Lipids Oils Phospholipids Steroids

Lipids are chemical components of the cell that are insoluble in water but soluble in nonpolar solvents. Lipids include fatty acids, fats, oils, phospholipids, glyco-lipids, and steroids. Insolubility in water makes lipids an ideal structural component of cell membranes. Lipids make up the containers that separate the interior of the cell from its external environment. Lipids are also used for long-term energy storage and for insulation. We all store extra calories from food as lipids, some of us more than others. 

This chapter is organized around the four major classes of biological macromolecules. Recognize what most macromolecules have in common They are assembled from simple monomer units. Proteins are assembled from amino acids, carbohydrates are assembled from monosaccharides, and nucleic acids are assembled from nucleotides. Lipid is a catchall classification that includes fats, oils, phospholipids, waxes, steroids, and some other molecules. Organize your study into these four categories. 

Lipids are another important class of nutrients in our diet. They are found in dairy products, grains, meats, and oils. A lipid is a type of biochemical that does not dissolve in water, has a high percentage of C and H atoms, and is soluble in nonpolar solvents. As a class, lipids are not nearly as similar to each other as carbohydrates are. Long-chain fatty acids, phospholipids, steroids, and cholesterol are lipids. 

Classes of lipids include waxes, fats and oils, phospholipids, and steroids. 

Lipids are substances of biological origin that are soluble in non-polar solvents. There are saponifiable lipids, such as acylglycerols (fats and oils), waxes and phospholipids, as well as non-saponifiable compounds, principally steroids. 

Additional naturally occurring lipids may be minor components of oral lipid-based formulations. Terpenes such as peppermint oil (>50% menthol) are fairly hydrophobic but can provide some solvent capacity. Steroids such as cholesterol, while important in topical and in parenteral liposomal products, are not important as oral pharmaceutical adjuvants. Phospholipids (e.g., egg or soybean phosphatidylcholine) an essential component of cell membranes, are considered polar lipids, and have surfactant properties. 

Lipids are fats and oils. Fats exist as solids while oils exist as liquids at room temperature. Lipids are mainly composed of triglycerides, but may also contain steroids, phospholipids, fatty acids, monoglycerides, diglycerides and other amphi-pathic molecules with long alkyl chains. The intramolecular order of these molecules is largely determined by the conformational order of the alkyl chain. The conformational order is dependent on many factors such as chain length, temperature,... 

The structures of lipids are quite varied triacylglycerols (fats and oils), waxes, phospholipids, sphingolipids, steroids, eicosanoids, fat soluble vitamins, and pigments. Some lipids are simple in structure while others are more complex. Among these molecules are those which are esters in nature and therefore saponifiable in aqueous base. Others are nonsaponifiable. Many are completely nonpolar while others are amphipathic, that is, they have a polar/nonpolar nature. 

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. 

Other principal classes of lipids, besides fats and oils, are phospholipids, glyco-lipids, and steroids (see Figure 20.1). The phospholipids are found in all animal and... 

Lipids are a group of substances that are insoluble in water but soluble in common organic solvents. They include the fats and oils, the glycolipids, the phospholipids, the lipoproteins, the steroids and the terpenes. 

Crude fats and oils consist primarily of glycerides. However, they also contain many other lipids in minor quantitites. Com oil, for example, may contain glycerides plus phospholipids, glycolipids, many isomers of sitosterol and stigmasterol (plant steroids), several tocopherols (vitamins E), vitamin A, waxes, unsaturated hydrocarbons such as squalane and dozens of carotenoids and chlorophyll compounds, as well as many products of decomposition, hydrolysis, oxidation, and polymerization of any of the natural constituents. 

Lipids are found in living organisms and are insoluble in water but soluble in nonpolar solvents. Lipids may be divided into three classes (1) fats, oils, and phospholipids, (2) waxes, and (3) lipids (usually) without ester groups, such as steroids. 

Is not everybody worried about cholesterol And cholesterol is a steroid. Well then, are not steroids bad What are steroids, anyway Chemically, they belong to a group of compounds called lipid. Lipid is a fancy (collective) term for oil-soluble compounds and includes fats, phospholipids, and steroids. Fats are chanically long chain fatty acids and almost like wax. Phospholipids are combination of fatty acids and glycerine with some special groups on top and make up the membrane of cells (Fig. 1.5). By the way, cholesterol also makes up an essential part of cell manbranes along with phospholipids. Cholesterol is indeed a necessity. Only excess presence of cholesterol is a health hazard. 

Extraction of biological material with nonpolar solvents gives a wide assortment of compounds that includes terpenes and steroids (Section 4-7), fats and oils, and a variety of other low-polarity substances collectively called lipids (lipos, Greek, fat). Lipid fractions include phospholipids, important components of cell membranes, which are derived from carboxylic acids and phosphoric acid. In the phosphoglycerides, glycerol is esterified with two adjacent fatty acids and a phosphate unit that bears another substituent derived from a... 

Within the lipid family, there are specific structures that distinguish the different types of lipids. Lipids such as waxes, fats, oils, and phospholipids are esters that can be hydrolyzed to give fatty acids along with other molecules. Steroids are characterized by the steroid nucleus of four fused carbon rings. They do not contain fatty acids and cannot be hydrolyzed. Figure 15.1 illustrates the types and general structure of Upids we will discuss in this chapter. 

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