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Why Can't Ketogenic Amino Acids Make Glucose

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In this video I discuss what are amino acids, what are amino acids made of, and what do amino acids do in the body. I also cover what are peptide bonds, polypeptide chains, how amino acids form proteins, some functions of amino acids, and what are amino acids used to build. Transcript We are going to start by looking at the molecular structure of a typical amino acid, dont worry, I am going to make it easy to understand. The basic structure of amino acids is that they consist of a carboxyl group, a lone hydrogen atom, an amino group, and a side chain, which is often referred to as an R-group. The formation of the side chain is what makes amino acids different from one another. As you can see in this diagram, these 4 are all connected to a carbon atom, which is referred to as the alpha carbon. Not every amino acid follows this exact structure, but, most do. On the screen I have 3 different amino acids, lysine, tryptophan, and leucine. You can see that each has a carboxyl group, an alpha carbon, a amino group, and an R-group that is different from each other. There are 23 total amino acids that are proteinogenic. Proteinogenic amino acids are precursors to proteins, which means they are compounds that participate in a chemical reaction to produce another compound. Of these 23 amino acids, 20 of them are called standard amino acids, and the other 3 are non-standard amino acids. These are listed on the screen. In this video we are going to focus on the standard amino acids, as they are what make up proteins. These amino acids can be classified many different ways, we are going to classify them in a basic nutritional way. Essential and nonessential. Essential amino acids cannot be made by the body, so, they must come from foods we eat. Nonessential amino acids are amino acids that our bodies can produce even if we dont get them from the food we eat. There is a subgroup of nonessential amino acids that are considered to be conditional amino acids. The list of conditional amino acids is not definitive. For instance, in times of illness or stress, there are certain amino acids the body cant produce sufficiently, and children's bodys havent developed the ability to produce certain amino acids yet. There are 9 essential and 11 nonessential amino acids, ive listed them on the screen. So, how do amino acids form proteins? Proteins are built from the 20 standard amino acids. Well, the first thing that happens is that 2 amino acids come together to form a peptide bond. A peptide bond is when the carboxyl group of one amino acid bonds with the amino group of another amino acid, as you can see here. If you notice 2 hydrogen atoms and one oxygen atom have been removed from the peptide bonding process. So, the peptide bonding results in the release of a water moleculeh20. But, we are not finished. More amino acids can link in, and form what is called a polypeptide chain. Some proteins are single polypeptide chains, and other proteins have polypeptide chains linked together. Not all protein contains all 20 of the standard amino acids. Not all protein contains all 20 of the standard amino acids. Proteins are often labeled as complete or incomplete protein. A Complete protein is a protein source that contains a sufficient quantity of all 9 of the essential amino acids that we discussed earlier. An incomplete protein does not contain a sufficient quantity of all 9 of the essential amino acids. Complete protein foods includeanimal foods such as red meat, poultry, pork and fish. Eggs and dairy products such as cows milk, yogurt, and cheese. Plant foods such as soy products, black beans, kidney beans, pumpkin seeds, quinoa, pistachios, just to name a few. You can also combine incomplete protein foods to create a complete protein meal. Amino acids also make up most enzymes. These Enzymes are proteins, so they are made by linking amino acids together in a specific and unique order. This chain of amino acids then forms a unique shape that allows the enzyme created to serve a single specific purpose. Enzymes function as catalysts, which means that they speed up the rate at which metabolic processed and reactions occur. Amino acids can also be metabolized for energy. Some hormones like epinephrine, also known as adrenaline, are amino acid derived. Some neurotransmitters like serotonin are derived from amino acids. The amino acid arginine is a precursor of nitric oxide, which helps regulate blood pressure, improves sleep quality and increases endurance and strength. Glutathione, which is a powerful antioxidant is formed from amino acids. Other sources... https://en.wikipedia.org/wiki/Amino_acid http://www.fitday.com/fitness-article... http://www.ivyroses.com/HumanBiology/...

