Fatty Acid and Lipid Metabolism
Some birds can fly thousands of miles over water without stopping to eat. Bears can hibernate for months without the need to wake and forage. Boundaries allow for the existence of cells and, by extension, organisms. All of these circumstances are possible because of a crucial class of biomolecules—
Triacylglycerols are the most efficient fuels because they are more reduced than carbohydrates. However, this increase in energy efficiency comes at the cost of biochemical versatility. Unlike carbohydrates, lipid metabolism requires the presence of molecular oxygen to form ATP.
Not only are lipids important fuel molecules, but they also serve a structural purpose. The common forms of membrane lipids are phospholipids, glycolipids, and cholesterol. A phospholipid is built on a backbone of either glycerol or sphingosine, an amino alcohol. These lipids contain a phosphoryl group and an alcohol, in addition to fatty acids. Sphingosine-
In Chapter 27, we will examine how triacylglycerols are processed to yield fatty acids and how the fatty acids are degraded in a process called β oxidation that ultimately results in the synthesis of much ATP. In Chapter 28, we will see how fatty acids are synthesized and how fatty acid degradation and synthesis are coordinated. In Chapter 29, we will study lipid synthesis and transport, with a particular emphasis on cholesterol synthesis and its regulation.
✓ By the end of this section, you should be able to:
✓ 1 Identify the repeated steps of fatty acid degradation.
✓ 2 Describe ketone bodies and their role in metabolism.
✓ 3 Explain how fatty acids are synthesized.
✓ 4 Explain how fatty acid metabolism is regulated.
✓ 5 Describe the relation between triacylglycerol synthesis and phospholipid synthesis.
✓ 6 List the regulatory steps in the control of cholesterol synthesis.