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What Amino Acids Can Be Converted To Glucose?

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 >>

Glucogenic Amino Acid

Glucogenic Amino Acid

Paulo Ricardo Nazrio Viecili*12, ... Jonatas Z. Klafke*3, in Advances in Clinical Chemistry , 2017 TGs are lipid molecules formed by glycerol derived from carbon hydrates and/or gluconeogenic amino acids, bound to three FAs. These FAs have a similar conformation in most TG molecules: there is a saturated FA in position 1, an unsaturated FA in position 2, and a long-chain FA in position 3 (see Fig. 1) [1]. TGs are the most abundant lipids in nature, and their main characteristic is their essentially nonpolar nature, since the polar regions of their precursors (glycerol hydroxyls and carboxyls of the FAs) vanish when the ester bonds are formed. Animal fats and vegetable oils are complexes formed by TGs, the difference between them being the specific FAs that compose them. TGs in animal fats are predominantly composed of saturated FAs, lending them their solid appearance, while unsaturated FAs predominate in vegetable oils, giving them their liquid consistency. Both animal fats and vegetable oils can be digested in the organism thanks to hydrolysis by lipases [15]. TGs are synthesized through two main pathways: the glycerol phosphate pathway and the monoacylglycerol (MAG) pathway. The glycerol phosphate pathway is more common and is present in various cell types. This pathway is based on the acylation of glycerol 3-phosphate through the addition of FA groups, each of which is catalyzed by a different enzyme. In contrast, the MAG pathway predominates in the small intestine and generates TGs based on MAG derived from dietary fat. The glycerol phosphate pathway occurs as follows: first, acylation of glycerol 3-phosphate (addition of FA) occurs by the glycerol 3-phosphate acyltransferase, which is present in the endoplasmic reticulum and mitochondria, forming lysophosphatidic Continue reading >>

Glucogenic Amino Acids | The Biochemistry Questions Site

Glucogenic Amino Acids | The Biochemistry Questions Site

A free Biochemistry Question Bank for premed, medical students and FMG Answer to Biochemistry Question AM-02 about Amino acid Metabolism. Answer: (b) Ketogenic (Since the question only make reference to acetoacetyl CoA, we assume that it is the final product of the catabolism of this amino acid and no glucogenic metabolites are produced.) Amino acids are used for different purposes in our body. Most of the metabolic pool of amino acids is used as building blocks of proteins, and a smaller proportion is used to synthesize specialized nitrogenated molecules as epinephrine and norepinephrine, neurotransmitters and the precursors of purines and pyrimidines. Since amino acids can not be stored in the body for later use, any amino acid not required for immediate biosynthetic needs is deaminated and the carbon skeletonis used as metabolic fuel (10-20 % in normal conditions) or converted into fatty acids via acetyl CoA. The main products of the catabolism of the carbon skeleton of the amino acids are pyruvate, oxalacetate, a-ketoglutarate, succinyl CoA, fumarate, acetyl CoA and acetoacetyl CoA. When carbohydrates are not available (starvation, fasting) -or cannot be used properly, as in diabetes mellitus, amino acids can become a primary source of energy by oxidation of their carbon skeleton, but also by becoming an important source of glucose for those tissues that only can use this sugar as metabolic fuel. The formation of glucose from amino acids (gluconeogenesis) in liver and kidney is intensified during starvation and this process becomes the most important source of glucose for the brain, RBC and other tissues. Amino acids in skeletal proteins can be used, in a situation of prolonged starvation as an emergency energy store that can yield 25000 kcal. Amino acids can be cl Continue reading >>

