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Why Can't Fat Be Converted To Glucose

The Catabolism Of Fats And Proteins For Energy

The Catabolism Of Fats And Proteins For Energy

The Catabolism of Fats and Proteins for Energy Before we get into anything, what does the word catabolism mean? When we went over catabolic and anabolic reactions , we said that catabolic reactions are the ones that break apart molecules. To remember what catabolic means, think of a CATastrophe where things are falling apart and breaking apart. You could also remember cats that tear apart your furniture. In order to make ATP for energy, the body breaks down mostly carbs, some fats and very small amounts of protein. Carbs are the go-to food, the favorite food that cells use to make ATP but now were going to see how our cells use fats and proteins for energy. What were going to find is that they are ALL going to be turned into sugars (acetyl) as this picture below shows. First lets do a quick review of things you already know because it is assumed you learned cell respiration already and how glucose levels are regulated in your blood ! Glucose can be stored as glycogen through a process known as glycogenesis. The hormone that promotes this process is insulin. Then when glycogen needs to be broken down, the hormone glucagon, promotes glycogenolysis (Glycogen-o-lysis) to break apart the glycogen and increase the blood sugar level. Glucose breaks down to form phosphoglycerate (PGAL) and then pyruvic acid. What do we call this process of splitting glucose into two pyruvic sugars? Thats glycolysis (glyco=glucose, and -lysis is to break down). When theres not enough oxygen, pyruvic acid is converted into lactic acid. When oxygen becomes available, lactic acid is converted back to pyruvic acid. Remember that this all occurs in the cytoplasm. The pyruvates are then, aerobically, broken apart in the mitochondria into Acetyl-CoA. The acetyl sugars are put into the Krebs citric aci 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 >>

Evolving Health: Why Can't We Convert Fat To Glucose?

Evolving Health: Why Can't We Convert Fat To Glucose?

As evident by many sugar-laden soda pop "potbellies" of North America, lipogenesis can obviously occur from drinking and eating too much sugar (1). Wouldnt it be just grand to reverse the process and be able to lose all that fat via gluconeogenesis? Unfortunately mammals do not have the ability to synthesize glucose from fats (1). The fact is that once glucose is converted to acetyl coA there is no method of getting back to glucose. The pyruvate dehydrogenase reaction that converts pyruvate to acetyl CoA is not reversible (1p252). Because lipid metabolism produces acetyl CoA via beta-oxidation, there can be no conversion to pyruvate or oxaloacetate that may have been used for gluconeogenesis (1p252). Further, the two carbons in the acetyl CoA molecule are lost upon entering the citric acid cycle (1p252). Thus, the acetyl CoA is used for energy (1p252). There are some fatty acids that have an odd number of carbon atoms that can be converted to glucose, but these are not common in the diet (1p253). Maybe they should be made more common. Do they taste good? 1. Gropper SS, Smith JL, Groff JL. Advanced Nutrition and Human Metabolism. Belmont, CA: Thomson Wadsworth, 2009. Continue reading >>

Fat-to-glucose Interconversion By Hydrodynamic Transfer Of Two Glyoxylate Cycle Enzyme Genes

Fat-to-glucose Interconversion By Hydrodynamic Transfer Of Two Glyoxylate Cycle Enzyme Genes

Fat-to-glucose interconversion by hydrodynamic transfer of two glyoxylate cycle enzyme genes 1Department of Nutrition and Food Sciences, Physiology and Toxicology, University of Navarra, Pamplona, Spain 2Laboratory of Animal Physiology and Nutrition, School of Agronomy, Public University of Navarra, Pamplona, Spain Received 2008 Sep 29; Accepted 2008 Dec 10. Copyright 2008 Cordero et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( ), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The glyoxylate cycle, which is well characterized in higher plants and some microorganisms but not in vertebrates, is able to bypass the citric acid cycle to achieve fat-to-carbohydrate interconversion. In this context, the hydrodynamic transfer of two glyoxylate cycle enzymes, such as isocytrate lyase (ICL) and malate synthase (MS), could accomplish the shift of using fat for the synthesis of glucose. Therefore, 20 mice weighing 23.37 0.96 g were hydrodinamically gene transferred by administering into the tail vein a bolus with ICL and MS. After 36 hours, body weight, plasma glucose, respiratory quotient and energy expenditure were measured. The respiratory quotient was increased by gene transfer, which suggests that a higher carbohydrate/lipid ratio is oxidized in such animals. This application could help, if adequate protocols are designed, to induce fat utilization for glucose synthesis, which might be eventually useful to reduce body fat depots in situations of obesity and diabetes. Thousands of different life-related biochemical processes, such as cell respiration and many other metabolic reactions, can lead to the producti 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 >>

