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Can Fatty Acids Be Converted To Glucose?

Insulin And Glucagon

Insulin And Glucagon

Acrobat PDF file can be downloaded here. The islets of Langerhans The pancreatic Islets of Langerhans are the sites of production of insulin, glucagon and somatostatin. The figure below shows an immunofluorescence image in which antibodies specific for these hormones have been coupled to differing fluorescence markers. We can therefore identify those cells that produce each of these three peptide hormones. You can see that most of the tissue, around 80 %, is comprised of the insulin-secreting red-colored beta cells (ß-cells). The green cells are the α-cells (alpha cells) which produce glucagon. We see also some blue cells; these are the somatostatin secreting γ-cells (gamma cells). Note that all of these differing cells are in close proximity with one another. While they primarily produce hormones to be circulated in blood (endocrine effects), they also have marked paracrine effects. That is, the secretion products of each cell type exert actions on adjacent cells within the Islet. An Introduction to secretion of insulin and glucagon The nutrient-regulated control of the release of these hormones manages tissue metabolism and the blood levels of glucose, fatty acids, triglycerides and amino acids. They are responsible for homeostasis; the minute-to-minute regulation of the body's integrated metabolism and, thereby, stabilize our inner milieu. The mechanisms involved are extremely complex. Modern medical treatment of diabetes (rapidly becoming "public enemy number one") is based on insight into these mechanisms, some of which are not completely understood. I will attempt to give an introduction to this complicated biological picture in the following section. Somewhat deeper insight will come later. The Basics: secretion Let us begin with two extremely simplified figur 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 >>

Chapter 24 -nutrition, Metabolism, And Body Temperature Regulation

Chapter 24 -nutrition, Metabolism, And Body Temperature Regulation

Nutrient - substance that promotes normal growth, maintenance and repair Major nutrients - carbohydrates, lipids, and proteins Other nutrients - vitamins and minerals (and technically speaking, water) Carbohydrates Complex carbohydrates (starches) are found in bread, cereal, flour, pasta, nuts, and potatoes Simple carbohydrates (sugars) are found in soft drinks, candy, fruit, and ice cream Glucose is the molecule ultimately used by body cells to make ATP Neurons and RBCs rely almost entirely upon glucose to supply their energy needs Excess glucose is converted to glycogen or fat and stored The minimum amount of carbohydrates needed to maintain adequate blood glucose levels is 100 grams per day Starchy foods and milk have nutrients such as vitamins and minerals in addition to complex carbohydrates Refined carbohydrate foods (candy and soft drinks) provide energy sources only and are referred to as "empty calories" Lipids The most abundant dietary lipids, triglycerides, are found in both animal and plant foods Essential fatty acids - linoleic and linolenic acid, found in most vegetables, must be ingested Dietary fats: Help the body to absorb vitamins Are a major energy fuel of hepatocytes and skeletal muscle Are a component of myelin sheaths and all cell membranes Fatty deposits in adipose tissue provide: A protective cushion around body organs An insulating layer beneath the skin An easy-to-store concentrated source of energy Dietary Requirements Higher for infants and children than for adults The American Heart Association suggests that: Fats should represent less than 30% of one's total caloric intake Saturated fats should be limited to 10% or less of one's total fat intake Daily cholesterol intake should not exceed 200 mg Proteins Complete proteins that meet all the b Continue reading >>

Converting Carbohydrates To Triglycerides

Converting Carbohydrates To Triglycerides

Consumers are inundated with diet solutions on a daily basis. High protein, low fat, non-impact carbohydrates, and other marketing “adjectives” are abundant within food manufacturing advertising. Of all the food descriptors, the most common ones individuals look for are “fat free” or “low fat”. Food and snack companies have found the low fat food market to be financially lucrative. The tie between fat intake, weight gain, and health risks has been well documented. The dietary guidelines suggest to keep fat intake to no more than 30% of the total diet and to consume foods low in saturated and trans fatty acids. But, this does not mean that we can consume as much fat free food as we want: “Fat free does not mean calorie free.” In many cases the foods that are low in fat have a large amount of carbohydrates. Carbohydrate intake, like any nutrient, can lead to adverse affects when over consumed. Carbohydrates are a necessary macronutrient, vital for maintenance of the nervous system and energy for physical activity. However, if consumed in amounts greater than 55% to 65% of total caloric intake as recommended by the American Heart Association can cause an increase in health risks. According to the World Health Organization the Upper Limit for carbohydrates for average people is 60% of the total dietary intake. Carbohydrates are formed in plants where carbons are bonded with oxygen and hydrogen to form chains of varying complexity. The complexity of the chains ultimately determines the carbohydrate classification and how they will digest and be absorbed in the body. Mono-and disaccharides are classified as simple carbohydrates, whereas polysaccharides (starch and fiber) are classified as complex. All carbohydrates are broken down into monosaccharides before b 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 >>

