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Gluconeogenesis: Glucose
Metabolism from Fat, Proteins |
Carbs in Food |
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Information About Carbs | Carbohydrates Guide | Low Carb Diets |
GluconeogenesisGluconeogenesis - meaning, "the creation of a new form of glucose" - is the process of making glucose (sugar) from its own breakdown products or from the breakdown products of lipids (fats) or proteins. Gluconeogenesis occurs mainly in the liver or kidney. It's a "new form of glucose" because normally glucose-for-energy comes from carbohydrates. Maintains Blood-Glucose LevelsExperts describe gluconeogenesis as the process by which the liver contributes to the maintenance of normal blood glucose levels (and thus energy metabolism) through synthesis of glucose. This process occurs in the fasting state, such as at night, and requires the presence of amino acids, lactate, and glycerol. The process is controlled, among other things, by the balance among various hormones - especially cortisol from the cortex of the adrenal glands and insulin from the pancreas. Non-Carbohydrate SourcesOnce all the liver glycogen is used up (after 24 hours of fasting, or much sooner if you exercise) the liver has to make glucose from non-carbohydrate sources. The process is called gluconeogenesis. The liver can make glucose from lactic acid, if available, but its prime raw ingredient is protein. Fats cannot be turned back into glucose. Ketone BodiesWhen the liver engages in gluconeogenesis it burns fats (which are the energy for the gluconeogenic process), but is unable to fully metabolize them to carbon dioxide and water. These semi-metabolized fat products are then converted into ketone bodies. They are released into the blood, from where they are taken up and utilized by most tissues, where they are turned into carbon dioxide and water. The heart utilizes ketone bodies, so do the muscles, and also the brain which normally only burns glucose, although the brain cannot survive without glucose. |
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Carbs-Information.com provides general information about different types of carbohydrate, like monosaccharides, disaccharides, oligosaccharides, polysaccharides, as well as nutritional value of carbohydrates, carb-content of foods, plus details of GI values of all food groups, plus advice about diabetes, impaired glucose tolerance and insulin resistance. But no information is intended as a substitute for medical advice. Copyright 2003-2006. |