How Does The Body Adapt To Starvation?

How Does The Body Adapt To Starvation?

- [Instructor] In this video, I want to explore the question of how does our body adapt to periods of prolonged starvation. So in order to answer this question, I actually think it's helpful to remind ourselves first of a golden rule of homeostasis inside of our body. So in order to survive, remember that our body must be able to maintain proper blood glucose levels. I'm gonna go ahead and write we must be able to maintain glucose levels in our blood, and this is important even in periods of prolonged starvation, because it turns out that we need to maintain glucose levels above a certain concentration in order to survive, even if that concentration is lower than normal. And this of course brings up the question, well, how does our body maintain blood glucose levels? So let's go ahead and answer this question by starting off small. Let's say we have a mini case of starvation, let's say three or four hours after a meal. Your blood glucose levels begin to drop, and so what does your body do to resolve that? Well, at this point, it has a quick and easy solution. It turns to its glycogen stores in the liver. Remember that our body stores up these strings of glucose inside of our body so that we can easily pump it back into the blood when we're not eating. But unfortunately humans only have enough glycogen stores to last us about a day, so after a day of starvation, our body's pretty much reliant exclusively on the metabolic pathways involved in gluconeogenesis, which if you remember is the pathway by which we produce new or neo glucose. And we produce this glucose from non-carbohydrate precursor molecules. So let's think about what else we have in our body. Remember that our other two major storage fuels are fats, and we usually think about fatty acids containing most of th Continue reading >>

Diet

Diet

There is an old saying that "You are what you eat". Thisappears to be a self-evident truth. However, our body is more complicated than this. Our body is like a chemical lab that has thousands of reactions going on simultaneously at any given second. It is not surprising that what we eat might turn into something we haven't thought about after some of these reactions. Our goal is to loss fat. Therefore while there are hundreds of reactions happening in our body, we should onlybe concerned about nutrients that have the potential to be turned into fat. It turns out that after my intensive research in the fieldof metabolicbiochemistry, in addition to fat, protein and carbohydrate are the twomajor nutrients that has the potential to become fat. In this section, I will first tell you how proteins,carbohydrates and fat are turned into fat and then get stored.Then I will devise a diet that while lowering your chance ofgetting fat accumulated, it won't make you starve and allowyou to function at full capacity. Carbohydrates are broken down into glucose in intestine.Glucose provides immediate energy for our brain and red blood cells.Execessive glucose are transported to liver and converted into glycogenand storedin liver and muscle. On average, each person can store 2,000 calories of glycogen in their body. Thatis about 500g of carbohydrate. When we don't have any more capacity to store glycogen,excessive glucose will be turned into fat for storage. During thisconversion, 23% of energy stored in glucose is lost. Unfortunately, suchconversion is accounts for only 5% of the carb we consume. The rest of the carb is either stored as glycogen or oxidized to spare fat burn. Proteins were broken down into amino acids (protein is by definition a chain of amino acids) and absorbed in the Continue reading >>

