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Saturday, March 14, 2009

The krebs cycle

The Krebs cycle is a series of enzymatic reactions that catalyzes the aerobic metabolism of fuel molecules to carbon dioxide and water, thereby generating energy for the production of adenosine triphosphate (ATP) molecules. The Krebs cycle is so named because much of its elucidation was the work of the British. The Krebs cycle is present in virtually all eukaryotic cells that contain mitochondria, but functions only as part of aerobic metabolism (when oxygen is available). The Krebs Cycle is the central metabolic pathway in all aerobic organisms. The Krebs cycle is also known as the citric acid cycle or the tri-carboxylic acid cycle (TCA Cycle) in physiology textbooks. The Krebs cycle is the �energy cycle� for the body. The Krebs cycle is called a cycle because one of the molecules it starts with, the four-carbon oxaloacetate,is regenerated by the end of the cycle to start the cycle over again.
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Cycle

Many types of fuel molecules can be drawn into and utilized by the cycle, including acetyl coenzyme A (acetyl CoA), derived from glycolysis or fatty acid oxidation. The sequence of events known as the Krebs cycle is indeed a cycle; oxaloacetate is both the first reactant and the final product of the metabolic pathway (creating a loop). In the first reaction of the cycle, acetyl CoA condenses with oxaloacetate to form citric acid. After citrate has been formed, the cycle machinery continues through seven distinct enzyme-catalyzed reactions that produce, in order, isocitrate, α-ketoglutarate, succinyl coenzyme A, succinate, fumarate, malate, and. Acetyl CoA utilized in this way by the cycle has been produced either via the oxidation of fatty acids, the breakdown of certain amino acids, or the oxidative decarboxylation of pyruvate (a product of glycolysis). The freshly produced oxaloacetate, in turn, reacts with yet another molecule of acetyl CoA, and the cycle begins again. Each turn of the Krebs cycle produces two molecules of carbon dioxide, one guanosine triphosphate molecule (GTP), and enough electrons to generate three molecules of NADH and one molecule of FADH2. This oxygen requirement is owing to the close relationship between the mitochondrial electron transport chain and the Krebs cycle. In the Krebs cycle, four oxidation–reduction reactions occur. ) As the enzymes of the Krebs cycle oxidize fuel molecules to carbon dioxide, the coenzymes NAD+, FAD, and coenzyme Q (also known as ubiquinone) are reduced. In order for the cycle to continue, these reduced coenzymes must become reoxidized by transferring their electrons to oxygen, thus producing water. Therefore, the final acceptor of the electrons produced by the oxidation of fuel molecules as part of the Krebs cycle is oxygen. This reaction is not really part of the Krebs Cycle,however, since pyruvate is most often generated by glycolysis(which occurs in the cytoplasm of the cell) and the oxidation ofpyruvate occurs in the mitochondrion, it is usually associatedwith the cycle.
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Reactions

Reactions that yield energy, such as most catabolic reactions, are called exergonic, whereas those that require an input of energy, such as most anabolic reactions, are called endergonic. Reactions that form intermediates of the cycle are called anaplerotic reactions. Krebs cycle series of chemical reactions carried out in the living cell; in most higher animals, including humans, it is essential for the oxidative metabolism of glucose and other simple sugars.
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Aerobic

Aerobic Respiration (with oxygen present)The Krebs Cycle (or citric acid cycle)—The Krebs cycle takes place in the fluid matrix of the cristae compartments of the mitochondria. Aerobic Cell Respiration Aerobic respiration is more efficient and more complicated than anaerobic respiration. Aerobic cellular respiration is a gradual process that prevents energy loss as heat. Aerobic cellular respiration has already shown the catabolism of glucose. Aerobic respiration occurs in the presence of oxygen,while anaerobic respiration does not use oxygen. Aerobic respiration uses oxygen and glucose to produce carbon dioxide, water, and ATP. Aerobic Cellular Respiration Cellular respiration includes all metabolic pathways where carbohydrates and other metabolites are broken down to build up ATP.
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Body

