Lipid Metabolism Analysis in Depth



Lipid metabolism can be defined as the processes that involve the creation and degradation of lipids. The types of lipids involved include bile salts, cholesterols, eicosanoids, glycolipids, ketone bodies, fatty acids, phospholipids, sphingolipids, steroids, triacylglycerols etc. The major aspects of lipid metabolism are involved with fatty acid oxidation to produce energy or the synthesis of lipids which is called Lipogenesis.

The Steps of Lipid Metabolism

The first and the basic step in lipid metabolism is the hydrolysis of the lipid in the cytoplasm to produce glycerol and fatty acids. Since glycerol is a three carbon alcohol, it is metabolized quite readily into an intermediate in glycolysis, dihydroxyacetone phosphate.

The last reaction is readily reversible if glycerol is needed for the synthesis of a lipid. The hydroxyacetone, obtained from glycerol is metabolized into one of two possible compounds. Dihydroxyacetone may be converted into pyruvic acid through the glycolysis pathway to make energy. In addition, the dihydroxyacetone

Fatty acids are synthesized from carbohydrates and occasionally from proteins. Actually, the carbohydrates and proteins have first been catabolized into Acetyl CoA. Depending upon the energy requirements, the acetyl CoA enters the citric acid cycle or is used to synthesize fatty acids in a process known as Lipogenesis.

A Technical Analysis of Metabolism

Metabolism relates to the physical and chemical processes that occur inside the cells of the body and that maintain life. Metabolism consists of anabolism (the constructive phase) and catabolism (the destructive phase, in which complex materials are broken down). The conversion of the macronutrients carbohydrates, fats, and proteins in food to energy, and other physiological processes are parts of the fat metabolism process. ATP (adinosene triphosphate) is the major form of energy used for cellular metabolism. The fuel that your body runs on is called glucose and fat metabolism is significant for this. You get most of your glucose from carbohydrates. Ideally, you will only take in enough to use. If you take in more carbohydrates than you can break down you will stock up it as fat. If you begin to use more carbohydrates than you need to fuel your body, you have alternate pathways to break down fat that can be converted into glucose. So the fat is converted back into carbohydrate and used as fuel for your body.

Fats contain mostly carbon and hydrogen, some oxygen, and sometimes other atoms. The three main forms of fat found in food are glycerides (principally triacylglycerol, the form in which fat is stored for fuel), the phospholipids, and the sterols (principally cholesterol). Fats provide 9 kilocalories per gram (kcal/g), compared with 4 kcal/g for carbohydrate and protein. Triacylglycerol, whether in the form of chylomicrons (microscopic lipid particles) or other lipoproteins, is not taken up directly by any tissue, but must be hydrolyzed outside the cell to fatty acids and glycerol, which can then enter the cell as a part of fat metabolism.


Endogenous triglycerides represent the largest fuel reserve in the body. Most triglycerides are compactly stored in adipose tissue as oil. Triglycerides are also present in skeletal muscle and in plasma very low-density lipoproteins. The total amount of energy stored as triglyceride is 65-fold greater than the amount of energy stored as glycogen. Therefore, the use of fat as a fuel during endurance exercise permits sustained physical activity and delays the onset of hypoglycemia. The relative contribution of different endogenous fat depots for energy production Durham endurance exercise is not precisely known because of methodological limitations. The major source of fatty acids oxidized during prolonged exercise is derived from adipose tissue. The rate of lipolysis depends on the intensity and duration of the exercise bout, previous exercise training, and recent dietary intake. Modifications in dietary intake before exercise can cause changes in lipid metabolism during exercise.