Amino Acid Metabolism

Amino acids are categorized into two types - non-essential amino acids (can be synthesized by the body) and essential amino acids which cannot, and have to be provided from the diet. The non-essential amino acids are glycine, alanine, serine, asparagine, aspartic acid, glutamine, glutamic acid, proline, cysteine, tyrosine and arginine. The essential amino acids include valine, leucine, isoleucine, phenylalanine, tryptophan, methionine, threonine, lysine and histidine. The amino acids arginine, methionine and phenylalanine are considered essential because their rate of synthesis is insufficient to meet the growth needs of the body. Most of synthesized arginine is cleaved to form urea. Methionine is required in large amounts to produce cysteine if the latter amino acid is not adequately supplied in the diet. Similarly, phenylalanine is needed in large amounts to form tyrosine if the latter is not adequately supplied in the diet. The amino acid pool comes from protein degradation in the gastro-intestinal tract, intracellular protein degradation and de novo synthesis and is used in protein synthesis and metabolism. Each amino acid type has its own metabolic fate and specific functions. Continue reading >>

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Popular Questions

  1. manohman

    Why can't fat be converted into Glucose?

    So the reason cited is that beta oxidation/metabolism of fats leads to formation of acetyl coa, a 2 carbon molecule, and that because of that it cannot be converted back into glucose.
    Why exactly is that the case?
    If Glucogenic amino acids can be converted into citric acid cycle intermediates and then turn back into glucose via gluconeogensis, then why cant Fatty Acids which yield Acetyl Coa. Can't you just have Acetyl Coa enter the citric acid cycle and produce the same intermediates that the glucogenic amino acids creat?

  2. Czarcasm

    manohman said: ↑
    So the reason cited is that beta oxidation/metabolism of fats leads to formation of acetyl coa, a 2 carbon molecule, and that because of that it cannot be converted back into glucose.
    Why exactly is that the case?
    If Glucogenic amino acids can be converted into citric acid cycle intermediates and then turn back into glucose via gluconeogensis, then why cant Fatty Acids which yield Acetyl Coa. Can't you just have Acetyl Coa enter the citric acid cycle and produce the same intermediates that the glucogenic amino acids creat?
    Click to expand... Both glucose and fatty acids can be stored in the body as either glycogen for glucose (stored mainly in the liver or skeletal cells) or for FA's, as triacylglycerides (stored in adipose cells). We cannot store excess protein. It's either used to make other proteins, or flushed out of the body if in excess; that's generally the case but we try to make use of some of that energy instead of throwing it all away.
    When a person is deprived of nutrition for a period of time and glycogen stores are depleted, the body will immediately seek out alternative energy sources. Fats (stored for use) are the first priority over protein (which requires the breakdown of tissues such as muscle). We can mobilize these FA's to the liver and convert them to Acetyl-CoA to be used in the TCA cycle and generate much needed energy. On the contrary, when a person eats in excess (a fatty meal high in protein), it's more efficient to store fatty acids as TAG's over glycogen simply because glycogen is extremely hydrophilic and attracts excess water weight; fatty acids are largely stored anhydrously and so you essentially get more bang for your buck. This is evolutionary significant and why birds are able to stay light weight but fly for periods at a time, or why bears are able to hibernate for months at a time. Proteins on the other hand may be used anabolically to build up active tissues (such as when your working out those muscles), unless you live a sedentary lifestyle (less anabolism and therefore, less use of the proteins). As part of the excretion process, protein must be broken down to urea to avoid toxic ammonia and in doing so, the Liver can extract some of that usable energy for storage as glycogen.
    Also, it is worth noting that it is indeed possible to convert FA's to glucose but the pathway can be a little complex and so in terms of energy storage, is not very efficient. The process involves converting Acetyl-CoA to Acetone (transported out of mitochondria to cytosol) where it's converted to Pyruvate which can then be used in the Gluconeogenesis pathway to make Glucose and eventually stored as Glycogen. Have a look for yourself if your interested: http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1002116.g003/originalimage (and this excludes the whole glycogenesis pathway, which hasn't even begun yet).
    TLDR: it's because proteins have no ability to be stored in the body, but we can convert them to glycogen for storage during the breakdown process for excretion. Also, in terms of energy, it's a more efficient process than converting FA's to glycogen for storage.

