cells of the liver, muscle and fat tissue, and have the opposite effects of insulin. When you are not eating, or you are exercising, your body must draw on its internal energy stores. Your body's prime source of energy is glucose. In fact, some cells in your body, such as brain cells, can get energy only from glucose. The first line of defense in maintaining energy is to break down carbohydrates, or glycogen, into simple glucose molecules -- this process is called glycogenolysis. Next, your body breaks down fats into glycerol and fatty acids in the process of lipolysis. The fatty acids can then be broken down directly to get energy, or can be used to make glucose through a multi-step process called gluconeogenesis. In gluconeogenesis, amino acids can also be used to make glucose. In the fat cell, other types of lipases work to break down fats into fatty acids and glycerol. These lipases are activated by various hormones, such as glucagon, epinephrine and growth hormone. The resulting glycerol and fatty acids are released into the blood, and travel to the liver through the bloodstream. Once in the liver, the glycerol and fatty acids can be either further broken down or used to make glucose. Losing Weight and Losin Continue reading >>

Why Can't Animals Turn Fatty Acids Into Glucose?

Why Can't Animals Turn Fatty Acids Into Glucose?

Animals can’t turn fatty acids into glucose because fatty acids are metabolized 2 carbons at a time into the acetyl units of acetyl-CoA, and we have no enzymes to convert acetyl-CoA into pyruvate or any other metabolite in the gluconeogenesis pathway. Essentially, as I tell my students, the pyruvate dehydrogenase reaction is crossing the Rubicon: once it’s done, you can’t go back. The oxidative decarboxylation of pyruvate is irreversible, and there is no reverse bypass in animal cells. Acetyl-CoA of course enters the Krebs cycle, which ends with oxaloacetate, which is on the gluconeogenic pathway, but the Krebs cycle starts by reacting acetyl-CoA with OAA, and thus OAA production is balanced by OAA consumption: there is no net conversion of acetyl-CoA into OAA. Plants, fungi, and some microbes do have a way to do this: a bypass in the Krebs cycle called the glyoxylate cycle. Isocitrate, instead of being oxidized to alpha-ketoglutarate, is split into succinate and glyoxylate (HC(O)-COO), by an enzyme called isocitrate lyase. The glyoxylate reacts with another acetyl-CoA to form malate, in a reaction catalyzed by malate synthase. The succinate and malate both undergo their usual reactions in the Krebs cycle, resulting in the formation of two oxaloacetates. Thus the cell achieves a net conversion of two acetyl-CoA into OAA, and the OAA can be used for gluconeogenesis. This allows, among other things, plant seeds to store energy and carbon in the form of fats, but use them to create glucose and thus cellulose for cell walls when the seed germinates into a sprout. If we had isocitrate lyase and malate synthase, we could do this trick to, and diabetics wouldn’t have to worry about ketoacidosis. But, we don’t. Edit: for the sake of accuracy, I should mention that fat Continue reading >>

When Does Glucose Convert To Fat?

When Does Glucose Convert To Fat?

Despite the fact that eating a jelly doughnut seems to deposit fat directly on your hips, converting sugar to fat is actually a relatively complex chemical process. Sugar conversion to fat storage depends not only upon the type of foods you eat, but how much energy your body needs at the time you eat it. Video of the Day Your body converts excess dietary glucose into fat through the process of fatty acid synthesis. Fatty acids are required in order for your body to function properly, playing particularly important roles in proper brain functioning. There are two kinds of fatty acids; essential fatty acids and nonessential fatty acids. Essential fatty acids refer to fatty acids you must eat from your diet, as your body cannot make them. Nonessential fatty acids are made through the process of fatty acid synthesis. Fatty Acid Synthesis Fatty acids are long organic compounds having an acid group at one end and a methyl group at the other end. The location of their first double bond dictates whether they are in the omega 3, 6, or 9 fatty acid family. Fatty acid synthesis takes place in the cytoplasm of cells and requires some energy input. In other words, your body actually has to expend some energy in order to store fat. Glucose is a six-carbon sugar molecule. Your body first converts this molecule into two three-carbon pyruvate molecules through the process of glycolysis and then into acetyl CoA. When your body requires immediate energy, acetyl CoA enters the Citric Acid Cycle creating energy molecules in the form of ATP. When glucose intake exceeds your body's energy needs--for example, you eat an ice-cream sundae and then go relax on the sofa for five hours--your body has no need to create more energy molecules. Therefore, acetyl CoA begins the process of fatty acid syn Continue reading >>

