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Fatty acids are a family of molecules classified within the lipid macronutrient class. One role of fatty acids within animal metabolism is energy production in the form of adenosine triphosphate (ATP) synthesis. When compared to other macronutrient classes (carbohydrates and protein), fatty acids yield the most ATP on an energy per gram basis by a pathway called β-oxidation.〔(Oxidation of fatty acids )〕 In addition, fatty acids are important for energy storage, phospholipid membrane formation, and signaling pathways. Fatty acid metabolism consists of catabolic processes that generate energy and primary metabolites from fatty acids, and anabolic processes that create biologically important molecules from fatty acids and other dietary sources. == Overview == *Lipolysis, the removal of the fatty acid chains from the glycerol to which they are bound in their storage form as triglycerides or fats, is carried out by lipases. *Once freed from glycerol, free fatty acids can enter blood, which transports them, attached to plasma albumin, throughout the body. *Free fatty acids enter the metabolizing cells (i.e. most living cells in the body except red blood cells and neurons in the central nervous system) by diffusion through the cell membrane. * Once inside the cell they are linked to co-enzyme A to form acyl-CoA chains through the action of acyl-CoA synthase in the outer membrane of the mitochondrion. Carnitine then carries the acyl-CoA chains into the mitochondrial matrix. *Beta oxidation, in the mitochondrial matrix, then cuts the long carbon chains of the fatty acids (in the form of acyl-CoA molecules) into a series of two-carbon (acetate) units, which, combined with co-enzyme A, form molecules of acetyl CoA, which can eventually enter the TCA cycle.〔 :Briefly, the steps in β-oxidation (the initial breakdown of free fatty acids) are as follows:〔 #Dehydrogenation by acyl-CoA dehydrogenase, yielding 1 FADH2 #Hydration by enoyl-CoA hydratase #Dehydrogenation by 3-hydroxyacyl-CoA dehydrogenase, yielding 1 NADH #Cleavage by thiolase, yielding 1 acetyl-CoA and a fatty acid that has now been shortened by 2 carbons (forming a new, shortened acyl-CoA) This cycle repeats until the fatty acid has been completely reduced to acetyl-CoA or, in the case of fatty acids with odd numbers of carbon atoms, acetyl-CoA and 1 molecule of propionyl-CoA per molecule of fatty acid. The glycerol released by lipase action is phosphorylated by glycerol kinase, and the resulting glycerol 3-phosphate is oxidized to dihydroxyacetone phosphate. The glycolytic enzyme triose phosphate isomerase converts this compound to glyceraldehyde 3-phosphate, which is oxidized via glycolysis. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「fatty acid metabolism」の詳細全文を読む スポンサード リンク
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