Lipids Terpenes Waxes

Q Classify simple and complex lipids. Identify waxes, triglycerides, phospholipids, steroids, prostaglandins, and terpenes. 

Unlike protein and polysaccharides, lipid and resin are not polymers so they could not form stand-alone films. Edible lipids include waxes and oils for example, paraffin wax, beeswax (BW), candelilla wax, camauba wax, rice bran wax, jojoba oil, triglycerides (milkfat fractions), fatty acids, fatty alcohols, and sucrose fatty acid esters. Resins include shellac and terpene (Krochta, 2002). Due to their hydrophobic nature, lipid-based films and coatings exhibit high water resistance and low surface energy (Han and Gennadios, 2005). Generally, edible lipids have been incorporated into proteins and polysaccharides as emulsion or multilayer composite films to improve moisture barrier. 

Lipid A large, varied class of water insoluble organic molecules, including steriods, fatty acids, prostaglandins, terpenes, and waxes. 

In this chapter we will examine how cells and enzymes are used in the transformation of lipids. The lipids are, of course, a very diverse and complex series of molecular entities including fatty acids, triglycerides, phospholipids, glycolipids, aliphatic alcohols, waxes, terpenes and steroids. It is usual to teach about these molecules, in a biochemical context, in more or less the order given above, since this represents a logical sequence leading from simple molecules to the more complex. Here, however, we have adopted a different strategy. 

When plant or animal tissues are extracted with nonpolar solvents, a portion of the material dissolves. The components of this soluble fraction are called lipids and include fatty acids, triacylglycerols, waxes, terpenes, postagladins, and steroids. The insoluble portion contains the more polar plant components including carbohydrates, lignin, proteins, and nucleic acids. 

The resinite macerals are in some ways the most varied group. They are derived from both the wound resins (terpenes) of plants and various other plant fats and waxes making up the lipid resins. The terpene-derived resinites are the most abundant type and they are found in most North American coals as ovoid masses. However, 1n some coals, especially in the western USA the resinite occurs mainly as a secondary form showing... 

All these actions involve the use, misuse, or manipulation of lipids. Steroids, prostaglandins, fats, oil, waxes, terpenes, and even the colorful carotenes in the falling leaves are all lipids. In our study of organic chemistry, we have usually classified compounds according to their functional groups. Lipids, however, are classified by their solubility Lipids are substances that can be extracted from cells and tissues by nonpolar organic solvents. 

Problem 19.50. Which of the following are nonhydrolyzable lipids (a) triacylglycerols, ib) prostaglandins, (c) waxes, id) leukotrienes, (e) sphingomyelins, if) steroids, (g) glycolipids, ih) cerebrosides, ii) terpenes, ij) plasmalogens, ik) phosphoglycerides. 

The composition of hpids on the surface of leaves, stems, and fruits is quite different from that of hpids that form intracellular membranes. Their role is the protection of sensitive plant tissues against the loss of water and other biologically important volatiles. Waxes (i.e., esters of FA with monofunctional alcohols) are the most important components of these lipids. Some plant waxes are of commercial importance, such as camauba or candellila wax. They are solid at room temperature and in temperate climates, with the exception of liquid jojoba wax, and are plastic or even liquid in tropical climates. They contain bound saturated long-chain FA and alcohols. Waxes on the surface of apples and other fruits from temperate zones are solids or semisolid pastes, consisting of terpenes, ceryl cerotate, ceryl palmitate, and other esters. In the wax from lettuce leaves, higher alcohols prevail, with only small amounts of free FA (Bakker et al., 1998). Other components, such as alkanes, ketones, esters, secondary alcohols, were detected in other vegetables (e.g., in kale or rutabaga). 

Lipids have a variety of functions in living organisms. Fats and oils are a convenient and concentrated means of storing food energy in plants and animals. Phospholipids and sterols, such as cholesterol, are major components of cell membranes see upid bilayer). Waxes provide vitai waterproofing for body surfaces. Terpenes include tamins A, E, and K, and phytol (a component of chlorophyll) and occur in essential oils, such as menthol and camphor. Steroids include the adrenal hormones, sex hormones, and bile acids. 

Classify lipids both into the large classifications (such as simple lipids, complex lipids, phospholipids, etc.) and into the more specific classifications (such as waxes, triglycerides, cephalins, lecithins, steroids, prostaglandins, terpenes, etc.). 

Hydrocarbons found in the environment are of diverse structure and are widely distributed in the biosphere, predominantly as surface waxes of leaves, plant oils, cuticles of insects, and the lipids of microorganisms. Straight-chain HC, or alkanes, with carbon number maxima in the range of C17 to C21 are typically produced by aquatic algae. Conversely terrestrial plants typically produce alkanes with C25 to C33 maxima. Plants also synthesize aromatic HC such as carotenoids, lignin, aUcenoids, terpenes, and flavenoids. Polycyclic... 

Lipid (Section 23.1) A substance of biological origin that is soln-ble in nonpolar solvents. Lipids include fatty acids, triacylglycerols (fats and oils), steroids, prostaglandins, terpenes and terpenoids, and waxes. 

Natural waxes can consist of a wide range of different lipid classes, including esters of various kinds, hydrocarbons, ketones, hydroxy-ketones, p-diketones, aldehydes, acids and terpenes. With cmde mixtures of this kind, it is usually necessary to react them with diazomethane to methylate free carboxyl groups, to acetylate (or to prepare TMS... 

---