€¢ Several Principles Govern Metabolic Pathways:
Energy and Electrons from Glucose • The sugar glucose (C6H12O6) is the most common form of energy molecule. • Cells obtain energy from glucose by the chemical process of oxidation carried out through a series of metabolic pathways. • Metabolic pathways are formed by complex chemical transformations in the cell which occur in a number of separate reactions. • Each reaction in the pathway is catalyzed by a specific enzyme. • Metabolic pathways are similar in all organisms, from bacteria to humans. • Many metabolic pathways are compartmentalized in eukaryotes, with certain reactions occurring inside an organelle. • The operation of each metabolic pathway can be regulated by the activities of key enzymes. Cells trap free energy while metabolizing glucose • When burned in a flame, glucose releases heat, carbon dioxide, and water. • C6H12O6 + 6 O2 ( 6 CO2 + 6 H2O + energy (heat and light). • The same equation applies for the biological, metabolic use of glucose. This process, however, has many steps and is carefully controlled. • About one-third of the energy is collected in ATP. • ï„G for the complete conversion of glucose is –686 kcal/mol. • The reaction is therefore highly exergonic, and it drives the endergonic formation of ATP. • Some kinds of cells metabolize glucose incompletely, and others completely. • The incomplete breakdown is called fermentation and is anaerobic (no oxygen required). Fermentation has steps that are common to all organisms. • Complete capture of the energy in the hydrocarbon bonds of glucose requires oxygen. • The two main metabolic processes for complete use of glucose are glycolysis and cellular respiration. • Glycolysis is a ser Continue reading >>
Basics Of Metabolism
Voiceover: Let's talk about this thing called metabolism. I remember being told in medical school that metabolism was the sum total of all of the chemical reactions in the human body, but I never actually knnew what that meant. I like to think of metabolism as kind of like the balance in the body between the reactions that build things up, and another way of saying that is anabolism. On the other side of the scale, the reactions that break things down. The medical way of saying that is catabolism, or catabolism. So, metabolism is kind of the balance between building things up, or repairing or storing inside the body and breaking things down, usually for energy needs. How are the things that we eat broken down for energy or stored within the body? Let's start by looking at carbohydrates. So, we eat our carbohydrates, and they are in the form of starches or sugars, and we saw in our last video that those could get broken down into their kind of component parts. The major component, or the major single unit currency of carbohydrates is called glucose. That glucose, and this is very big-picture, can get broken down further into a compound called pyruvate. The pyruvate then gets broken down into a very important molecule that's kind of the center of making energy in the body, and that molecule is called acetyl-CoA. Now, I think of acetyl-CoA kind of like one of those little trampolines you see in the gym, and basically acetyl-CoA can be moved around to different parts. We'll put the trampoline there, and then we'll put it over there, and then we'll put it over there. Basically, different chemcals bounce on and off of that little portable trampoline as they're going around this cycle. This cycle is called the TCA cycle. That stands for tricarboxylic acid cycle, or it's someti Continue reading >>
Amino Acids Rather Than Glucose Account For The Majority Of Cell Mass In Proliferating Mammalian Cells
Go to: Abstract Cells must duplicate their mass in order to proliferate. Glucose and glutamine are the major nutrients consumed by proliferating mammalian cells, but the extent to which these and other nutrients contribute to cell mass is unknown. We quantified the fraction of cell mass derived from different nutrients and find that the majority of carbon mass in cells is derived from other amino acids, which are consumed at much lower rates than glucose and glutamine. While glucose carbon has diverse fates, glutamine contributes most to protein, and this suggests that glutamine’s ability to replenish TCA cycle intermediates (anaplerosis) is primarily used for amino acid biosynthesis. These findings demonstrate that rates of nutrient consumption are indirectly associated with mass accumulation and suggest that high rates of glucose and glutamine consumption support rapid cell proliferation beyond providing carbon for biosynthesis. Go to: Rapidly proliferating cells have different metabolic needs from non-proliferating cells. During each cell cycle, proliferating cells must synthesize all of the components needed to duplicate cell mass (Lunt and Vander Heiden, 2011). One metabolic feature common to many proliferating cells is high glycolytic flux to lactate in the presence of oxygen, a phenomenon referred to as aerobic glycolysis or the Warburg effect. Why proliferating cells, including cancer cells, consume large quantities of glucose only to excrete the majority of this carbon as lactate is a subject of debate (Brand, 1985; Brand et al., 1986; DeBerardinis et al., 2008; Gatenby and Gillies, 2004; Hsu and Sabatini, 2008; Hume et al., 1978; Jiang and Deberardinis, 2012; Koppenol et al., 2011; Lunt and Vander Heiden, 2011; Newsholme et al., 1985; Vander Heiden et al., 2 Continue reading >>
