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All Amino Acids Can Be Used To Produce Glucose True Or False

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 >>

Dynamic Adaptation Of Nutrient Utilization In Humans

Dynamic Adaptation Of Nutrient Utilization In Humans

Most cells use glucose for ATP synthesis, but there are other fuel molecules equally important for maintaining the body's equilibrium or homeostasis. Indeed, although the oxidation pathways of fatty acids, amino acids, and glucose begin differently, these mechanisms ultimately converge onto a common pathway, the TCA cycle, occurring within the mitochondria (Figure 1). As mentioned earlier, the ATP yield obtained from lipid oxidation is over twice the amount obtained from carbohydrates and amino acids. So why don't all cells simply use lipids as fuel? In fact, many different cells do oxidize fatty acids for ATP production (Figure 2). Between meals, cardiac muscle cells meet 90% of their ATP demands by oxidizing fatty acids. Although these proportions may fall to about 60% depending on the nutritional status and the intensity of contractions, fatty acids may be considered the major fuel consumed by cardiac muscle. Skeletal muscle cells also oxidize lipids. Indeed, fatty acids are the main source of energy in skeletal muscle during rest and mild-intensity exercise. As exercise intensity increases, glucose oxidation surpasses fatty acid oxidation. Other secondary factors that influence the substrate of choice for muscle include exercise duration, gender, and training status. Another tissue that utilizes fatty acids in high amount is adipose tissue. Since adipose tissue is the storehouse of body fat, one might conclude that, during fasting, the source of fatty acids for adipose tissue cells is their own stock. Skeletal muscle and adipose tissue cells also utilize glucose in significant proportions, but only at the absorptive stage - that is, right after a regular meal. Other organs that use primarily fatty acid oxidation are the kidney and the liver. The cortex cells of the Continue reading >>

Gluconeogenesis Flashcards | Quizlet

Gluconeogenesis Flashcards | Quizlet

synthesis of new glucose from NON-CARBOHYDRATE source (making new glucose in fasting state) TRUE/FALSE: Gluconeogenesis is a synthesis pathway because making new glucose. FALSE --> new glucose is being made, BUT it happens in a catabolic state (fasting/starving), so it is a catabolic pathway b/c availability of glucose for the brain & nervous system is very important (in fasting state body needs way to provide) Is gluconeogenesis the reverse of glycolysis? Not quite, b/c glycolysis->pyruvate had out of 10 glycolytic enzymes, 3 enzymes that were non-reversible; therefore, these 3 enzymes (hexokinase, PFK-1, pyruvate kinase) create an activation barrier; to pass activation barrier new enzymes are needed - alpha-keto Amino Acids (all 18 except Leucine and Lysine) TRUE/FALSE: Gluconeogenesis is a series of enzymatic reactions that produce Glucose from carbohydrates. FALSE --> Gluconeogenesis sources are non-carbohydrate (lactate, glycerol, TCA cycle intermediates, alpha-keto acids/amino acids) Enzymes reactions specific to gluconeogenesis for bypassing the irreversible steps of glycolysis: In absence of dietary carbohydrates, liver glycogen is depleted ___. (so after 16-17 hrs fasting, pretty much exhausted all body's glucose stores & body goes to catabolic state) ____ is released into the blood by cells lacking mitochondria, such as occurs in RBCs or during anaerobic conditions like exercising skeletal muscle. Lactate from muscle circulates to liver where converted to Glucose and released back to blood... (concerns only muscle and liver tissue; lactate recyclation) (no mitochondria present; cannot brk dwn fats w/o mitochondria) ___ is released during hydrolysis of triaglycerols in adipose tissue and delivered to blood by liver. ___ are derived from the metabolism of gluco Continue reading >>

There Are Four Major Categories Of Organic Compounds Found In Living Cells.

There Are Four Major Categories Of Organic Compounds Found In Living Cells.