  3. soccerman93

    This is where biochem comes in handy. Czarcasm gives a really good in depth answer, but a simpler approach is to count carbons. The first step of gluconeogenesis(formation of glucose) requires pyruvate, a 3 carbon molecule. Acetyl Co-A is a 2 carbon molecule, and most animals lack the enzymes (malate synthase and isocitrate lyase) required to convert acetyl co-A into a 3 carbon molecule suitable for the gluconeogenesis pathway. The ketogenic pathway is not efficient, as czarcasm pointed out. While acetyl co-A can indeed be used to form citric acid intermediates, these intermediates will be used in forming ATP, not glucose. Fatty acid oxidation does not yield suitable amounts of pyruvate, which is required for gluconeogenesis. This is part of why losing weight is fairly difficult for those that are overweight, we can't efficiently directly convert fat to glucose, which we need a fairly constant supply of. Sorry, that got a little long-winded

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Nutr 251 Exam 2 Review (minus Lipids)

Briefly outline the process of digestion and absorption of beef protein. 2) Stomach-HCL denature proteins, pepsin is activated to further break down proteins to smaller polypeptides 3) Small intestine-90% of digestion of proteins occurs here, pancreatic/enzymes break polypeptides down further to amino acids 4) Absorbed by active transport, travels to the portal vein and then to the liver 4 functions of essential amino acids other than protein synthesis 1) Act as precursors (ex- tryptophan can be converted to serotonin) 2) Used for fuel, but to lesser degree than fatty acids and glucose 3) Converted to fatty acids and put into fat cell storage when energy in is greater than energy out (there is too much protein being converted to fat) 4) Carbon portion can be converted to glucose in a process called gluconeogenesis which happens in starvation Chemical structure of protein vs. complex carbohydrates -A protein is made of long chains of amino acids linked together by peptide bonds -Complex carbohydrates are made of glucose units in straight or branched chains How is the chemical structure of a monosaccharide different from that of an amino acid? 1) Collagen- the framework for bone/tee Continue reading >>

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Popular Questions

  1. manohman

    Why can't fat be converted into Glucose?

    So the reason cited is that beta oxidation/metabolism of fats leads to formation of acetyl coa, a 2 carbon molecule, and that because of that it cannot be converted back into glucose.
    Why exactly is that the case?
    If Glucogenic amino acids can be converted into citric acid cycle intermediates and then turn back into glucose via gluconeogensis, then why cant Fatty Acids which yield Acetyl Coa. Can't you just have Acetyl Coa enter the citric acid cycle and produce the same intermediates that the glucogenic amino acids creat?

  2. Czarcasm

    manohman said: ↑
    So the reason cited is that beta oxidation/metabolism of fats leads to formation of acetyl coa, a 2 carbon molecule, and that because of that it cannot be converted back into glucose.
    Why exactly is that the case?
    If Glucogenic amino acids can be converted into citric acid cycle intermediates and then turn back into glucose via gluconeogensis, then why cant Fatty Acids which yield Acetyl Coa. Can't you just have Acetyl Coa enter the citric acid cycle and produce the same intermediates that the glucogenic amino acids creat?
    Click to expand... Both glucose and fatty acids can be stored in the body as either glycogen for glucose (stored mainly in the liver or skeletal cells) or for FA's, as triacylglycerides (stored in adipose cells). We cannot store excess protein. It's either used to make other proteins, or flushed out of the body if in excess; that's generally the case but we try to make use of some of that energy instead of throwing it all away.
    When a person is deprived of nutrition for a period of time and glycogen stores are depleted, the body will immediately seek out alternative energy sources. Fats (stored for use) are the first priority over protein (which requires the breakdown of tissues such as muscle). We can mobilize these FA's to the liver and convert them to Acetyl-CoA to be used in the TCA cycle and generate much needed energy. On the contrary, when a person eats in excess (a fatty meal high in protein), it's more efficient to store fatty acids as TAG's over glycogen simply because glycogen is extremely hydrophilic and attracts excess water weight; fatty acids are largely stored anhydrously and so you essentially get more bang for your buck. This is evolutionary significant and why birds are able to stay light weight but fly for periods at a time, or why bears are able to hibernate for months at a time. Proteins on the other hand may be used anabolically to build up active tissues (such as when your working out those muscles), unless you live a sedentary lifestyle (less anabolism and therefore, less use of the proteins). As part of the excretion process, protein must be broken down to urea to avoid toxic ammonia and in doing so, the Liver can extract some of that usable energy for storage as glycogen.
    Also, it is worth noting that it is indeed possible to convert FA's to glucose but the pathway can be a little complex and so in terms of energy storage, is not very efficient. The process involves converting Acetyl-CoA to Acetone (transported out of mitochondria to cytosol) where it's converted to Pyruvate which can then be used in the Gluconeogenesis pathway to make Glucose and eventually stored as Glycogen. Have a look for yourself if your interested: http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1002116.g003/originalimage (and this excludes the whole glycogenesis pathway, which hasn't even begun yet).
    TLDR: it's because proteins have no ability to be stored in the body, but we can convert them to glycogen for storage during the breakdown process for excretion. Also, in terms of energy, it's a more efficient process than converting FA's to glycogen for storage.