Cell Metabolism And Cancer Cell Metabolism
Home | Cancer Systems Biology | Targeting mutant p53 cancers | Cancer Cell Metabolism | Network Analysis | Human dynamics | Resources As with any living "organism", cancer cells require metabolism to sustain their existence. This include the support of several functions, including cell maintenance, proliferation, motility and the excretion of extracellular factors. Common to all this activities is the demand for energy, mainly in the form of ATP. Cells utilize two major pathways for energy generation, glycolysis and oxidative phosphorylation (OxPhos). Glycolysis converts glucose into pyruvate generating two molecules of ATP for each molecule of glucose. In human cells pyruvate can be converted to lactate, which is then excreted to the extracellular media. This pathway does not require oxygen and it is the default when cells are deprived from oxygen (hypoxia). OxPhos takes place in the mitochondria and can metabolize different substrates (e.g., pyruvate, fatty acids, amino acids) to generate ATP. For example, OxPhos generates 32 molecules of ATP per molecule of glucose. In contrast to glycolysis, OxPhos requires oxygen and can only occur its presence (normoxia). Given that OxPhos has a higher yield of ATP, we would expect it should be the default pathway when oxygen is present. However, the German physiologist and Nobel laureate Otto Warburg observed that cancer cells simultaneously exhibit glycolysis with lactate secretion and OxPhos even in the presence of oxygen, a phenomenon now known as the Warburg effect. The maintenance of this mixed metabolic phenotype is seemingly counter intuitive given that aerobic glycolysis is far less efficient in terms of ATP yield per moles of glucose than mitochondrial respiration. The leading hypothesis in the cancer metabolism communit Continue reading >>
Metabolism & Nutrition
Sort The sum of all biochemical reactions that take place in the human body at any given time is called __________. phosphorylation anabolism catabolism metabolism metabolism The breakdown of carbohydrates into glucose in the body is classified as: synthesis. anabolism. catabolism. homeostasis catabolism Which of the following is NOT a nutrient monomer used by the body to generate ATP? fatty acids glucose nucleic acids amino acids nucleic acids Which of the following reactions requires energy, such as ATP, to proceed? exergonic reactions phosphorylation reactions oxidation reactions endergonic reactions endergonic reactions What process involves the donation of a phosphate group from ATP to a reactant to "pay" for a cellular process? oxidation anabolism phosphorylation synthesis phosphorylation When electrons are lost from one substance, they are transferred to another molecule in reactions known as: endergonic reactions. synthesis reactions. oxidation-reduction reactions. phosphorylation reactions. oxidation-reduction reactions Complete the formula for glucose catabolism (cell reparation): C6H12O6 + ___ --> 6H2O + 6CO2 + _____+ heat 6O2; lactate 6O2; 38 ATP 2 ATP; 38 ATP 6CO2; 6O2 6O2; 38 ATP __________ ATP molecules are produced via the electron transport chain and oxidative phosphorylation. 4 2 38 34 34 The molecule that acts as the final electron acceptor of the electron transport chain is __________. glucose carbon dioxide water oxygen oxygen Under anaerobic conditions, what happens to pyruvate? Pyruvate is reduced to lactate. Pyruvate is oxidized in the mitochondrion. Pyruvate undergoes decarboxylation. Pyruvate enters the citric acid cycle. Pyruvate is reduced to lactate. Julia has diabetes mellitus and is experiencing ketoacidosis. What does her body use to gene Continue reading >>
Metabolism And Nutrition Mastering Assignments
Sort When body temperature increases above the normal range, thermoreceptors in the skin and hypothalamus detect the increase in body temperature. The heat-loss center of the hypothalamus is activated, which sends signals to blood vessels and sweat glands. In response, blood vessels in the skin dilate and sweat glands release sweat. Determine the part of this negative feedback loop that serves as the effector(s). blood vessels and sweat glands Which statement is TRUE regarding complete proteins? a. Complete proteins can only be obtained from animal proteins. b. Complete proteins provide all of the essential amino acids. c. Complete proteins can be synthesized from carbon skeletons. d. Complete proteins lack one or more essential amino acids. b. Complete proteins provide all of the essential amino acids. Continue reading >>