Macromolecules Up to this point we have considered only small molecules. Many of the molecules important to biological processes are HUGE. These are known as macromolecules. Most macromolecules are polymers, which are long chains of subunits called monomers. These subunits are often very similar to each other, and for all the diversity of polymers (and living things in general) there are only about 40 - 50 common monomers. Making and breaking polymers Joining two monomers is achieved by a process known as dehydration synthesis. One monomer gives up a hydroxyl (OH) group and one gives up a (H). These combine to make a water molecule. Hence the name dehydration synthesis. Polymers are broken apart by a process known as hydrolysis. Bonds between monomers are broken by the addition of water. (3.3, pg 36) Carbohydrates Carbohydrates are the sugars and their polymers. Simple sugars are called monosaccharides. These can be joined to form polysaccharides (3.5, pg 38). Glucose is an important monosaccharide. Sucrose, a disaccharide (consisting of two monosaccharides), is table sugar. (Note the ending "ose" common to most sugars.) Polysaccharides may be made from thousands of simple sugars linked together. These large molecules may be used for storage of energy or for structure. First a couple of storage examples: Starch is a storage polysaccharide of plants. Its is a giant string of glucoses. The plant can utilize the energy in starch by first hydrolyzing it, making the glucose available. Most animals can also hydrolyze starch. That's why we eat it. Animals store glycogen as a supply of glucose. It is stored in the liver and muscles. (3.7, pg 39) And some examples of structural carbohydrates: Cellulose is a polysaccharide produced by plants. Its is a component of the cell walls. Continue reading >>

Metabolism And Energy

Metabolism And Energy

Countless chemical reactions take place in cells and are responsible for all the actions of organisms. Together, these reactions make up an organism's metabolism. The chemicals taking part in these reactions are called metabolites. In all reactions: chemical bonds in the reacting molecules are broken; this takes in energy new chemical bonds form to make the products; this gives out energy When a chemical reaction takes place energy is either taken in or released. This depends on the relative strengths of bonds being broken and bonds being formed. In an exergonic reaction, energy is released to the surroundings. The bonds being formed are stronger than the bonds being broken. In an endergonic reaction, energy is absorbed from the surroundings. The bonds being formed are weaker than the bonds being broken. Hydrogen and chlorine - an exergonic reaction You may also come across the terms exothermic and endothermic reactions. These describe exergonic and endergonic reactions when the energy released or absorbed is heat energy. In an exothermic reaction the temperature of the surroundings increases. In an endothermic reaction the temperature of the surroundings decreases. Anabolism and catabolism Two types of metabolic reactions take place in the cell: 'building up' (anabolism) and 'breaking down' (catabolism). Anabolic reactions use up energy. They are endergonic. In an anabolic reaction small molecules join to make larger ones. For example, the following condensation reactions that occur in cells are anabolic: amino acids join together to make dipeptides: e.g. NH2CHRCOOH + NH2CHRCOOH NH2CHRCONHCHRCOOH + H2O and the process continues as large protein molecules are built up small sugar molecules join together to make dissacharides: e.g. C6H12O6 + C6H12O6 C12H22O11 + H2O and t Continue reading >>