  3. soccerman93

    This is where biochem comes in handy. Czarcasm gives a really good in depth answer, but a simpler approach is to count carbons. The first step of gluconeogenesis(formation of glucose) requires pyruvate, a 3 carbon molecule. Acetyl Co-A is a 2 carbon molecule, and most animals lack the enzymes (malate synthase and isocitrate lyase) required to convert acetyl co-A into a 3 carbon molecule suitable for the gluconeogenesis pathway. The ketogenic pathway is not efficient, as czarcasm pointed out. While acetyl co-A can indeed be used to form citric acid intermediates, these intermediates will be used in forming ATP, not glucose. Fatty acid oxidation does not yield suitable amounts of pyruvate, which is required for gluconeogenesis. This is part of why losing weight is fairly difficult for those that are overweight, we can't efficiently directly convert fat to glucose, which we need a fairly constant supply of. Sorry, that got a little long-winded

  4. -> Continue reading
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What is GLUCONEOGENESIS? What does GLUCONEOGENESIS mean? GLUCONEOGENESIS meaning - GLUCONEOGENESIS definition - GLUCONEOGENESIS explanation. Source: Wikipedia.org article, adapted under https://creativecommons.org/licenses/... license. SUBSCRIBE to our Google Earth flights channel - https://www.youtube.com/channel/UC6Uu... 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) and fatty acid catabolism. Gluconeogenesis is a ubiquitous process, present in plants, animals, fungi, bacteria, and other microorganisms. 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. 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. In ruminants, because dietary carbohydrates tend to be metabolized by rumen organisms, gluconeogenesis occurs regardless of fasting, low-carbohydrate diets, exercise, etc.

Gluconeogenesis

Gluconeogenesis (GNG) is a metabolic process of making glucose, a necessary body fuel, from non-carbohydrate sources such as protein (amino acids), lactate from the muscles and the glycerol component of fatty acids. Blood glucose levels must be maintained within a narrow range for good health. If blood sugar is too high, it results in tissue and organ damage. If it is too low, cellular respiration and energy production can suffer, especially if the body is "carbohydrate-adapted," meaning the body uses glucose as it's primary fuel. Therefore, the ability of the liver and kidneys to “make new sugar” and regulate blood sugar levels is critical. The main advantage of this process is that it helps the body maintain steady blood sugar levels when foods containing carbohydrates or stored sugars (glycogen reserves) are unavailable. Without gluconeogenesis, you wouldn't live very long, especially without food, as your body must have a constant and steady level of blood glucose to keep the brain and red blood cells going. Mold Test Kits Easy to Use, Fast Results Available Interpretive Lab Report moldtesting.com Glucose and Ignorance If you decide to stop eating, or you decide to follow a Continue reading >>

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Popular Questions

  1. manohman

    Why can't fat be converted into Glucose?