Metabolism And Nutrition
Sort ATP production by direct transfer of a phosphate group from a phosphate-containing molecule to ADP is called __________. A.)substrate-level phosphorylation B.)oxidation-reduction reaction C.)oxidative phosphorylation D.)citric acid cycle A.)substrate-level phosphorylation The sum of all biochemical reactions that take place in the human body at any given time is called __________. A.)phosphorylation B.)anabolism C.)catabolism D.)metabolism D.)metabolism What process involves the donation of a phosphate group from ATP to a reactant to "pay" for a cellular process? A.)oxidation B.)synthesis C.)anabolism D.)phosphorylation D.)phosphorylation When electrons are lost from one substance, they are transferred to another molecule in reactions known as: A.)oxidation-reduction reactions. B.)synthesis reactions. C.)endergonic reactions. D.)phosphorylation reactions. A.)oxidation-reduction reactions. Complete the formula for glucose catabolism (cell reparation): C6H12O6 + ___ --> 6H2O + 6CO2 + _____+ heat A.)6O2; lactate B.)6O2; 38 ATP C.)2 ATP; 38 ATP D.)6CO2; 6O2 B.)6O2; 38 ATP __________ ATP molecules are produced via the electron transport chain and oxidative phosphorylation. A)38 B.)34 C.)4 D.)2 B.)34 Under anaerobic conditions, what happens to pyruvate? A.)Pyruvate is reduced to lactate. B.)Pyruvate is oxidized in the mitochondrion. C.)Pyruvate enters the citric acid cycle. D.)Pyruvate undergoes decarboxylation. A.)Pyruvate is reduced to lactate. Julia has diabetes mellitus and is experiencing ketoacidosis. What does her body use to generate ATP? A.)glucose B.)glycogen C.)fatty acids D.)glycerol C.)fatty acids Which hormone stimulates the uptake of glucose by cells, lowering the concentration of glucose in the blood? A.)cortisol B.)insulin C.)epinephrine D.)glucagon B.)i Continue reading >>
Energy Levels Under Ketosis – Fats, Carbs, And Atp
Update 2017: This post has been deprecated (not in line with my current thoughts. Read more on the ‘about’ page) Ever since I started my ketogenic lifestyle I’ve been experiencing higher energy levels. Basically I have the same increased energy from the minute I wake up at ~7 A.M. up until I go to sleep at 2 A.M. at night. No post-prandial (after-meal) fatigue and no sleepiness during the day. It’s been quite amazing because during my entire life I was kind of suffering of moments of tiredness throughout the day. As I began researching what happens inside the body under high-fat-very-low-carb nutrition, I wanted to know what could be the possible explanation of the higher energy levels. I’ve learned that carbohydrate metabolism yields lower amounts of ATP compared to beta-oxidation (fat metabolism). Carbohydrate Metabolism It basically starts with glycolysis which has the purpose of converting 1 molecule of glucose to two molecules of pyruvic acids (pyruvates). Glycolysis yields 4 ATPs, but it requires 2 ATPs to be completed, so the net gain of energy is 2 ATPs. After glycolysis, the 2 pyruvates react with Coenzyme A to form 2 molecules of Acetyl-CoA, which will later go into the TCA Cycle (Citric Acid Cycle or Krebs Cycle). In the TCA Cycle there are series of chemical reactions which lead to the release of more ATPs (yet, very decent amounts), CO2, CoA, and H+. So far, we’ve only gained 4 ATPs, 2 from glycolysis and 2 from the TCA Cycle. The next step is oxidative phosporylation or the Electron Transport Chain. This is where the hydrogen made available in the early stages of glucose metabolism will be oxidized. This is also where the most energy in the form of ATP is created. The ETC gives roughly 30 ATPs, yet there are 4 hydrogen atoms remaining which are Continue reading >>
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 >>
Work And Energy In Muscles
Silly question? Let us take a look at data from the 1964 summer Olympic games. The participants were extremely motivated individuals. We can assume that they "gave all they had", running as fast as possible while still managing to come to the finish line. What lies behind the undisputable observation that those competing in short distance races ran faster than competitors in longer races? Why must we reduce speed if we want to run long distances over extended time intervals? Even the most motivated athletes are bound by this simple rule. We can see this in the following graph. Running speed is plotted against the duration of the race. Competitors running more than 30-40 seconds reduced their velocity markedly and a continual and gradual decrease occurred after about 2 minutes. Marathon runners ran a little more than half of the speed of sprinters. The explanation for this phenomena is that while the only direct fuel for muscles is ATP, we do not "use up" ATP while working. Even extremely hard work does not lower ATP concentrations by more than about 20 %. Several differing energy sources are used by working muscles to maintain ATP levels. Phosphocreatine, muscle glycogen, blood glucose and fatty acids from adipose tissue are those possible energy sources. Let us look at the striking differences between these. A 100 meter sprint takes less than 10 seconds to complete. During this very short period the major driving forces are stored high-energy phosphates and anaerobic glycolysis. The runners can perform almost without breathing, using energy stored as ATP, creatine phosphate and glycogen (that is, anaerobic metabolism) in the active muscles. In contrast to long-distance runners, sprinters are often large, very muscular people. Sprinters have a dominance of so-called fas Continue reading >>