Amino Acid

Amino Acid

Amino acid, any of a group of organic molecules that consist of a basic amino group (−NH2), an acidic carboxyl group (−COOH), and an organic R group (or side chain) that is unique to each amino acid. The term amino acid is short for α-amino [alpha-amino] carboxylic acid. Each molecule contains a central carbon (C) atom, called the α-carbon, to which both an amino and a carboxyl group are attached. The remaining two bonds of the α-carbon atom are generally satisfied by a hydrogen (H) atom and the R group. The formula of a general amino acid is: The amino acids differ from each other in the particular chemical structure of the R group. Proteins are of primary importance to the continuing functioning of life on Earth. Proteins catalyze the vast majority of chemical reactions that occur in the cell. They provide many of the structural elements of a cell, and they help to bind cells together into tissues. Some proteins act as contractile elements to make movement possible. Others are responsible for the transport of vital materials from the outside of the cell (“extracellular”) to its inside (“intracellular”). Proteins, in the form of antibodies, protect animals from disease and, in the form of interferon, mount an intracellular attack against viruses that have eluded destruction by the antibodies and other immune system defenses. Many hormones are proteins. Last but certainly not least, proteins control the activity of genes (“gene expression”). This plethora of vital tasks is reflected in the incredible spectrum of known proteins that vary markedly in their overall size, shape, and charge. By the end of the 19th century, scientists appreciated that, although there exist many different kinds of proteins in nature, all proteins upon their hydrolysis yield Continue reading >>

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 >>

Human Nutrition Exam 3

Human Nutrition Exam 3

Which of the following statements about essential amino acids is FALSE? A.Without essential amino acids, we lose our ability to make proteins and other nitrogen-containing compounds we need. B.Nine of the 20 amino acids in the body are classified as essential. C.Our bodies can synthesize essential amino acids in sufficient amounts, so we do not need to consume them in our diet. D.Our bodies cannot synthesize essential amino acids in sufficient amounts, so we must consume them in our diet. Once the instructions have been transcribed to mRNA, the mRNA leaves the nucleus and binds to a ribosome in the cytoplasm. The ribosome moves along the mRNA reading the code to begin the process of translation. Which of the following statements correctly describes the function of tRNA during translation? A.During translation, tRNA collects and transports the amino acids to the ribosome. B.During translation, tRNA carries the mRNA to the ribosome. C.During translation, tRNA carries the gene's instructions to the ribosome. D.During translation, tRNA transfers the instructions to the DNA. The sequential order of the amino acids in a protein is called the __________ of the protein. Which of the following statements is TRUE? A.Protein denaturation affects the primary structure of proteins. B.Protein denaturation affects both the shape and function of proteins. C.Heat exposure, but not acid, will cause proteins to denature. D.Protein denaturation affects only the shape, but not the function of proteins. How does the body use the protein once it has been ingested? Consider the following statements and select the correct ones regarding protein use. A.The liver uses amino acids to create glucose. B.Amino acids are used to create new proteins. C.If you ingest more protein than your body needs, 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 >>

Gluconeogenesis Flashcards | Quizlet

Gluconeogenesis Flashcards | Quizlet

The LIVER is the major site of gluconeogenesis. However, the kidneys and the small intestine do play important roles in the pathway. What enzyme is present in large amounts in the liver, kidney, and small intestine that allow them to perform gluconeogenesis? These 2 locations do NOT contain glucose 6-phosphatase. However, they do contain pyruvate carboxylase! Heart muscles and skeletal muscles DO NOT have glucose 6-phosphatase, but they do have pyruvate carboxylase Is the brain able to perform gluconeogenesis? These tissues are poorly vascularized, resulting in lactate being the major fate of pyruvate. One of them is the eyes. What are 2 other locations? Lets pretend that it is Lent and you have decided to give up carbs. In the short run, how long can your livers glycogen stores hold you up? Your livers glycogen stores can only meet the demands of the body for about 10-18 hours in the absence of carbs. Normally, the liver is the main organ for gluconeogenesis. However, you are stuck on a totally carb-less island for weeks. Which organ in your body will start become the major glucose producing organ? Once hepatic glycogen stores are depleted, the KIDNEYS become the major glucose producing organs Name the 4 Major Precursors that result in glucose via gluconeogenesis. Glucogenic Amino Acids such as alanine and glutamate form what via gluconeogenesis? a-ketoacids (oxaloacetate and a-ketoglutarate) Derived from the backbone of triacylglycerols Glycerol is released during the hydrolysis of triacylglycerols in muscle tissue. Glycerol is released during the hydrolysis of triacylglycerols in ADIPOSE TISSUE. Adipose tissue cannot phosphorylate glycerol themselves because they lack what enzyme? Imagine you are a glycerol molecule that traveled from adipose tissue into the liver. 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 >>