Fat For Fuel: Why Dietary Fat, Not Glucose, Is The Preferred Body Fuel

Fat For Fuel: Why Dietary Fat, Not Glucose, Is The Preferred Body Fuel

Contrary to popular belief, glucose is NOT the preferred fuel of human metabolism; the fact is that burning dietary fat for fuel may actually be the key to optimal health Carbohydrate intake is the primary factor that determines your body's fat ratio, and processed grains and sugars (particularly fructose) are the primary culprits behind our skyrocketing obesity and diabetes rates According to experts, carbs should make up only 20 percent of your diet, while 50-70 percent of your diet should be healthy fats. Fat is far more satiating than carbs, so if you have cut down on carbs and feel ravenous, this is a sign that you need more healthy fat to burn for fuel By Dr. Mercola While we may consider ourselves to be at the pinnacle of human development, our modern food manufacturing processes have utterly failed at improving health and increasing longevity. During the Paleolithic period, many thousands of years ago, our ancestors ate primarily vegetables, fruit, nuts, roots and meat—and a wide variety of it. This diet was high in fats and protein, and low in grain- and sugar-derived carbohydrates. The average person's diet today, on the other hand, is the complete opposite, and the average person's health is a testament of what happens when you adhere to a faulty diet. Humans today suffer more chronic and debilitating diseases than ever before. And there can be little doubt that our food choices play a major role in this development. Quite simply, you were not designed to eat large amounts of refined sugar, high fructose corn syrup, cereal, bread, potatoes and pasteurized milk products. As Mark Sisson states in the featured article:1 "If you want to live a better life and eat the best foods nature provided for health and fitness, then it's time to ditch the old paradigms an Continue reading >>

How The Body Uses Carbohydrates, Proteins, And Fats

How The Body Uses Carbohydrates, Proteins, And Fats

How the Body Uses Carbohydrates, Proteins, and Fats The human body is remarkably adept at making do with whatever type of food is available. Our ability to survive on a variety of diets has been a vital adaptation for a species that evolved under conditions where food sources were scarce and unpredictable. Imagine if you had to depend on successfully hunting a woolly mammoth or stumbling upon a berry bush for sustenance! Today, calories are mostly cheap and plentifulperhaps too much so. Understanding what the basic macronutrients have to offer can help us make better choices when it comes to our own diets. From the moment a bite of food enters the mouth, each morsel of nutrition within starts to be broken down for use by the body. So begins the process of metabolism, the series of chemical reactions that transform food into components that can be used for the body's basic processes. Proteins, carbohydrates , and fats move along intersecting sets of metabolic pathways that are unique to each major nutrient. Fundamentallyif all three nutrients are abundant in the dietcarbohydrates and fats will be used primarily for energy while proteins provide the raw materials for making hormones, muscle, and other essential biological equipment. Proteins in food are broken down into pieces (called amino acids) that are then used to build new proteins with specific functions, such as catalyzing chemical reactions, facilitating communication between different cells, or transporting biological molecules from here to there. When there is a shortage of fats or carbohydrates, proteins can also yield energy. Fats typically provide more than half of the body's energy needs. Fat from food is broken down into fatty acids, which can travel in the blood and be captured by hungry cells. Fatty aci Continue reading >>

Chapter 05 Part 2 -- Metabolism Of Lipids

Chapter 05 Part 2 -- Metabolism Of Lipids

-- glucose is converted into glycogen and fat -- can be used for energy via the same pathways used for the metabolism of pyruvate -- hydrolyzed into glycerol and three fatty acids -- can be converted into acetyl CoA which can then enter the Krebs cycle -- DIAGRAM (3 long chains which are the 3 fatty acids + glycerol) Conversion of Glucose into Glycogen and Fat -- if energy is being delivered to the body faster than it is being consumed (used), excess glucose will enter 2 potential routes for storage: 1) glycogenesis (converting glucose into glycogen molecules) and 2) lipogenesis (converting glucose intermediates into fats) -- When cells have adequate levels of ATP (energy), they down-regulate the respiratory enzymes involved in glycolysis and the Krebs cycle thus the glucose can ONLY enter either glycogenesis or lipogenesis for the purpose of energy storage and NOT complete glycolysis and enter the Krebs cycle and electron transport chain to generate even more ATP (energy). Lipid Metabolism: Lipogenesis (creating fats) -- as ATP levels rise after an energy-rich meal, production of ATP is inhibited: 1. glucose enters glycolysis as normal and the resulting pyruvate is converted into acetyl CoA (acetyl CoA does not enter Krebs cycle though)(the acetyl CoA already formed is joined together to produce a variety of lipids, including cholesterol, ketone bodies, and fatty acids 2. fatty acids combine with glycerol to form triglycerides in the adipose tissue and liver (lipogenesis) -- primarily occurs in two locations: 1. adipose tissue; and 2. liver (fatty liver disease) 1. 80-85% of energy is stored as fat (14,000 kcal) 2. less than 2,000 kcal is stored as glycogen (2/3 of which is stored in skeletal muscle) 3. 15-20% of energy is stored as protein (not extensively used for e 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 >>

