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Lipids are water-insoluble heterogeneous group of compounds, which are soluble in organic solvents. Besides being an important constituent of the diet, lipids have many other uses. A great diversity of lipids occurs in nature, and it is very important to get the right kind of lipid in a diet. Lipids are among the biomolecules required for structure and functions of the cell. Since they are mostly stored in seeds or fruits of some plants, these are the main sources for obtaining dietary lipids. Studying the diversity and the metabolism of lipids is important. A brief introduction to diversity in structure and functions of lipids is taken in this chapter besides learning about the classification and nomenclature of fatty acids. The chapter includes the pathways, the role of enzymes, and the organelles involved in the lipid metabolism. Studying the catabolism of lipids is significant in germinating fatty seeds, since they have primarily oils as the storage form. In fatty seeds the stored lipids are not the source of energy directly. Lipids are metabolized to produce soluble form of sugars in the storage organs, which are translocated to the meristematic regions in the growing seedlings. A study of pathways, enzymes, and organelles involved in lipid metabolism in germinating seeds is also included in the chapter. Though there is similarity in lipid metabolism of plants and animals, a great degree of disparity also exists. In plants lipid metabolism is more complex and involves many cell organelles. Fatty acid synthesis and fatty acid oxidation occur in different subcellular locations and involve different metabolic pathways and different sets of enzymes. There is successive removal of two-carbon units as acetyl-CoA during oxidation of fatty acids. Elongation of hydrocarbon chain also requires, at the time of fatty acid synthesis, addition of two carbons at a time. However, precursors for fatty acid synthesis are three-carbon compounds, malonyl-CoA, except one acetyl-CoA, which is required as a primer. The condensation reaction is coupled with simultaneous release of one carbon as CO2 (Fig. 10.1).
KeywordsAcyl carrier protein β-Oxidation Coenzyme A Gluconeogenesis Glyoxylate cycle Malonyl-CoA Oleosin Phosphatidic acid Phosphatidylcholine Triglycerides
Suggested Further Readings
- Browsher C, Steer M, Tobin A (eds) (2008) Plant biochemistry. Garland Science, Tailor & Francis Group, New York, pp 303–329Google Scholar
- Nelson DL, Cox MM (2017) Lehninger principles of biochemistry, 7th edn. WH Freeman, MacMillan Learning, New York, pp 649–668Google Scholar
- Ohlrogge J, Browse J, Jaworski J, Chris S (2013) Lipids. In: Buchanan BB, Gruissem W, Jones RL (eds) Biochemistry and molecular biology of plants. Wiley-Blackwell, Chichester, pp 337–396Google Scholar