Glucogenic Amino Acids

Glucogenic Amino Acids

DOUGLAS C. HEIMBURGER MD, in Handbook of Clinical Nutrition (Fourth Edition) , 2006 The major aim of protein catabolism during a state of starvation is to provide the glucogenic amino acids (especially alanine and glutamine) that serve as substrates for endogenous glucose production (gluconeogenesis) in the liver. In the hypometabolic/starved state, protein breakdown for gluconeogenesis is minimized, especially as ketones become the substrate preferred by certain tissues. In the hypermetabolic/stress state, gluconeogenesis increases dramatically and in proportion to the degree of the insult to increase the supply of glucose (the major fuel of reparation). Glucose is the only fuel that can be utilized by hypoxic tissues (anaerobic glycolysis), by phagocytosing (bacteria-killing) white cells, and by young fibroblasts. Infusions of glucose partially offset a negative energy balance but do not significantly suppress the high rates of gluconeogenesis in the catabolic patient. Hence, adequate supplies of protein are needed to replace the amino acids utilized for this metabolic response. In summary, the two physiologic states represent different responses to starvation. The hypometabolic patient, who conserves body mass by reducing the metabolic rate and using fat as the primary fuel (rather than glucose and its precursor amino acids), is adapted to starvation. The hypermetabolic patient also uses fat as a fuel but rapidly breaks down body protein to produce glucose, the fuel of reparation, thereby causing loss of muscle and organ tissue and endangering vital body functions. Joerg Klepper*, in Handbook of Clinical Neurology , 2013 Gluconeogenesis, predominantly in the liver, generates glucose from noncarbohydrate substrates such as lactate, glycerol, and glucogenic amino acid Continue reading >>

Glucogenic And Ketogenic Amino Acids

Glucogenic And Ketogenic Amino Acids

Amino acids can be classified as being “glucogenic” or “ketogenic” based on the type of intermediates that are formed during their breakdown or catabolism. The catabolism of glucogenic amino acids produces either pyruvate or one of the intermediates in the Krebs Cycle. The catabolism of ketogenic amino acids produces acetyl CoA or acetoacetyl CoA (see Figure 1). There is a rare medical condition in which a person is deficient in the pyruvate dehydrogenase enzyme that converts pyruvate to acetyl CoA – a precursor for the Krebs Cycle. Signs and symptoms vary, but there are generally two main manifestations. First, patients can have an elevated blood lactate (lactic acid) level. Second, patients may have neurological defects, including microcephaly (a small head circumference) and/or mental retardation. Treatment is currently limited and not very effective. Moreover, damage to the brain is often irreversible. Your biochemistry study partner looks at Figure 1 and exclaims, “This doesn’t make sense - why can’t acetyl-coA and the ketogenic amino acids be converted back to pyruvate to create glucose using pyruvate dehydrogenase?” With your knowledge of basic chemistry, you answer: 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 >>

Amino Acid Metabolism!

Amino Acid Metabolism!

Our current examination of proteins and amino acids will cover the metabolism of the protein we eat, dietary protein, and catabolic situations in the body. Amino acids are the "building-blocks" of proteins. Proteins, from the Greek word meaning "of prime importance," constitute an array of structures. Examples of these structures include hormones, enzymes, and muscle tissue. The primary function of protein is growth and repair of body tissue (anabolism). Proteins can also be used as energy through catabolic (breakdown of tissues) reactions, such as gluconeogenesis-the process of making glucose from amino acids, lactate, glycerol, or pyruvate in the liver or kidneys. Our current examination of proteins and amino acids will cover the metabolism of the protein we eat, dietary protein, and catabolic situations in the body. A general understanding of the molecular structure of proteins and amino acids is needed to understand their metabolism. Protein is comprised of carbon, hydrogen, oxygen and, most importantly, nitrogen. Protein may also contain sulfur, cobalt, iron, and phosphorus. These elements form the "building blocks" of protein, amino acids . A protein molecule is made up of long chains of amino acids bonded to each other by amide bonds, or peptide linkages. The food (protein) we eat contains different amino acids depending on the type of amino acids present. An almost endless combination of amino acid bonds can exist. The combination of amino acids governs the protein's properties. Just as the combination of amino acids governs the specific proteins properties, the structure of individual amino acids determines its function in the body. An amino acid is made up of a central carbon atom, a positively charged amine group (NH2) at one end and a negatively charged car 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 >>