We Really Can Make Glucose From Fatty Acids After All! O Textbook, How Thy Biochemistry Hast Deceived Me!

We Really Can Make Glucose From Fatty Acids After All! O Textbook, How Thy Biochemistry Hast Deceived Me!

Biochemistry textbooks generally tell us that we can’t turn fatty acids into glucose. For example, on page 634 of the 2006 and 2008 editions of Biochemistry by Berg, Tymoczko, and Stryer, we find the following: Animals Cannot Convert Fatty Acids to Glucose It is important to note that animals are unable to effect the net synthesis of glucose from fatty acids. Specficially, acetyl CoA cannot be converted into pyruvate or oxaloacetate in animals. In fact this is so important that it should be written in italics and have its own bold heading! But it’s not quite right. Making glucose from fatty acids is low-paying work. It’s not the type of alchemy that would allow us to build imperial palaces out of sugar cubes or offer hourly sweet sacrifices upon the altar of the glorious god of glucose (God forbid!). But it can be done, and it’ll help pay the bills when times are tight. All Aboard the Acetyl CoA! When we’re running primarily on fatty acids, our livers break the bulk of these fatty acids down into two-carbon units called acetate. When acetate hangs out all by its lonesome like it does in a bottle of vinegar, it’s called acetic acid and it gives vinegar its characteristic smell. Our livers aren’t bottles of vinegar, however, and they do things a bit differently. They have a little shuttle called coenzyme A, or “CoA” for short, that carries acetate wherever it needs to go. When the acetate passenger is loaded onto the CoA shuttle, we refer to the whole shebang as acetyl CoA. As acetyl CoA moves its caboose along the biochemical railway, it eventually reaches a crossroads where it has to decide whether to enter the Land of Ketogenesis or traverse the TCA cycle. The Land of Ketogenesis is a quite magical place to which we’ll return in a few moments, but n 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 >>

The Catabolism Of Fats And Proteins For Energy

The Catabolism Of Fats And Proteins For Energy

Before we get into anything, what does the word catabolism mean? When we went over catabolic and anabolic reactions, we said that catabolic reactions are the ones that break apart molecules. To remember what catabolic means, think of a CATastrophe where things are falling apart and breaking apart. You could also remember cats that tear apart your furniture. In order to make ATP for energy, the body breaks down mostly carbs, some fats and very small amounts of protein. Carbs are the go-to food, the favorite food that cells use to make ATP but now we’re going to see how our cells use fats and proteins for energy. What we’re going to find is that they are ALL going to be turned into sugars (acetyl) as this picture below shows. First let’s do a quick review of things you already know because it is assumed you learned cell respiration already and how glucose levels are regulated in your blood! Glucose can be stored as glycogen through a process known as glycogenesis. The hormone that promotes this process is insulin. Then when glycogen needs to be broken down, the hormone glucagon, promotes glycogenolysis (Glycogen-o-lysis) to break apart the glycogen and increase the blood sugar level. Glucose breaks down to form phosphoglycerate (PGAL) and then pyruvic acid. What do we call this process of splitting glucose into two pyruvic sugars? That’s glycolysis (glyco=glucose, and -lysis is to break down). When there’s not enough oxygen, pyruvic acid is converted into lactic acid. When oxygen becomes available, lactic acid is converted back to pyruvic acid. Remember that this all occurs in the cytoplasm. The pyruvates are then, aerobically, broken apart in the mitochondria into Acetyl-CoA. The acetyl sugars are put into the Krebs citric acid cycle and they are totally broken 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 >>

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