Macronutrients
Overview Carbohydrates, fats and proteins are macronutrients. We require them in relatively large amounts for normal function and good health. These are also energy-yielding nutrients, meaning these nutrients provide calories. On This Page: What are Carbohydrates? Carbohydrates Understanding Carbohydrates Every few years, carbohydrates are vilified as public enemy number one and are accused of being the root of obesity, diabetes, heart disease and more. Carb-bashers shun yogurt and fruit and fill up on bun-less cheeseburgers. Instead of beans, they eat bacon. They dine on the tops of pizza and toss the crusts into the trash. They so vehemently avoid carbs and spout off a list of their evils that they may have you fearing your food. Rest assured, you can and should eat carbohydrates. In fact, much of the world relies on carbohydrates as their major source of energy. Rice, for instance, is a staple in Southeast Asia. The carbohydrate-rich potato was so important to the people of Ireland that when the blight devastated the potato crop in the mid 1800s, much of the population was wiped out. What are Carbohydrates? The basic structure of carbohydrates is a sugar molecule, and they are classified by how many sugar molecules they contain. Simple carbohydrates, usually referred to as sugars, are naturally present in fruit, milk and other unprocessed foods. Plant carbohydrates can be refined into table sugar and syrups, which are then added to foods such as sodas, desserts, sweetened yogurts and more. Simple carbohydrates may be single sugar molecules called monosaccharides or two monosaccharides joined together called disaccharides. Glucose, a monosaccharide, is the most abundant sugar molecule and is the preferred energy source for the brain. It is a part of all disaccharides Continue reading >>
Anatomy, Chapter 23, Homework Questions
Sort ATP production by direct transfer of a phosphate group from a phosphate-containing molecule to ADP is called ___________________. a. substrate-level phosphorylation b. oxidative phosphorylation c. oxidation-reduction reaction d. citric acid cycle a. substrate-level phosphorylation The sum of all biochemical reactions that take place in the human body at any given time is called ___________________. a. metabolism b. anabolism c. catabolism d. phosphorylation a. metabolism What process involves the donation of a phosphate group from ATP to a reactant to "pay" for cellular process? a. synthesis b. oxidation c. phosphorylation d.anabolism c. phosphorylation When electrons are lost from one substance, they are transferred to another molecule in reactions known as: a. endergonic reactions b. synthesis reactions c. oxidation reduction reactions d. phosphorylation reactions c. oxidation-reduction reactions ____________________ ATO molecules are produced via the electron transport chain and oxidative phosphorylation. a. 4 b. 2 c. 34 d. 38 c. 34 Under anaerobic conditions, what happens to pyruvate? a. Pyruvate us reduced to lactate b. Pyruvate undergoes decarboxylation c. Pyruvate is oxidized in the mitochondrion d. Pyruvate enters the citric acid cycle a. Pyruvate is reduced to lactate Julia has diabete mellitus and is experiencing ketoacidosis. What does her body use to generate ATP? a. fatty acids b. glycerol c. glucose d. glycogen a. fatty acids Which hormone stimulates the uptake of glucose by cells, lowering the concentration of glucose in the blood? a. epinephrine b. insulin c. glucagon d. cortisol b. insulin Julian likes to ride his bike every day. Determine the effect of exercise on his basal metabolic rate. a. The metabolic rate increases during exercise as much as Continue reading >>
Incomplete Oxidation
