Triglycerides are dietary and storage fats. When you consume fat, you break it into smaller molecules and absorb it from the intestine. Your cells can then metabolize the fat, burning it to generate energy. Many metabolic processes take place that involve triglycerides as either a reactant or as a product.
Triglyceride Chemistry
While there are many chemical compounds that technically fall under the heading of fats, nutritional fats and storage fats are all triglycerides. A triglyceride is a molecule made up of a glycerol backbone, and three fatty acids. The glycerol backbone is an alcohol molecule -- chemically related, but not identical to drinking and rubbing alcohol. Fatty acids are long chains of carbon and hydrogen, with two oxygen atoms at one end.
Metabolism
The word "metabolism" refers to the sum of all chemical reactions that take place in your body. Metabolism further divides into two subcategories of reactions -- catabolic reactions break large molecules into smaller ones, generally producing energy in the process, and anabolic reactions build larger molecules from smaller ones. You can catabolize fat, breaking it down to liberate energy, or you can anabolize fat from other nutrient molecules, like sugars and proteins.
Fat Catabolism
When you break down triglycerides, whether from the food you eat or from stores of triglycerides in your fat cells, you first separate the glycerol backbone from its fatty acids. You can burn glycerol for energy by converting it into the molecule glyceraldehyde-3-phosphate, which you also make when you burn sugars for energy, explain Drs. Reginald Garrett and Charles Grisham in their book, "Biochemistry." You burn the three fatty acids through the beta oxidation process, which produces the small molecules of acetyl-coA.
Fate of Acetyl-CoA
The acetyl-coA that you make by breaking down fatty acids goes on to enter an energy-producing reaction series called the Krebs Cycle, explain Drs. Mary Campbell and Shawn Farrell in their book, "Biochemistry." During the Krebs Cycle, you join acetyl-coA to a molecule called oxaloacetate to form citrate, which your cells then process to liberate carbon dioxide and regenerate oxaloacetate. This process yields energy, which the cells use to run a variety of reactions.
Fat Anabolism
Because your body stores large amounts of energy in the form of fat, it's important that you be able to make fat from other nutrients, like sugar. When you anabolize, or build, fat, your cells start by partially burning sugar to produce acetyl-coA. You then assemble the acetyl-coA into fatty acids, through a process roughly opposite to that you use to break down fatty acids, explain Drs. Garrett and Grisham. Anabolism of fat from other nutrients ensures that you store enough energy to help you through periods of fasting.
References
- "Biochemistry"; Reginald Garrett, Ph.D. and Charles Grisham, Ph.D.; 2007
- "Biochemistry"; Mary Campbell, Ph.D. and Shawn Farrell, Ph.D.; 2005
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