Catabolism

Catabolism

Types of Catabolism Catabolism is the set of metabolic processes that break down large molecules. Learning Objectives Summarize various types of catabolism included in metabolism (catabolism of carbohydrates, proteins and fats) Key Takeaways Key Points The purpose of the catabolic reactions is to provide the energy and components needed by anabolic reactions. Microbes simply secrete digestive enzymes into their surroundings, while animals only secrete these enzymes from specialized cells in their guts. Fats are catabolised by hydrolysis to free fatty acids and glycerol. Amino acids are either used to synthesize proteins and other biomolecules, or oxidized to urea and carbon dioxide as a source of energy. Carbohydrates are usually taken into cells once they have been digested into monosaccharides and then processed inside the cell via glycolysis. Key Terms polymer: A long or larger molecule consisting of a chain or network of many repeating units, formed by chemically bonding together many identical or similar small molecules called monomers. A polymer is formed by polymerization, the joining of many monomer molecules. acetyl CoA: Acetyl coenzyme A or acetyl-CoA is an important molecule in metabolism, used in many biochemical reactions. Its main function is to convey the carbon atoms within the acetyl group to the citric acid cycle (Krebs cycle) to be oxidized for energy production. catabolism: Destructive metabolism, usually includes the release of energy and breakdown of materials. Overview of Catabolism Catabolism is the set of metabolic processes that break down large molecules. These include breaking down and oxidizing food molecules. The purpose of catabolic reactions is to provide the energy and components needed by anabolic reactions. The exact nature of these ca 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 >>

Milk Composition - Milk Fat

Milk Composition - Milk Fat

Summary of Fatty Acid Synthesis Reactions: Each cycle through the malonyl-CoA pathway results in two carbons being added to the FA chain. The total reaction is (given here for synthesis of palmitate; C16): Acetyl-CoA + 7 Malonyl-CoA + 14 NADPH2 are catalyzed by Fatty Acid Synthetase to yield = The Fatty Acid Synthesis Pathway involves the following steps : The steps involved in the malonyl-CoA pathway occur with the growing FA chain esterified to an acyl carrier protein. Fatty acid synthetase is a large complex of enzymatic activities which are responsible for the reactions of FA synthesis. In addition, there are enzyme activities called acylthioesterases which are responsible for cleaving off the growing FA chain from the acyl carrier protein once it has reached a certain chain length. The long chain acylthioesterase is part of the fatty acid synthetase complex and cleaves off FA chain lengths longer that C16. The medium chain acylthioesterase cleaves off the growing FA chain at or before it reaches C16. In nonruminants, the medium chain acylthioesterase is cytoplasmic and cleaves off free FAs (unesterified). In the ruminant, the medium chain acylthioesterase is associated with the fatty acid synthetase complex and releases acyl-CoA thioesters. Below is a diagram of the pathway of fatty acid synthesis. Note that acetate carbons come into play twice, once as the source of acetyl-CoA to enter the malonyl-CoA pathway and once as the source of malonyl-CoA that adds the two carbons to each cycle of the fatty acid synthetase. In the latter case, conversion of acetyl-CoA to malonyl-CoA is the rate limiting step in fatty acid synthesis. The reaction is catalyzed by acetyl-CoA carboxylase, a biotinylated protein. Acetyl-CoA carboxylase activity is regulated by lactogenic hormo Continue reading >>

Lipid Metabolism

Lipid Metabolism

on on Fats (or triglycerides) within the body are ingested as food or synthesized by adipocytes or hepatocytes from carbohydrate precursors ([link]). Lipid metabolism entails the oxidation of fatty acids to either generate energy or synthesize new lipids from smaller constituent molecules. Lipid metabolism is associated with carbohydrate metabolism, as products of glucose (such as acetyl CoA) can be converted into lipids. Lipid metabolism begins in the intestine where ingested triglycerides are broken down into smaller chain fatty acids and subsequently into monoglyceride molecules (see [link]b) by pancreatic lipases, enzymes that break down fats after they are emulsified by bile salts. When food reaches the small intestine in the form of chyme, a digestive hormone called cholecystokinin (CCK) is released by intestinal cells in the intestinal mucosa. CCK stimulates the release of pancreatic lipase from the pancreas and stimulates the contraction of the gallbladder to release stored bile salts into the intestine. CCK also travels to the brain, where it can act as a hunger suppressant. Together, the pancreatic lipases and bile salts break down triglycerides into free fatty acids. These fatty acids can be transported across the intestinal membrane. However, once they cross the membrane, they are recombined to again form triglyceride molecules. Within the intestinal cells, these triglycerides are packaged along with cholesterol molecules in phospholipid vesicles called chylomicrons ([link]). The chylomicrons enable fats and cholesterol to move within the aqueous environment of your lymphatic and circulatory systems. Chylomicrons leave the enterocytes by exocytosis and enter the lymphatic system via lacteals in the villi of the intestine. From the lymphatic system, the chylo Continue reading >>