It can help bodybuilders get toned, cut, and have more energy. Energy drives all biological, physiological, and chemical reactions in the body. In the human body adenosine tri-phosphate (ATP) is the short-term energy storage unit that is produced within the microscopic mitochondria within every cell in the body. It is estimated that humans use half their body weight each day in ATP production. ) which translates into the body's overall health. Whether you are looking for an endurance-boosting way to increase lean muscle mass, train harder at higher intensity, or trim off a few pounds (or more) by burning fat up to 48% faster, Bodybuilding. The Krebs cycle is the main provider of raw materials such as malic acid that can be converted to blood sugar (Figure 2) when the body uses up its supply.
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Metabolism

Metabolism refers to all the biochemical reactions that occur in a cell or organism. Metabolism of Glucose and Exercise Despite oxidative phosphorylation's large capacity forenergy production, the rate of electron transport and therefore ATP generation is limited by oxygen, the final electron acceptor/oxidizing agent in the chain. Metabolism takes place in sequences of biochemical reactions called pathways.
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Fat

The Krebs cycle can use fatty acids, proteins and glucose for energy production. In the simplest form, the energy cycle shows the intricate balance of food (carbohydrates, fats, proteins) with the proper quantity and quality of vitamins, minerals, probiotics, and enzymes resulting in energy production. Oxygen combines with carbohydrates, fat or protein to release energy for cell function. In addition,intermediates from the Krebs Cycle can go the other direction and be used to synthesize molecules such as amino acids and fatty acids. Within the Krebs cycle, energy in the form of ATP is usually derived from the breakdown of glucose, although fats and proteins can also be utilized as energy sources. The Krebs cycle affects all types of life and is, as such, the metabolic pathway within the cells, which chemically converts carbohydrates, fats and proteins into carbon dioxide and converts water into serviceable energy.
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Exercise

Exercise strategies, weight loss and carbohydrates The metabolism of carbohydrates can also be considered in the context of exercise strategies. Exercise intensity above 85% utilizes only type IIb fibers- anaerobic. Besides fat loss benefits, pyruvate enhances the transport of glucose and protein into muscle cells thereby boosting performance levels in exercise. Calcium pyruvate supplements can help you lose weight by increasing your capacity for endurance exercise. The more exercise you are able to perform, the more calories are used up and less likely to be is stored as fat. During aerobic exercise when the primary muscle fibers being utilized are type I,FFA are used even in the presence of adequate glucose. Note: it would take a lot of exercise to deplete the glycogen stores in muscle. Since the sympathetic nervous system inhibits the gastrointestinal tract during exercise, any remaining quantities of food in the stomach may lead to cramping and acid reflux into the esophagus. Furthermore, dietitians also recommend that people avoid meals high in fats and proteins before exercise, since these foods inhibit gastric emptying and require longer to digest than other foods. Since most people are trying to become leaner by burning fat through exercise, eating a meal before exercise may not be the best idea for losing weight. The best time of the day to exercise with the intention of losing weight is in the morning. If exercise is intense and the cardiovascular system is unable to supply cells with oxygen quickly enough, carbohydrate must be used to produce ATP. The oxidative system as a whole is used primarily during rest and low-intensity exercise. Put another way, if you run out of carbohydrate stores (as in long duration events), exercise intensity must reduce as the body switches to fat as its primary source of fuel.
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Weight

Weight loss may be realized but the type of weight that is actually lost may include muscle mass as well as fat. Research indicates that pyruvate not only has great effects on weight loss by burning fat, but also stimulates energy for higher performance in exercise. Calcium pyruvate may also contribute to weight loss by stimulating cellular respiration, or the amount of energy the mitochondria uses. Helps In Weight Loss Helps in loosing weight while strengthening the internal system. It has been reported as prime substance in weight and cholesterol control. Will pyruvate really help you lose weight, or stimulate greater performance and/or endurance. As you just saw, there is some data showing it may be useful for weight loss, but the results were hardly conclusive.
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Conclusion

The Krebs cycle is an energy cycle in the body of enzymes and chemical actions that yield direct precursors to ATP or ATP itself. The Krebs cycle is the final common pathway for the oxidation of food molecules such as sugars and fatty acids. The Krebs Cycle is like a chain, you are only as strong as your weakest link. The Krebs cycle is therefore another preparatory stage in the respiratory process. Therefore, the main purpose of the Krebs Cycle is to provide high-energy electrons in the form of FADH2 and NADH to be passed onward to the electron transport chain. The Krebs Cycle is a series of complex chemical reactions that occur within the cells of the body to create a form of energy in the body.


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