True Or False

True Or False

(See related pages) 1 Anabolic reactions are those chemical reactions that release energy, usually by the breakdown of larger organic molecules into smaller organic molecules. 2 Aerobic cellular respiration and ventilation describe two very different processes. 3 Within a cell, the oxygen used during aerobic metabolism of nutrients ultimately becomes water. 4 Damage to the mitochondria of a cell would inhibit glycolysis. 7 To summarize glycolysis, one glucose molecule is broken down sequentially to two molecules of pyruvic acid, releasing two NADH + H+ molecules, and generating a net gain of two ATP. 8 It is common for certain tissues like skeletal muscle to derive energy (ATP) from anaerobic respiration on a daily basis without permanent injury or damage to the tissue. 9 Red blood cells only use glycolysis in the catabolism of glucose. 10 Phosphorylation of glucose "traps" the glucose molecule within the cell. 11 In aerobic respiration, pyruvic acid is formed from glucose but lactic acid is not. 12 The enzyme, glycogen phosphorylase, catalyzes the conversion of glycogen to glucose-1-phosphate. 13 Organic molecules with phosphate groups such as glucose 6-phosphate are cell "prisoners" because they cannot cross cell membranes. 14 The liver can supply the skeletal muscle with energy in the form of free glucose but the opposite is not true. 15 Tissue cells that are anaerobic would have to burn relatively more glucose molecules to maintain a steady supply of ATP than would those tissues that are supplied with oxygen. 16 During exercise, the liver can metabolize the lactic acid produced by the skeletal muscle cells and provide glucose to the cells of the body. 17 During aerobic respiration, the reaction that results in the conversion of pyruvic acid to acetyl CoA and CO2, oc 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 >>

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 >>

Harvesting Energy

Harvesting Energy

Why do we humans eat food? What do we need it for, and get out of it? W O R K T O G E T H E R Cellular respiration is an: Endergonic process Exergonic process Exergonic OR endergonic process, depending on the organism. In which organelle does cellular respiration occur? Chloroplast Mitochondria Depends on whether it’s a plant or an animal. What is “food†(i.e. source of metabolic energy) for plants? Sunlight Sugar Water Oxygen Minerals cristae mitochondrion inner membrane outer membrane intermembrane space matrix Cellular respiration takes place in the mitochondria. net exergonic “downhill†reaction glucose protein amino acids CO2 + H2O + heat ADP + heat Review: ATP is produced and used in coupled reactions endergonic (ATP synthesis) exergonic (ATP breakdown) exergonic (glucose breakdown) endergonic (protein synthesis) Energy released by the exergonic breakdown of glucose is used for: The endergonic production of ATP. The exergonic production of ATP. The endergonic breakdown of ATP. The exergonic breakdown of ATP. 2 pyruvate electron transport chain (cytosol) (mitochondrion) glycolysis Krebs (citric acid) cycle 2 acetyl CoA 2 NADH Total 36 or 38 ATPs 2 ATP 6 NADH 2 FADH2 glucose 32 or 34 ATPs 2 ATP 2 NADH Overview Glycolysis splits sugar into two 3-carbon chains (pyruvate), producing 2 ATPs Cellular respiration breaks the sugar down further, producing 32-34 ATPs. NADH and FADH (derived from vitamins B3 and B2) act as electron carriers. 34 or 36 ATP in mitochondria– oxygen required in cytosol– no oxygen required glycolysis glucose fermentation pyruvate 2 ATP cellular respiration O2 if no O2 available ethanol + CO2 or lactic acid CO2 H2O fructose bisphosphate ATP ADP 1 Glucose activation in cytosol 2 Energy harvest NAD+ NADH ATP AD Continue reading >>

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