Why Can Fatty Acids Not Be Converted Into Glucose? : Mcat

Why Can Fatty Acids Not Be Converted Into Glucose? : Mcat

Rudeness or trolling will not be tolerated. Be nice to each other, hating on other users won't help you get extra points on the MCAT, so why do it? Do not post any question information from any resource in the title of your post. These are considered spoilers and should be marked as such. For an example format for submitting pictures of questions from practice material click here Do not link to content that infringes on copyright laws (MCAT torrents, third party resources, etc). Do not post repeat "GOOD LUCK", "TEST SCORE", or test reaction posts. We have one "stickied" post for each exam and score release day, contain all test day discussion/reactions to that thread only. Do not discuss any specific information from your actual MCAT exam. You have signed an examinee agreement, and it will be enforced on this subreddit. Do not intentionally advertise paid products or services of any sort. These posts will be removed and the user banned without warning, subject to the discretion of the mod team Learn More All of the above rules are subject to moderator discretion C/P = Chemical and Physical Foundations of Biological Systems CARS = Critical Analysis and Reasoning Skills B/B = Biological and Biochemical Foundations of Living Systems P/S = Psychological, Social, and Biological Foundations of Behavior 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 >>

Chapter 23: Metabolism

Chapter 23: Metabolism

What enzyme is involved in the digestion of carbs -the completion of this digestion occurs in the brush border of the jejunal villi What is produced when amylase digests carbs? What mechanism is involved in the absorption of carbs -sodium-dependent cotransport: a transport protein on the luminal border of the epithelial cells pulls sodium into the cell down its concentration gradient -at the same time brings along a glucose molecule against its concentration gradient -sodium ions are kept low inside the cell by a Na+-K+ ATPase pump on the basal border of the cell -once the glucose is concentrated in the cell it can leave the basolateral border of the cell by facilitated diffusion What enzyme is involved in the digestion of lipids What products are produced by hydrolysis of proteins? trypsin which activates, chymotrypsin, carboxypeptidase, and elastase What mechanism is involved in the absorption of proteins? Describe the Na+ dependent co-transport mechanism a transport protein on the luminal border of the epithelial cells pulls sodium into the cell down its concentration gradient -at the same time brings along a glucose molecule against its concentration gradient -sodium ions are kept low inside the cell by a Na+-K+ ATPase pump on the basal border of the cell -once the glucose is concentrated in the cell it can leave the basolateral border of the cell by facilitated diffusion Glycolysis: occurs in the cytoplasm of the cell doesn't require oxygen (anaerobic) glucose is converted to 2 molecules of pyruvate and energy is liberated in the form of 2ATP and 2NADH. Pyruvates are used by the mitochondria in the citric acid cycle Citric Acid Cycle: the role is to harvest the energy from small organic molecules and transfer it to coenzymes. when there is a lot of O2 pyruvates pr Continue reading >>

Amino Acid Metabolism

Amino Acid Metabolism

What is anabolism? Does it require or release energy? Synthesis of biological compounds. Require energy. What is catabolism? Does it require or release energy? The breakdown of compounds. Releases energy. What is the main dietary source of amino acids? Which dietary source is the most efficient in catabolism but yields the lowest amount of energy? What is the downfall of using protein catabolism to yield an intermediate amount of energy? Nitrogen containing byproduct must be eliminated. 1. Synthesis of nonessential amino acids. 2. Removal and breaking down of excess amino acids. 3. Removal of ammonia from the blood and converting it to urea. 4. Making other nitrogen-containing compounds What are three ways amino acids feed into other pathways? Pyruvate, acetyl CoA, and TCA intermediates. Because amino acids can by converted to pyruvate, they can also be further converted to? Are fatty acids able to be converted to glucose? Nope, they are converted to AcetylCoA which can not be used to make glucose. When the liver converts lactic acid back to glucose. What are the options for pyruvate conversion in anaerobic and aerobic situations? Anaerobic - Quick energy needs. Pyruvate is converted to lactate which can be turned into glucose in the liver. Aerobic - Slower energy needs. Pyruvate is converted to acetyl CoA Amino acids that can be used to make glucose. Amino acids that are converted to acetyl CoA. What is the first step in converting amino acids into glucose or other intermediates? What is the most common mechanism for deamination? The most common mechanism for deamination. The exchange of the amino group with the keto group on alpha-keto glutarate resulting in glutamic acid. What is a key intermediate in amino acid metabolism? What can be deaminated to give free ammoni Continue reading >>

