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Chemistry LibreTexts

7: Lipids

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    • 7.1: Fatty Acids
      Fatty acids are carboxylic acids that are the structural components of many lipids. They may be saturated or unsaturated. Most fatty acids are unbranched and contain an even number of carbon atoms. Unsaturated fatty acids have lower melting points than saturated fatty acids containing the same number of carbon atoms.
    • 7.2: Triglycerides
      Fats and oils are composed of molecules known as triglycerides, which are esters composed of three fatty acid units linked to glycerol. An increase in the percentage of shorter-chain fatty acids and/or unsaturated fatty acids lowers the melting point of a fat or oil. The hydrolysis of fats and oils in the presence of a base makes soap and is known as saponification. Double bonds present in unsaturated triglycerides can be hydrogenated to convert oils (liquid) into margarine (solid).
    • 7.3: Phospholipids
      Lipids are important components of biological membranes. These lipids have dual characteristics: part of the molecule is hydrophilic, and part of the molecule is hydrophobic. Membrane lipids may be classified as phospholipids, glycolipids, and/or sphingolipids. Proteins are another important component of biological membranes. Integral proteins span the lipid bilayer, while peripheral proteins are more loosely associated with the surface of the membrane.
    • 7.4: Osmosis and Diffusion
      Fish cells, like all cells, have semipermeable membranes. Eventually, the concentration of "stuff" on either side of them will even out. A fish that lives in salt water will have somewhat salty water inside itself. Put it in freshwater, and the freshwater will, through osmosis, enter the fish, causing its cells to swell, and the fish will die. What will happen to a freshwater fish in the ocean?
    • 7.5: Steroids
      One major class of lipids is the steroids, which have structures totally different from the other classes of lipids. The main feature of steroids is the ring system of three cyclohexanes and one cyclopentane in a fused ring system as shown below. There are a variety of functional groups that may be attached. The main feature, as in all lipids, is the large number of carbon-hydrogens which make steroids non-polar.
    • 7.E: Lipids (Exercises)
      Problems and select solutions for the chapter.
    • 7.S: Lipids (Summary)
      To ensure that you understand the material in this chapter, you should review the meanings of the bold terms in the following summary and ask yourself how they relate to the topics in the chapter.

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