Lipids - Phospholipids look just like lipids except that...

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Lipids Lipids  are a class of substances that are insoluble in water (and other polar solvents), but are soluble  in nonpolar substances (such as ether or chloroform). There are three major groups of lipids:  Triglycerides  include fats, oils, and waxes. They consist of three fatty acids bonded to  a glycerol molecule (Figure 2). Fatty acids are hydrocarbons (chains of covalently bonded  carbons and hydrogens) with a carboxyl group (–COOH) at one end of the chain. A  saturated fatty acid has a single covalent bond between each pair of carbon atoms, and  each carbon has two hydrogens bonded to it. You can remember this fact by thinking that  each carbon is “saturated” with hydrogen. An unsaturated fatty acid occurs when a double  covalent bond replaces a single covalent bond and two hydrogen atoms (Figure 2).  Polyunsaturated fatty acids have many of these double bonds. 
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Unformatted text preview: Phospholipids look just like lipids except that one of the fatty acid chains is replaced by a phosphate (P0 4 3 ) group (Figure 3). Additional chemical groups (indicated by R in Figure 3) are usually attached to the phosphate group. Since the fatty acid tails of phospholipids are nonpolar and hydrophobic and the glycerol and phosphate heads are polar and hydrophilic, phospholipids are often found oriented in sandwichlike formations with the hydrophobic heads oriented toward the outside. Such formations of phospholipids provide the structural foundation of cell membranes. Steroids are characterized by a backbone of four linked carbon rings (Figure 4). Examples of steroids include cholesterol (a component of cell membranes) and certain hormones, including testosterone and estrogen....
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This note was uploaded on 11/10/2011 for the course PT 101 taught by Professor Staff during the Spring '10 term at Texas State.

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