In the second phase of the release of energy from food (phase II), the small molecules produced in the first phase—sugars, glycerol, a number of fatty acids, and about 20 varieties of amino acids—are incompletely oxidized (in this sense, oxidation means the removal of electrons or hydrogen atoms), the end product being (apart from carbon dioxide and water) one of only three possible substances: the two-carbon compound acetate, in the form of a compound called acetyl coenzyme A; the four-carbon compound oxaloacetate; and the five-carbon compound α-oxoglutarate. The first, acetate in the form of acetyl coenzyme A, constitutes by far the most common product—it is the product of two-thirds of the carbon incorporated into carbohydrates and glycerol; all of the carbon in most fatty acids; and approximately half of the carbon in amino acids. The end product of several amino acids is α-oxoglutarate; that of a few others is oxaloacetate, which is formed either directly or indirectly (from fumarate). These processes occur in animals, plants, bacteria, fungi, and other organisms capable of oxidizing their food materials wholly to carbon dioxide and water. Complete oxidation Total oxidation of the relatively few products of phase II occurs in a cyclic sequence of chemical reactions known as the tricarboxylic acid (TCA) cycle, or the Krebs cycle, after its discoverer, Sir Hans Krebs; it represents phase III of energy release from foods. Each turn of this cycle (see below The tricarboxylic acid [TCA] cycle) is initiated by the formation of citrate, with six carbon atoms, from oxaloacetate (with four carbons) and acetyl coenzyme A; subsequent reactions result in the reformation of oxaloacetate and the formation of two molecules of carbon dioxide. The carbon atoms that go into Continue reading >>
Metabolism And Nutrition
Sort When body temperature increases above the normal range, thermoreceptors in the skin and hypothalamus detect the increase in body temperature. The heat-loss center of the hypothalamus is activated, which sends signals to blood vessels and sweat glands. In response, blood vessels in the skin dilate and sweat glands release sweat. Determine the part of this negative feedback loop that serves as the effector(s). Blood vessels and sweat glands Energy is released from _______ catabolic reaction. This energy is used to fuel the ______ anabolic reaction of _____ synthesis. ATP is broken down in an ______ reaction. The energy from ATP breakdown fuels other _______ reactions in the cell. Exergonic, Endergonic, ATP, Exergonic, Endergonic Cells harness ATP energy by removing the 3rd phosphate group in a ______ reaction. ATP hydrolysis is highly _____ but cell is only able to harness about _____% of the released energy to perform work. the other 60% is lost as _____/ Most processes that burn fuel lose about _____-_____% of their energy as heat Hydrolysis, Exergonic, 40%, heat, 70-90% The overall yield of Glycolysis: Spent ____ molecules of ATP. Synthesized ___ molecules of ATP. Synthesized ___ molecules of NADH. Split glucose into ____ pyruvate molecules. The net energy yield is: ____ molecules of ATP and ____ molecules of NADH 2, 4, 2, 2, 2, 2, Under aerobic conditions pyruvate moves into the mitochondria, is ____ and then enters the citric acid cycle. Pyruvate loses a carbon atom to yield ____ and _____. Acetate is oxidized by NAD+ and linked to a coenzyme A(CoA) molecule to make ______ and NADH. and the 2 molecules of acetyl- CoA then enter the citric acid cycle oxidized, acetate and CO2. Acetyl- CoA (Citric Acid Cycle): Overall yield per glucose from beginning of catabolism Continue reading >>
Amino Acids As Metabolic Substrates During Cardiac Ischemia
Go to: Introduction The heart is a highly active organ that consumes 10% of the body’s total oxygen uptake and produces upwards of 35 kg of ATP every day. (1) This high rate of energy flux is required to accomplish the monumental task of pumping over 6500 liters of blood per day at a relatively constant pressure and flow rate in the average human heart. This extraordinary amount of work requires a constant supply of metabolic substrates and oxygen (Figure 1). An understanding of metabolism is essential for any study of the heart. Metabolism is the fundamental system that governs the entire organ’s behavior and it ties together all fields of study, including molecular physiology, electrophysiology, toxicology and clinical cardiology. All cardiac behaviors are highly ATP-dependent and, without ATP, the heart will cease to function in a matter of minutes. In many types of heart disease and dysfunction, metabolism is the first area affected, which can then lead to channelopathies, ion imbalance, decreased contractile function, increased free radical production and cardiac death. Amino acids play a central role in cardiac metabolism, but their cardioprotective roles as a source of acetyl-CoA and as a substrate for anaplerotic reactions during cardiac ischemia, their ability to contribute to NADH and FADH2 production after reoxygenation and the conversion of glutamine and glutamate to free radical scavengers may not be fully appreciated. Fortunately, the heart is also quite resilient, being able to maintain contractile function even under ischemic and anoxic conditions. It has been shown that an increase in non-oxidative ATP production in the ischemic and reperfused heart is associated with decreased cell death and increased functional recovery both in vivo and in culture Continue reading >>
