1. Biochemistry Lecture 13

2. Convergence of Pathways

4. Oxidation of Fatty Acids is a Major Energy-Yielding Pathway in Many Organisms About one third of our energy needs comes from dietary triacylglycerols About 80% of energy needs of mammalian heart and liver are met by oxidation of fatty acids Many hibernating animals, such as grizzly bears relay almost exclusively on fats as their source of energy

5. Fatty Acids and Energy Fatty acids in triglycerides are the principal storage form of energy for most organisms. –Hydrocarbon chains are a highly reduced form of carbon. –The energy yield per gram of fatty acid oxidized is greater than that per gram of carbohydrate oxidized.

9. Hydrolysis of Fats Yields Fatty Acids and Glycerol hydrolysis of triacylglycerols is catalyzed by lipases some lipases are regulated by hormones glucagon and epinephrine epinephrine means: “we need energy now” glucagon means: “we are out of glucose”

15. Step 2. Dehydrogenation of Alkane to Alkene Step 3. Hydration of Alkene

16. Step 4: Dehydrogenation of Alcohol and Step 5: Transfer of Fatty Acid Chain

17. Trifunctional Protein Hetero-octamer –Four  subunits enoyl-CoA hydratase activity  -hydroxyacyl-CoA dehydrogenase activity Responsible for binding to membrane –Four  subunits long-chain thiolase activity May allow substrate channeling Associated with inner mitochondrial membrane Processes fatty acid chains with 12 or more carbons; shorter ones by enzymes in the matrix

19. Oxidation of Monounsaturated Fatty Acids

20. Oxidation of Polyunsaturated Fatty Acids

22. Formation of Ketone Bodies Entry of acetyl-CoA into citric acid cycle requires oxaloacetate When oxaloacetate is depleted, acetyl-CoA is converted into ketone bodies Formation occurs when the amount of acetyl CoA produced is excessive compared to the amount of oxaloacetate available to react with it and take it into the TCA; for example: –Dietary intake is high in lipids and low in carbohydrates. –Diabetes is not suitably controlled. –Starvation. The first step is reverse of the last step in the  -oxidation: thiolase reaction joins two acetate units