Fatty Acid Synthesis

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  • 28.1 Fatty Acid Synthesis Takes Place in Three Stages

  • 28.2 Additional Enzymes Elongate and Desaturate Fatty Acids

  • 28.3 Acetyl CoA Carboxylase Is a Key Regulator of Fatty Acid Metabolism

  • 28.4 Metabolism in Context: Ethanol Alters Energy Metabolism in the Liver

To prepare for their winter hibernation, bears feed into the fall, storing excess energy as fat in the form of triacylglycerols. These energy stores sustain a bear during hibernation.

As we have seen, fatty acids play a variety of crucial roles in biological systems. For instance, they serve as fuel reserves, signal molecules, and components of membrane lipids. Because our diet meets our physiological needs for fats and lipids, adult human beings have little need for fatty acid synthesis. However, many tissues, such as liver and adipose tissue, are capable of synthesizing fatty acids, and this synthesis is required under certain physiological conditions. For instance, fatty acid synthesis is necessary during embryonic development and during lactation in mammary glands. Too much fatty acid synthesis in an alcoholic’s liver contributes to liver failure.

Acetyl CoA, the end product of fatty acid degradation, is the precursor for virtually all fatty acids. The biochemical challenge is to link the two-carbon units together and reduce the carbon atoms to produce palmitate, a C16 fatty acid. Palmitate then serves as a precursor for the variety of other fatty acids.