Gluconeogenesis - An Overview | Sciencedirect Topics

Gluconeogenesis - An Overview | Sciencedirect Topics

Gluconeogenesis is the process that leads to the generation of glucose from a variety of sources such as pyruvate, lactate, glycerol, and certain amino acids. Larry R. Engelking, in Textbook of Veterinary Physiological Chemistry (Third Edition) , 2015 Gluconeogenesis occurs in the liver and kidneys. Gluconeogenesis supplies the needs for plasma glucose between meals. Gluconeogenesis is stimulated by the diabetogenic hormones (glucagon, growth hormone, epinephrine, and cortisol). Gluconeogenic substrates include glycerol, lactate, propionate, and certain amino acids. PEP carboxykinase catalyzes the rate-limiting reaction in gluconeogenesis. The dicarboxylic acid shuttle moves hydrocarbons from pyruvate to PEP in gluconeogenesis. Gluconeogenesis is a continual process in carnivores and ruminant animals, therefore they have little need to store glycogen in their liver cells. Of the amino acids transported to liver from muscle during exercise and starvation, Ala predominates. b-Aminoisobutyrate, generated from pyrimidine degradation, is a (minor) gluconeogenic substrate. N.V. Bhagavan, Chung-Eun Ha, in Essentials of Medical Biochemistry , 2011 Gluconeogenesis refers to synthesis of new glucose from noncarbohydrate precursors, provides glucose when dietary intake is insufficient or absent. It also is essential in the regulation of acid-base balance, amino acid metabolism, and synthesis of carbohydrate derived structural components. Gluconeogenesis occurs in liver and kidneys. The precursors of gluconeogenesis are lactate, glycerol, amino acids, and with propionate making a minor contribution. The gluconeogenesis pathway consumes ATP, which is derived primarily from the oxidation of fatty acids. The pathway uses several enzymes of the glycolysis with the exception of enzymes 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 >>

Does The Body Ever Convert Fat To Glycogen? - Crossfit Discussion Board

Does The Body Ever Convert Fat To Glycogen? - Crossfit Discussion Board

Does the body ever convert fat to glycogen? Nutrition Diet, supplements, weightloss, health & longevity "Basically, a diet high in fat activates the lipolytic (fat burning) enzymes in your body and decreases the activity of the lipogenic (fat producing) enzymes. Dietary free fatty acids and triglycerides become the body's main energy source. The triglycerides are broken down to free fatty acids and some of the fatty acids are metabolized to ketones, which in turn can be used for energy by body cells. The use of ketones for energy is especially important to the brain that can only use glucose and ketones for energy. In short, the free fatty acids and ketones take the place of glucose and the I always thought that the body could convert fat to glycogen. My question is does the body always use tryglicerides directly in the absense of glycogen or are there situations where it will convert fat to glycogen? This link may answer your question The body can convert glycerol to glucose but it prefers to use amino acids for gluconeogenesis. "Oxidation of fatty acids yields enormous amounts of energy on a molar basis, however, the carbons of the fatty acids cannot be utilized for net synthesis of glucose. The two carbon unit of acetyl-CoA derived from b-oxidation of fatty acids can be incorporated into the TCA cycle, however, during the TCA cycle two carbons are lost as CO2. Thus, explaining why fatty acids do not undergo net conversion to carbohydrate. The glycerol backbone of lipids can be used for gluconeogenesis. This requires phosphorylation to glycerol-3-phosphate by glycerol kinase and dehydrogenation to dihydroxyacetone phosphate (DHAP) by glyceraldehyde-3-phosphate dehydrogenase(G3PDH). The G3PDH reaction is the same as that used in the transport of cytosolic reducing equ Continue reading >>