Muscle Physiology - Metabolism Of Fatty Acids

Muscle Physiology - Metabolism Of Fatty Acids

Fat molecules consist of three fatty acid chains connected by a glycerol backbone. Fatty acids are basically long chains of carbon and hydrogen and are the major source of energy during normal activities. Fatty acids are broken down by progressively cleaving two carbon bits and converting these to acetyl coenzyme A. The acetyl CoA is the oxidized by the same citric acid cycle involved in the metabolism of glucose. For every two carbons in a fatty acid, oxidation yields 5 ATP s generating the acetyl CoA and 12 more ATP s oxidizing the coenzyme. This makes fat a terrific molecule in which to store energy, as the body well knows (much to our dismay). The only biological drawback to this, and other, forms of oxidative metabolism is its dependence on oxygen. Thus, if energy is required more rapidly than oxygen can be delivered, muscles switch to the less efficient anaerobic pathways. Interestingly, this implies that an anaerobic workout will not "burn" any fat, but will preferentially deplete the body of glucose. Of course, your body can't survive very long on just anaerobic metabolism...it just can't generate enough energy. Last Updated: Friday, 13-Jan-2006 15:56:16 PST For questions or comments regarding this site, please e-mail the webmaster . Copyright 2000, University of California Regents. All rights reserved. Continue reading >>

Glucose Can Be Synthesized From Noncarbohydrate Precursors - Biochemistry - Ncbi Bookshelf

Glucose Can Be Synthesized From Noncarbohydrate Precursors - Biochemistry - Ncbi Bookshelf

Glucose is formed by hydrolysis of glucose 6-phosphate in a reaction catalyzed by glucose 6-phosphatase. We will examine each of these steps in turn. 16.3.2. The Conversion of Pyruvate into Phosphoenolpyruvate Begins with the Formation of Oxaloacetate The first step in gluconeogenesis is the carboxylation of pyruvate to form oxaloacetate at the expense of a molecule of ATP . Then, oxaloacetate is decarboxylated and phosphorylated to yield phosphoenolpyruvate, at the expense of the high phosphoryl-transfer potential of GTP . Both of these reactions take place inside the mitochondria. The first reaction is catalyzed by pyruvate carboxylase and the second by phosphoenolpyruvate carboxykinase. The sum of these reactions is: Pyruvate carboxylase is of special interest because of its structural, catalytic, and allosteric properties. The N-terminal 300 to 350 amino acids form an ATP -grasp domain ( Figure 16.25 ), which is a widely used ATP-activating domain to be discussed in more detail when we investigate nucleotide biosynthesis ( Section 25.1.1 ). The C -terminal 80 amino acids constitute a biotin-binding domain ( Figure 16.26 ) that we will see again in fatty acid synthesis ( Section 22.4.1 ). Biotin is a covalently attached prosthetic group, which serves as a carrier of activated CO2. The carboxylate group of biotin is linked to the -amino group of a specific lysine residue by an amide bond ( Figure 16.27 ). Note that biotin is attached to pyruvate carboxylase by a long, flexible chain. The carboxylation of pyruvate takes place in three stages: Recall that, in aqueous solutions, CO2 exists as HCO3- with the aid of carbonic anhydrase (Section 9.2). The HCO3- is activated to carboxyphosphate. This activated CO2 is subsequently bonded to the N-1 atom of the biotin ring to Continue reading >>

Why Is It That Glucose Is Preferred As The Prime Energy Source?

Why Is It That Glucose Is Preferred As The Prime Energy Source?

1) Since all carbohydrates share certain structural features in common they are likely to also share certain metabolic steps. Strings of such steps are usually referred to as metabolic pathways. These would generally be most employed for the energy extraction from the most readily available substrate. The metabolism of other similar substrates would employ some portions of the same pathways with the aid of specialized 'adapter' steps. Doing so conserves cellular resources. 2) Mammals generally store carbohydrate energy in the form of glycogen, and most tissues are generally primed to channel resources either for energy storage or energy utilization from stores, in response to hormonal signals. Most cells constitutively express receptors for glucose, and certain organs are almost wholly dependent on it for energy. 3) While other carbohydrate forms may also be used in most tissues, the necessary receptors are at least to some extent inducible. This helps conserve resources. 4) What the above reasoning leads us to is the following conclusion: A preferred substrate is employed in order to conserve resources. One could still argue: but why glucose? Would this kind of question be resolved if the preferred molecule was different? Continue reading >>

How Does Fat Get Converted To Calories?

How Does Fat Get Converted To Calories?