    So the reason cited is that beta oxidation/metabolism of fats leads to formation of acetyl coa, a 2 carbon molecule, and that because of that it cannot be converted back into glucose.
    Why exactly is that the case?
    If Glucogenic amino acids can be converted into citric acid cycle intermediates and then turn back into glucose via gluconeogensis, then why cant Fatty Acids which yield Acetyl Coa. Can't you just have Acetyl Coa enter the citric acid cycle and produce the same intermediates that the glucogenic amino acids creat?

  2. Czarcasm

    manohman said: ↑
    So the reason cited is that beta oxidation/metabolism of fats leads to formation of acetyl coa, a 2 carbon molecule, and that because of that it cannot be converted back into glucose.
    Why exactly is that the case?
    If Glucogenic amino acids can be converted into citric acid cycle intermediates and then turn back into glucose via gluconeogensis, then why cant Fatty Acids which yield Acetyl Coa. Can't you just have Acetyl Coa enter the citric acid cycle and produce the same intermediates that the glucogenic amino acids creat?
    Click to expand... Both glucose and fatty acids can be stored in the body as either glycogen for glucose (stored mainly in the liver or skeletal cells) or for FA's, as triacylglycerides (stored in adipose cells). We cannot store excess protein. It's either used to make other proteins, or flushed out of the body if in excess; that's generally the case but we try to make use of some of that energy instead of throwing it all away.
    When a person is deprived of nutrition for a period of time and glycogen stores are depleted, the body will immediately seek out alternative energy sources. Fats (stored for use) are the first priority over protein (which requires the breakdown of tissues such as muscle). We can mobilize these FA's to the liver and convert them to Acetyl-CoA to be used in the TCA cycle and generate much needed energy. On the contrary, when a person eats in excess (a fatty meal high in protein), it's more efficient to store fatty acids as TAG's over glycogen simply because glycogen is extremely hydrophilic and attracts excess water weight; fatty acids are largely stored anhydrously and so you essentially get more bang for your buck. This is evolutionary significant and why birds are able to stay light weight but fly for periods at a time, or why bears are able to hibernate for months at a time. Proteins on the other hand may be used anabolically to build up active tissues (such as when your working out those muscles), unless you live a sedentary lifestyle (less anabolism and therefore, less use of the proteins). As part of the excretion process, protein must be broken down to urea to avoid toxic ammonia and in doing so, the Liver can extract some of that usable energy for storage as glycogen.
    Also, it is worth noting that it is indeed possible to convert FA's to glucose but the pathway can be a little complex and so in terms of energy storage, is not very efficient. The process involves converting Acetyl-CoA to Acetone (transported out of mitochondria to cytosol) where it's converted to Pyruvate which can then be used in the Gluconeogenesis pathway to make Glucose and eventually stored as Glycogen. Have a look for yourself if your interested: http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1002116.g003/originalimage (and this excludes the whole glycogenesis pathway, which hasn't even begun yet).
    TLDR: it's because proteins have no ability to be stored in the body, but we can convert them to glycogen for storage during the breakdown process for excretion. Also, in terms of energy, it's a more efficient process than converting FA's to glycogen for storage.

  3. soccerman93

    This is where biochem comes in handy. Czarcasm gives a really good in depth answer, but a simpler approach is to count carbons. The first step of gluconeogenesis(formation of glucose) requires pyruvate, a 3 carbon molecule. Acetyl Co-A is a 2 carbon molecule, and most animals lack the enzymes (malate synthase and isocitrate lyase) required to convert acetyl co-A into a 3 carbon molecule suitable for the gluconeogenesis pathway. The ketogenic pathway is not efficient, as czarcasm pointed out. While acetyl co-A can indeed be used to form citric acid intermediates, these intermediates will be used in forming ATP, not glucose. Fatty acid oxidation does not yield suitable amounts of pyruvate, which is required for gluconeogenesis. This is part of why losing weight is fairly difficult for those that are overweight, we can't efficiently directly convert fat to glucose, which we need a fairly constant supply of. Sorry, that got a little long-winded

  4. -> Continue reading
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