Protein Will Not Make You Fat

Protein Will Not Make You Fat

Here's what you need to know... While it's biochemically possible for protein to turn into fat by ingesting extremely high numbers of calories or extremely large amounts of protein, it's unlikely you'll ever be in that situation. You can pretty much eat as much protein as you want and it won't turn to fat. That old chestnut about only being able to absorb 30 grams of protein in one sitting is bunk. Aside from building muscle, protein provides essential amino acids that serve as the building blocks for other proteins, enzymes, and hormones within the body that are vital for normal functioning. Without this steady supply of amino acids, the body resorts to breaking down its own proteins – typically from muscle – in order to meet this demand. Protein has its share of misconceptions. It's not uncommon to hear claims that dietary protein eaten in excess of some arbitrary number will be stored as body fat. Even those who are supposed to be reputable sources for nutrition information propagate this untenable dogma. While paging through a nutrition textbook I came across a section in the protein chapter regarding amino acids and energy metabolism (1). To quote the book directly: "Eating extra protein during times of glucose and energy sufficiency generally contributes to more fat storage, not muscle growth. This is because, during times of glucose and energy excess, your body redirects the flow of amino acids away from gluconeogenesis and ATP-producing pathways and instead converts them to lipids. The resulting lipids can subsequently be stored as body fat for later use." This is, more or less, supported by another textbook I own (2): "In times of excess energy and protein intakes coupled with adequate carbohydrate intake, the carbon skeleton of amino acids may be used to s Continue reading >>

Lipid Metabolism | Tocris Bioscience

Lipid Metabolism | Tocris Bioscience

When glucose supplies are low, the body is able to draw upon lipids as an alternative energy source. Lipids are generally stored as triglycerides and the first step in lipid metabolism is the conversion to glycerol and fatty acids. Glycerol (dihydroxyacetone phosphate) can enter the glycolysis pathway, and proceed to the Krebs cycle and oxidative phosphorylation . Fatty acids are converted to acetyl CoA, which can directly enter the Krebs cycle and subsequently oxidative phosphorylation. Each fatty acid molecule produces many acetyl CoA molecules (whereas glucose yields two), so much more ATP can be generated from a single fatty acid molecule than one glucose molecule. Ketones are produced as a by-product of lipid metabolism and can be used by the nervous system as a partial alternative to glucose. This is a protective mechanism, allowing the body to conserve glucose when energy intake becomes limited. Lipid metabolism and glucose metabolism are closely linked. Type II diabetes is associated with dyslipidemia, which is characterized by increased triglyceride and reduced high density lipoprotein cholesterol (HDL-C) levels. Impaired glucose control results in elevated glucose levels, which promotes hepatic and intestinal lipoprotein overproduction and hypertriglyceridemia. However, lipid changes could also be a cause of impaired glucose metabolism, as well as a consequence, since elevated triglyceride levels lead to increased free fatty acid (FFA) levels, which appear to induce insulin resistance and cell dysfunction, although the mechanisms by which this occurs are at present unclear. It has been proposed that this effect on insulin resistance may be the result of FFAs inducing inflammation, possibly via activation of Toll-like receptor 4 or the inflammasome. Disorders Continue reading >>

Chapter 1: Introduction

Chapter 1: Introduction

This chapter defines the aspects of the metabolism of the end-products of digestion that limit the productivity of ruminants. Using this information it should be possible to combine efficiently the feed resources that are available to provide the nutrients needed for diverse functions such as work, growth, reproduction and milk production. The metabolites needed for the above functions are oxidative energy (acetate and butyrate, referred to as C2 energy), glucogenic energy, arising largely from propionate or in some situations alimentary glucose (C3 + C6 energy), amino acids (largely microbial protein and dietary bypass protein) and dietary long-chain fatty acids (LCFAs). The gross inter-relationships of these metabolites for synthesis of tissues and milk and for work are shown in Figure 4.1. Figure 4.1 Ruminant requirements for major metabolites according to productive state To provide the background for the recommendations made in the guidelines for feeding ruminants given in Chapter 7, the pathways of metabolism of VFAs and protein are discussed, emphasising the interrelationships that exist between, for instance, fat synthesis, glucose metabolism and availability of dietary LCFAs. The pathways of metabolism of the VFAs are illustrated in Figure 4.2, indicating the sites at which high-energy phosphate bonds are generated. Theoretically, complete oxidation of acetyl CoA, propionyl CoA and butyryl CoA is coupled to the generation of 12, 20 and 29 moles of ATP per mole, respectively. Two moles of ATP are required per mole of VFA activated to its CoA derivative. Figure 4.2 Metabolism of VFA in ruminants in relation to the availability of ATP. The conversion of a large proportion of butyrate to ketone bodies and of propionate to glucose before oxidation reduces the effic Continue reading >>

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