Gluconeogenesis: Endogenous Glucose Synthesis

Gluconeogenesis: Endogenous Glucose Synthesis

Reactions of Gluconeogenesis: Gluconeogenesis from two moles of pyruvate to two moles of 1,3-bisphosphoglycerate consumes six moles of ATP. This makes the process of gluconeogenesis very costly from an energy standpoint considering that glucose oxidation to two moles of pyruvate yields two moles of ATP. The major hepatic substrates for gluconeogenesis (glycerol, lactate, alanine, and pyruvate) are enclosed in red boxes for highlighting. The reactions that take place in the mitochondria are pyruvate to OAA and OAA to malate. Pyruvate from the cytosol is transported across the inner mitochondrial membrane by the pyruvate transporter. Transport of pyruvate across the plasma membrane is catalyzed by the SLC16A1 protein (also called the monocarboxylic acid transporter 1, MCT1) and transport across the outer mitochondrial membrane involves a voltage-dependent porin transporter. Transport across the inner mitochondrial membrane requires a heterotetrameric transport complex (mitochondrial pyruvate carrier) consisting of the MPC1 gene and MPC2 gene encoded proteins. Following reduction of OAA to malate the malate is transported to the cytosol by the malate transporter (SLC25A11). In the cytosol the malate is oxidized to OAA and the OOA then feeds into the gluconeogenic pathway via conversion to PEP via PEPCK. The PEPCK reaction is another site for consumption of an ATP equivalent (GTP is utilized in the PEPCK reaction). The reversal of the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) reaction requires a supply of NADH. When lactate is the gluconeogenic substrate the NADH is supplied by the lactate dehydrogenase (LDH) reaction (indicated by the dashes lines), and it is supplied by the malate dehydrogenase reaction when pyruvate and alanine are the substrates. Secondly, one mo Continue reading >>

Can Amino Acids Be Used By The Body To Make Glucose & Fatty Acids?

Can Amino Acids Be Used By The Body To Make Glucose & Fatty Acids?

Amino acids are nitrogen-containing molecules that are the building blocks of all proteins in food and in the body. They can be used as energy, yielding about 4 calories per gram, but their primary purpose is the synthesis and maintenance of body proteins including, but not limited to, muscle mass. Video of the Day During normal protein metabolism, a certain number of amino acids are pushed aside each day. When these amino acids are disproportionate to other amino acids for the synthesis of new protein, your liver and kidneys dispose of the nitrogen as urea, and the rest of the molecule is used as energy in a variety of ways. Then certain amino acids -- minus their nitrogen -- can enter the citric acid cycle -- the biochemical pathway that converts food into energy. Others can be converted to glucose or fat. This process may be enhanced when you take in more protein than you need. Your body relies on a continuous supply of glucose and fatty acids for energy for physical activity and cellular needs during rest. When you exercise, your body relies still more on glucose because fat is slower to metabolize. The higher your exercise intensity is, the more your body requires quicker-burning glucose. Some glucose is stored as glycogen in the liver and muscles and can be recruited when blood glucose is used up. When glycogen becomes depleted, the process of gluconeogenesis can take over -- the creation of new glucose from another source. The usual source for gluconeogenesis is amino acids. Healthy people store adequate body fat to cover their energy needs. Although certain amino acids can be converted to fatty acids, there should be no need for this to occur in order to supply energy. But if a very high protein intake adds substantially more calories, theoretically those extra Continue reading >>

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