Opinions expressed by Forbes Contributors are their own. Answer by Bart Loews , passionate exercise enthusiast, on Quora : How is fat being converted into calories at cellular level? First lets get some term clarification: A calorie is a measure of energy, specifically heat. Its a measurement of an indirect use of your biological fuels. Your body doesnt really convert things to calories, it converts them to ATP which is used as energy. Calories are, sadly, the best way we have to measure this process.Ill assume that the point of this question is: How does fat turn into energy? Fat is a term used interchangeably with lipids and with adipose tissue. Lipids are molecules that consist of a hydrophobic tail with a hydrophilic head. Because of this polarized set up, they are able to cluster together to form barriers between water and non water, like bubbles. Your cell membranes are composed of lipids. Adipose tissue is what makes you fat. Adipose tissue stores lipids in the form of triglycerides or 3 fatty acid chains with a glycerol backbone. These triglycerides are what is broken down to be used for energy. Adipose tissue is made up of collections of adipocytes or fat cells. Adipose tissue is used for insulation, cushioning, and energy storage. You get a particular number of fat cells (between 30 and 300 billion) during adolescence and childhood. You don't lose them naturally, but you can gain more if they grow more than 4 fold from their original size. They grow and shrink as they take on more energy. Fat cells have a few other roles in the endocrine system, they release the hormone, Leptin when they receive energy from insulin. Leptin signals to your body that you're full. The more fat cells you have, the more leptin is released. It's been found that obese people are lep Continue reading >>

In Silico Evidence For Gluconeogenesis From Fatty Acids In Humans

In Silico Evidence For Gluconeogenesis From Fatty Acids In Humans

In Silico Evidence for Gluconeogenesis from Fatty Acids in Humans Affiliation Department of Bioinformatics, School of Biology and Pharmaceutics, Friedrich Schiller University of Jena, Jena, Germany Affiliation Department of Bioinformatics, School of Biology and Pharmaceutics, Friedrich Schiller University of Jena, Jena, Germany Affiliation Department of Bioinformatics, School of Biology and Pharmaceutics, Friedrich Schiller University of Jena, Jena, Germany Affiliation Systems Biology/Bioinformatics Group, Leibniz Institute for Natural Product Research and Infection Biology Hans Knll Institute, Jena, Germany Affiliations Department of Human Nutrition, Institute of Nutrition, University of Jena, Jena, Germany, Department of Clinical Nutrition, German Institute of Human Nutrition, Potsdam-Rehbrcke, Nuthetal, Germany Affiliation Department of Bioinformatics, School of Biology and Pharmaceutics, Friedrich Schiller University of Jena, Jena, Germany In Silico Evidence for Gluconeogenesis from Fatty Acids in Humans The question whether fatty acids can be converted into glucose in humans has a long standing tradition in biochemistry, and the expected answer is No. Using recent advances in Systems Biology in the form of large-scale metabolic reconstructions, we reassessed this question by performing a global investigation of a genome-scale human metabolic network, which had been reconstructed on the basis of experimental results. By elementary flux pattern analysis, we found numerous pathways on which gluconeogenesis from fatty acids is feasible in humans. On these pathways, four moles of acetyl-CoA are converted into one mole of glucose and two moles of CO2. Analyzing the detected pathways in detail we found that their energetic requirements potentially limit their capacity. T Continue reading >>

Why Can't Fat Produce Glucose?

Why Can't Fat Produce Glucose?

Tousief Irshad Ahmed Sirwal Author has 77 answers and 106.2k answer views Acetyl CoA is NOT a substrate for gluconeogenesis in animals 1. Pyruvate dehydrogenase reaction is irreversible. So, acetyl CoA cannot be converted back to pyruvate. 2. 2C Acetyl CoA enters the TCA cycle by condensing with 4C oxaloacetate. 2 molecules of CO2 are released & the oxaloacetate is regenerated. There is no NET production of oxaloacetate. Animals cannot convert fat into glucose with minimal exceptions 1. Propionyl CoA derived from odd chain fatty acids are converted to Succinyl CoA Glucogenic 2. Glycerol derived from triglycerides are glucogenic. Answered Mar 26, 2017 Author has 942 answers and 259.1k answer views Yijia Xiong pointed out that the glycerol portion of triglycerides (fats) can indeed be converted to glucose. It is not so energy-inefficient that it is avoided by our bodies. If nutritionally, we are in a gluconeogenesis mode (building up glucose stores rather than consuming them), glycerol would be a perfectly acceptable precursor. However, I think the original question had more to do with the vast bulk of the triglycerides that are not glycerol, but are fatty acids. And it is true that we cant produce glucose from fatty acids. The reason is that the catabolic reactions of fatty acids break off two carbon atoms at a time as Acetyl-CoA. But our metabolic suite of pathways has no way to convert a two-carbon fragment to glucose. The end product of glycolysis is pyruvate, a three-carbon compound. Pyruvate can be back-synthesized into glucose. But the committing reaction for the Krebs cycle is the pyruvate dehydrogenase step, forming acetyl-CoA. That reaction is not reversible. Once pyruvate loses a carbon atom, it cant go back. The three main macronutrients are carbohydrates, pr Continue reading >>

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